Annals of the Sri Lanka Department of Agriculture. 2008.10:105-116.
EFFECT OF PLANT DENSITY AND NUTRIENT MANAGEMENT ON HYBRID MAIZE (Zea mays L.) GROWN ON RAIN-FED UPLANDS M.A.P.W.K. MALAVIARACHCHI, K.P. JAYASIRI and D.M.G. ETHAKADE Field Crops Research and Development Institute, Mahailluppallama
ABSTRACT Hybrid varieties do not equally perform as Open Pollinated Varieties (OPV) under the same set of management practices used for OPV. Agronomic studies reported on maize in Sri Lanka are related to OPV. Therefore, this study was conducted to develop an appropriate agronomic management package with reference to plant density, N, P and K requirements for the locally developed hybrid maize variety “Samapath” under rain-fed upland condition. The experiments were conducted as onfarm research at Anuradhapura (ANP) and Monaragala (MNG) districts during maha 2006/07 and maha 2007/08. Effects of N, P and K were tested against different plant densities in three independent studies. Three N levels (100, 150, 200 kg/ha), three P levels (22.5, 45, 67.5 kg/ha) and three K levels (15, 30, 45 kg/ha) were used under low, medium and high plant densities (55555, 88888, 111111 plants/ha) with the variety Sampath. Measured growth parameters and grain yield showed an increasing trend up to 200 kgN per hectare but no response was observed with respect to increasing P and K levels. Grain yield and number of seeds per cob decreased at medium and at high densities compared to low density and no differences were observed between medium and high density. With increasing density, plant height showed an increasing trend whereas leaf area did not vary. Nitrogen rate and plant density suitable for the hybrid variety “sampath” under rain-fed conditions were 150 kgN/ha and 55555 plants/ha, respectively. Application of P and K based upon a soil test would be highly advisable and further studies are needed to determine how often these two nutrients should be added to the same piece of land. KEYWORDS: Hybrids, Plant density, N P K requirement.
INTRODUCTION Exotic hybrid maize varieties have become popular among Sri Lankan farmers in the recent past due to their high yield potential. All these varieties have been imported as there were no locally developed hybrids available. In 2005, the Department of Agriculture (DOA) released the first local hybrid variety named ‘sampath’ which had a yield potential of 9 t/ha under current management practices adopted for the OPV (Karunarathna, 2004). However, Hybrid varieties which are known to be highly input responsive would not equally perform as OPV’s under the same set of management practices used for the OPV. Therefore, raising of hybrid maize either under supplementary irrigation or under total rain fed upland conditions demands an intensive approach with appropriate management packages to realize higher yields. Components of such an intensive package necessarily include agronomic practices, particularly optimum plant density and fertilizer application.
106 MALAVIARACHCHI et al.
The yield of any crop depends to a great extent on the number of plants per unit area which in turn depends on the variety, agro-climatic status of the area, the productivity of soil and the amounts of inputs supplied. Malaviarachchi et al. (2007) reported that the plant density for hybrid maize could be increased up to 88888 plants per hectare under supplementary irrigation. However, there was no research evidence to support that we could go for the same density under rain fed conditions which accounts for 90 % of total maize extent in Sri Lanka. The optimum plant population for maximum economic yield varies with cultivar and environment (Bruns and Abbas, 2005) and the actual nutrient uptake has been found to vary widely depending on the fertility level of soil and environmental conditions (Berger, 1962). Interaction between the variety and the environment had been observed during the development process of the local hybrid variety by Karunarathna (2001). Hybrids which are known to be stress tolerant compared to earlier cultivars due to some characters like erect leaves are grown at higher plant populations to increase the interception of solar radiation (Tollenaar, 1991). Maize has a high demand for nitrogen. Maize needs mostly