113
3.2.3.4 Effect of nitrogen dose and planting density on corn yield components
i) Effect of nitrogen dose and planting density on ear length
o Corn length through protein doses
In Long An, the cob length in the Winter-Spring crop reached its highest at 280 kg N/ha (17.6 cm) and was statistically different from all other treatments (Table 3.30). In the Spring-Summer crop, the cob length reached its highest at 280 kg N/ha (14.8 cm) and was not different from the treatments of 240 kg N/ha (14.0 cm) and 200 kg N/ha (14.1 cm); the treatments of 120 kg N/ha and 160 kg N/ha had the lowest cob length (Table 3.31).
In Dong Thap, the ear length in both crops reached the highest level at 280 kg N/ha (18.9 - 19.4 cm) and was not different from the treatments of 240 kg N/ha (18.6 - 19.0 cm) and 200 kg N/ha (18.2 - 18.5 cm) but the ear length tended to decrease (Table 3.30 and Table 3.31). The treatments of 120 kg N/ha (16.3 - 17.1 cm) and 160 kg N/ha (17.6 - 18.1 cm) had the lowest ear length. Planting density from 57,000 to 71,000 plants/ha resulted in the highest cob length. In the winter-spring crop, cob length at a density of 84,000 plants/ha showed no difference compared to that at a density of 84,000 plants/ha (18.8 cm and 18.5 cm, respectively).
o Corn length through planting densities
Ear length has an indirect effect on corn yield through the number of grains/row and grain weight (Sumalini and Manjulatha, 2012) [149]. Planting density from 5.7 to 7.1 thousand plants/ha leads to the highest ear length, increasing density to higher levels reduces ear length (Table 3.30 and Table 3.31). The results reported by Fromme et al. (2019) [89] show that increasing density reduces ear length, number of grains/row and ultimately reduces corn yield.
In conclusion, nitrogen fertilizer dose and planting density had statistically significant effects on ear length at experimental sites and across growing seasons. Increasing nitrogen dose resulted in increased ear length while increasing planting density decreased ear length at experimental sites and growing seasons.
114
Table 3.30 Cob length of hybrid corn MN585 (cm) through nitrogen doses and planting density, Winter-Spring crop 2016 - 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
11.0 | 8.4 | 7.1 | 5.7 | Medium | 11.0 | 8.4 | 7.1 | 5.7 | Medium | |
120 | 13.5 | 14.7 | 15.7 | 15.1 | 14.7 d | 16.3 | 17.2 | 17.1 | 17.7 | 17.1 d |
160 | 14.6 | 16.1 | 15.8 | 16.8 | 15.8 c | 17.3 | 17.7 | 18.8 | 18.7 | 18.1 c |
200 | 14.8 | 15.4 | 16.5 | 17.3 | 16.0 c | 17.5 | 18.4 | 19.1 | 19.0 | 18.5 bc |
240 | 15.0 | 15.9 | 17.9 | 17.8 | 16.7b | 17.3 | 19.3 | 19.1 | 20.4 | 19.1 ab |
280 | 15.8 | 17.8 | 18.1 | 18.7 | 17.6a | 17.6 | 19.8 | 20.1 | 20.1 | 19.4a |
Medium | 14.7 c | 16.0b | 16.8a | 17.2a | 17.2 c | 18.4b | 18.8 ab | 19.2a | ||
CV (%) | 9.32 | 7.13 | ||||||||
F (N) | 27.46* | 17.52* | ||||||||
F (MD) | 35.34* | 20.1* | ||||||||
F (N˟MĐ) | 1.3 Ns | 1.11 Ns | ||||||||
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In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
Table 3. 31 Ear length of hybrid corn MN585 (cm) through nitrogen doses and planting density, Spring-Summer crop 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
