CSIRO PUBLISHING
www.publish.csiro.au/journals/trj
The Rangeland Journal, 2011, 33, 307–313
The effect of bovine saliva on growth attributes and forage quality of two contrasting cool season perennial grasses grown in three soils of different fertility M. Kerim Gullap A, H. Ibrahim Erkovan B and Ali Koc B,C A
Narman Vocational High School, University of Ataturk, Narman, Erzurum, Turkey. Department of Field Crops, Faculty of Agriculture, University of Ataturk, Erzurum, Turkey. C Corresponding author. Email: akoc@atauni.edu.tr B
Abstract. The aim of this study was to determine the response of Dactylis glomerata L. (Orchardgrass) and Festuca ovina L. (Sheep fescue), to bovine saliva application in a loamy soil (most fertile), a sandy loam and a sandy soil (least fertile). The effects of cutting and cutting + saliva on relative height growth rate (RHGR), above- and belowground biomass and forage quality attributes [crude protein, NDF (neutral detergent fibre) and ADF (acid detergent fibre)] were investigated. The results showed that the cutting and cutting + saliva treatments resulted in greater RHGR than the control, but only with D. glomerata in the sandy soil did the application of saliva increase the RHGR. However, saliva applied after cutting increased the aboveground biomass averaged over all species and all three soils. Saliva applied to D. glomerata increased the belowground biomass in the sandy loam and sandy soils but decreased it in F. ovina in the sandy soil. The application of saliva had no effect on the crude protein or the NDF content of either species in any of the soils. On the other hand, the application of saliva after clipping increased the ADF of F. ovina but decreased that of D. glomerata averaged over all three soils. Averaged over both species, the ADF was increased by the addition of saliva in the sandy soil, had no significant effect in the sandy loam (P > 0.05) and was slightly increased in the loam. Additional keywords: above- and belowground biomass, clipping, plant, soil texture.
Introduction Rangelands have made important contributions to farming systems and the environment in which we live since prehistoric times (Pagnotta et al. 1997). Enhancing the balance between forage production and herbivore consumption provides for sustainable use of forage resources and stability in the energy flow from grazing lands to humans. Plant species respond to grazing by herbivores in many different ways and it is important to apply this information to better understand the management of plants and herbivores. Some grassland communities may be stimulated to increase productivity by grazing (McNaughton 1985; Frank et al. 2002; Schaffers 2002), and the ecological literature accepts that grazing includes positive, negative, and neutral effects on grass productivity (Boyd and Svejcar 2004; Loeser et al. 2004). Knowledge of plant–herbivore interactions is important for establishing sustainable grazing management of rangelands. In general, herbivory reduces biomass production in grazed plants but whether or not herbivory can promote plant production, has been a subject of recent debate (Teng et al. 2010). Grass production increases following suitable grazing management practices but if grazing intensity becomes excessive, grass production can decrease to below that of ungrazed plants (Schaffers 2002). Proper grazing contributes to compensatory growth by accelerating nutrient cycling, improving effective use Australian Rangeland Society 2011
of soil moisture (by decreasing transpiration surface), promoting regrowth, etc. (Holechek et al. 2004; Wang and Ba 2008). Frank et al. (2002) found that herbivory stimulated aboveground annual net primary production by 21% and belowground production by 35% in Yellowstone National Park, USA. Loeser et al. (2004) reported similar results in the semiarid highland rangelands of Arizona, USA. Deposition of animal saliva on plants during grazing is known to stimulate plant growth (Reardon et al. 1972) and the active ingredient is probably thiamin (McNaughton 1985; Dyer et al. 1993; Zhang et al. 2007; Teng et al. 2010). On the other hand, some research showed that addition of pure bovine saliva to grasses did not cause statistically significant effects on above- and belowground biomass (Johnston and Bailey 1972; Reardon et al. 1974; Detling et al. 1980). Different plant species such as Artemisia frigida Willd. and Leymus chinensis (Trin.) Tzvelev react differently to sheep saliva (Zhang et al. 2007). We hypothesised that there are different responses to saliva of different species of plants following cutting or grazing in different soil types because of different responses following defoliation. The response of plants to saliva varies depending on soil type. Experiments with thiamin and bovine saliva have shown that they can promote plant growth although the results have been 10.1071/RJ10063
