Effect of treatment factors on plant height
The location, plant density and nitrogen rates had significant (p≤ 0.05) effect on maize plant height during the 2015/16 and 2016/17 planting seasons (Table 3). During the 2015/16 planting season, WEMA maize planted in Molelwane had taller plant height (217.23 cm) than Taung. This may possibly relate to variations in soil texture and in the rainfall. This observation is in agreement with Amnaullah
et al (2009) findings that the reduction in maize plant height relates to fluctuations in the distribution of rainfall and the total amount of rain falling across the planting seasons. Maize sown at 44,444 plants/ha had tallest plant height (221.61 cm) than maize planted under other plant densities. This conforms to the findings of Murányi and Pepó (2013) who reported that the plants become taller as the plant density increases. The application of 60 kg N/ha had tallest plant height (222.14 cm) and shortest plant height was recorded in the plots applied with 240 kg N/ha at 84 days after planting. At 115 days after planting, taller plant height (257.83 cm) was recorded in Taung than Molelwane. The tallest plant height (246.55 cm) was obtained in the plots under 55,555 plants/ha than 33,333 plants/ha. This conforms to the findings of Muranyi and Pepo (2013) who reported that the plants become taller as the plant density increases. The plots treated with 240 kg N/ha had tallest plant height (247.02 cm) and shortest plant height (232.17) was recorded in the unfertilized plots. During the 2016/17 planting season, higher plant height (269.63 cm) was observed in Molelwane at 84 days after planting while higher plant height (254.10 cm) was recorded in Taung at 115 days after plating. The plant density of 55,555 plants/ha had tallest plant height (271.51 cm) than rest plant densities at 115 days after planting. The tallest plant height (273.56 and 248.21 cm) was obtained in the plot fertilized with 240 kg N/ha than unfertilized plots at 84 and 115 days after planting respectively. This is in consonance with the results of Sebetha and Modi (2016), showed that maize plants use nitrogen during their active cell division process to form building blocks of protein that are essential for cell development. The interactions of location, plant density and nitrogen rates had significant (p≤0.05) on plant height. However, the interactions effect was non- significant (p≥0.05) at 115 days after planting during the 2016/17 planting season.
Effect of treatment factors on number of leaves
The number of leaf was significantly (p≤0.05) affected by treatment factors during the 2015/16 and 2016/17 planting seasons (Table 3). Maize sown in Molelwane had higher number of leaves (14.11) at 84 days after planting while Taung showed higher number of leaves (15. 87) at 115 days after planting during the 2015/16 planting season. This can possibly be attributed to the favourable environmental conditions. Highest number of leaves (14.12 and 13.70) were observed in the plots under 44,444 and 55, 5555 plants/ha than 33,333 plants/ha at 84 and 115 days after planting respectively. This agreed with the finding of Yada (2011) who reported that low plant density produce the highest number of leaves. The application of 180 kg N/ha had highest number of leaves (14.37) and least number of leaves (13.48) was recorded with the application of 60 kg N/ha at 84 days after planting. At 115 days after planting, the plots treated with 60 kg N/ha had significantly highest number of leaves (13. 40) than unfertilized plots. During the 2016/17 planting season, highest number of leaves (16.33) was attained at Molelwane at 84 days after planting and Taung had higher number of leaves (13.63) at 115 days after planting. Maize planted under the plant density of 33,333 plants/ha showed highest number of leaves (15.83) at 84 days after planting and shortest number of leaves (13.81) was observed under plant density of 44,444 plants/ha. The plant density of 44,444 plants/ha produced higest number of leaves (13.80) than plant density of 33,333 plants/ha at 115 days after planting. The plots applied with 240 kg N/ha had highest number of leaves (15.95) and at 84 than 0 kg N/ha. Similarly, at 115 days after planting application 240 kg N/ha had highest number of leaves (14. 02) than the application of 60 kg N/ha. Amin (2011) obtained highest number of leaves per plant to the application of 180 kg N/ha to increase the number of nodes. The interaction between location x plant density x N rates had non-significant effect (p ≥ 0.05) on number of leaves at 84 days after planting and significant (p≤0.05) at 115 days after planting during the 2015/16 and 2016/17 planting seasons.
