[Comprehensive method for evaluating soil quality in cotton fields in Xinjiang, China]

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Soil quality is crucial for cotton production in Xinjiang, a major global supplier.
• Understanding soil physicochemical properties and heavy metal contamination is vital for sustainable agriculture.

Purpose of the Study:

• To evaluate the soil quality in major Xinjiang cotton-growing regions.
• To develop a comprehensive soil quality index (SQI) based on key soil parameters.
• To identify factors influencing soil quality and heavy metal pollution.

Main Methods:

• Measured 11 soil quality indices including pH, salt, organic matter, total N, available P, available K, and heavy metals (Cr, Cu, Zn, As, Pb).
• Collected samples from representative cotton-growing regions: Hami, Bole, Changji, Shihezi, Aksu, Kashgar, and Kuitun.
• Calculated a comprehensive soil quality index (SQI) and Nemerow comprehensive pollution index (PN).

Main Results:

• Soils are alkaline (average pH 7.87) and mildly saline (average salt 3.44 g·kg⁻¹).
• Organic matter and total N were low; available P and K were relatively high.
• Average heavy metal concentrations (Cr, Cu, Zn, As, Pb) were below national standards, but Cu, Zn, and As exceeded background levels, indicating accumulation.
• Soil organic matter, total N, Cu, Zn, As, and Pb significantly affected soil quality.
• Overall soil quality in Xinjiang cotton fields is medium, with Changji and Kuitun showing the highest SQI (0.52) and Aksu the lowest (0.31).

Conclusions:

• Xinjiang's cotton fields generally possess medium soil quality, influenced by organic matter, nitrogen, and specific heavy metals.
• While heavy metal levels are within safe limits, accumulation of Cu, Zn, and As warrants attention for long-term soil health.
• Soil quality varies regionally, being highest in northern Xinjiang and lowest in the southern areas, necessitating tailored management strategies.