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ENERGY RECOVERY BY CROPS IN DEPENDENCE ON THE INPUT OF MINERAL FERTILIZER

MARTIN-LUTHER-UNIVERSITY HALLE-WITTENBERG Agroecological Institute

Institute of Agronomy and Crop Science

Final Report Energy Recovery by Crops in Dependence on the Input of Mineral Fertilizer

by BIERMANN, S., G.-W. RATHKE, K.-J. HÜLSBERGEN & W. DIEPENBROCK Halle (Saale), May 1999

Proposer: Project Coordinator: Dr. U. Pigla Prof. Dr. habil. W. Diepenbrock Agroecological Institute Director of the Agroecological Institute at the Martin-Luther-University Halle-Wittenberg Director of the Institute of Agronomy and Crop Science c/o The Dean of the Agricultural Faculty Martin-Luther-University Halle-Wittenberg Ludwig-Wucherer-Straße 2 Ludwig-Wucherer-Straße 2 D-06108 Halle (Saale) D-06108 Halle (Saale)

List of Contents

Introduction and Problem Definition

2 2.1 2.2

Methodical Approaches to Energy Balancing in Crop Farming Definition of System Boundaries and Involved Energy Fluxes Survey of Energy Equivalents in Crop Farming

2 3 4

3 3.1 3.1.1 3.1.2 3.2 3.3 3.3.1 3.3.2 3.4

Material and Methods Description of the Field Experiments Site Characteristics Experimental Schedule Description of the Farms Methodics of Energy Balancing Energy Input Energy Output Evaluation by Use of Mathematical Statistics

9 9 9 10 11 12 12 16 17

4 4.1 4.1.1 4.1.2 4.2 4.2.1 4.2.2 4.3 4.3.1 4.3.2 4.4 4.5 4.5.1 4.5.1.1 4.5.1.2 4.5.1.3 4.5.1.4

Results and Discussion Energy Input Energy Input in Field Experiments Energy Input in Farms Yields Yields in Field Experiments Yields in Farms Energy Output Energy Output in Field Experiments Energy Output in Farms Energy Output Compared with Energy Input Energy Efficiency Energy Gain Energy Gain in Field Experiments Energy Gain in Farms Comparison of Energy Gain in Field Experiments and in Farms Influence of Different Energy Equivalents on the Energy Gain

18 18 18 21 22 22 24 24 24 26 27 27 28 28 31 31 32

4.5.2 4.5.2.1 4.5.2.2 4.5.2.3 4.5.2.4

Energy Intensity Energy Intensity in Field Experiments Energy Intensity in Farms Comparison of Energy Intensity in Field Experiments and in Farms Influence of Different Energy Equivalents on the Energy Intensity

34 34 37 37 38

Conclusions

Prospects

References

III

List of Contents

List of Tables Table 1:

Comparison between the eco-energetic and the economic method in energy balancing

Table 2: Table 3:

Parameters of the energy balance sheet

4 9

Table 4: Table 5: Table 6: Table 7: Table 8: Table 9: Table 10: Table 11: Table Table Table Table Table Table Table

12: 13: 14: 15: 16: 17: 18:

Site characteristics of the experimental stations GroĂ&#x; Kreutz and Leipzig-Seehausen Characteristics of the farms

Energy balancing factors in crop farming Energy equivalents for mineral fertilizer Direct energy input (MJ ha-1) with capital goods Indirect energy input (MJ ha-1) with capital goods Gross energy contents (GJ t-1 DM) and grain equivalent (GE) conversion code for the evaluation of the harvested products

Relative share (%) of input factors Influence of different energy equivalents on the total energy input to winter wheat -1

Crop-related energy input (GJ ha ) in farms

Winter barley yields (dt ha-1) in Leipzig-Seehausen, calculated values Yields (dt ha-1) in the farms Energy output (GJ ha-1) in field experiments Energy output (GJ ha-1) in farms -1 Energy gain (GJ ha ) in farms Energy intensity (MJ GE-1) in farms

12 13 13 15 15 17 19 20 21 22 24 25 26 31 37

List of Contents

List of Figures Energy flux scheme Fig. 1: Fig. 2: Distribution of rainfall in the experimental station Leipzig-Seehausen Fig. 3: Modification of the field experiment F1-70 in Leipzig-Seehausen Fig. 4: Energetic evaluation of the production technology to winter wheat Fig. 5: Energy input (GJ ha-1) in Leipzig-Seehausen Fig. 6: Fig. 7:

Energy input (GJ ha-1) for mineral-N fertilizer to winter wheat and sugar beet in farms

4 10 11 16 18 21 23

-1

Fig. 8:

Winter wheat yield (dt ha ) in dependence on nitrogen fertilization in the experimental station Leipzig-Seehausen (1995)

Fig. 9:

Winter wheat yield (dt ha-1) in dependence on nitrogen fertilization in the experimental station Groß Kreutz (1992)

Fig. 10:

Development of the energy output (GJ ha-1) in the field experiment F170 in Leipzig-Seehausen

Fig. 11: Fig. 12: Fig. 13:

Energy output (GJ ha-1) and energy input (GJ ha-1) on the example of winter wheat and sugar beet -1

28 29 30

Fig. 14: Fig. 15:

Energy gain (GJ ha ) in Leipzig-Seehausen 1971-1981 -1 Energy gain (GJ ha ) in Leipzig-Seehausen 1989-1992 -1 Energy gain (GJ ha ) of winter wheat in Leipzig-Seehausen and Groß Kreutz

Fig. 16: Fig. 17: Fig. 18:

Site-related energy gain (GJ ha ) of winter wheat -1 Influence of different energy equivalents on the energy gain (GJ ha ) of winter wheat

34 35 36

Fig. 19: Fig. 20:

Energy intensity (MJ GE-1) in Leipzig-Seehausen 1971-1981 Energy intensity (MJ GE-1) in Leipzig-Seehausen 1990-1994 Energy intensity (MJ GE-1) of winter wheat in Leipzig-Seehausen and Groß Kreutz

38 39

32 33

-1

Site-related energy intensity (MJ GE-1) of winter wheat Influence of different energy equivalents on the energy intensity (MJ GE-1) of winter wheat

List of Contents

Abbreviations A AI aPAR b BP +BP -BP CH4 CO2 CR Ct dm do DM e EI f FM gb ge G GE I k K2O LAI m Ma n N NOx Nt O p P2O5 PAR Pot PPA sz SB SpB WB WW

appendix active ingredient absorbed photosynthetically active radiation fuel oil (in the energy flux scheme) byproduct with byproduct without byproduct methane carbon dioxide crop rotation total carbon mineral fertilizer (in the energy flux scheme) organic fertilizer (in the energy flux scheme) dry matter electricity (in the energy flux scheme) energy intensity byproduct (in the energy flux scheme) fresh matter energy for providing seed/plant material (in the energy flux scheme) calorific value of seed/plant material (in the energy flux scheme) energy gain grain equivalent energy input (in the energy flux scheme) diesel (in the energy flux scheme) potassium oxide leaf area index machines (in the energy flux scheme) maize equipment (in the energy flux scheme) nitrogen nitrogen oxide total nitrogen energy output (in the energy flux scheme) main product (in the energy flux scheme) phosphorus oxide photosynthetically active radiation potatoes plant protection agents plant protection agents (in the energy flux scheme) sugar beet spring barley winter barley winter wheat

Introduction and Problem Definition

The project "Energy Recovery by Crops ..." is targeted on the quantification of energy recovery in the plant yield of selected crops depending on the input of mineral fertilizer. An appropriate means for estimating the energy recovery of crop plants in dependence on mineral fertilizer application are energy balance sheets. They have been commonly recognized as tool for estimating intensity and environmental acceptability of crop production (ECKERT & BREITSCHUH 1994, SRU 1994, HĂ&#x153;LSBERGEN & KALK 1997). One handicap is that no standardized method (especially for system boundaries and energy equivalents) is available for energy balancing in agricultural enterprises. Thus, the energy balance sheets given by various authors are not or only partially comparable. It is also necessary to note that the energy budget is closely related to site conditions, farm structure (crop ratio, livestock numbers), technological design of a farm and its yield level. Due to this, the energetic calculations are based on the results obtained from field experiments as well as from farms. Thus, the influence of crop rotation and site conditions etc. on energy efficiency can be discussed. Subject of this Final Report is the derivation and substantiation of the applied methodical approaches in energy balancing as well as the presentation of results obtained for selected crop species and sites. The methodical approaches include the definition of system boundaries and involved energy fluxes as well as the derivation and substantiation of the used energy coefficients for assessment. This includes also a sensitivity analysis for the energetical evaluation of mineral fertilizer and plant protection agents. According to these results site and crop-related statements are made referring to the amount of energy input and output as well as the energy efficiency after differentiated nitrogen supply. To describe the energy efficiency, energy gain and energy intensity were calculated. The fertilizer rates leading to maximum energy yields and optimal rates of energy efficiency are determined, too.

