EFFECTS OF MIXED CONTROLLED RELEASE AND NORMAL UREA ON MAIZE (ZEA MAYS L) GROWTH, GRAIN YIELD AND NITROGEN BALANCE AND USE EFFICIENCY IN NORTHEAST CHINA

Abstract

Mixed application of controlled release urea (CRU) and normal urea (NU) are effective N fertilization plural to improve crop yield and nitrogen use efficiency (NUE). In this study, field experiments were conducted for two consecutive years in 2018 and 2019 on two contrasting soil types. The treatments included one solely NU and four mixture ratios of CRU and NU under an identical N rate of 180 kg N ha -1 as single basal fertilizer before sowing. The results showed that the highest maize yields were obtained from the CRU30% treatment, increasing by 24% on sandy soil and 11% on clay soil as compared to CRU0% treatment. The yield improvements were mainly attributed to increased seed setting percentage and grain numbers per ear. Maize plants grown in CRU30% treatment accumulated more dry biomass (DM) and N uptake after silking, and thereby increasing grain yield and NUE. This work demonstrates that the appropriate mixture of CRU and NU increases maize yield and NUE while reducing N loss, by optimizing N fertilizer release and soil N availability to match the crop N demand, and 30%CRU and 70%NU was determined as the optimal mixture ratio on both sandy and clay soils in Northeast China.