Effects of cotton stubble return and subsoiling on dry matter accumulation, nutrient uptake, and yield of cotton in coastal saline-alkali soil

: To study the effects of cotton straw returning and deep loosening on cotton yield, salt subsoiling tillage (SRT) were conducted using Lumianyan 36 as experimental material. The results showed that cotton stubble return increased cotton yield across two years. Lint yield of SR was 33.9% higher than CT, and SRT 32.1% higher than SR. Subsoiling increased cotton yield in 2017 and had no effect on it in 2018. Cotton stubble return reduced the salt content of 0–40 cm soil layer. The salt content of SR was 22.4% lower than that of CT, and the soil salt content of SRT was 20.7% lower than that of ST at the late growth stage in cotton. However, the effect of subsoiling on the salt content of 20–40 cm soil layer was incon-sistent during the two-year experiment. The soil salt content of ST was 16.5% lower than of CT at late growth stage in 2017, but subsoiling had no effect on soil salt content in 2018. The accumulation dynamic of dry matter and N, P, K in cotton were consis-tent with the Logistic growth curve. Cotton stubble return increased maximal accumulation of dry matter and N, P, K in two years. The maximum accumulation of dry matter, N, P, and K in SR was 35.5%, 38.3%, 53.4%, and 55.0% higher than that in CT, and the accumulation of SRT was 27.0%, 30.7%, 21.2%, and 42.4% higher than that in ST. Compared with CT, the dry matter, N, P, and K accumulation of ST increased by 17.8%, 22.2%, 51.3%, and 40.6% in 2017, respectively, but had no effect in 2018. The dynamic of dry matter and nutrient accumulation were mainly affected by the maximum accumulation rate and rapid accumulation duration. Stubble return increased the amount and proportion of dry matter and N, P, K allocated to reproductive organs of cotton in the two-year experiment. Compared with CT, ST increased the allocation amount of dry matter and N, P, K to reproductive organs in 2017, but had no effect in 2018. In summary, the results revealed that cotton stubble return (SR) or cotton stubble return + subsoiling tillage (SRT) could be recommended tillage measures for soil improvement and high cotton yield in coastal sa-line-alkali cotton area.