Methodical Approaches to Energy Balancing in Crop Farming

The agricultural energy balance sheet is the quantitative juxtaposition of energy output and energy input. According to FLUCK & BAIRD (1980), in energy balancing two methodical approaches can be followed: (1) the eco-energetic method and (2) the economic method. The principal differences underlying these two methodical approaches are summarized in Table 1. Table 1: Comparison between the eco-energetic and the economic method in energy balancing (according to FLUCK & BAIRD 1980) Eco-energetic approach Economic approach Definition Modelling of systems by evaluation of energy Determination of the energy consumption for fluxes production and handling of agricultural products Scope of the system Interdependences and links between anthro- Use and depletion of energy resources pogenic and nature-supported systems Evaluated energy resources Renewable and non-renewable energy resources

Non-renewable (fossil) energy resources

Rating of energy quality Use of solar energy equivalents

Total amount of usable energy and energy losses in the production of all inputs Rating of human labour

Human labour as high-quality energy factor

Human labour as minimum energy neglectable in industrial systems

factor

Which methodical approach should be chosen for energy balancing in crop farming depends on the balance target. According to KOROSCHITZ (1985) the question arises how ecological energy inputs can be measured, evaluated and related to anthropogenic energy inputs. If the eco-energetic approach was applied to an economically oriented issue, solar energy would be the dominating energy input, provided it has an economic value like fossil energy. In this case, cost-intensive energy carriers (mineral fertilizer e.g.) would have only marginal importance. The main objective of the project "Energy Recovery by Crops ..." is the quantification of energy recovery in the harvested biomass of selected crops depending on the input of mineral fertilizer. Therefore, the report follows exclusively the economic approach.

2.1

Definition of System Boundaries and Involved Energy Fluxes

The definition of balancing target and method is followed by the definition of system boundaries. According to REINHARDT (1993) system boundaries can be formulated under material, temporal and spatial aspects. The material boundaries stipulate which criteria are to be used in balancing (energy, CO2, CH4, NOx, operating expendables p.ex.). The temporal boundaries should consider both the reference period of the sampled data as well as the balanced period and possible time-related effects (for example crop rotation effects) of the various balancing parameters. In crop production, the temporal boundaries may comprise one

growth period or one crop rotation. The spatial boundaries allow to regard a restricted area (field, farm, region). It is important to define them in order to coordinate the single parameters in the different balance sheets for the purpose of comparison.

Energy balancing in agriculture requires consideration of the energy consumption, on-farm energy fluxes and energy output (KALK et al. 1996). According to HEYLAND & SOLANSKY (1979) energy inputs can be differentiated for direct (e.g. crude oil, diesel) and indirect (e.g. machinery, fertilizer and plant protection agents) types. The below given energy flux scheme according to KALK et al. (1995) elucidates the system boundaries selected for the included field cropping experiments and the resulting energy fluxes (Fig. 1). The equations for calculating the energy balance sheets in Fig. 1 are summarized in Table 2.

Fig.1: Energy flux scheme (according to KALK et al. 1995) Table 2: Parameters of the energy balance sheet Parameter Equation

No.

Energy input (I)

I = k + b + e + gb + dm + do + sz + m + n

Energy output (O)

O = p + f - ge

Energy gain (G)

G=O窶的

Energy intensity (EI)

EI = I / GE

GE: Grain Equivalent, see Table 9; for symbols and their meaning see Fig. 1.

2.2

Survey of Energy Equivalents in Crop Farming

Direct energy input in farming takes place mainly in form of diesel and fuel oil, gas and electricity. The energy equivalents connected with the use of diesel were determined on the basis of the indirect energy inputs (extraction, processing, transport) as well as the direct consumption of fuel oil. According to the approach of W ERSCHNITZKY et al. (1987), energy carriers are evaluated only for the calorific value they have for the generation of efficient energy. Energy losses occurring during the conversion of primary energy into the final energy form remain unconsidered. In contrast to this, REINHARDT (1993) includes and converts into energy equivalents all energy carriers involved in the production and handling process. Operation expendables resources in crop farming as indirect energy input include seed/plant material, fertilizers, plant protection agents as well as capital goods.

For the energetic evaluation of seed material, various methods have been reported. If the seed and plant material is identical with the harvested material, its cultivation corresponds to that of the related crop plant. If not, the production process has to be defined in detail (KALTSCHMITT & REINHARDT 1997). HEICHEL (1980) suggests to deduct the share of seed and plant material from the harvested yield, in this case it does no longer appear in the final energy balance statement. As shown in Fig. 1, the present study regards the energy for providing as energy input, and the calorific value is deducted from the energy output. For the energetic assessment of plant protection agents (PPA) the following approaches could be made. According to GAILLARD et al. (1997), each plant protection agent should be evaluated separately. PIMENTEL (1980) calculated mean energy consumption values for various pesticide groups: 238.68 MJ kg-1 AI (active ingredient) for herbicides, 184.43 MJ kg-1 AI for insecticides and 92.16 MJ kg-1 AI for fungicides. KALTSCHMITT & REINHARDT (1997) and REINHARDT (1993), however, assume one common average value. This simplification seems to be justified indeed in view of the low energy input for plant protection agents in the whole energy balance sheet. Yet, it should be considered that the provision of plant protection agents involves high expenditures for research activities and energy. So far, however, development expenses have not been considered in energetic assessments of plant protection agents (HAAS & KÖPKE 1994). Data about the energy consumption of mineral fertilizers differ widely. This refers notably to nitrogen and less to phosphorus and potassium fertilizers. Literature reports, however, do not always clearly impart which upstream processes and production technologies are concerned. The indirect energy input via capital goods seems to remain principally unconsidered in the production of mineral fertilizers. Detailed information about ammonia synthesis were given, among others, by APPEL (1997), PATYK & REINHARDT (1997) and KONGSHAUG (1998). According to APPEL (1997) and KONGSHAUG (1998) there has been a significant decline of the energy comsumption for ammonia synthesis during the last 30 years. The values given by APPEL (1997) range from 48.2 MJ kg-1 N in 1966 to 34.10 MJ kg-1 N in 1991, those by KONGSHAUG (1998) from approx. 47 MJ kg-1 N to 34.5 MJ kg-1 N. There are not only temporal changes in the energy consumption of ammonia plants p.ex. but also regional changes. When in 1995 ammonia synthesis in modern European plants consumed approx. 36.93 MJ kg-1 N, older plants needed about 43.08 MJ kg-1 N (VAN BALKEN 1998) at the same time. In contrast to the energy input for nitrogen fertilizer, the data for phosphorus varied between 5.1 MJ kg-1 P2O5 (EFMA 1997) to 26.4 MJ kg-1 P2O5 (PIMENTEL et al. 1990) and for potassium from 4.0 MJ kg-1 K2O (MUDAHAR & HIGNETT 1982) to 13.7 MJ kg-1 K2O (PATYK & REINHARTD 1997). On principle, it should be taken into account that from the energetic point of view the nitrogen supply to plant stands is more relevant than the phosphorus and potassium input. Own studies have shown that the portion of mineral nitrogen fertilizer may come up to 50 % of the whole input of fossil energy. In contrast to this, phosphorus and potassium fertilizer amount to about 5 to 10 % only (RATHKE & DIEPENBROCK 1998). Other than for mineral fertilizers, few information is found in literature about the energetic evaluation of organic fertilizers (HEYLAND & SOLANSKY 1979, HÜLSBERGEN & KALK 1997). If the organic fertilizer input was not included in the energy balance sheet, its effect on energy recovery in the yield could not be traced back to the actual energy expenditure, and this would mean that additional energy recovery is possible without additional input of fossil energy. In most cases nutrients contained in organic fertilizers are energetically evaluated via mineral fertilizer equivalents (corresponding to their fertilization effect compared with mineral fertilizer). Figures about mineral fertilizer equivalents are given, among others, by GÖRLITZ et al. (1985),

VETTER & STEFFENS (1986) and GALLER (1989). In this connection it should be considered that there is no common production procedure of organic fertilizer and thus no standard yardstick for their nutrient concentration as, for example, in the production of mineral fertilizers (RATHKE & DIEPENBROCK 1998). In simplified balance sheets the not exactly quantifiable energy consumption for capital goods (machinery and equipment as well as buildings and plants) left unconsidered for practical reasons (ECKERT & BREITSCHUH 1994). This procedure may lead to misinterpretations in energy balancing as studies by KALK & HÜLSBERGEN (1996) have demonstrated. If the indirect energy input via capital goods was neglected, the entire actual energy input would be underestimated. This might become a problem if different management practices are compared (mineral vs. organic fertilization, tillage vs. no-tillage e.g.). In literature (HEYLAND & SOLANSKY 1979, DOERING 1980, VON OHEIMB 1987, KOHLER 1994, SCHOLZ & KAULFUSS 1995, KALK & HÜLSBERGEN 1996) different attempts of problem-solving are found. In the project "Energy Recovery by Crops ..." the detailed method by KALK & HÜLSBERGEN (1996) was used. The economic method of energy balancing by FLUCK & BAIRD (1980) (see Table 1) doesn´t usually take into account human labour. Compared with fossil energy, it has only minor importance in modern agriculture. In 1978, for example, the energy share of human labour in the total consumption of energy in crop production was only 4 % in Germany (HEYLAND & SOLANSKY 1979). On the other hand, no generally acceptable energy equivalent for human labour has been defined so far (KALK et al. 1996, KALK & HÜLSBERGEN 1997). FLUCK (1992) proposed nine assessment methods for human labour. Five of them refer to the directly measurable energy actually consumed during work, whereas the other four approaches base on indirect rating. For detailed information see DIEPENBROCK et al. (1995). When rating crop plants from the energetic aspect, the total energy input can be devided into the two components solar energy or photosynthetically active radiation (PAR) and fossil energy. Following the economically oriented approach by FLUCK & BAIRD (1980), solar energy is given no consideration in energy balancing (see Chapter 1). Thus, the inputs include fossil energy only. This is to be explained more profoundly. The photosynthetically active radiation contributes decisively to yield formation via the processes of energy recovery and energy conversion in the plants. In this connection, plant productivity is controlled by the utilization of solar energy or PAR. The PAR received by the plants is differently utilized owing to stand architecture and enzyme availability, whereby the latter is closely related to the nitrogen content in the leaves. The degree of PAR conversion on its part is closely related to the size of the photosynthetically active area (LAI) and the duration of LAI (LAD). Both criteria respond positively to nitrogen treatment up to a species and variety specific maximum value (see GREEF et al. 1993, HANSEN 1994, RATHKE et al. 1996, 1997). In the following, the transformation of solar energy to biomass energy is shortly outlined.

