Late sowing with reduced nitrogen rate promotes relative maturation and nitrogen use efficiency without compromising yield in cotton

Abstract

Context

High production costs and difficulties in mechanized harvesting in the Yellow River Valley cotton-growing region of China are primarily attributed to excessive fertilizer application and poor relative maturation. Sowing date significantly affects relative maturation, while nitrogen (N) application directly impacts the production costs. This study aims to explore how late sowing and reduced N rate enhance relative maturation, nitrogen use efficiency (NUE), and cost reduction without compromising seed cotton yield.

Method

A two-year (2019–2020) field experiment was conducted across the two sites using a split-plot design to investigate the effects of sowing date (mid-April and early May) and N rate (0 kg ha⁻¹, reduced to 180 kg ha⁻¹, and typical at 240 kg ha⁻¹) on seed cotton yield, earliness, relative maturation, and NUE.

Results

Under normal sowing, reducing nitrogen rate to 180 kg N ha⁻¹ led to a decrease in seed cotton yield compared to typical N rate. However, this reduced N rate under late sowing did not reduce yield; instead, it increased nitrogen use efficiency (NUE) and achieved a higher net return. Furthermore, applying 180 kg N ha⁻¹ under late sowing improved grouped flowering and boll formation, achieving a greater proportion of mid-season bolls and fewer rotten bolls, ultimately enhancing cotton relative maturation. This combined strategy also shortened the duration of rapid N accumulation and improved the average N accumulation rate, particularly by 7.0–9.0 % in reproductive organs, contributing to more efficient nitrogen allocation to cotton bolls. In contrast, the typical N rate under late sowing promoted excessive vegetative growth, decreasing earliness, relative maturation, and NUE, ultimately compromising yield stability. The entropy-TOPSIS comprehensive evaluation of seed cotton yield, earliness, relative maturation, NUE, and net return indicated that reducing N rate to 180 kg ha⁻¹ under late sowing achieved the highest relative proximity, surpassing the typical N rate under normal sowing.

Conclusion

Overall, late sowing with reduced N input shows promise for light-simplified and cost-effective cotton production in the Yellow River Valley and similar regions. This study highlights how optimizing sowing date and N rate can enhance relative maturation and reduce N inputs without compromising yield, supporting the safe, stable and sustainable development of the cotton industry.