Row spacing and fertilizer nitrogen effects on plant growth and grain yield of maize

Abstract

Conflicting reports have led to a renewed interest in the effects of narrow row spacing and high plant population densities on maize (Zea mays L.) grain yield. Field experiments were conducted to evaluate maize response to row spacing and N fertility over a 4-yr period (1997–2000). A randomized complete block design, arranged in a split plot was used with four replications each year with modifications of treatments over years. Row spacings of 0.51 m, 0.76 m and 0.76 m paired row alone or in combination with hybrid were tested in the subplot whereas combination of fertilizer N by population density (1997 and 1998) or N alone was assigned to the main plot. In 1997 and 1998, combinations of N by density consisted of 0 , 60, 120, 180 and 240 kg N ha-1 at 89 000 plants ha-1, and 60 and 180 kg N ha-1 at 69 000 plants ha-1 using a single hybrid, Pioneer 3893. In 1999 and 2000, N fertility levels of 0, 80 and 180 kg N ha-1 >were the main plots and six combinations of hybrids (Pioneer 3893 and Pioneer 38P06 Bt) by row spacing were grown in the subplots at 69 000 plants ha-1. Row spacing and fertility levels showed no significant interaction for any parameter at any developmental stage. In both 1997 and 1998, row spacing had no significant effect on yield (yield differed by 5% among row spacing treatments) or harvest index (varied from 0.45 to 0.53). For Pioneer 38P06 Bt in 1999, grain yield of the 0.51 m row spacing with the 80 kg N ha-1 fertilizer rate was 14.6% higher than the conventional 0.76 m row spacing. In 2000, the substantially lower (11%) yield of the 0.76 m paired row spacing than the other row spacing treatments was more likely the result of an exceptionally cool and wet season. In 1997 and 1998, plant density showed no effect on shoot or root DM. The lower density (69 000 plants ha-1) did, however, show a higher root to shoot ratio than the higher density. Shoot DM, root DM and root to shoot ratio did not differ between the 60 and 180 kg N ha-1 fertility treatments. While higher N levels increased above- and below-ground crop N contents, row spacing showed no consistent effects on maize plants at the early stages. Under the conditions of this study, narrow rows did not result in higher yield or N use efficiency even plant density and N fertility varied. Key words: Maize (Zea mays L.), nitrogen use, population density, root/shoot ratio, row spacing