N, more K and little P for its optimum growth. Nagarajah (1970) reported that the objective of K dressing was to prevent lodging with high N application with respect to OPVs. However, due to preferential absorption and large removal of K by maize compared to several other crops like chilli, and legumes etc. grown on upland soils of Dry Zone (Amarasiri and Perera, 1975) and less P content in RBE soils (Amarasiri and Perera, 1975; Kalpage, 1974) there is a need to test P and K requirements also for Hybrid maize. Studies related to plant density and nutrient requirement on maize were fairly old and were solely conducted on OPV’s (Nagarajah, 1970; Hindagla et al., 1971; Kathirgamathaiyah and Dharmarajah, 1970) while related information with respect to hybrid maize under local conditions is scarce. Since there is a need to provide a complete agronomic package for the farmer along with the newly released local hybrid variety, the objective of this study was to develop an appropriate agronomic management package with reference to plant density, N, P and K requirements for the locally developed hybrid maize variety “Samapath� under total rain-fed upland condition. MATERIALS AND METHODS The experiment was conducted as an on-farm research during maha 2006/07 and maha 2007/08 seasons at Anuradhapura (Low Country Dry Zone-DL1b) and Monaragala (Low country Intermediate Zone-IL1c) districts where maize was extensively grown by the farmers. Three independent
PLANT DENSITY AND NUTRIENT MANAGEMENT OF MAIZE 107
studies were carried out for N, P and K as no interactions have been observed among the three nutrients on growth of maize (Kathiragamathaiyah and Dharmarajah, 1970; Hindagala et al., 1971) in each district using 3 farmers from the same land area. The three N, P and K levels used were 100 kg/ha, 150 kg/ha, 200 kg/ha of N, 22.5, 45, 67.5 kg/ha of P 2O5 and 15, 30, 45 kg/ha of K2O under three plant densities (55555 plants/ha at 60 cm x 30 cm spacing, 88888 plants/ha at 75 cm x 15 cm spacing and 111111 at 60 cm x 15 cm spacing). For the independent experiment of N, levels of P and K used were one and half times of the current DOA recommendation (70 kg/ha P 2O5 and 45 kg/ha K2O) in order to avoid any limitations with increasing N levels. In the independent experiment of P, level of N used was the maximum level used in the N study (200 kg/ha) and K level was one and half times of the current recommendation (45 kg/ha K2O). In the independent experiment of K, level of N used was the maximum level used in the N study (200 kg/ha) and P level was one and half times of the current recommendation (70 kg/ha P2O5). The treatments were replicated three times and plots were arranged in a split plot design in each site taking fertilizer levels as the main plots and densities as the sub plots. Local hybrid maize variety sampath was used in all experiments. The sub plot size was 4.2 m x 3.6 m. Other management practices were followed as stated in the “Technoguide�, (Anon., 1990). Initial status of soil P, K, organic matter, pH, and EC were determined before the crop establishment. Yield components were measured using the net plot area while a sample of 10 randomly selected plants from each plot was taken to measure the plant height and leaf area. The leaf area was estimated using the leaf product method viz. length x maximum width x 0.75, as proposed by Montgomery (1911) using the ear bearing leaf (Blackmer and Schepers, 1995). All the data were analyzed using SAS statistical software. RESULTS AND DISCUSSION Rainfall data obtained from the nearest meteorological stations are illustrated in Figures 1a and 1b. Rainfall in Anuradhapura was lower compared to Monaragala in both seasons whereas the initial status of soil P, K, organic matter, pH, and EC were more or less similar in both seasons (Table 1). As there were no interactions observed between plant density and fertilizer levels, only main effects are discussed in all three experiments.
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600
50 0
400
300
200
10 0
0 O cto b er
N o vem b er
D ecem b er
A N P
January
M NG
Figure 1a. Rainfall during maha 2006/07.
450 400 350 300 250 200 15 0 10 0 50 0 O c to be r
N o vem ber A NP
D ecem ber M NG
Figure 1b. Rainfall during maha 2007/08.