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complicated and contradictory. However, Reardon and Merrill (1978) suggested that the effect may be greater if plants are grown under nutrient-limiting conditions. Growth of different species of grasses are affected by environmental conditions (Dyer et al. 1993; Wang and Ba 2008; Schacht and Volesky 2010). Dactylis glomerata (L.) is an important plant for sown pasture establishment in the Eastern Anatolia Region of Turkey (Koc et al. 1998) and other temperate areas of the world (Acikgoz 2001) and Festuca ovina (L.) is the dominant grass in the natural rangelands of the region (Koc 2001; Erkovan et al. 2003; Oztas et al. 2003) and is suitable for grazing whereas D. glomerata is suitable for both grazing and cutting for hay. The effects of bovine saliva on the nutrient content of grasses are also not well known. The quality of forage is a function of nutrient concentration of the forage and is influenced by soil fertility, other environmental conditions, and plant growth stage (Buxton and Mertens 1995). Generally, in addition to more forage production, plants grown in fertile soils have better forage quality (Cilliers et al. 1995; Gokkus and Koc 1996). Cilliers et al. (1997) estimated that crude protein (CP) and neutral detergent fibre (NDF) content of forage increased but acid detergent fibre (ADF) decreased in relation to nitrogen fertiliser application. Similar results were reported by the other researchers (Rubio et al. 1996; Johnston et al. 2001; Malhi et al. 2004; Aydin and Uzun 2005; Comakli et al. 2005). The aim was to determine (1) the effects of bovine saliva on relative height growth rate (RHGR), above- and belowground biomass and forage quality of D. glomerata and F. ovina and (2) how these effects are modified by the type of soil in which the plants are growing. Material and methods Experiment design, plant and soil description This study was carried out under greenhouse conditions at the Faculty of Agriculture, University of Ataturk, Erzurum, during the years of 2008 and 2009. The experiment was a completely randomised design with three treatments, two plant species, three soil types, with 10 replications. Defoliation/saliva treatments were (1) plants clipped at the heading stage (control), (2) plants clipped at early stem elongation and no bovine saliva applied (cut), and (3) plants clipped at early stem elongation and bovine saliva applied (cut + saliva). The early elongation stage was selected because it is the ideal maturity for grazing (Gokkus and Koc 2001). Thus the cutting and cutting + saliva application treatment was applied about every 2 months and control plants reached heading stage about every 4 months. Plant clones of a commercial cultivar (Tohum islah) of D. glomerata were collected from hay production fields and wild plants of F. ovina from the Ataturk University natural rangeland area at the beginning of the growing season of 2008 and transplanted into the pots. Treatments were applied from August 2008 to August 2009. Clipped stubble heights were 4 cm for F. ovina (Koc and Gokkus 1994) and 5 cm for D. glomerata (Serin and Tan 2004). Three different soils were collected from natural areas of Ataturk University, and were then analysed to determine their texture and fertility levels (Table 1). Sixty pots (20 20 cm) were
M. K. Gullap et al.
Table 1. Characteristics of the experimental soils Soil
Loamy
Sandy loam
Sandy
Sand (%) Silt (%) Clay (%) Organic matter (%) pH Lime (%) Phosphorus (kg/ha–1) Potassium (kg/ha–1)
36.5 39.8 23.7 2.9 7.8 2.7 102.0 781.0
55.7 31.3 13.0 1.5 7.8 2.0 105.0 820.0
100 <0.05 <0.05 <0.05 <0.05 7.5 <0.05 <0.05
used for each soil type, making the total number of pots 180. Each pot was filled with soil after sieving through a 2-mm mesh screen. The loamy textured soil had the largest amount of plant available phosphorus and organic matter as well as the highest clay content among the experimental soils (Table 1). Therefore, it was considered a rich soil, the sandy-loam textured soil as of moderate fertility and the sandy textured soil as poor. Bovine saliva was collected by inserting a sponge into the mouths of 12 1-month-old calves in the calf herd at Ataturk University ranch. The sponge was sterilised with 70% alcohol and then dried before it was used. When enough saliva was collected, 1 mL of bovine saliva was diluted with 10 mL of distilled water and was sprayed on the plants after they had been clipped (Zhang et al. 2007). The height of the tallest stem of each plant was measured before clipping. Estimation of biomass and herbage quality After the final clipping, the stubble of plants was removed at crown level and added to the clipped material and the pots were filled with tap water. After 2 h, the contents of the pots were removed and plant roots were separated from the soil by washing with tap water. All plant samples (below- and