| Soil quality assessment of continuous cropping cotton fields for different years in Manas River Basin |
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| DOI：10.7606/j.issn.1000-7601.2021.04.24 |
| Key Words: continuous cropping years cotton soil quality heavy metals soil quality assessment |
| Author Name | Affiliation | | JIANG Yan | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi, Xinjiang 832000, China | | LIU Dongyang | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi, Xinjiang 832000, China | | LI Jianmei | Economic Crop Work Station in Tongliao, Tongliao, Inner Mongolia 028000, China | | WANG Peng | Institute of Crop Sciences, Xinjiang Academy of Agricultural Sciences, Shihezi, Xinjiang 832000, China |
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| Abstract: |
| The long\|term continuous cropping of cotton is a common planting pattern in the Manas River Basin, Xinjiang Province, and it may inevitably lead to unbalance in soil nutrients, diminishing soil fertility and degrading soil quality. In 2017 and 2018, 0~20 cm depth soil samples were collected from six continuous cropping cotton fields, with different cultivation times (1, 5, 10, 15, 20 years and 25 years respectively). This study aimed to evaluate soil quality across continuous cropping cotton fields for different years by analyzing six physical and chemical properties (organic matter, pH, salt, total N, available P and available K) and six soil heavy metals (As, Cd, Cr, Ni, Cu, and Pb). The factor analysis and the comprehensive soil quality index (SQI) were applied to quantitatively evaluate soil quality grades. Muller geo\|accumulation index (ISHM) was calculated to assess the pollution of heavy metals. The results: (1) 1 year and 25 years had the highest pH, with an average of 7.90, while 5 years and 10 years cropping had the lowest pH value. The salt content of the soil increased year by year, with an average salinity of 3.65 g·kg-1 at 5 years and 3.87 g·kg-1 at 25 years. The organic matter was the highest at 10 years (19.97 g·kg-1), and the lowest for 1 year and 25 years. The variation trend of available K was similar to that of organic matter. The contents of total N and available P increased from 1 year, and reached the maximum at 25 years, with average total N of 0.903 g·kg-1, available P 55.1 mg·kg-1. (2) The concentrations of heavy metals (Cr, Ni, Cu, Pb, As and Cd) increased along with increasing years of cultivation, with an average Cr, Ni and Cd of 93.87, 33.18 and 0.23 mg·kg-1 at 15 years respectively, and these numbers were greater than the background numbers in Xinjiang, indicating the accumulation of those elements in the soils. The content of As was 12.03 mg·kg-1 at 20 years and 13.53 mg·kg-1 at 25 years, indicating micro\|pollution. Heavy metal pollution index (ISHM) revealed that Pb had no pollution in continuous cropping 1~25 years (ISHM<0) and the content of Cu exceeded the standard (ISHM>0). (3) Soil quality assessment values (SQAV) based on factor analysis showed that 10 years had the highest SQAV (0.437), followed by 5 years (0.247), 1 year and 25years had the lowest numbers. The integrated soil quality index evaluation method (SQI) showed that the soil quality of 5 years and 10 years were “high” (SQI were 1.02 and 1.10 respectively), 1 year and 25 years were “low” (SQI were 0.63 and 0.61 respectively), and 15 years and 20 years were “medium”. In summary, the SQAV based factor analysis and SQI were all the most suitable methods for evaluating the soil quality of cotton fields with different continuous cropping years qualitatively and quantitatively. |
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