J a n u a ry
PLANT DENSITY AND NUTRIENT MANAGEMENT OF MAIZE 109 Table 1. Soil characteristics of different locations. Location Monaragala
Anuradhapura
Site 1 (Nitrogen) Site 2 (Phosphorous) Site 3 (Potassium) Site 1 (Nitrogen) Site 2 (Phosphorous) Site 3 (Potassium)
pH (1:2soil: water) 6.5- 6.6
EC (ds/m)
P (ppm)
K (ppm)
OM (%)
0.21-0.23
8-12
380-390
2.35-2.67
6.2- 6.4
0.25-0.27
10-15
300-315
1.90-2.20
6.4- 6.6
0.25- 0.26
10-12
205-210
2.00-2.56
6.6- 6.7
0.21-0.23
9-14
320-325
1.30-1.98
6.4-6.6
0.24-0.25
12-15
250-275
1.85-2.05
6.4- 6.6
0.21-0.25
10-16
290-305
2.25-2.75
Effect of nutrient management Nitrogen Leaf area of the ear bearing leaf showed an increasing trend up to 150 kgN/ha and beyond that there was no increase observed in both locations (Table 2). Plant height showed a similar trend in Anuradhapura but in Monaragala it increased continuously up to 200 kg/ha. Out of the yield parameters, grain yield increased by 11-13% compared to 100 kgN/ha (Table 3). However, there was no such increase observed beyond 150 kgN/ha. Since there were no significant difference observed in number of cobs per plant and 100 seed weight and number of seeds per cob was 10-14% higher at high N levels in both locations, the main contributing factor for grain yield difference was the number of seeds per cob. Other studies have also proved that the yield was more strongly associated with grain number per ear (Monneveux et al., 2005; Lemcoff and Loomis, 1986) in addition to the number of ears per unit area (Russell, 1968). Table 2. Effect of different Nitrogen rates on some growth parameters of Hybrid maize variety “Sampath�. Nitrogen level (kg/ha)
Ear bearing leaf area (cm2)
Plant height (cm)
ANP MNG ANP MNG 100 374 b 411 b 217 b 203 c 150 465 a 504 a 252 a 236 b 200 444 a 536 a 249 a 266 a CV (%) 5.4 15.0 2.0 9.1 Values followed by the same letter are not significantly different, following DMRT at p=0.05
110 MALAVIARACHCHI et al. Table 3. Effect of different Nitrogen rates on some yield parameters of Hybrid maize variety “Sampath”. Nitrogen level (kg/ha)
Cobs/plant
Seeds/cob
100 seed weight (g)
Grain yield (kg/ha)
ANP MNG ANP MNG ANP MNG ANP MNG 100 0.95 a 0.94 a 403 b 466 b 25.6 a 31.9 a 4358 b 5323 b 150 0.93 a 0.93 a 458 a 515 a 26.0 a 31.7 a 4825 a 6017 a 200 0.94 a 0.94 a 444 a 483 b 25.5 a 31.3 a 4808 a 5292 b CV (%) 5.2 5.8 3.9 5.1 2.7 6.6 3.9 9.7 Values followed by the same letter are not significantly different, following DMRT at p=0.05
Phosphorous All the growth (Table 4) and yield (Table 5) parameters measured were not significant with respect to different P rates. This may be due to the accumulation of P in the soil due to continuous application for a long period by farmers which was also reflected by high soil P content of the sites where experiments were conducted (Table 1). Although most of the areas in the dry zone of Sri Lanka are low in P (Kalpage, 1974), repeated application would increase the P in soil to a point where application of P could be uneconomic and a response to the added P could hardly be expected (Amarasiri and Perera, 1975). Nagarajah (1970) reported that OPVs did not response to added P above 30 kg P2O5/ha. Therefore, application of this nutrient based on a soil test would be highly advisable. Table 4. Effect of different P rates on some growth parameters of Hybrid maize variety “Sampath”. Ear bearing leaf area (cm2) Plant height (cm) ANP MNG ANP MNG 22.5 422.4 a * 247 a * 45 396.3 a * 254 a * 67.5 423.0 a * 253 a * CV (%) 6.9 8.6 Values followed by the same letter are not significantly different, following DMRT at p=0.05 * Not measured P2O5 level (kg/ha)
Table 5. Effect of different P rates on some yield parameters of Hybrid maize variety “Sampath”. P2O5 level (kg/ha)
Cobs/plant
Seeds/cob
100 seed weight Grain yield (g) (kg/ha) ANP MNG ANP MNG ANP MNG ANP MNG 22.5 0.93a 0.96 ab 409a 338 a 24.1a 24.3 a 4525a 3500 a 45 0.95a 0.98 a 415a 350 a 24.8a 23.9 a 4428a 3880 a 67.5 0.93a 0.88 b 407a 344 a 25.6a 23.6 a 4517a 4420 a CV (%) 3.2 9.7 3.0 10.8 6.1 6.3 5.9 20.3 Values followed by the same letter are not significantly different, following DMRT at p=0.05
PLANT DENSITY AND NUTRIENT MANAGEMENT OF MAIZE 111
