Effects of nitrogen application on biomass accumulation, remobilization, and soil water Contents in a rainfed wheat field

Abstract

This study examined the effects of different levels of N fertilization on dry matter accumulation andremobilization, and soil water contents in a rainfed winter wheat field. The experiments were carried outduring growth seasons in 20092012 in a hilly region in Shandong Province, China. The N rates applied were0 (N0, the control), 90 (N1), 120 (N2), 150 (N3), 180 (N4), and 210 (N5) kg N ha 1. Our results showed that Nfertilization significantly increased dry matter accumulation and post-anthesis assimilates compared withcontrols. At anthesis, total above -ground biomass increased signific antly with increasing N rate up to 150 kgha 1 and then leveled off in the 20092010 and 20112012 growth seasons. However, the biomass in the 2010 2011 growth season did not vary with different N rates. At maturity, the accumulation of dry matter invegetative organs significantly increased with increasing N rate up to 150 kg ha 1 and then leveled off in allgrowth seasons. Of all the treatments, N3 and N4 had relatively higher total above -ground biomass at maturity.In contrast, dry matter remobilization efficiency showed a declining trend under increasing N rate. The higherpost- anthesis assimilates and the contribution of pre -anthesis assimilates to grains were obtained at N rates of150 and 180 kg ha 1 in all growth seasons. Soil water contents in 0120, 0100, and 40160 cm soil layersduring each growth season decreased significantly with increasing N rate up to 150 kg ha 1. The maximumgrain yields were obtained under N rate of 150 kg ha 1 in all growth seasons, with the highest grain yield being7160.8 kg ha 1 in the 20112012 growth season. Our results suggested that N fertilization at 150 kg N ha 1 wasoptimal for grain production via promoting above-ground biomass and soil water consumption in deep soillayers. These results should help provide guidance for N fertilization management for optimal and sustainablewheat production in the said region.