Effect of Plant Density and Nitrogen Fertilizer Rate on Growth, Nitrogen Use Efficiency and Grain Yield of Different Maize Hybrids under Rainfed Conditions in Southern Vietnam

Abstract

Plant density (PD) and nitrogen (N) fertilizer are considered the most important crop management practices in improving maize grain yield. Two identical field experiments in Vietnam, in Ba Ria and Dong Nai provinces, were conducted in the wet season 2011 to study the effects of PD and the N fertilizer rate on two maize hybrids. The experiment was laid out in a split-split plot in a randomized complete block design with three replications. Two maize hybrids, NK7328 and LVN10, constituted the main plots and three PD values (57,000, 71,000, and 84,000 plants.ha-1) were the subplots. Five N rates (0, 60, 120, 180 and 240 kg.ha-1) were the sub subplots. The results revealed that NK7328 had a greater leaf area index (LAI) than LVN10 (4.32 versus 3.92 and 4.31 versus 4.11) at both Ba Ria and Dong Nai, respectively. NK7328 also had a greater grain yield than LVN10 at both locations (8.11 versus 7.15 and 8.04 versus 6.72 t.ha-1, respectively). This greater grain yield in these experiments was attributed to a greater number of kernels per ear (KNo) and a greater 1,000-kernel weight (KWt). NK7328 exhibited higher nitrogen use efficiency (NUE) than LVN10 (27.0 versus 21.4 and 29.3 versus 16.4, respectively). Increased PD from 57,000 to 84,000 plants.ha-1 and increased N application rate from 0 to 180 kg.ha-1 increased the anthesis-silking interval and LAI. The grain yield, KNo and KWt decreased with the increased PD and decreased N fertilizer rate. The NUE of the maize hybrid was significantly affected by the N fertilizer rate but there was no effect from PD. The NUE was not associated with the maize grain yield. The optimum PD and N rate were 71,000 plants.ha-1 and 120 kg.ha-1 to be applied for maize under rainfed conditions in southern Vietnam.