aboveground) were oven-dried at 658C to constant weight. While aboveground production was determined by combining the weights of oven-dried material of the three cuttings of the control treatment and the six cuttings with and without saliva, plus the stubble at the final harvest, belowground production was only determined at the final sampling. After weighing, aboveground material was ground to pass through a 2-mm sieve. Total N content of the samples was determined by the Kjeldahl method and multiplied by 6.25 to give the crude protein content (Jones 1981). NDF and ADF content were measured using an ANKOM fibre analyser (ANKOM Technology, Fairport, NY, USA) following the procedure described by Van Soest et al. (1991). Data analyses To determine RHGR of both species, plant height was measured every month before every harvest, and RHGR calculated as follows (Ishikawa and Kachi 2000). RHGR ¼ ðln H2 ln H1 Þ=ðt2 t1 Þ
ð1Þ
where H1 is the plant or stubble height at time t1 and H2 the plant height at time t2. All data were subjected to ANOVA based on general linear models for factorial arrangement of treatments in a
Bovine saliva, grass growth and soil type
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Results Growth effects All the main effects as well as the first- and second-order interactions were significant (P < 0.05) for RHGR (Table 2). With all three soils and with both species, the cut and cut + saliva treatments resulted in greater RHGR than the control treatments (Fig. 1). However, it was only with D. glomerata in the sandy soil that the application of saliva increased the RHGR (Fig. 1). Aboveground biomass was significantly affected by treatments (F(2,162) = 4.774, P < 0.0097) (Table 3), and cut + saliva plants (3.95 g) produced more aboveground biomass compared with cut plants (3.59 g). The plant species soil interaction had significant effects on aboveground biomass (F(2,162) = 6.107, P < 0.0028) (Fig. 2). Aboveground biomass was higher for F. ovina than D. glomerata in the sandy soil but there was no difference between species in the other two soils (Fig. 2). All the first-order and second-order interactions were significant (P < 0.05) for the belowground biomass (Table 4). The application of saliva after clipping (cut + saliva) increased the belowground biomass of D. glomerata compared with the cut treatment, in the sandy loam and sandy soils but had no effect in the loamy soil (Fig. 3). On the other hand, the application of Table 2. Analysis of variance table (ANOVA) of relative height growth rate (cm day–1)
Treatments Plant species Soil Treatments plant species Treatments soil Plant soil Treatments plant species soil Residual
d.f.
F
P
2 1 2 2 4 2 4 162
384.854 36.156 116.852 6.841 6.521 28.674 3.595 –
<0.0001 <0.0001 <0.0001 <0.0014 <0.0001 <0.0001 <0.0077 –
saliva after clipping decreased the belowground biomass of F. ovina in the sandy soil (Fig. 3). Quality effects The application of saliva had no effect on the crude protein content of the two species averaged over all soils (Table 5). However, the crude protein level was lower for the control treatments compared with the two clipping treatments (Fig. 4a). The treatments and the plant species main effects were the only factors significant (P < 0.05) for the NDF (Table 6). The application of saliva after clipping had no effect on the NDF with the cut treatment being 60.3% and cut + saliva 60.5%. Both Table 3. Analysis of variance table (ANOVA) of aboveground biomass (g plant–1)
Treatments Plant species Soil Treatments plant species Treatments soil Plant species soil Treatments plant species soil Residual
Aboveground biomass (g plant–1)
completely randomised design using the Statview statistical package (SAS Institute 1998). Multiple comparisons with Bonferroni/Dunn were used to determine the effects of treatment, plants and soil (control, cut and cut + saliva) on the RHGR, aboveand belowground biomass, crude protein, NDF and ADF.
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6
d.f.
F
P
2 1 2 2 4 2 4 162
4.774 1.835 154.135 1.518 1.836 6.107 0.665 –
0.0097 0.1774 <0.0001 0.2223 0.1244 0.0028 0.6172 –
D. glomerata
A
F. ovina
A
5
B
B
4 C
3 D
2 1 0 Loamy
Sandy Sandy
Sandy loam
Soil Control
RHGR (cm day–1)
1.2
Cutting
B
1.0
C
C
C
BC
D
D
D
E
E F
0.4
Fig. 2. Aboveground biomass of Dactylis glomerata and Festuca ovina as affected by soil type (bars 1 s.e.) (F(2,162) = 6.107, P < 0.0028).
B
0.8 0.6
Cutting+Saliva
A A
F
F
G
F
0.2 0 Loamy Sandy loam Sandy
D. glomerata
Loamy
Table 4. Analysis of variance table (ANOVA) of belowground biomass (g plant–1)
Sandy loam Sandy
F. ovina
Fig. 1. Relative height growth rate (RHGR) Dactylis glomerata and Festuca ovina as affected by treatments and soil type. Bars indicate 1 s.e. (F(4,162) = 3.595, P < 0.0077).
Treatments Plant species Soil Treatments plant species Treatments soil Plant species soil Treatments plant species soil Residual
d.f.