Solar Radiation 3 006 MJ m-2 45 % × Photosynthetically Active Radiation (PAR) 1 353 MJ m-2 75 - 85 % × Absorbed PAR (aPAR) 1 015 - 1 150 MJ m-2

1-3%

Ă&#x2014;

Chemical Energy in Biomass 10.15 - 34.50 MJ m-2

The values demonstrate that the efficiency of use of the available solar energy by the plants in the course of photosynthesis is rather poor. An essential reason for this inefficiency of solar energy lies not in the low transformation level, but in its absolute amount. This becomes clear when solar and fossil energy inputs are directly compared. In winter rape growing in the station Leipzig-Seehausen, for example, the ratio between fossil and solar energy input (or PAR) stretches from 0.03 % (0.06 %) to 0.08 % (0.2 %). This result agrees with calculations by DIEPENBROCK et al. (1995), who reported for winter rape a value of 0.13 % (related to PAR). It becomes obvious that, compared to the input of solar energy, fossil energy is neglectable. Therefore, if solar energy is also considered in energy balancing, production-related differences in the input of fossil energy, as they occur mainly with the supply of mineral fertilizer and tillage operations, cannot be discovered. The project, however, is targeted on the quantification of energy recovery in the harvested yield of selected crops, depending on the input of mineral fertilizer. In general, any products leaving the system can be regarded as energy outputs. Depending on the investigated problem, a subdivision can be made between harvested and derived products. The energy output indicated in the balance statement results from the yield per area and the energy yield of the harvested product. So, when determining the energy removal, the harvested yield is converted into energy yields by the use of energy equivalents basing on calorific values. For the determination of energy intensity (input of fossil energy per product unit) KALK et.al. (1995) propose to convert the harvested yield into grain equivalents in order to allow the pooling of different products, as purposeful in case of crop rotations and in case of the comparison of various farms.

Material and Methods

As mentioned in the introduction, the energy input and thus also energy balancing is decisively influenced by site conditions, farm structure and technological design of a farm. Therefore, this chapter comments both the assumptions of the two field experiments and those made for the actual farms.

3.1 3.1.1

Description of the Field Experiments Site Characteristics

Both field experiments, F1-70 in Leipzig-Seehausen and M 4 in Groß Kreutz (Potsdam), were established at the same moment with the same objectives. The site characteristics are summarized in Table 3.

Table 3: Site characteristics of the experimental stations Groß Kreutz and Leipzig-Seehausen Parameter Groß Kreutz Leipzig-Seehausen

0 Annual precipitation

537.0 mm

551.0 mm

0 Annual temperature

8.9 °C

9.3 °C

Above sea level

42 m

132 m

> 20 m

20 m

Loamy sand

Sandy loam

Albic Luvisol / Luvic Arenosol

Stagno-Luvic Gleysol

3.0 % 20.9 % 76.1 % 1.56 g cm-3 16.0 (mass-%) 0.70 % 0.07 %

8.1 % 45.0 % 46.9 % 1.5 to 1.6 g cm-3 26.7 (mass-%) 1.02 % 0.093 %

Ground water table Soil type FAO-Classification Soil texture Clay Silt Sand Dry bulk density Water holding capacity Ct Nt

Annual precipitation and distribution are often yield-limiting factors in both locations. The level of annual rainfall was nearly the same on the two locations. Yet, there were deviations in single years in distribution and amount of precipitation. In single years the annual rainfall may be essentially lower than the long-term average. This holds true for Leipzig-Seehausen in 1976, for example. Such dry years may cause considerable yield losses, thus influencing the test results (chemical components, energy content, energy gain p.ex.). In the following graph (Fig. 2), rainfall distribution and amount are demonstrated for the experimental location LeipzigSeehausen.

Rainfall (mm)

1967-1997: 551 mm 1967-1978: 551 mm 1979-1997: 551 mm

0 Jan.

Feb.

Mar.

Apr.

May June

1967-1997

July

1967-1978

Aug.

Sep.

1979-1997

Oct.

Nov.

Dec.

1976

Fig. 2: Distribution of rainfall in the experimental station Leipzig-Seehausen

3.1.2

Experimental Schedule

Both long term trials were established in 1967 as two-factorial experiments with four replications. The factors have been stable manure and mineral nitrogen as well as their combinations. This includes 16 variants in Leipzig-Seehausen and 25 variants in Groß Kreutz. Averaging the years, 0, 50, 100 and 150 kg N ha-1 a-1 were supplied in form of stable manure and mineral fertilizer. In Groß Kreutz another 200 kg N ha-1 a-1 were applied. Stable manure was only applied to root crops. Phosphorus and potassium were given in constant rates to all variants. The trial F1-70 in Leipzig-Seehausen was demonstrated using the data sampled between 1967 and 1996. This trial was modified several times. A survey about the alterations is given in Fig. 3. In 1979 the crop sequence in Leipzig-Seehausen was supplemented by a cereal field:

Χ Crop rotation from 1967 to 1978: potatoes - winter wheat - sugar beet - spring barley. Χ Crop rotation since 1979: potatoes - winter wheat - winter barley - sugar beet - spring barley. Only once, in 1984, potatoes were replaced by silage maize. Beside modifications of the crop rotation pattern, other changes took place as well. They refer mainly to variety changes and the increasing application of plant protection means. The test-specific intensity of chemical plant protection was gradually adapted to the intensity used in practice. Growth regulators were applied on winter wheat for the first time in 1976, fungicides in 1985.

CR 1

CR 2

CR 3

CR 4

CR 5

CR 6

CR 7

1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

other cultivars Pot WW SB SpB Pot WW SB SpB Pot WW SB SpB Pot WW WB SB SpB Ma WW WB SB SpB Pot WW WB SB SpB Pot WW WB

Modified crop rotation pattern

Inclusion of an additional crop

Application of growth regulators

Fungicide application

Number of used plant protection agents: 2

CR = crop rotation Pot = potatoes WW = winter wheat SB = sugar beet

SpB = spring barley Ma = maize WB = winter barley

Fig. 3: Modification of the field experiment F1-70 in Leipzig-Seehausen The data from the experiment M4 in GroĂ&#x; Kreutz refer to the period 1989 - 1992. In contrast to Leipzig-Seehausen in this field experiment the test variants were not altered. The experiment had the following crop rotation pattern:

Î§ potatoes - winter wheat - sugar beet - spring barley.

3.2

Description of the Farms

In order to come to conclusions about the practical relevance of the results obtained in the field trials, data from eight real farms in Saxony and Saxony-Anhalt were collected and analysed. The farms operated under differing site conditions and cropping structures (Table 4). The analyses comprised the years 1995 and 1996 and concerned the production technologies applied in field experiments. The mean farm area was 1 500 ha and varied between 300 and 3 300 hectare. On the average approx. 160 kg N ha-1 were supplied to winter wheat and 95 kg N ha-1 to sugar beet. No farm was keeping livestock.

Table 4: Characteristics of the farms Farm

Field index Farm area Cropping area

ha ha

VII

VIII

1 228 1 228

1 610 1 610

1 480 1 480

309 309

2 290 2 290

1 472 379 3 294 1 197 379 3 294 Cropping structure

Cereals Rape Root crops Legumes

% CA % CA % CA % CA

55.5 14.2 15.7 3.30

59.0 59.8 50.3 4.90 5.5 17.4 4.1 9.5 3.8 0.7 Mineral fertilization

58.2 48.2 11.4 2.4

76.3 12.8 7.2 -

55.2 12.9 6.7 4.0

50.9 11.9 4.6 -

P per ha FA K per ha FA N per ha - Winter wheat - Winter barley - Winter rape - Sugar beet

kg ha-1 kg ha-1 kg ha-1 kg ha-1 kg ha-1 kg ha-1 kg ha-1

8.40 22.2

16.6

71.9 136.6

4.00 11.3

25.7 60.0

13.8 -

32.0 21.5

12.3 23.2

200 190 172 75

149 149 176 130

240 160

170 155 160 140

140 135 170 40

120 130 135 125

135 125 137 60

130 125 130 30

CA: cropping area; FA: farm area; N: total N (NO3 + NH4)

3.3 3.3.1

Methodics of Energy Balancing Energy Input

For the energy balancing of field trials and actual farms uniform methodics were adopted (see also Chapter 2). Table 5 shows the input and output factors considered in the energy balance sheets.