14.3 | 9.5 | 7.1 | 5.7 | Medium | 14.3 | 9.5 | 7.1 | 5.7 | Medium | |
120 | 11.5 | 11.9 | 12.6 | 14.0 | 12.5 c | 15.1 | 16.3 | 16.7 | 17.0 | 16.3 c |
160 | 11.8 | 13.0 | 14.3 | 14.7 | 13.5b | 16.3 | 17.4 | 17.8 | 18.8 | 17.6b |
200 | 12.7 | 14.3 | 14.7 | 14.8 | 14.1 ab | 16.7 | 17.4 | 19.3 | 19.4 | 18.2 ab |
240 | 12.0 | 14.3 | 14.7 | 15.0 | 14.0 ab | 18.1 | 18.2 | 19.0 | 19.0 | 18.6a |
280 | 13.5 | 14.7 | 15.3 | 15.8 | 14.8a | 17.9 | 18.8 | 19.1 | 19.7 | 18.9a |
Medium | 12.3 c | 13.6b | 14.3 ab | 14.8a | 16.8 c | 17.6b | 18.4a | 18.8a | ||
CV (%) | 11.52 | 8.32 | ||||||||
F (N) | 6.96* | 12.77* | ||||||||
F (MD) | 13.92* | 11.34* | ||||||||
F (N˟MĐ) | 0.36 Ns | 0.49 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
115
i) Effect of nitrogen dose and planting density on corn diameter
The results presented in Table 3.32 and Table 3.33 show that nitrogen doses and planting densities have different effects on corn diameter in different locations and growing seasons. In general, corn diameter is highest in the Winter-Spring crop in Dong Thap and lowest in the Spring-Summer crop in Long An.
In Long An, corn diameter did not differ across nitrogen doses and planting density (reaching 4.2 - 4.5 cm) in the Winter-Spring crop but did differ across nitrogen levels and planting density in the Spring-Summer crop. Increasing nitrogen doses led to increased corn diameter (3.9 cm) and reached its highest level at 200 kg N/ha; density up to 71,000 plants/ha led to corn diameter (3.8 cm) that was not different from density 57,000 plants/ha (3.9 cm).
Nitrogen fertilizer dose had a statistically significant effect on corn diameter in Dong Thap. Low nitrogen dose (160 kg N/ha in the Winter-Spring crop and 120 kg N/ha in the Spring-Summer crop) resulted in low corn diameters, which were different from the treatments with high nitrogen doses. Nitrogen levels from 200 kg N/ha in the Winter-Spring crop and from 160 kg N/ha in the Spring-Summer crop resulted in high corn diameters (4.8 cm and 5.4 cm, respectively). Continuing to increase nitrogen dose did not result in statistically significant differences in corn diameter. Planting density had a statistically significant effect on corn diameter in the Spring-Summer crop. Increasing density reduced corn diameter. Corn diameter averaged 4.7 - 4.8 cm in the Winter-Spring crop and reached a high density of 71,000 plants/ha (4.6 cm) in the Spring-Summer crop.
Experimental results showed that corn diameter was affected differently by seasons and planting locations. In general, increasing the amount of nitrogen fertilizer led to an increase in corn diameter because corn plants absorbed more nutrients for growth and grain formation. Increasing planting density decreased corn diameter due to competition for nutrients and light during growth. The report of Sarwar et al. (2016) [141] also showed that increasing density decreased corn diameter.
In summary, at 200 - 240 kg N/ha and a density of 71,000 plants/ha, the corn diameter achieved high results across the growing seasons at both experimental sites.