F
P
2 1 2 2 4 2 4 162
2.253 7.842 12.157 5.337 5.333 38.338 9.900 –
0.1083 0.0057 <0.0001 0.0057 0.0005 <0.0001 <0.0001 –
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Control
Cutting
14
Cutt ing+ Saliva
(a)
A
20
B
B BC
15
B
BC C
C C
C
C
C C
10
CD
D
D D
D
5 0 Loamy Sandy loam Sandy
Loamy Sandy loam Sandy
D. glomerata
F. ovina
B
10 8 6 4 2
Fig. 3. Belowground biomass production of Dactylis glomerata and Festuca ovina as affected by treatments and soil type (bars 1 s.e.) (F(4,162) = 9.900, P < 0.0001).
0 70 60
Table 5. Analysis of variance table (ANOVA) of crude protein content (%) d.f.
F
P
2 1 2 2 4 2 4 162
6.231 2.744 17.473 2.532 0.360 2.976 1.443 –
0.0029 0.1011 <0.0001 0.0851 0.8362 0.0561 0.2263 –
(b) B
A
A
Cutting
Cutting+Saliva
50
NDF (%)
Treatments Plant species Soil Treatments plant species Treatments soil Plant species soil Treatments plant species soil Residual
A
A
12
Crude protein content (%)
Belowground biomass (g plant–1)
310
40 30 20 10 0 Control
Treatments
these treatments resulted in higher NDF content compared with the control plants (58.3%). Lower NDF content was found in D. glomerata (57.3%) than in F. ovina (62.0%) (Table 6) averaged over all treatments and soils (Fig. 4b). The application of saliva after the clipping reduced the ADF of D. glomerata and increased that of F. ovina averaged over all soil types (Table 7, Fig. 5). Also averaged over both species, the addition of saliva increased the ADF in the loamy and sandy soil but not in the sandy loam (Fig. 6). Discussion Both grasslands and grazing herbivores evolved during the Tertiary and so for some 20 million years, there have been reciprocal evolutionary effects on both the grasses and the grazing animals (Barnard and Frankel 1964). The tribe Festuceae, which includes both D. glomerata and F. ovina, has a concentration of genera and species in the Mediterranean region extending to eastern Turkey as well as in the USA (Hartley 1973). Both of these regions were centres of evolution of the grazing herbivores (Barnard and Frankel 1964) and so the two species chosen for this study have been associated with grazing animals for many millions of years. D. glomerata is native to Europe, North Africa and parts of Asia (Van Santen and Sleper 1996; Barnes et al. 2003) whereas F. ovina occurs naturally in the rangelands of eastern Turkey and in similar habitats in the western USA (Cronquist et al. 1977). D. glomerata most commonly occurs on fertile soils (well drained loams and silt loams) and has
Fig. 4. The effects of treatments on crude protein content (a) (F(2,162) = 6.231, P < 0.0029) and neutral detergent fibre (NDF) content (b) (F(2,162) = 6.251, P < 0.0029). Table 6. Analysis of variance table (ANOVA) of neutral detergent fibre content (%)
Treatments Plant species Soil Treatments plant species Treatments soil Plant species soil Treatments plant species soil Residual
d.f.
F
P
2 1 2 2 4 2 4 162
6.251 70.923 2.195 1.882 2.901 1.628 1.117 –
0.0029 <0.0001 0.1172 0.1582 0.1262 0.2020 0.3537 –
been introduced into many temperate areas of the world as a sown pasture grass for grazing or for fodder conservation (Van Santen and Sleper 1996; Barnes et al. 2003; Altin et al. 2005). F. ovina, on the other hand, is most common in upland rangelands, generally on infertile soils (Cronquist et al. 1977; Altin et al. 2005) and both species are tolerant of grazing. Different species have evolved different mechanisms for survival in grazed grasslands as a result of this long association between grasses and grazers (Harradine and Whalley 1981;
Bovine saliva, grass growth and soil type
The Rangeland Journal
Table 7. Analysis of variance table (ANOVA) of acid detergent fibre content (%)
Treatments Plant species Soil Treatments plant species Treatments soil Plant species soil Treatments plant species soil Residual
Control
40
C
B
d.f.
F
P
2 1 2 2 4 2 4 162
0.516 24.773 4.491 3.250 2.700 4.878 0.258 –
0.5988 <0.0001 0.0138 0.0433 0.0355 0.0097 0.9042 –
Cutting
B
D
Cutting+Saliva B
A
35
ADF (%)
30 25 20 15 10 5 0 D D. glomerata
F F. ovina
Plant Fig. 5. Levels of acid detergent fibre (ADF) content of Dactylis glomerata and Festuca ovina as affected by treatments (bars 1 s.e.) (F(2,162) = 2.700, P < 0.0355).
