Straw mulching combined with an optimal nitrogen rate split into two applications enhances wheat yield, grain quality and nitrogen efficiency in a semi-arid area

Abstract Appropriate soil water and nitrogen (N) management strategies are critical for achieving sustainable agricultural development in drylands. Straw mulching has been used to improve crop yield and water use efficiency (WUE), but N management strategies may need to be adjusted from conventional practice. The current study investigated the interactive effects of N application rate (conventional and high N rate), N application frequencies (single, and split N in 2 – 3 applications) and seasonal conditions on wheat population density dynamics, yield, harvest index (HI), grain protein content, water- and N-use efficiency, and residual soil N under straw mulching on the Loess Plateau of China. Nitrogen rate had no effect on yield, HI, WUE and grain protein content, but high N rate resulted in lower grain weight and nitrogen partial factor productivity (PFPN), and higher soil N residue. Splitting N applications significantly improved grain yield (7%), HI (9%), grain protein content (5%), PFPN and N harvest index, along with a reduction in soil N residue, compared to single application. However, there was no difference in above traits between split-N in 2 and 3 applications. Conventional N rate (vs. high N rate) and split N application (vs. single application) both alleviated the negative correlation between grain yield and grain protein content, and split N application increased grain N removal per unit yield compared to single N application. It is concluded that conventional N rate combined with split application in two doses, is suitable for straw mulching in drylands of the Loess Plateau, China.