Performance of water-efficient maize variety under variable planting densities and nitrogen fertilizer rates at two localities in North West Province, South Africa
Abstract
Water Efficient Maize for Africa (WEMA) variety is a newly-released drought-tolerant maize variety that is being adopted at increasingly high rates by South African smallholder farmers. Nonetheless, information on the improved agronomic practices required to maximize its production is currently limited. Two years field experiment was conducted at two localities (Molelewane and Taung) in North West Province, South Africa to investigate the performance of WEMA variety under different nitrogen fertilizer rates and plant density. Similarly, greenhouse studies were carried out to investigate water use efficiency of WEMA variety as influenced by different nitrogen fertilizer rates, soil moisture level and soil types. The field experiment was laid out during the 2016/17 and 2017/18 planting seasons in a split plot arrangement fitted into a randomized complete block design with four replications in each location. Plant density of 44,444, 55,555 and 33,333 plants/ ha constituted the main plot effect, while nitrogen fertilization rates of 0, 60, 120, 180 and 240 kg N /ha were applied to the sub-plots at each of the sites. On the other hand, greenhouse trial was laid out in 5 x 2 x 2 factorial, fitted into complete randomized design with three replications. The treatments comprised five nitrogen fertilization rates (0, 60, 120, 180 and 240 kg N /ha), two soil moisture levels (45 % and 100% field capacity (FC)) and two soil types (Ferric Luvisol and Rhodic Ferralsol soil types). The growth, and dry matter parameters, root system architecture, yield and its components, nutritional composition and water-use efficiency were measured. Data were subjected to an analysis of variance test of Genstat 11ᵗʰ edition and the means were separated with LSD (p≤0.05). The relationships between the treatment factors were analyzed using regression, correlation and path analyses. Planting season x location x plant density x nitrogen rates had a significant (P<0.05) effect on the growth parameters and analysis. The tallest plant height (309.35 cm) was recorded during 2016/17 planting season at Molelwane under 55,555 plants/ha on plots supplied with 240 kg N/ha. The highest net assimilation index of 1.180 g/g/day was recorded during 2015/16 from Molelwane trial under 33,333 plants/ha plant density with 240 kg N/ha fertilizer. The predicted optimum N fertilizer rate for better growth ranged between 180 – 225 kg N/ha depending plant density. The root architecture system was significantly affected by interaction between planting season, location, planting density and N rates. The highest deep and steep brace root angle of 73.75° was obtained during 2016/17 planting season at Taung at a plant density of 33,333 plants/ha in the unfertilized plots. The deepest and steepest crown root angle (84.25°) was recorded during the 2016/17 planting season at Taung was under 44,444 plants/ha supplied with 180 kg N/ha. The interactions amongst planting season, location, planting density and N rates had significant (P<0.05) effect on yield and yield components. WEMA had highest grain yield (7.78 t/ha) in plots with 55,555 plants/ha and fertilized with 120 kg N/ha during 2016/17 planting season at Molelwane. The WEMA showed highest harvest index (0.81) during 2016/17 planting season at Molelwane under 33,333 plants/ha in unfertilized plots. The interaction between the nitrogen fertilizer rates and plant densities indicated an optimum nitrogen level of 148 kg N /ha at a plant density of 44, 444 plants /ha The interaction effect of planting season x location x plant density x N rates had significant (P<0.05) effect on the nutritional composition of WEMA variety. The highest starch content (5 166.00kg/ha) was obtained at Taung during 2016/17 growing season at a plant density of 55, 555 plants/ha from plots fertilized with 180 kg N/ha, and highest protein yield (1 592.00 kg/ha) from plots in Taung with palnt density of 33,333 plants/ha supplied with 120 kg N/ha during 2015/16 planting season. In the greenhouse experiments, the interaction amongst nitrogen fertilizer rates x soil moisture levels x soil types had significant (P<0.05) effect on growth parameters, grain yield, yield components and water use efficiency of WEMA Maize. Highest number of leaves was recorded in Ferric Luvisol treated with 240 kg N/ha under 45 % soil moisture level. Furthermore, the Ferric Luvisol produced the highest grain yield (3.49 t/ha) with applications of 180 kg N/ha under 100 % FC. WEMA had highest (41.73 %) water use efficiency on Rhodic Ferralsol soil supplied with 180 kg N/ha had at 45 % FC. In conclusion WEMA 3127 performed better under moderate drought condition and revealed significant locational responses with better performance recorded at Molelwane than at Taung. This maize variety had better water use efficiency in Rhodic Ferralsol than in Ferric Luvisol.