116
Table 3.32 Corn diameter of hybrid corn MN585 (cm) through nitrogen doses and planting density, Winter-Spring crop 2016 - 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
11.0 | 8.4 | 7.1 | 5.7 | Medium | 11.0 | 8.4 | 7.1 | 5.7 | Medium | |
120 | 4.2 | 4.1 | 4.2 | 4.3 | 4.2a | 4.6 | 4.6 | 4.6 | 4.6 | 4.7b |
160 | 4.2 | 4.3 | 4.2 | 4.4 | 4.3a | 4.7 | 4.7 | 4.6 | 4.7 | 4.7b |
200 | 4.2 | 4.3 | 4.4 | 4.4 | 4.3a | 4.7 | 4.7 | 4.8 | 4.8 | 4.8a |
240 | 4.1 | 4.4 | 4.5 | 4.6 | 4.4a | 4.8 | 4.8 | 4.8 | 4.9 | 4.8a |
280 | 4.3 | 4.4 | 4.4 | 4.6 | 4.4a | 4.7 | 4.9 | 4.7 | 4.9 | 4.8a |
Medium | 4.2a | 4.3a | 4.4a | 4.5a | 4.7a | 4.7a | 4.7a | 4.8a | ||
CV (%) | 6.12 | 2.72 | ||||||||
F (N) | 1.22 Ns | 8.55* | ||||||||
F (MD) | 2.42 Ns | 0.95 Ns | ||||||||
F (N˟MĐ) | 0.39 Ns | 0.83 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
Table 3. 33 Corn diameter of hybrid corn MN585 (cm) through nitrogen doses and planting density, Spring-Summer crop 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
14.3 | 9.5 | 7.1 | 5.7 | Medium | 14.3 | 9.5 | 7.1 | 5.7 | Medium | |
120 | 3.3 | 3.5 | 3.5 | 3.6 | 3.5b | 4.0 | 4.3 | 4.4 | 4.3 | 4.2b |
160 | 3.4 | 3.6 | 3.8 | 3.9 | 3.7 ab | 4.3 | 4.6 | 4.6 | 4.6 | 4.5a |
200 | 3.7 | 3.9 | 3.9 | 4.1 | 3.9a | 4.4 | 4.5 | 4.8 | 4.8 | 4.6a |
240 | 3.2 | 3.9 | 3.9 | 4.1 | 3.8a | 4.3 | 4.6 | 4.7 | 4.7 | 4.6a |
280 | 3.5 | 3.6 | 3.7 | 4.0 | 3.7 ab | 4.4 | 4.6 | 4.6 | 4.7 | 4.6a |
Medium | 3.4 c | 3.7b | 3.8 ab | 3.9a | 4.3 c | 4.5b | 4.6a | 4.6a | ||
CV (%) | 9.13 | 5.28 | ||||||||
F (N) | 4.14* | 17.01* | ||||||||
F (MD) | 10.25* | 25.23* | ||||||||
F (N˟MĐ) | 0.86 Ns | 0.6 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
117
ii) Effect of nitrogen dose and planting density on number of rows/ear
The results of the effects of nitrogen fertilizer dose and planting density on the number of rows/ear are presented in Table 3.34 and Table 3.35.
The experimental results showed that different doses of N fertilizer did not have a statistical effect (P>0.05) on the number of rows/ear at both experimental sites across the growing seasons. This result is also consistent with the report of Mandić et al. (2016) [116], the number of rows/ear is a genetic trait that depends more on the characteristics of the variety than on the growing conditions. The report of Nemati (2012) [119] also showed that the number of rows was not affected by the dose of nitrogen fertilizer.
Different planting densities did not affect the number of rows/ear in Dong Thap conditions. However, increasing planting density resulted in a statistically significant decrease in rows/ear in Long An. Experimental results showed that increasing the density to 71,000 plants/ha resulted in the number of rows/ear not being different from the density of 57,000 plants/ha (reaching 13.7 - 14.3 cm in the Winter-Spring crop, 13.3 - 13.5 cm in the Spring-Summer crop). Reports by Abuzar et al. (2011) [58], Sarwar et al. (2016) [141] also showed that the number of rows/ear was affected by planting density, increasing the planting density to high levels resulted in a decrease in the number of rows/ear compared to low planting density.
In summary, nitrogen dosage did not affect the number of rows/ear at the experimental sites. Increasing planting density did not affect the number of rows/ear under Dong Thap conditions, however, increasing planting density resulted in a statistically significant decrease in rows/ear in Long An.
