Deep placement of mixed controlled-release and conventional urea improves grain yield, nitrogen use efficiency of rainfed spring maize

Abstract

ABSTRACT Controlled-release urea (CRU) mixed with conventional urea can promote grain yield (GY). Whether the deep placement of mixed nitrogen fertilizer can further enhance GY, nitrogen use efficiency is rarely reported. In this study, four CRU-urea mixtures and two fertilizer placement depths were tested on rainfed spring maize. Fertilizer placement at a depth of 16 cm created a soil environment of lower temperature and higher water content than that at a depth of 8 cm. Increasing the fertilizer depth or the CRU ratio increased DM and total plant N content at maturity but lowered N remobilization efficiency (NRE) and DW remobilization efficiency (DRE). Maximum GY and partial factor productivity of nitrogen (PFPN) were achieved when CRU and urea were mixed at a ratio (1:0 and 2:1) and the fertilizer was placed at a depth of 16 cm. Although fertilizer deep placement increased production inputs, the increase in net benefits was even more dramatic, especially when CRU was mixed with urea. In summary, a 2:1 mixture of CRU and conventional urea is the most promising fertilization strategy for spring maize production, particularly when combined with 16 cm deep fertilizer placement.