The Effect of Nitrogen Fertilizer Source, Cultivar and Field Condition on the Growth Performance of Sorghum

Nitrogen fertilizer sources respond differently under dryland and irrigated fields and that affects sorghum growth. This study was carried out during the 2018/19 and 2019/20 planting seasons at Molelwane farm, North West, South Africa. The objective of this study was to determine the effect of nitrogen fertilizer source, cultivar and field condition on the growth performance of sorghum. The experiment was a 2x5x2 factorial arranged in a split-split plot experiment that was fitted into a randomized complete block design. The main plot factor was irrigation and dryland field conditions, the subplot factor was nitrogen sources (limestone ammonium nitrate, urea, ammonium sulphate, ammonium sulphate nitrate, and control) and the sub-sub plot was the cultivars (Titan and Avenger). The measured growth parameters included plant height, number of leaves, leaf chlorophyll content, leaf area and stem diameter. Nitrogen fertilizer source had no significant effect (P>0.05) on sorghum plant height and number of leaves during the 2018/19 and 2019/20 planting seasons. Even though no significant effects were observed during both planting seasons, the sorghum treated with urea and ammonium sulphate nitrate attained a higher plant height. Field conditions had a significant effect (P<0.05) on plant height and the number of leaves of sorghum plants for both planting seasons. Sorghum planted under dryland field conditions had taller plant and a higher number of leaves. In conclusion nitrogen fertilizer source like ammonium sulphate nitrate and urea significantly enhanced sorghum growth, with split application recommended to reduce nutrient loss. Cultivars such as Avenger and Titan perform well and should be chosen based on the environmental conditions. Effective practices including limestone ammonium nitrate application and moisture management, are essential for sustainable sorghum production, even in dryland conditions.