118
Table 3.34 Number of rows/ear of hybrid corn MN585 through nitrogen doses and planting density, Winter-Spring crop 2016 - 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
11.0 | 8.4 | 7.1 | 5.7 | Medium | 11.0 | 8.4 | 7.1 | 5.7 | Medium | |
120 | 12.0 | 12.7 | 12.7 | 13.3 | 12.7a | 13.8 | 13.6 | 13.3 | 13.1 | 13.5a |
160 | 12.0 | 12.7 | 13.7 | 14.0 | 13.1a | 12.9 | 14.0 | 13.1 | 13.8 | 13.4a |
200 | 12.7 | 13.3 | 14.0 | 14.7 | 13.7a | 13.1 | 13.8 | 13.6 | 13.8 | 13.6a |
240 | 12.7 | 13.3 | 14.0 | 14.7 | 13.7a | 12.9 | 13.6 | 12.7 | 13.6 | 13.2a |
280 | 12.0 | 13.3 | 14.0 | 14.7 | 13.5a | 13.1 | 13.1 | 13.6 | 13.3 | 13.3a |
Medium | 12.3 c | 13.1b | 13.7 ab | 14.3a | 13.2a | 13.6a | 13.2a | 13.5a | ||
CV (%) | 9.03 | 5.18 | ||||||||
F (N) | 2.24 Ns | 0.55 Ns | ||||||||
F (MD) | 10.58* | 1.3 Ns | ||||||||
F (N˟MĐ) | 0.18 Ns | 0.71 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
Table 3.35 Number of rows/ear of hybrid corn MN585 through nitrogen doses and planting density, Spring-Summer crop 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
14.3 | 9.5 | 7.1 | 5.7 | Medium | 14.3 | 9.5 | 7.1 | 5.7 | Medium | |
120 | 12.0 | 12.4 | 12.4 | 12.9 | 12.4a | 13.1 | 13.3 | 13.1 | 13.5 | 13.3a |
160 | 12.0 | 12.4 | 13.1 | 13.5 | 12.8a | 14.0 | 12.7 | 13.6 | 13.3 | 13.4a |
200 | 12.4 | 13.1 | 13.8 | 13.1 | 13.1a | 13.6 | 13.4 | 14.2 | 13.8 | 13.7a |
240 | 12.4 | 12.9 | 13.3 | 14.0 | 13.1a | 13.5 | 14.4 | 14.2 | 14.0 | 14.1a |
280 | 12.0 | 13.3 | 13.5 | 14.2 | 13.3a | 13.5 | 13.1 | 14.0 | 14.0 | 13.7a |
Medium | 12.2 c | 12.8b | 13.3 ab | 13.5a | 13.6a | 13.4a | 13.8a | 13.7a | ||
CV(%) | 7.17 | 5.19 | ||||||||
F (N) | 2.14 Ns | 2.52 Ns | ||||||||
F (MD) | 8.00* | 1.29 Ns | ||||||||
F (N˟MĐ) | 0.51 Ns | 1.05 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
119
iii) Effect of nitrogen dose and planting density on number of seeds/row
Number of grains/row is a factor that directly affects corn yield (Sumalini and Manjulatha, 2012) [149]. The results of the study showed that nitrogen fertilizer dose and planting density had different effects on number of grains/row depending on location and crop season.
In Long An, nitrogen fertilizer dose and planting density had a statistically significant effect (P<0.05) on the number of grains/row in both experimental crops. The lowest number of grains/row was in the 120 kg N/ha treatment, increasing the nitrogen dose from 160 - 280 kg N/ha resulted in a statistically insignificant number of grains/row in both the Winter-Spring (32.7 - 33.9 grains/row) and Spring-Summer (27.7 - 28.9 grains/row) crops. Increasing planting density reduced the number of grains/row in both crops, increasing density from 57,000 - 71,000 plants/ha resulted in a high number of grains/row and no statistically insignificant number of grains/row in both the Winter-Spring (34.4 - 36.1 grains/row) and Spring-Summer (29.4 - 31.1 grains/row) crops (Table 3.36 and Table 3.37).