Control
40
B
C
B
Cutting B
A
Cutting+Saliva AB
B
B
A
35
ADF (%)
30 25 20 15 10 5 0 Loamy
Sandy loam
Sandy
Soil Fig. 6. Levels of acid detergent fibre (ADF) content of Dactylis glomerata and Festuca ovina as affected by treatments and different soil types (bars 1 s.e.) (F(2,162) = 3.250, P < 0.0433).
Hodgkinson et al. 1989). Some species of grasses, particularly those which naturally occur on fertile soils have high digestibility and have evolved mechanisms for tolerance to grazing (e.g. Cenchrus ciliaris, Hodgkinson et al. 1989) whereas others, particularly species adapted to infertile soils, have become very stalky with high fibre content, low leaf : stem ratio and low digestibility and palatability (e.g. Aristida ramosa,
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Harradine and Whalley 1981). D. glomerata is clearly in the former group whereas F. ovina appears to be in the latter. The results of this experiment appear to reflect both the adaptation of these two species to soils of different fertility and also the results of their co-adaptation with grazing animals (McNaughton 1985) in that D. glomerata appears to be able to tolerate grazing whereas F. ovina appears able to avoid it. The saliva application had a positive effect on RHGR in the sandy soil compared with clipped plants for D. glomerata but no effect (P > 0.05) for F. ovina. However, saliva applied to clipped plants produced increased amounts of biomass compared with clipping alone, averaged over all soils and both species. The contrast in responses to saliva between the two species was also apparent on belowground biomass with saliva associated with a reduction in F. ovina in the sandy soil only but an increase in D. glomerata in the sandy loam and the sandy soil but not in the soil of highest fertility. It is interesting that the F. ovina generally produced more underground biomass in the lowest fertility soil compared with the other two soils, whereas D. glomerata generally produced more underground biomass in the most fertile soil. Aboveground defoliation results in a decline in root mass, but there is specific evidence that it may be triggered from belowground to aboveground production in some species (Dawson et al. 2000). Increased shoot growth produced by saliva (Zhang et al. 2007) may stimulate photosynthate production and subsequent root productivity. However, environmental factors such as soil type, nutrient and precipitation may affect belowground biomass (Loeser et al. 2004). These results again reflect the general adaptation to soils of different fertility of these two species. Perhaps the species with the potential for the highest growth rate is more responsive to the thiamine in the saliva. Thiamine, in general, promotes root growth in plants (Bonner 1937; Robbins and Bartley 1937). Most of the studies in the literature showed that the effect of saliva in tall plants was greater than in short ones (Zhang et al. 2007). After the bovina saliva application the photosynthesis rate increases due to less self-shading, the reallocation of growth from elsewhere, the activation and proliferation of meristems, reduction of the rate of leaf senescence and greater water-use efficiency (Teng et al. 2010). Plant growth responses to saliva or exogenously applied thiamine, have widely varied responses in the literature (Reardon et al. 1972; McNaughton 1985; Dyer et al. 1993; Zhang et al. 2007; Teng et al. 2010) and the results presented in this study contribute to the knowledge about these responses. Generally, young plant tissues and plants grown in nutrientrich soils have better forage quality (Cilliers et al. 1995, 1997; Aydin and Uzun 2005; Erkovan et al. 2009). It is interesting that saliva application had no effect on protein or NDF content of the forage produced, decreased ADF content of D. glomerata but increased that of F. ovina. These changes indicate a possible increase in digestibility of the forage produced by D. glomerata under grazing but a decrease for F. ovina. These differences can again be possibly explained by the differences in these two species in terms of their different mechanisms for grazing tolerance. D. glomerata is taller, more leafy with higher palatability and better adapted to fertile soils than the shorter growing, more stemmy F. ovina.
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Conclusions These results go some way towards explaining some of the confusion in the literature concerning the effects of grazing animal saliva and clipping on different forage species, particularly those with different adaptations for co-existing with grazing animals. Belowground production responses interacted with several variables, including soil type. Saliva application had little effect on forage quality except to enhance existing differences between that of the two species chosen for the study. The interacting effects of saliva deposition and defoliation frequency on production were not addressed in this study. However, this study reinforces one of the essential differences between grazing and clipping treatments when examining the interactions among different forage species in grazed landscapes. Acknowledgements We are grateful to Dr Walter H. Schacht, Department of Agronomy and Horticulture, University of Nebraska, Lincoln, USA, and Dr R. D. B. Whalley, Botany, School of Environmental and Rural Sciences, University of New England, Armidale, Australia for his critical review and valuable advice.
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Manuscript received 18 October 2010; accepted 11 August 2011
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