Effect of treatment factors on chlorophyll content
The analysis of variance showed that the treatment factors had significant effect (p≤ 0.05) on chlorophyll content of WEMA maize (Table 3). Taung had higher chlorophyll content (41.71 SPAD - units) at 84 days after planting while Molelwane showed higher chlorophyll content (28.02 SPAD - units) during 115 days after planting during the 2015/16 planting season. This may relates to the application of nitrogen fertilizer and favourable environmental conditions. Highest chlorophyll content (55.23 and 28.07 SPAD-units) was recorded under the plant density of 33,333 and 55,555 plants/ha at 84 and 115 days after planting respectively. This result is corroborrated by the findings of
Capici et al., (2010) who stated that the chlorophyll content decreases significantly with increasing plant density levels.The plots fertilized with 180 N kg/ha had highest chlorophyll content (50.87 and 24.89 SPAD - units) at 84 and 115 days after planting than other fertilizer rates.During the 2016/17 planting season, the higher chlorophyll content (57.39 SPAD - units) was attained at Taung at 84 days after planting whereas higher chlorophyll content (28.82 SPAD-units) was recorded in Molelwane at 115 days after planting. WEMA planted in the plots under 33,333 and 44,444 plants/ha had highest chlorophyll content (57.86 and 30.68 SPAD - units) at 84 and 115 days after planting respectively. The application of 240 kg N/ha showed highest chlorophyll content (59.63 and 29.47 SPAD - units) at 84 and 115 days after planting respectively. This agreed the earlier findings
(Tajul et al., 2013), who reported an increase in the chlorophyll content index as the rate of nitrogen fertilizer increases. Chlorophyll content was significantly affected by interaction between location x plant density x nitrogen rates during 2015/16 and 2016/17 planting season and non- significant (p ≥0.05) at 84 days after planting during the 2016/17 planting season.
Effect of treatment factors on stem diameter
The stem diameter was significantly (p≤0.05) affected by location, plant density and N rates (Table 4). During the 2015/16 planting season, thicker stem diameter (1.98 and 2.92 mm) was recorded in Taung at 84 and 115 days after planting respectively. This may possibly due to variations in the environmental conditions and the soil factor. The plant density of 55,555 produced thickest stem diameter (1.98 and 2.92 mm) at 84 and 115 days respectively. The plot treated with 120 kg N/ha had thickest stem diameter (1.97 mm) than plot applied with 240 kg N/ha at 84 days after planting. At 115 days after planting, application of 180 kg N/ha showed thickest stem diameter (2.76 mm) and the thinnest stem diameter (2.46 mm) was recorded in unfertilized plots. The Taung location had thickest stem diameter (3.38 and 2.91 mm) at 84 and 115 days after planting during the 2016/17 planting season. The thickest stem diameter (3.43 mm) was recorded under the plant density of 33,333 than 55,555 plants/ha at 84 days after planting. However, the plant density of 55,555 plants/ha had thickest stem diameter (2.94 mm) than 44,444 plants/ha at 115 days after planting. At 84 days after planting, the application of 180 had thickest stem diameter (3.43 mm) than 0 kg N/ha. The plots treated with 120 kg N/ha showed thickest stem diameter (2.99 mm) than unfertilized plots at 115 kg N/ha. This is disagreed with the finding of
Mandi et al., (2015), who revealed that high plant density reduce photosynthesis and cause reductions in the stem diameter. Opoku (2017) pointed that an increase in the nitrogen fertilizer supply enhanced the growth of diameters of cells and stems. The interactions of location, plant density and nitrogen fertilizer rates had significant (p≤ 0.05) effect on stem diameter.
Effect of treatment factors on leaf area
The leaf area of WEMA maize was significantly (p≤ 0.05) affected by location, plant density and N rates during the 2015/16 and 2016/17 planting seasons (Table 4). Each locations had higher leaf area (647.78 and 712.86 cm
2) at 84 days after planting and (809.63 and 694.20 cm
2) at 115 days after planting during the 2015/16 and 2016/17 planting seasons respectively. This can be attributed to the favourable environmental conditions, in tandem with the adequate fertilization rates. During the 2015/16 planting seasons, the plant density of 55,555 plants/ha had highest leaf area (643.55 and 679.41 cm
2) at 84 and 115 days after planting respectively. Hokmalipour and Darbandi (2011) indicated that plant density affects leaf area. The plots fertilized with 60 kg N/ha had highest leaf areas (632.05 and 698.73 cm
2) than unfertilized plots at 84 and 115 days after planting respectivel. During the 2016/17 planting season, the highest leaf area (767.41 and 703.30 cm
2) was obtained in the plots under 33,333 plants/ha at 84 and 115 days after planting. The highest leaf area (774.06 cm
2) was obtained in the plot treated with 240 kg N/ha at 84 days after planting. The plots fertilized with 60 kg N/ha showed highest leaf area (678.60 cm
2) at 115 days after planting.
Amanullah et al., (2009) and Amin (2011) revealed that high fertilizer rates enhance cell division, which in its turn significantly promotes cell expansion, leaf development and expansion of the leaf area. The interactions between location x plant density x nitrogen rates had significant (p≤ 0.05) effect on leaf area.