Agronomic performance of hybrids of white lownitrogen maize Zea mays L inbred lines under managed nitrogen environments

This study evaluated the agronomic performance of 150 single cross hybrid maize under no-N, low-N and optimum-N as 0, 30 and 90 kg ha(-1), respectively, in a replicated trial laid out in a 19 x 8 lattice design in 2014 and 2015. Data collected were pooled across years and subjected to analysis of variance for each N level. Pearson's correlation was used to study the relationships between grain yield (GY) and other traits while Spearman's rank correlation was used to detect the association among the GY under the three N levels across years. Effects of genotypes and G x E (genotype x environment) were significant (P<0.01) for most of the traits under all the N levels. Grain yield and ear height (EH) increased while days to silking (DTS), anthesis-silking-interval (ASI), stay green (SG), plant aspect (PASP) and ear aspect (EASP) decreased with increase in N levels. Days to anthesis (DTA) were highest under no-N (59.30 days) than under low-N (57.98 days) and optimum-N (57.58 days). Plant height (PH) was lower under no-N than under low-N and optimum-N levels. The DTS, ASI, SG, PASP and EASP responded most to changes in N conditions, hence are effective in maize selection for N stress. The GY can be indirectly selected for any of DTS, PH, EH and SG under N stress, but PASP or EASP under optimum-N condition. Hybrids BD74-170xBD74-55, TZEI1xBD74-399 and BD74-175xBD74-152 were most promising under the three N conditions, and may be considered for use in a wide range of environments.