# Coupling effects of deep vertical rotary tillage and brackish water irrigation on soil water-salt dynamics and cotton productivity in arid regions

## TL;DR

This study explores how deep vertical rotary tillage and brackish water irrigation affect soil salinity and cotton productivity in arid regions.

## Contribution

The study introduces a novel combination of deep vertical rotary tillage and saline water irrigation to improve cotton productivity in saline soils.

## Key findings

- The DVRT-SWDI treatment improved soil water storage capacity, with D3M2 showing a 12.06% increase over the control.
- Deep vertical rotary tillage reduced salt accumulation in the root zone, with D3M1 being most effective.
- Optimal treatment D3M2 increased seed cotton yields by 31.84% in 2023 and delivered the highest overall benefit.

## Abstract

Soil salinization poses an urgent challenge by constraining cotton yields and exacerbating freshwater scarcity.

A two-year field experiment was carried out from 2023 to 2024. This study systematically assessed the effects of combining Deep Vertical Rotary Tillage (DVRT) with Saline Water Drip Irrigation (SWDI) on the soil salinity profile in the 0–100 cm layer, as well as on agronomic traits, fiber quality, yield, and water use efficiency (WUE) of cotton.

Results indicate that the DVRT-SWDI treatment significantly improved soil water storage capacity, among which the D3M2 treatment achieved the highest increment (12.06% higher than the control). Soil water storage exhibited a “decrease-increase-decrease” dynamic pattern throughout the growing season. Treatments with deep vertical rotary tillage (D2/ D3) effectively alleviated salt accumulation in the 0–60 cm root zone, with D3M1 showing the optimal salt-blocking effect, whereas shallow plowing combined with high-salinity water irrigation (D1M3) led to the most severe salt accumulation. Deep vertical rotary tillage integrated with low/medium-salinity water (M1/M2) significantly promoted cotton growth and yield formation. In 2023, the seed cotton yields under D2M2 and D3M2 treatments increased by 35.24% and 31.84%, respectively, compared with the control (CK). Comprehensive evaluation via the entropy weight method revealed that the D3M2 treatment delivered the highest overall benefit. Based on a multi-objective optimization model, the optimal combination of agronomic and tillage parameters was determined as a deep vertical rotary tillage depth of 40–45 cm and a saline water drip irrigation salinity of 2.82–3.29 g·L-1, which yielded seed cotton at 5767.38–6052.86 kg·ha-1.

This study clarifies the mechanisms of salt suppression and growth promotion by deep vertical rotary tillage under brackish water irrigation conditions, providing theoretical basis and technical support for the efficient utilization of water and soil resources and the suitable cultivation of cotton in saline-alkali lands of southern Xinjiang.