Table 5: Energy balancing factors in crop farming Input values Output values Input of expendables - Yields of fresh and dry matter mineral fertilizer - with byproduct (nitrogen, phosphorus, potassium, lime) - without byproduct organic fertilizer (stable manure) plant protection agents (PPA) seed/plant material -

Direct energy input and indirect energy input via capital goods primary tillage seedbed preparation and sowing cultivation fertilization spraying harvest transport

The energy input is mainly influenced by the different energy equivalents, especially for mineral nitrogen fertilizer. The energy equivalents used for mineral fertilizers consider

manufacturing and transport (Table 6). The energy equivalents for nitrogen rely on the calculations by APPEL (1997) and were adapted to the present development, that is to the technical progress and the improved energy efficiency in fertilizer production. For the mineral fertilizers phosphorus, potassium and lime constant energy equivalents were used because from literature recherches no significant changes in the energy input could be derived for their production and transport in the reference period.

Table 6: Energy equivalents for mineral fertilizer (according to APPEL 1997, amended) Nutrient Reference Period (year) 67-70

71-74

75-78

79-83

84-89

89-93

94-98

Nitrogen

MJ kg-1 N

49.4

47.0

42.5

38.0

35.3

Phosphorus

MJ kg-1 P2O5

15.8

Potassium

MJ kg-1 K2O

9.30

Lime

MJ kg-1 CaO

2.97

Organic fertilizers1 are energetically evaluated via their nutrient contents. For phosphorus and potassium, an equivalent of 100 % has been assumed, for nitrogen 60 % (resulting from field trial). Since manure has been supplied only to root crops and since the post-crops also profit from the manure effect, nutrient quantities and energy input for transport and manure application are apportioned to all crop species. The crop-related percentage results from the per cent yield increase of the pure manure treatments compared with the no-fertilizer control plot. The energetic evaluation of plant protection was made separately for the three categories herbicide, fungicide and insecticide. The following equivalents were used: herbicide: 288 MJ kg-1 active ingredient, insecticide: 237 MJ kg-1 active ingredient, fungicide: 196 MJ kg-1 active ingredient. In case of seed material only the fossil energy for provision (transport, storage, processing) was considered. For cereals and potatoes seeds/plants it was assumed that production requires the same energy input as the cultivation of related crop itself, and therefore deducting the quantity of seed from the harvested yield appeared to be justified (compare Fig. 1). For the evaluation of direct and indirect energy input via capital goods all operations related to 11

The authors hold the opinion that the energetic evaluation of the applied manure is necessary on the level of the system â&#x20AC;&#x2DC;field trialâ&#x20AC;&#x2122;. Without consideration of organic fertilizers in energy balancing, their effect on energy recovery in the yield cannot be allocated to the corresponding energy input. This would mean - additional energy recovery without additional input of fossil energy. In fact, fossil energy is needed for the production of organic fertilizer (e.g. for storage and processing). However, this energy input is hardly quantifiable. For practical reasons mineral fertilizer equivalents were adopted for evaluating the nutrient contents.

the production were included. The operations referred to practice-relevant machines and equipment, and therefore, also the development of the technical equipment had been taken into account. The energetic evaluation of the direct energy input was made via the calculated consumption of diesel oil, the indirect input was calculated via the recorded consumption of material. Tables 7 and 8 contain calculated examples. Principally, 20 ha fields with 2 km transport distance had been assumed, which guaranteed good transferrability of the results to practical farming in the reference area.

Table 7: Direct energy input (MJ ha-1) with capital goods (according to KALK 1997) Example: stubble ploughing to winter wheat Interpolation formula: Energy input = DK-consumption * energy equivalent for diesel DK-consumption = 10.2 + 0.6 * depth of ploughing Assuming 20 cm depth of ploughing and an energy equivalent of 39.6 MJ l-1 for diesel, the direct energy input is 879 MJ ha-1

Table 8: Indirect energy input (MJ ha-1) with capital goods Example: stubble ploughing to winter wheat Machine

Disk harrow

Working width (m)

Mass

Performance (kW) Tractor 140

(kg)

Total performance (ha)

Material consumption (kg ha-1)

4 070

4 200

0.97

7 140

(h) 10 000

(kg h-1) 0.715

Tractor hours (h ha-1)

0.3

Energy equivalent (MJ kg-1)

Energy input (MJ ha-1)

108

105

108

Total 128 MJ ha-1

Fig. 4 demonstrated a production technology for winter wheat in the experimental station Leipzig-Seehausen in 1995. The single operations were characterized by the energetic inputs with diesel, capital goods and operation expendables. The energy input per year in the 16 test variants was annually corrected with a view to treatment modifications and differences in yield performance. For the evaluation of the energy input in farms only the input of expendables was adapted. The direct and indirect energy input was the same as in the field experiments.

Sep

Oct

24.10. / 25. 10.

Nov 26.10.

Dec

18.11.

Seedbed Sowing Emergence preparation

Jan

Feb

Mar

07.03. 1st N-Appl

Apr 06.04. 1st PA

May

Jun

03.05. 09.05. 15.05. 2nd PA, 2nd N, 3rd PA

Jul

Aug 04.08.

Harvest Transport

Total (direct energy)

l/ha 25.2 7.0 3.4 GJ/ha 1.00 0.28 0.13

1.5 0.06

1.7 1.7 1.5 1.7 0.07 0.07 0.06 0.07

22.6 0.90

17.1 0.68

83.40 3.30

Machines

GJ/ha 0.18 0.07 0.05

0.03

0.03 0.03 0.03 0.03

0.53

0.19

1.18

Seed 230 1.27

N 80 3.80

Herb Fung N Fung 4 2 40 1,5 1.15 0.40 1.90 0.29

Diesel

(indirect energy)

other expenditures kg/ha

(indirect energy)

GJ/ha

10.98

Total fossil energy input: 15.46 GJ/ha

Fig. 4: Energetic evaluation of the production technology to winter wheat

3.3.2

Energy Output

Calculating the energy gain requires to determine the energy contents of the harvested crop. According to SCHIEMANN (1981) the gross energy contents (calorific values) of Table 9 were calculated using the equation Gross energy (kJ) =

23.9 (kJ g-1) * crude protein (g) + 39.8 (kJ g-1) * crude fat (g) + 20.1 (kJ g-1) * crude fibre (g) + 17.5 (kJ g-1) * N-free extracts (g).

The conversion of the harvested products into grain equivalents (Table 10) helps to determine the coefficient energy intensity.

Table 9: Gross energy contents (GJ t-1 DM) and grain equivalent (GE) conversion code for the evaluation of the harvested products

Crop Potatoes

Gross energy content (GJ t-1 DM) 17.2

GE conversion code (GE t-1 FM) 2.5

16.8 16.4 18.6 17.7 18.3 18.1 18.4 18.1

2.5 1.1 10.0 1.0 10.0 1.0 10.0 1.1

Sugar beet, roots Sugar beet, leaves Winter wheat, grain Winter wheat, straw Winter barley, grain Winter barley, straw Spring barley, grain Spring barley, straw

3.4

Evaluation by Use of Mathematical Statistics

The relationship between the test factors of the field trials (x1 = manure N in kg ha-1 and x2 = mineral-N in kg ha-1) and the target values (y = yield, energy gain, energy intensity) were estimated using multiple regression functions and gradual reduction of the polynom equation y = a + b1x1 + b2x2 + b11x12 + b22x22 + b12x1x2. The non-significant (â&#x2C6;&#x20AC; = 5 %) regression members were eliminated.

4 4.1 4.1.1

Results and Discussion Energy Input Energy Input in Field Experiments

The development of the crop-specific input of fossil energy is demonstrated in Fig. 5 on the example of the field trial F1-70 in Leipzig-Seehausen. For this purpose, all crops were reflected by the variant of exclusively mineral N fertilization on the level of 100 kg N ha-1 (Variant 0/2).

GJ ha -1 Potatoes

Winter wheat

Winter barley

Sugar beet

Spring barley

0 Crop rotation Min-N

Min-P

Min-K

Pesticide

Seeds

Direct energy

Capital goods

Fig. 5: Energy input (GJ ha-1) in Leipzig-Seehausen On the one hand, there are evident differences in the level of energy input to each crop species. On the other hand, differences between the various crop rotations were encountered. Particularly high was the input to the root crops potatoes and sugar beet, in contrast to a comparatively low energy input to cereal crops. This might be explained by higher fertilizer rates and an increased expenditure for cultivation, harvest and transport of root crops. When we regard the single rotations, the comparatively high energy input during the first crop rotation becomes evident.This can be explained by the relatively high amounts of mineral fertilizer visĂ -vis the other tested crop rotations (see appendix 1). If this first crop rotation is neglected, no trend can be recognized in the crop specific energy input over the reference period. Over time (crop rotation II - VII) there was a decline in the energy input via mineral nitrogen fertilizer. This decline results from the lower energy equivalent for nitrogen due to the assumed higher energy efficiency for production (see Table 6). At the same time an increase was recorded in other input factors, particularly in plant protection agents. Supplementing the above said, the relative share (%) of each input factor is shown in Table 10 on the example of winter wheat and winter barley, again for the variant with 100 kg mineral-N ha-1. Table 10: Relative share (%) of input factors Crop

Year

Mineral fertilizer

PPA

Seeds

Direct energy

Capital goods

Nitrogen

Phosphorus

Potassium

1968

35.6

11.7

11.5

5.1

6.9

19.2

10.0

1972

27.7

12.3

13.1

5.7

10.4

21.8

9.0

1976

27.2

13.4

14.3

7.7

21.2

8.5

1980

24.8

13.6

14.5

4.7

8.8

24.5

9.0

1985

23.5

12.9

13.8

8.9

9.1

22.8

9.0

1990

21.6

12.8

13.7

8.0

8.4

25.9

9.5

1995

21.8

12.9

13.8

6.6

9.8

26.1

9.1

1981

26.4

14.5

15.5

1.2

6.0

26.2

10.2

1986

28.2

12.4

13.3

6.1

5.6

25.2

9.2

1991

27.1

12.9

13.7

3.6

5.7

27.5

9.6

1996

27.6

13.1

14.0

6.8

4.9

24.1

9.5

WW: winter wheat; WB: winter barley; PPA: plant protection agents

Both in winter wheat and winter barley the mineral fertilizer supply was the most important energy input item. It amounted to about 52.4 % for winter wheat and 54.7 % for winter barley, with a variation between 48.1 % to 58.8 % and 53.7 % to 56.4 % resp. Apart from mineral fertilizers also the direct energy input proved to be very high, this holds true for winter wheat rather than winter barley. In case of winter wheat this has to be attributed mainly to the increased yield level. This entailed also higher expenditure for harvesting and transport. In contrast to mineral fertilizers and direct energy input the relative share for plant protection, seeds and capital goods was comparatively small.