Potassium All the tested growth (Table 6) and yield (Table 7) parameters were not affected by K rates in both locations. Generally Reddish Brown Earth soils are rich in K (Panabokke, 1996) and therefore, there would not be a response for the added K fertilizer. Nagarajah (1970) and Hindagla (1971) reported that no response was found for K as high exchangeable K in major maize growing areas in Sri Lanka. However, K is necessary for the growth of maize plant, especially to prevent lodging under high N application (Nagarajah, 1970). Table 6. Effect of different K rates on some growth parameters of Hybrid maize variety “Sampath”. Ear bearing leaf area (cm2) Plant height (cm) ANP MNG ANP MNG 15 450.0 a 482 a 232 a 225 a 30 435.0 a 422 a 231 a 244 a 45 398.0 a 410 a 235 a 230 a CV (%) 11.6 18.2 5.2 16.0 Values followed by the same letter are not significantly different, following DMRT at p=0.05 K2O level (kg/ha)
Table 7. Effect of different K rates on some yield parameters of Hybrid maize variety “Sampath”. K2O level (kg/ha)
Cobs/plant
Seeds/cob
100 seed weight Grain yield (g) (kg/ha) ANP MNG ANP MNG ANP MNG ANP MNG 15 0.93 a 0.94 a 408 a 469 a 23.0 a 25.7 a 5143 a 5657 a 30 0.93 a 0.94 a 380 a 482 a 24.1 a 25.0 a 5218 a 5925 a 45 0.95 a 0.93 a 379 a 479 a 23.0 a 24.9 a 5693 a 5909 a CV (%) 3.0 2.0 8.9 7.9 7.5 4.0 21.5 7.0 Values followed by the same letter are not significantly different, following DMRT at p=0.05
Effect of plant density Cob number per plant In the N study (Table 8) and the P study (Table 9), cob number per plant was not affected by the different densities. This was in agreement with Daynard and Muldoon (1983) who reported that there was no increase in number of barren plants with increasing plant density in recently developed hybrids as in the case of old hybrid varieties developed before 1970 which responded to super optimal plant populations with increase in barren plants. However, in the K study it has decreased by 7% with increasing density in Anuradhapura whereas no differences were found in Monaragala (Table 10).
112 MALAVIARACHCHI et al.
Seed number per cob In the N study, decrease in seed number in the medium density compared to the low density was 7% in Anuradhapura and 13% in Monaragala. However, in Monaragala, further reduction (21%) was observed at the high density (Table 8). In the P study, seed number increased by 13% at medium density and then reduced by 20% in Monaragala (Table 9). There was no significant difference in seed number between low and medium density but decreased by 7% at the high density in Anuradhapura. In the K study, no significant difference was observed with the increase in plant density in Anuradhapura but the seed number decreased with the increasing density by 9-14% in Monaragala (Table 10). Thus, on average, a decreasing trend was observed in terms of seed number with the increase in density. Dien (1997) also observed negative correlations between yield components and densities under normal NPK levels. Grain yield In the N study, there was a grain yield reduction both at Anuradhapura (9-11%) and Monaragala (16-32%) at high plant densities compared to low plant density (Table 8). There was no significant difference between medium and high densities in Anuradhapura whereas in Monaragala continuous decrease was observed from low to high densities tested. In the P study, grain yield increase between low and medium densities was not significant whereas at high density it decreased by 7% in Anuradhapura and 23% in Monaragla (Table 9). With reference to K trial (Table 10), although significant variations in grain yield was observed among treatments, data could not be validated due to very high CV in Monaragala. However, a 12% yield reduction was observed at higher densities at Monaragala. All the grain yield reductions observed at high populations levels could be due to high competitiveness under the same set of inputs at different densities under rainfed conditions which could create water stress for the crop. In irrigated studies, it has been reported that overall grain yield of maize increased due to increasing number of cobs per hectare under higher plant density (Dien, 1997). Berger (1962) concluded that planting too closely would result in smaller cobs but large cobs are secured only by sacrificing a considerable yield. However, some authors have observed a reduction in kernel rows and cob diameter at high plant densities, but an increase in grain yield (Hlaning, 1996; Dien, 1997).
