Cotton stubble effects on yield and nutrient assimilation in coastal saline soil

Stubble return is a proposed practice for soil amelioration and yield improvement. However, from the perspective of reducing soil salinity and improving soil nutrient availability, we have little knowledge of the effect of successive stubble return on cotton yield and nutrient uptake when cotton stubble is incorporated into saline field soil. Hence, a 5-year field study was conducted to investigate the effects of successive stubble management (stubble return and stubble removal) on lint yield and nutrient uptake of cotton, soil nutrients and salinity in the 0–80-cm soil profile. Stubble return increased lint yield by 22.7% and 47.3% in the fourth and fifth year, respectively, mainly through the production of more and larger bolls and the acquisition of more nutrients compared with stubble removal. 5-year cotton stubble return produced 20.0% more bolls and 7.7% larger bolls than stubble removal. Cotton plants accumulated 58.9% more nitrogen (N), 54.5% more phosphorus (P), and 48.2% more potassium (K) under stubble return than stubble removal during the last two years of the experiment. Stubble return increased internal N use efficiency (iNUE) and internal K use efficiency (iKUE) at the fourth or fifth year compared with stubble removal, without influence on internal P use efficiency (iPUE). Stubble return decreased soil pH and salinity in the 0–40-cm soil layer in the fourth and fifth year. The soil nitrate content below the 40-cm soil layer was reduced, while the nitrate concentration in the 0–20-cm soil layer increased after 4 years of stubble return. Available K in the 0–40-cm soil layer increased, while available P in the 0–20-cm soil layer was reduced after 5 years of stubble return. Our analyses demonstrate that cotton stubble return has the potential to improve cotton yield and may be an effective practice to apply in coastal saline areas.