The energy balance sheets are largely related to the used input factors and energy equivalents. Fig. 5 and Table 10 make it obvious that the whole energy input is decisively related to mineral fertilization. As mentioned in Chapter 2, the energy input for mineral fertilizer varies within large brackets. Therefore, the effect of different energy equivalents for mineral fertilizers was analysed on the example of winter wheat. For better transparency, sensitivity analyses for plant protection agents are also given. The results are shown in Table 11. The last column displays the per cent change of the total energy input that follows from using the lowest and the highest energy equivalent.

Table 11: Influence of different energy equivalents on the total energy input to winter wheat (Leipzig-Seehausen; 100 kg mineral-N per ha)

Energy equivalent (MJ kg-1) Input parameter

Mineral-N

Minimum

Maximum

Difference

of the total input %

35.3

80.0

44.7

30.7

Used

35.3

Change

Variation

Mineral-P

15.8

5.10

26.4

21.3

15.4

Mineral-K

9.30

4.00

13.7

9.70

12.7

PPA

242.0

114.1

365.0

250.9

5.5

Sensitivity analyses revealed that a large influence on the total energy input is exerted by the energy equivalent of mineral fertilizer, especially in case of nitrogen. Using an energy equivalent of 80 MJ kg-1 N instead of 35.3 MJ kg-1 N would lead to an approx. 30 % increase of the total energy input. Opposite to this, a per cent change of the total input of plant protection agents (5.5 %) is of minor importance.

4.1.2

Energy Input in Farms

The values for the energy input in the farms are given in Table 12. There is, as well as in the field experiments, a large difference between the single farms. This becomes particularly clear for the energy input to winter wheat and sugar beet. A decisive influence factor is the mineral N supply. Its relative share in the total energy input varies, for example, between approx. 38 % and 52 % in winter wheat growing and between about 10 % and 34 % in sugar beet growing. Fig. 6 indicates the energy input to winter wheat and sugar beet with mineral N fertilizer. The high energy input in farm III results from high P and K fertilization (compare Table 4). Table 12: Crop-related energy input (GJ ha-1) in farms (1995-96) Farm Crop Winter wheat Winter barley Winter rape Sugar beet Peas

III

VII

VIII

13.8 12.8 10.8 12.8 6.00

11.6 10.9 10.5 14.1 5.40

18.0 19.1 -

12.6 11.4 10.1 14.4 5.60

13.7 11.9 11.7 12.7 -

11.0 10.7 9.40 14.3 -

12.5 11.4 10.5 12.9 7.50

11.5 10.7 9.60 11.1 -

Fig. 6: Energy input (GJ ha-1) for mineral-N fertilizer to winter wheat and sugar beet in farms

Energy input (GJ/ha) Winter wheat Sugar beet

8 7 6 5 4 3 2 1 0

4.2 4.2.1

III

V Farm

VII

VIII

Yields Yields in Field Experiments

The yield development of the cultivated crops in the test period is demonstrated on the example of winter barley (Table 13) in the experimental station Leipzig-Seehausen. For winter barley production functions and theoretical values were calculated for all cropping years. The climatic influence is equally obvious as is the general yield increase owing to improved production technologies.

Table 13: Winter barley yields (dt ha-1)*) in Leipzig-Seehausen, calculated values zero only only mineral Combined organic and Year fertilization manure N-fertilizer mineral fertilization Yield Yield Yield Yield mineral-N mineral-N dt ha-1 (%) dt ha-1 (%) dt ha-1 (%) (= 100 %) (kg ha-1 a-1) (kg ha-1 a-1) 25.7 (36.6) 40.8 (58.1) 68.3 (97.2) 1981 157.5 70.3 131.0

1986

30.4 (39.1)

55.9 (71.9)

76.2 (98.0)

128.0

77.8

88.3

1991

14.8 (49.4)

62.6 (61.2)

100.0 (97.7)

148.6

102.4

101.5

1996

29.0 (56.1)

51.5 (64.3)

76.2 (95.3)

140.8

80.0

118.4

Grain yields at 86% DM, (x): relative values, maximum yields = 100 %

The high mineral-N requirement to winter barley may be partially explained by the unfavourable position of winter barley after a grain pre-crop. The impact of differing site conditions on yield was shown in Fig. 7 and 8 on the example of GE-yield related to N supply in the stations Leipzig-Seehausen and GroĂ&#x; Kreutz. There are

distinct differences between the two locations, both in the maximum yields and the required N quantity.

GE ha

60 64 68 72 76 80 84 88 92 96 100 104 108 112 116 120

-1

N eur an M g (k -1

)

N rale n Mi

ha (kg

-1 )

Fig. 7:

yield (GE ha-1) in dependence on nitrogen fertilization in the experimental station Leipzig-Seehausen (1992-96)

GE ha

36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81

-1

N eur an M g (k ha

ha (kg

-1 )

-1

N rale n Mi -1 yield (GE ha ) in dependence on nitrogen fertilization in the experimental station GroĂ&#x; Kreutz (1989-92)

)

Fig. 8:

4.2.2

Yields in Farms

Similar to the yield differences in the field trials, large yield deviations were recorded in the real farms. Hereby, the yields ranked in-between the yields of the field trials. The yields of the sampled farms are listed in Table 14. Table 14: Yields (dt ha-1) in the farms (1995-96) Farm Crop

III

VII

VIII

Winter wheat Winter barley Winter rape Sugar beet Pea

63.6 57.5 30.6 468.5 60.7

49.0 43.9 16.0 438.5 30.0

48.3 410.0 -

70.7 54.0 16.8 368.7 42.9

62.5 60.9 27.3 598.0 -

75.8 54.6 23.3 457.5 -

63.8 52.3 29.6 440.0 47.0

53.0 49.3 30.6 394.2 -

4.3

Energy Output

The energy output results from the natural yield (see 4.2) and its energy content (see Table 9).

4.3.1

Energy Output in Field Experiments

The energy output can be related either to the main harvest product only, or additionally to the byproduct. In Fig. 9 and Table 15 main and byproduct harvested in the field trials were distinguished for comparison.

GJ ha

-1

550

Potatoes

Winter wheat

Winter barley

Sugar beet

Spring barley

500 MP

450 400 350 300 250 200 150 100 50 0 Crop rotation

Fig. 9: Development of the energy output (GJ ha-1) in the field experiment F1-70 in LeipzigSeehausen (MP: main product; BP: byproduct)

Table 15: Energy output (GJ ha-1) in field experiments Leipzig-Seehausen (1989-1993) Variant

Potatoes

Min. N kg ha-1

-BP

Winter wheat

Winter barley

- BP

+ BP

Sugar beet - BP

+ BP

Spring barley - BP

+ BP

58.7

107.0

177.9

27.8

54.1

203.2

269.6

49.7

73.5

85.4

148.5

255.6

94.2

155.9

237.9

327.3

63.3

95.0

100

95.4

169.0

286.7

140.9

218.3

247.1

347.5

74.0

111.6

150

85.0

149.1

284.3

157.6

265.6

223.1

335.8

76.8

118.1

Groß Kreutz (1989-1992)* Variant

Sugar beet

Spring barley

Potatoes

Winter wheat

96.5

24.8

50.9

11.3

183.0

48.8

83.3

48.2

100

207.5

63.7

94.3

72.5

150

222.9

86.0

99.2

71.7

-: without; +: with; BP: byproduct; *: only main product

The energy output varies widely not only among the different sites but also among the tested crop species and the various N fertilization regimes. In Groß Kreutz, the energy output on the non-treated plot was much lower than in Leipzig-Seehausen. Yet, increasing the N quantity in Groß Kreutz up to the maximum furnished also the highest energy output. On the opposite, in Leipzig-Seehausen the highest energy output was generally achieved in the 0/2-variants. When both test sites are compared, it becomes evident that the energy outputs achieved with winter wheat in Groß Kreutz were not nearly as high as in Leipzig-Seehausen, despite the yield increasing effect of the N supply. With corresponding N-supply, the other crops (sugar beet, spring barley, potatoes), however, reached a similar and partially even higher yield level compared with Leipzig-Seehausen.

