NITROGEN USE EFFICIENCY AND YIELD STABILITY OF MAIZE (Zea mays L.) HYBRIDS UNDER MOISTURE STRESS AREAS OF CENTRAL RIFT VALLEY IN ETHIOPIA

Abstract

Maize is an important food security crop in the central rift valley of Ethiopia. Applying a Nitrogen fertilizer in maize production entails costs to smallholder farmers and results in nitrous oxide emission to the atmosphere exacerbating the problem of climate change. This experiment was conducted to determine the effect of nitrogen fertilizer on yield, morpho-agronomic traits and nitrogen use efficiency of maize hybrids, assess the relationship between yield and nitrogen use efficiency related traits and, group maize hybrids based on productivity, yield stability, nitrogen stress sensitivity. The eight maize hybrids were evaluated at three rates of N fertilizer with split-plot design with three replications at two locations (Dera and Melkassa) in 2020 main cropping season. The results from analysis of variance (ANOVA) at each location indicated that majority of yield and yield related traits, agronomic and physiological efficiency were significantly influenced either by one or two of the factors (nitrogen fertilizer and genotype) and/or the interaction effect of the two at both locations. The results of combined ANOVA over locations revealed that nitrogen fertilizer had significant effect on days to maturity, plant height, leaf area index, ear length, number of kernel per ear, thousand kernel weight, grain yield, biomass yield, harvest index, crop growth rate, agronomic and physiological efficiency and the genotypes also showed significant differences for all these traits except plant height and leaf area index. These traits except plant height were significantly influenced by one or more than one of the possible two factors interactions (nitrogen x genotype, location x nitrogen, and location x genotype). The interaction of the three factors (location, nitrogen and genotype) had significant effect on leaf area index, number of kernel per ear, agronomic and physiological efficiency. The hybrids grain yield ranged from 3489 (MH138Q) without nitrogen fertilizer to 8390 kg ha-1 (WE8206) due to application of 65 kg N ha-1 . The hybrids had mean grain yield of 3941, 6764.88 and 7704.13 kg/ha without nitrogen fertilizer, 32.5 and 65 kg N/ha application, respectively. Grain yield had significant and positive correlation with mean productivity, geometric mean productivity, harmonic mean, yield stability and yield index, while it had negative and significant correlation with. relative yield reduction, nitrogen stress sensitivity and abiotic tolerance index. Productivity, nitrogen sensitivity and tolerance indices estimated from N non-stress (65 kg N ha-1 ) and N stress (without fertilizer) grouped the maize hybrids in to two groups. The four hybrids, MH138Q, WE8203, WE7201 and WE6205 had higher nitrogen stress susceptibility (NSSI) and abiotic tolerance (ATI) than the average values of hybrids and except WE6205 had yield index (YI) and yield stability index (YSI) less than the average values of the hybrids. These hybrids had higher and lower yield at N non-stress and stress conditions, respectively. The other group consisted of WE5202, WE7210, WE8206 and MH140 characterized by lower NSSI and ATI but higher YSI than the average values of hybrids, and had higher yield at both nitrogen managements. Moreover, WE8206 and WE7210 had grain yield higher than the average yield of the hybrids in N stress and non-stress conditions, and MH138Q, WE7201 and WE8203 had grain yield higher than the average yield of the hybrids under N non-stress condition. Thus, WE8206 and WE7210 could be recommended for production in the study areas. However, this recommendation may not be effective to increase yield under drought stress areas and further studies are needed, because the two locations have received sufficient rainfall during the experiment, and these limited locations under N non-stress and stress conditions may not be sufficient to represent the dryland areas.