Optimal drip irrigation leaching amount and times enhance seed cotton yield and its stability by improving soil chemical environment and source-sink relationship

Context

The arid and semi-arid regions of northwest China play a pivotal role in the national cotton production. However, soil salinization poses a severe constraint on seed cotton yield in this region. Salt leaching by drip irrigation has become increasingly popular for ameliorating saline-alkali soils. Yet, the most effective approach for utilizing drip irrigation leaching to maximize cotton productivity remains uncertain.

Methods

Over a three-year period, field experiments were performed to explore the effects of four leaching amounts (75, 150, 225, and 300 mm) and four leaching times (seedling stage, budding stage, flowering stage, and boll-setting stage as one, two, three and four times) on soil-water dynamics, ion composition, source-sink relationships, seed cotton yield and its stability in saline-alkali cotton fields under drip irrigation.

Results

The study revealed that soil moisture significantly fluctuated during the cotton growing seasons. Timely irrigation significantly boosted soil moisture content by 11.3 %-23.5 %. Soil salinity was lower at the early growth stages of cotton, but it gradually increased over time, peaking at the flowering and boll-setting stages. Appropriate leaching effectively mitigated soil salinity, particularly at the flowering stage, resulting in a reduction of salt accumulation by 13.9 %-32.7 %. As leaching amount increased, the relative content of Ca²⁺ increased, while K⁺ and Na⁺ contents gradually decreased, thereby reducing the relative content of harmful ions and leading to a decrease in SAR by 7.07 %-34.3 %. In terms of biomass, the W3 treatment exhibited the highest level, whih was 1.68 %-25.4 % greater than that of the other treatments. Among the three years, the S3 and S4 treatments consistently produced the highest biomass, with increases of 12.66 %-35.25 % and a slight 0.85 % difference, respectively.

Significance

The optimal leaching strategy, combining the W3 irrigation amount with the S3 leaching times achieved the highest seed cotton yield with the lowest yield variability. This underscored the critical importance of suitable irrigation and management practices for enhancing seed cotton yield and mitigating the adverse effects of soil salinity on cotton production. Soil salinity indicators, such as sodium adsorption ratio and exchangeable sodium percentage, played a pivotal role in biomass accumulation and yield stability. A total leaching amount of 300 mm applied at the seedling, budding, flowering, and boll-setting stages was recommended to maximize cotton productivity.