4.3.2

Energy Output in Farms

The energy output in the sampled actual farms was comprised in Table 16. Here, too, the energy output was shown for the main product only since the byproduct straw was left on the field. Table 16: Energy output (GJ ha-1) in farms (without byproducts) Farm Crop Winter wheat Winter barley Winter rape Sugar beet Peas

III

VII

VIII

100.8 92.0 79.7 196.8 101.6

78.4 70.2 41.7 184.1 50.2

77.3 172.2 -

113.1 86.4 43.8 152.8 71.8

100.0 97.4 71.1 251.2 -

121.2 87.3 60.7 192.2 -

104.1 83.7 77.1 184.8 78.7

84.8 78.9 78.1 165.6 -

Similar to the comparison between the two experimental sites Leipzig-Seehausen and Groß Kreutz, large deviations were recorded between the energy outputs in practical farming. Between farm V and IV, for example, a difference of 98.4 GJ ha-1 was found in sugar beet cropping, although the energy input differed by not more than 1.7 GJ ha-1 .

4.4

Energy Output Compared with Energy Input

In Fig. 10 the energy output is compared with the energy input on the example of winter wheat and sugar beet in the experimental station Leipzig-Seehausen. In the graph, all values refer uniformly to the variant with 100 kg Mineral-N ha-1. Each crop rotation is indicated separately. It turned out that the energy output in the yield is extremely higher than the input of fossil energy. The energy output exceeded the mean energy input by approx. the ninefold for all test years both in winter wheat and sugar beet.

GJ ha

-1

300

Winter wheat 250

energy yield

Sugar beet

energy input

energy yield

energy input

200

150

100

0 Crop rotation

Fig. 10: Energy output (GJ ha-1) and energy input (GJ ha-1) on the example of winter wheat and sugar beet (experimental station Leipzig-Seehausen; 100 kg mineral-N ha-1)

4.5

Energy Efficiency

As parameters of energy efficiency energy gain and energy intensity are used. Both parameters lead to differing results. The parameter energy gain results from the difference between energy recovery in the harvested yield and the input of fossil energy. The fact that energy recovery in

the yield exceeded the input of fossil energy by about the power of ten, makes the energy gain mainly dependent on yield performance. Thus, the expenditure of mineral-N that furnished the highest energy gain was nearly identical with the N amount for the maximum yield. The parameter energy intensity follows from the ratio between the input of fossil energy and the harvested yield converted into grain equivalents. It allows to calculate the fertilizer quantity that involves a minimum input of fossil energy per product unit and thus a minimum consumption of finite resources.

4.5.1 Energy Gain 4.5.1.1 Energy Gain in Field Experiments Beside the influence of nitrogen fertilization the energy gain of each crop species follows a different pattern. Thus, the energy gain of various years in dependence on the mineral nitrogen fertilization is demonstrated for different crop species in the experimental station LeipzigSeehausen (Fig. 11, 12). The points in the graphs indicate the mineral-N fertilizer rates leading to maximum energy gains.

350

100

250

70 60

200 116 150

118

100

40 30

73 Potatoes 1971 Winter wheat 1972 Sugar beet 1973

-1

Energy gain (GJ ha-1)

Energy gain (GJ ha ) (Potatoes)

123

300

Winter barley 1981

0 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 11: Energy gain (GJ ha-1) in Leipzig-Seehausen 1971-1981 (incl. byproduct)

According to Fig. 11 it is obvious that the highest energy gain was yielded with sugar beet. In this case a maximum energy gain of approx. 327 GJ ha-1 was achieved with 123 kg N ha-1. The energy gain of winter wheat amounted to approx. 203 GJ ha-1 with a N rate of 116 kg N ha-1. The highest energy gain of winter barley was slighty lower (158 GJ ha-1). For potatoes a separate y-scale was used because of the extremely low energy gain. In 1971 the maximum

energy gain was only approx. 32 GJ ha-1. 100

350

80 70

106

250

130 200

50 40

150 30 Potatoes 1994 Winter wheat 1990 Winter barley 1991 Sugar beet 1992

100

-1

Energy gain (GJ ha )

300

Energgy gain (GJ ha ), Potatoes

147

10 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 12: Energy gain (GJ ha-1) in Leipzig-Seehausen 1989-1992 (incl. byproduct) About 20 years later, the highest energy gain was again recorded in sugar beet. With an amount of approx. 324 GJ ha-1 in 1992 there has been a slight decline since 1973. In contrast to sugar beet the energy gain of the other crops has increased. In the year 1989 potatoes yielded an energy gain of 93 GJ ha-1 p.ex. This means that there was a difference of 51.5 GJ ha-1 compared with the energy gain of 1971. The energy gain of winter barley increased to 243 GJ ha-1 in 1991, this is a difference of 85 GJ ha-1. The higher energy gains in potatoes, winter wheat and winter barley were achieved with nearly equal N rates.

Apart from the influence of the crop rotation pattern, a decisive impact on the energy gain was exerted by the site of cropping. Due to this, Fig. 13 presents a comparison between the energy gain of winter wheat in dependence on the input of mineral-N in the experimental stations Leipzig-Seehausen and GroĂ&#x; Kreutz.

280 Groß Kreuz 1992 Seehausen 1995

240

-1

Energy gain (GJ ha )

90 200

160

120

80 149

0 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 13:Energy gain (GJ ha-1) of winter wheat in Leipzig-Seehausen 1995 and Groß Kreutz 1992 (incl. byproduct)

The energy gain of winter wheat in the experimental station Groß Kreutz ranked much lower than that in Leipzig-Seehausen. This might be attributed primarily to the low soil fertility in Groß Kreutz (compare Table 3), allowing low yields only. In this example the increased energy gain on the account of mineral-N fertilization in Groß Kreutz amounted to approx. 62 % compared to that in Leipzig-Seehausen. Parallel to this, a higher relative increase of the energy gain vis-àvis the non-fertilized plot was recorded.The mineral-N amount required for obtaining the maximum energy gain was notably higher in Groß Kreutz than in Leipzig-Seehausen.

4.5.1.2 Energy Gain in Farms The crop-related energy gain in the various farms is shown in Table 17. The energy gain in the real farms varied considerably in correspondence with the different energy inputs (4.1) and outputs (4.3). Table 17: Energy gain (GJ ha-1) in farms (without byproducts) Farm Crop

III

VII

VIII

Winter wheat Winter barley Winter rape Sugar beet Peas

87.0 79.2 68.9 184.2 95.7

66.8 59.3 31.2 170.0 44.9

58.5 153.1 -

100.5 75.0 33.6 138.3 66.3

87.3 85.5 59.4 238.4 -

110.2 76.7 51.3 177.9 -

89.2 72.2 66.6 171.9 71.2

73.2 68.1 68.5 154.5 -

4.5.1.3 Comparison of Energy Gain in Field Experiments and in Farms Below, the energy gains recorded in the field trials and the sampled farms are compared with each other on the example of winter wheat cropping (Fig. 14). Additionally the site-related energy gain per unit mineral-N is shown.

-1

GJ ha

MJ kg

-1

Mineral-N 1000

140 800

120 100

600

80 400

60 40

200

20 0

0 Farms

Mean of the Farms

Trial F1-70

Groß Kreuz

Fig. 14: Site-related energy gain (GJ ha-1) of winter wheat The columns indicate the energy gain per hectare. For winter wheat it varied in the sampled farms between 58 and 110 GJ ha-1. Thus, it ranks in-between the energy gains which were recorded in the experimental stations Leipzig-Seehausen (approx. 115 GJ ha-1) and Groß Kreutz (approx. 60 GJ ha-1). This result agrees with calculations by BIERMANN et al. (1996), who reported a value of approx. 88.5 GJ ha-1 for farms. The same result was recorded for the energy gain per kg mineral-N, which is indicated by the curve. The average of approx. 550 MJ kg-1 N lies between the values given for Leipzig-Seehausen and Groß Kreutz.

4.5.1.4 Influence of Different Energy Equivalents on the Energy Gain The influence of different energy equivalents for mineral nitrogen fertilizer on the energy gain of winter wheat is shown in Fig. 15. The data refer to the field experiment F1-70 in LeipzigSeehausen.

300 106 104

-1

Energy gain (GJ ha )

250

200

150 86 100

-1

Variant I (Energy equivalent 35.3 MJ kg

-1

Variant II (Energy equivalent 80 MJ kg Variant III (without straw)

0 0

100

120

Mineral-N (kg ha-1)

Fig. 15: Influence of different energy equivalents on the energy gain (GJ ha-1) of winter wheat

As the energy output exceeds the energy input several times (compare 4.4) the effect of differing energy equivalents for mineral nitrogen fertilizer on the energy gain remains very low. In this example the difference is only 4.7 GJ ha-1. However, the energy gain varied clearly if the energy output of the byproduct (straw) remained unconsidered. Neglecting the straw reduced the energy gain from approx. 273 GJ ha-1 to 146 GJ ha-1, this means by approx. 40 %.

4.5.2

Energy intensity

The parameter energy intensity helps to determine the fertilizer quantity which involves a minimum input of fossil energy per product unit. As mentioned earlier the energy intensity is the ratio between the input of fossil energy (4.1) and the harvested yield (4.2) converted into grain equivalents (see Table 9).