In Dong Thap, increasing the nitrogen dose from 120 - 280 kg N/ha resulted in a statistically significant (P<0.05) reduction in the number of grains/row in the Winter-Spring crop (Table 3.36). In contrast, the number of grains/row in the Spring-Summer crop ranged from 34.5 - 36.2 grains/row and tended to increase when increasing the nitrogen level from 120 - 240 kg N/ha but there was no statistical difference (P>0.05) and the number of grains/row decreased (35.6 grains/row) when increasing the nitrogen dose to 280 kg N/ha. The number of grains/row reached its highest at 240 kg N/ha (36.2 grains/row) (Table 3.37). Increasing planting density resulted in a reduction in the number of grains/row (P<0.05) in both crops. In the Winter-Spring crop, increasing the density from 57,000 to 84,000 plants/ha resulted in a statistically insignificant number of seeds/row (P>0.05) (reaching 35.4 - 36.5 seeds/row) (Table 3.36). However, in the Spring-Summer crop, the planting density only increased to 71,000 plants/ha (P>0.05) (35.2 and 39.2, respectively). Continuing to increase the density resulted in a decrease in the number of seeds/row (Table 3.37). The research results of Abuzar et al. (2011) [58], Fromme et al. (2019) [89] showed that the number of seeds/row increased to a maximum at a certain planting density, continuing to increase the density reduced the number of seeds/row due to competition for light and nutrients.
In summary, increasing nitrogen fertilizer dose resulted in increased number of grains/row in Long An but decreased under Dong Thap conditions. Increasing planting density resulted in decreased number of grains/row in both experimental sites in this study.
120
Table 3.36 Number of grains/row of hybrid corn MN585 through nitrogen doses and planting density, Winter-Spring crop 2016 - 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
11.0 | 8.4 | 7.1 | 5.7 | Medium | 11.0 | 8.4 | 7.1 | 5.7 | Medium | |
120 | 25.8 | 30.0 | 30.2 | 33.2 | 29.8b | 40.1 | 42.2 | 42.3 | 41.8 | 41.6a |
160 | 28.6 | 32.6 | 34.5 | 35.0 | 32.7a | 35.3 | 35.7 | 36.3 | 36.6 | 36.0b |
200 | 28.8 | 31.3 | 35.0 | 37.6 | 33.2a | 34.8 | 35.3 | 36.9 | 37.4 | 36.1b |
240 | 28.0 | 33.8 | 36.2 | 37.6 | 33.9a | 32.6 | 32.7 | 33.1 | 34.8 | 33.3 c |
280 | 28.6 | 33.8 | 35.9 | 37.0 | 33.8a | 30.7 | 31.0 | 32.5 | 32.0 | 31.5d |
Medium | 28.0 c | 32.3b | 34.4 ab | 36.1a | 34.7b | 35.4 ab | 36.2a | 36.5a | ||
CV (%) | 1.00 | 10.82 | ||||||||
F (N) | 4.26* | 51.66* | ||||||||
F (MD) | 23.14* | 3.03* | ||||||||
F (N˟MĐ) | 0.31 Ns | 0.29 | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)
Table 3.37 Number of grains/row of hybrid corn MN585 through nitrogen doses and planting density, Spring-Summer crop 2017
Long An Dong Thap
Nitrogen dose (kg N/ha) Density (ten thousand trees/ha)
14.3 | 9.5 | 7.1 | 5.7 | Medium | 14.3 | 9.5 | 7.1 | 5.7 | Medium | |
120 | 20.8 | 25.0 | 25.2 | 28.2 | 24.8b | 31.6 | 33.5 | 37.9 | 35.0 | 34.5a |
160 | 23.6 | 27.6 | 29.5 | 30.0 | 27.7a | 31.4 | 33.4 | 40.3 | 35.7 | 35.2a |
200 | 23.8 | 26.3 | 30.0 | 32.6 | 28.2a | 33.4 | 34.2 | 38.7 | 35.9 | 35.5a |
240 | 23.0 | 28.7 | 31.2 | 32.6 | 28.9a | 35.4 | 34.2 | 40.0 | 34.9 | 36.1a |
280 | 23.6 | 28.8 | 30.9 | 32.0 | 28.8a | 33.5 | 35.0 | 39.2 | 34.4 | 35.6a |
Medium | 23.0 c | 27.3b | 29.4 ab | 31.1a | 33.1 | 34.1 bc | 39.2a | 35.2b | ||
CV (%) | 15.13 | 8.18 | ||||||||
F (N) | 4.26* | 1.57 Ns | ||||||||
F (MD) | 23.14* | 39.34* | ||||||||
F (N˟MĐ) | 0.31 Ns | 1.08 Ns | ||||||||
In the same column or row, characters followed by the same letter are not significantly different by Duncan's test (P>0.05). *: Statistically different (P<0.05)