PLANT DENSITY AND NUTRIENT MANAGEMENT OF MAIZE 113
100 seed weight 100 seed weight was not different among densities in both locations. A similar trend was also observed by Hlaning (1996) in several plant density studies with maize. Table 8. Response of some yield parameters to plant density in the Nitrogen study. Plant density (plants/ha)
Cobs/plant
Seeds/cob
100 seed weight (g)
Grain yield (kg/ha)
ANP MNG ANP MNG ANP MNG ANP MNG 55555 0.97 a 0.93 a 454 a 552 a 25.6 a 32.4 a 4996 a 6592 a 88888 0.92 a 0.96 a 424 b 478 b 25.7 a 31.4 a 4470 b 5532 b 111111 0.93 a 0.92 a 426 b 435 c 25.7 a 31.2 a 4526 b 4508 c CV (%) 5.2 5.2 5.4 3.9 3.3 2.7 3.9 3.9 Values followed by the same letter are not significantly different, following DMRT at p=0.05 Table 9. Response of some yield parameters to plant density in the Phosphorous study. Plant density (plants/ha)
Cobs / plant
Seeds/cob
100 seed weight (g)
Grain yield (kg/ha)
ANP MNG ANP MNG ANP MNG ANP MNG 55555 0.94 0.95 a 421 a 353 b 25.5 a 24.2 a 4588 a 4205 a 88888 0.93 0.97 a 419 a 397 a 25.0 a 24.2 a 4589 a 4275 a 111111 0.92 0.91 a 391 b 283 c 24.0 a 23.5 a 4292 b 3250 b CV (%) 3.2 9.7 3.0 10.8 6.1 6.3 5.9 20.3 Values followed by the same letter are not significantly different, following DMRT at p=0.05 Table 10. Response of some yield parameters to plant density in the Potassium study. Plant density (plants/ha)
Cobs per plant
Seeds/cob
100 seed weight (g)
Grain yield (kg/ha)
ANP MNG ANP MNG ANP MNG ANP MNG 55555 0.99 a 0.94 a 450 b 517 a 22.3 a 25.3 5135 ab 6343 a 88888 0.92 b 0.93 a 363 b 468 b 23/7 a 24.7 6243 a 5607 b 111111 0.90 b 0.93 a 355 b 444 b 23.1 a 25.6 4675 b 5541 b CV (%) 5.1 2.0 8.9 7.9 7.5 4.0 21.5 7.0 Values followed by the same letter are not significantly different, following DMRT at p=0.05
Leaf area and plant height The data showed that there were no significant difference observed in leaf area with the different densities in both locations (Tables 8, 10 and 12). However, plant height has increased at high densities indicating a negative influence on light penetration into the canopy causing low yields at high densities in all three trials.
114 MALAVIARACHCHI et al. Table 11. Response of some growth parameters to plant density in the Nitrogen study. Plant density (plants/ha)
Ear bearing leaf area (cm2)
Plant height (cm)
ANP MNG ANP MNG 55555 427 a 474 a 228 b 196 b 88888 426 a 498 a 244 a 245 a 111111 430 a 479 a 245 a 263 a CV (%) 5.4 5.4 12.0 2.0 Values followed by the same letter are not significantly different, following DMRT at p=0.05 Table 12. Response of some growth parameters to plant density in the Phosphorous study. Plant density (plants/ha)
Ear bearing leaf area (cm2)
Plant height (cm)
ANP MNG ANP MNG 55555 414.0 a * 235 b * 88888 422.8 a * 254 ab * 111111 405.1 a * 265 a * CV (%) 6.9 8.6 Values followed by the same letter are not significantly different, following DMRT at p=0.05 Table 13. Response of some growth parameters to plant density in the Potassium study. Plant density (plants/ha)
Ear bearing leaf area (cm2)
Plant height (cm)
ANP MNG ANP MNG 55555 467 a 442 a 210 a 199 b 88888 450 a 439 a 249 a 248 a 111111 408 a 432 a 240 a 250 a CV% 11.6 18.2 5.2 16.0 Values followed by the same letter are not significantly different, following DMRT at p=0.05
CONCLUSIONS Nitrogen and plant density suitable for the hybrid variety “sampath� when it is grown under total rain-fed conditions are 150 kgN/ha, and 55555 plants/ha, respectively. Application of P and K based upon a soil test would be highly advisable and further studies are needed to determine how often these two nutrients should be added to the same piece of land based on the existing soil P contents. ACKNOWLEDGEMENTS Author wishes to thank Council for Agricultural Research Policy for providing funds to conduct this study and the Agriculture Instructors in Nachchaduwa, Rambewa in Anuradhapura district and Ethimale in Monaragala district for the extensive support given in on-farm experiments. REFERENCES
PLANT DENSITY AND NUTRIENT MANAGEMENT OF MAIZE 115
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116 MALAVIARACHCHI et al. Panabokke, C.R. 1996. Soils and Agro-ecological Environment of Sri Lanka. Natural Resources Series No. 2 Natural Resources Energy and Science Authority, Colombo Sri Lanka. 37p. Russel, W.A. 1968. Test cross of one-and two ears types of Corn Belt maize inbreds. I. Performance at four plant stand densities. Crop Science 8:244-247. Tollenaar, M. 1991. Physiological basis of genetic improvement of maize hybrids grown in Ontario from 1959 to 1988. Crop Science 31: 119-124.