4.5.2.1 Energy Intensity in Field Experiments Analogous to the description of the energy gain, the development of energy intensity in dependence on mineral-N application is shown for different crop species and different years (Fig. 16 and Fig. 17). The data refer to the field experiment F1-70 in Leipzig-Seehausen. 800 Potatoes 1971 Winter wheat 1972 Sugar beet 1973 Winter barley 1981

700

300

600 37

-1

Energy intensity (MJ GE -1)

350

Energy intensity (MJ GE ) (Potatoes)

400

250

500

200

400 90

150

100

300

200

100 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 16: Energy intensity (MJ GE-1) in Leipzig-Seehausen 1971-1981 The energy intensity varied within a wide range. It is obvious that with increasing mineral-N rates the energy intensity fell back to a minimum value. After this point it rose again. The decline of the energy intensity with increasing N input can be explained by the strong yield rises in dependence on the N level. The mineral-N demand that involved a minimum energy intensity was lower than the N rates which furnished a maximum energy gain. The energy intensity increased from sugar beet, winter wheat and winter barley up to potatoes. In sugar beet the lowest energy intensity (approx. 111 MJ GE-1) was achieved with approx. 73 kg N ha1 . There were only small differences between the minimum energy intensity of winter wheat (167 MJ GE-1) and winter barley (178 MJ GE-1). However, there were large differences in the fertilizer rates leading to this minimum. Due to the optimum crop sequence position of winter wheat after potatoes, no mineral-N fertilizer was necessary for this minimum. This may be caused by the mineralization of harvest residues and the after-effects of manure application to potatoes. The mineral-N requirement of winter barley (approx. 90 kg N ha-1) may be partially explained by the unfavourable position after winter wheat . The minimum energy intensity of potatoes (approx. 509 MJ GE-1) was rather high. On the one hand, the energy input was high (see Fig. 5), on the other hand, potatoes gave only a low yield with low energy concentration.

400

300 250

300

200

103 200

150

55 99

100

100 50 0

-1

Energy intensity(MJ GE -1)

350

Energy intensity(MJ GE ), Potatoes

500 Potatoes 1994 Winter wheat 1990 Sugar beet 1991 Winter barley 1992

0 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 17: Energy intensity (MJ GE-1) in Leipzig-Seehausen 1990-1994 No mineral-N was necessary for sugar beet to reach the minimum energy input (100 MJ GE-1). The differences in the response of the two cereals are evident. In contrast to winter wheat the energy intensity of the untreated variant of winter barley was markedly higher. Also the mineral-N doses leading to a minimum energy intensity were significantly higher than in case of winter wheat - 125 MJ GE-1 and 99 kg N ha-1 for winter barley, 123 MJ GE-1 and 55 kg N ha-1 for winter wheat. Compared with the curves from Fig. 16, there was a large decline in the energy intensity to potatoes (from 509 to 264 MJ GE-1). At the same time the mineral-N rate increased (from 37 to 103 kg N ha-1). The influence of the different site conditions in Leipzig-Seehausen and GroĂ&#x; Kreutz on the energy intensity is demonstrated on the example of winter wheat (Fig. 18).

900 Groß Kreuz 1992 Seehausen 1995

700

-1

Energy intensity (MJ GE )

800

600 500 130 400 300 200 54

100 0 0

100

120

140

-1

Mineral-N (kg ha )

Fig. 18: Energy intensity (MJ GE-1) of winter wheat in Leipzig-Seehausen 1995 and Groß Kreutz 1992 (incl. byproduct) Due to the low productivity in the experimental station Groß Kreutz (see 4.2.1), here the energy intensity of winter wheat was much higher than in Leipzig-Seehausen. In Groß Kreutz approx. 130 kg N ha-1 led to a minimum energy intensity of 493 MJ GE-1. In Leipzig-Seehausen the minimum energy intensity (164 MJ GE-1) was achieved with approx. 54 kg N ha-1. Increasing mineral-N input, however, reduced the energy intensity in Groß Kreutz much stronger. The reason for this was the higher yield increase per kilogram of applied mineral nitrogen.

4.5.2.2 Energy Intensity in Farms The crop-related energy intensity in farms is summarized in Table 21. Table 18: Energy intensity (MJ GE-1) in farms Farm Crop Winter wheat Winter barley Winter rape Sugar beet Peas

III

VII

VIII

218.3 222.5 207.0 106.9 98.5

235.7 247.8 384.9 128.7 179.1

389.4 186.5 -

178.2 311.4 354.3 158.8 129.8

202.9 196.2 254.5 85.2 -

145.5 195.4 238.0 124.9 -

195.4 218.9 209.2 117.6 159.7

217.7 217.6 188.6 112.3 -

The results presented for the energy input and the yields in the sampled farms reveal that also the energy intensity varies considerably. The data document differs between the farms in comparison of the single crop species. In winter wheat cropping, for example, the farms differed by up to 243.9 MJ GE-1, in sugar beet growing by up to 101.3 MJ GE-1. Crop comparisons disclose that both cereal and rape growing involve extremely high energy intensity, whereas sugar beet and peas usually rank low. High values go mostly back to higher energy input. In sugar beet growing, the energy intensity is positively influenced by the comparatively high yields despite nearly equal energy input. With peas, on the other hand, the low energy intensity can be explained primarily by an extremely low energy input, parallel to slightly lower yields than in the case of cereal crops. But if there are only low yields, the energy intensity in pea cropping can be much higher (compare RATHKE et al. 1999).

4.5.2.3 Comparison of Energy Intensity in Field Experiments and in Farms In the following energy intensity in field trials and actual farms is juxtaposed for winter wheat cropping (Fig.19). According to energy gain, the values of energy intensity in practical winter wheat cropping rank between those which were obtained in the field experiments. It is shown that seven of the sampled farms lie closely together with values from 150 to 235 MJ GE-1. Only in one farm (III) the energy intensity amounted to approx. 390 MJ GE-1 due to excessively high mineral fertilizer rates under the given productivity conditions (see Table 4).

MJ GE

-1

500

400

300

200

100

0 Farms

Mean of the Farms

Trial F1-70

GroĂ&#x; Kreuz

Fig. 19: Site-related energy intensity (MJ GE-1) of winter wheat (F1-70: Leipzig-Seehausen)

4.5.2.4 Influence of Different Energy Equivalents on the Energy Intensity The influence of different energy equivalents on the energy intensity of winter wheat is shown in Fig. 20. The data refer to the field experiment F1-70 in Leipzig-Seehausen. The figure also demonstrates the effect the byproduct straw has on the energy intensity. In contrast to the energy gain (see Fig. 15) different energy equivalents for mineral nitrogen fertilizer have a big influence on the energy intensity. The course of the curve depends on the used energy equivalent; the latter, however, influences the fertilizer rate that minimizes the energy intensity. In our example, a higher energy equivalent (80 MJ kg-1 N) led to minimum energy intensity at about 26 kg N ha-1 only. However, N doses exceeding this level raised the energy intensity rapidly. Against this, minimum energy intensity on the basis of a low energy equivalent (here 35.3 MJ kg-1 N) was reached only on a higher fertilizer level; yet, any N rate surpassing this level involved a more moderate increase of the energy intensity. This can be explained by the different position of the energy input in the definitions of the two efficiency parameters (see above). While the energy gain represents a difference (output minus input), energy intensity results from a ratio (input per GE). Neglecting the straw has no major effect on the energy intensity. This goes back to the relatively low GE factor for straw (see Table 9). In the case of winter wheat and winter barley it amounts to not more than a tenth of the GE factor for grain.

200 -1

-1

Energy intensity (MJ GE )

Variant I (Energy equivalent 35.3 MJ kg

-1

Variant II (Energy equivalent 80 MJ kg Variant III (without straw) Variant IV (without capital goods)

175

150

26 53

125 55 51 100 0

100

120

-1

Mineral-N (kg ha )

Fig. 20: Influence of different energy equivalents on the energy intensity (MJ GE-1)

Conclusions

Summary and Conclusion Problem description and subject of the studies Photosynthesis, the central process of energy binding in crop plants, involves the binding of radiation energy from the sunlight and its chemical fixation. Modern cropping systems are characterized by additional input of fossil energy. The growing intensification of agricultural production over decades has raised the input of fossil energy and also yields. This implies the question whether the energy efficiency has altered. Energy balance sheets furnish information on production intensity, the consumption of finite resources, CO2 release and climatic effects. They are also used for the energetic optimization of cropping systems and for determining the energy input that guarantees the highest possible efficiency under specific site and management conditions. Previous studies have shown that an essential part of the total input of fossil energy is consumed by mineral fertilizer. The main objective of this study was to quantify the effect of mineral fertilizer on the energy recovery in

