Late nitrogen fertilization improves cotton yield through optimizing dry matter accumulation and partitioning

Cotton (Gossypium hirsutum L.) production efficiency is constrained by issues such as a low nitrogen (N) utilization rate (30-35 %) and high N application rate (300-350 kg ha-1) in particular arid climates, such as Xinjiang, the largest irrigated cotton-producing region in China. These issues could be alleviated by allocating more N to late application to satisfy plant needs for growth and development. Over a three-year (2019-2021) field experiment, 240 kg ha-1 N was applied in 3 periods (squaring, flowering to peak boll, and late peak boll). The amount of N applied in the second period was fixed at 60 %, and the remaining 40 % was split between the first and the third periods, with five ratios (treatments), i.e., 0:6:4 (N064), 1:6:3 (N163), 2:6:2 (N262), 3:6:1 (N361) and 4:6:0 (N460), to investigate cotton response in terms of growth, biomass accumulation, and yield. Compared with the conventional treatment (N262), the N064 treatment narrowed the plant width by 11.7-12.0 %, increased canopy light transmittance by 6.1-56.9 %, extended the boll growth period by 8.8-9.4 %, improved defoliation by 9.3-11.7 % and increased both seed cotton yield and N partial factor productivity by 7.1-8.1 %, depending on the year. N064 accumulated 4.3-39.5 % more biomass (K) than N262, with the average and maximum growth rates of the reproductive organs (Vt and Vm, respectively) increasing by 8.6-89.0 % and 6.9-125.7 %, respectively, while the fast growth duration (& UDelta;t) shortened by 9.9-31.6 %. Again, N064 partitioned 1.5-35.8 % more biomass to bolls (higher partitioning index, PIboll). Seed cotton yield was significantly positively correlated with K, t1, Vt, Vm and PIboll and negatively correlated with & UDelta;t in reproductive organs. Collectively, the data suggest that allocating more N to late application could be an efficient N fertilizer management strategy in arid areas under N-reduced cultivation and fertigation.& COPY; 2023 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).