the harvested biomass of selected crops. Methodics of energy balancing In agreement with the objective of the study, only the input of fossil energy has been analysed. Solar energy as well as human labour remained unconsidered. All expenses for operating resources and machine use were converted into energy equivalents and were thus considered as primary energy inputs. The energy equivalents used for mineral N fertilizer were adapted to the technical progress in the last decades and refer to modern production facilities. It was assumed that the energy input declined from 49.4 MJ kg-1 N in the period 1967-1970 to 35.3 MJ kg-1 N in 1994-98. The energy output (calorific value of the harvested biomass) was calculated on the basis of the dry matter yield and the chemical components. The parameters energy input, energy intensity and energy gain are indicated in dependence on the mineral N input. The balance sheets were prepared on the level of field experiments (plots < 100 mÂ˛) and on real farm level (300 to > 2000 ha) for sandy and black-earth (loess) sites. In the field experiments measurement series were used that had been made over 30 years documenting the influence of organic and mineral fertilizers in intensive cereal-root crop rotations. The management data reflect the present situation in farm practice; included were also cash crop farms in the central German agricultural region (Saxony and Saxony-Anhalt) . Results of energy balancing Energy Input - In the field experiments the energy input varied between 10 GJ ha-1 in spring barley and 25 GJ ha-1 in sugar beet cropping. It was strongly related to crop species and production technology. With root crops it was principally higher than with cereal crops. - The decline of indirect energy input via mineral N, as recorded throughout the reference period, goes back to the risen energy efficiency in fertilizer production. This, however, was largely compensated by an increase in other input parameters. The relative share of mineral N in the energy input to winter wheat declined from 35.6 % to 21.8 %. The portion of mineral fertilizer in the total energy input was 48.1 to 58. 8 % in winter wheat and 53.7 bis 56.4 % in winter barley. - In practical farming the energy input varied considerably among the different crops. The deviations from the data obtained in field experiments were mainly caused by differences in the applied fertilizer doses. - The energy input to winter wheat (11.0 to 18.0 GJ ha-1 or 120 bis 240 kg Nmin ha-1) was in some cases clearly higher than the inputs on the test plots. In sugar beet, however, energy inputs of 11.1 to 19.1 GJ ha-1 connected with mineral-N rates of 30 to 140 kg N ha-1 produced lower values than in the experimental plots. Yield effects of nitrogen input - At a given site the yield of a particular crop depends mainly on its place in the crop rotation and on the nitrogen supply. In field experiments, yield responses to increasing nitrogen rates showed a typical optimum curve. - Under the given loess conditions wheat yields over 30 years rose from about 50 dt ha-1 to more than 100 dt ha-1 in case of Nmin doses of less than 120 kg ha-1. In winter barley, too, yields above 100 dt ha-1 were achieved, yet with higher N rates of about 150 kg N ha-1. Sugar beet yields in the variants with purely mineral fertilization reached 450 to 600 dt ha-1, however, a clear yield tendency was not noticed. - Under practical conditions yields were lower than on the test plots despite partially higher fertilizer doses. The following yields were recorded: winter wheat - 48.3 to 75.8 dt ha-1, winter barley - 43.9 to 60.9 dt ha-1, sugar beet - 369 to 598 dt ha-1. Energy Output - The energy output corresponds to the energy bound in the harvested biomass. It depends largely on the fact whether the byproducts are also harvested. - The energy output followed the behaviour of the yields. It increased with the nitrogen rate applied up to a maximum and then declined. The cultivated crop, the local growing conditions and agrotechnical factors, especially the nitrogen rate, had a marked influence on the energy output. - In the experiment launched on loess soil, the fertilizer-related energy output between 1989 and 1993 amounted to 59-95 GJ ha-1 in potatoes, 107-169 GJ ha-1 in winter wheat (with

straw up to 287 GJ ha-1), 203-247 GJ ha-1 in sugar beet (with leaves up to 348 GJ ha-1). - In real farms the energy output in winter wheat without byproducts reached 98 (77 to 121) GJ ha-1, in sugar beet 188 (152 to 251) GJ ha-1 on average. Energy Intensity - The energy intensity is the ratio of fossil energy input and the harvested yield converted into cereal equivalents. The amount of mineral-N that furnished a minimal energy intensity was clearly lower than that leading to maximum yield and maximum energy gain. - In the field experiments, the energy intensity was largely related to weather and site conditions. The byproducts had only a minor effect. - Between 1990 and 1994 the following results were obtained on the loess site: potatoes 264 to > 500 MJ GE-1 (min. at 103 kg N ha-1), winter wheat - 123 to > 160 MJ GE-1 (min. at 55 kg N ha-1), winter barley - 125 to > 450 MJ GE-1 (min. at 99 kg N ha-1). - In real farms the energy intensity in winter wheat amounted to 223 (146-389) MJ GE-1, in winter barley to 230 (195-311) MJ GE-1, in sugar beet to 128 (85-186) MJ GE-1.

Energy gain - The difference between input of fossil energy and output of energy in the agricultural produce signifies the energy gain. The parameter â&#x20AC;&#x161;energy gainâ&#x20AC;&#x2DC; helps determine the fertilizer input that is required for achieving a maximum binding of net energy. - Averaging all investigated cropping systems, the energy output exceeded the input of fossil energy by the factor of 4.0 to 19.8, or the mean value of 10.2. The expenditure of mineral Nfertilizer that furnished the highest energy gain was nearly identical with the N amount for the maximum yield. - From 1990 to 1994 the following maximum energy gain (incl. byproducts) was achieved on the loess site: sugar beet - 202 to 307 GJ ha-1 (max. at 116 kg N ha-1), potatoes - 40 to 93 GJ ha-1 (max. at 148 kg N ha-1), winter barley - 38 to 245 GJ ha-1 (max. at 130 kg N ha-1), winter wheat - 178 to 273 GJ ha-1 (max. at 106 kg N ha-1), - In the real farms no byproducts were harvested. The mean energy gain in sugar beet was 174 (138 to 238) GJ ha-1, in winter wheat 84 (58 to 110) GJ ha-1, in winter barley 74 (59 to 86) GJ ha-1. Conclusions and perspectives The results are site and management specific, and therefore they cannot be unreservedly transferred to other conditions. Future studies should purposefully increase the number of the hitherto investigated crop species, including also new locations. Apart from the cash crop farms in the Central German dry loess region, which were analysed in the past, mainly forage cropping farms and the growing of renewable resources are recommended for investigation. The results in the balance sheets are generally influenced by the set system boundaries and the assumed energy equivalents. A harmonization of the energy balancing methods would be desirable in order to guarantee the comparability of the results. Energy equivalents are to be adjusted to the current technical level and with regard to regional pecularities - as done in the present paper on the example of mineral nitrogen. Attention should be paid to the deviating contents of the different energetic indices. Energy output and energy gain are decisive target values if there is a necessity to increase the plant produce despite a limited cropping area, which is a matter of fact in many parts of the world due to growing populations numbers. Maximizing the energy gain ranks first, also from the angle of the energetic use of renewable resources. The energy intensity is particularly suited for rating product-related impacts on the environment (resources and energy consumption, CO2 emission) and for deriving optimal fertilizer and production intensity levels. 6 Prospects Beside energy balancing in cash crop farms, it seems to be necessary to investigate how the energy efficiency changes in animal farms with forage cropping under the influence of mineralN fertilization. In such farms silage maize, field forage crops and grassland occupy large areas. Analogous to the energetic assessment of cash crop farms, it would be interesting to find out to which extent the use of fossil energy and the energy recovery by the crops have changed in

these farms. Furthermore, the question arises on which level the energy optimum of mineral N input ranks under such conditions.

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Appendix 1: Fertilization of the Variants in the long term trial, organ = Manure-N (kg ha-1 a-1), min = Mineral-N (kg ha-1 a-1) Variant/

Crop rotation I

Fertilization Pot 1967

Crop rotation II SpB

Pot

Crop rotation III SpB

Pot

Crop rotation IV

SpB

Pot

Crop rotation V SpB 83

Mai WB 84

Crop rotation VI SpB

Pot

Crop rotation VII

Mean

SpB

Pot

1967 -

1990

0/0 organ min

0,0

0/1 organ min

0,0

100

52,1

0/2 organ min

0,0

200

110

200

120

150

120

160

120

100

160

120

100

160

120

100

104,2

0/3 organ min

0,0

300

165

300

180

120

180

120

225

180

120

240

180

120

150

240

180

120

150

240

180

120

150

156,3

1/0 organ

155

125

100

125

150

160

150

52,5

0,0

155

125

100

125

150

160

150

52,5

min 1/1 organ min 1/2 organ min

100

52,1

155

125

100

125

150

160

150

52,5 104,2

200

110

200

120

150

120

160

120

100

160

120

100

160

120

100

1/3 organ min

155

125

100

125

150

160

150

52,5

300

165

300

180

120

180

120

225

180

120

240

180

120

150

240

180

120

150

240

180

120

150

156,3

2/0 organ

310

250

188

160

200

188

200

250

300

176

300

320

300

105,1

0,0

250

188

160

200

188

200

250

300

176

300

320

300

105,1

min 2/1 organ min

310

100

52,1

2/2 organ

310

250

188

160

200

188

200

250

300

176

300

320

300

105,1

min 2/3 organ min

200

110

200

120

150

120

160

120

100

160

120

100

160

120

100

104,2

310

250

188

160

200

188

200

250

300

176

300

320

300

105,1

300

165

300

180

120

180

120

225

180

120

240

180

120

150

240

180

120

150

240

180

120

150

156,3

3/0 organ min

465

375

282

240

300

282

300

375

450

264

450

480

450

157,6

0,0

3/1 organ min

465

375

282

240

300

282

300

375

450

264

450

480

450

157,6

100

52,1

3/2 organ

465

375

282

240

300

282

300

375

450

264

450

480

450

157,6

min 3/3 organ min

200

110

200

120

150

120

160

120

100

160

120

100

160

120

100

104,2

465

375

282

240

300

282

300

375

450

264

450

480

450

157,6

300

165

300

180

120

180

120

225

180

120

240

180

120

150

240

180

120

150

240

180

120

150

156,3