Abstract:

The restriction of the “Three Red Lines” strategy of water resources makes the areas dominated by agricultural water gradually conduct “reducing water consumption by returning farmland” measures, which effectively ensures a control index of total water consumption and produces the decline of soil quality of abandoning some land after returning farmland. Taking the returning farmland soil in the Manas River irrigation area in Xinjiang as the research object under the condition of “three red lines,” this paper analyzes the indexes of soil pH value, total dissolved salt, organic matter, total nitrogen, total phosphorus, alkali hydrolyzed nitrogen (AN), and available potassium (AK), and calculates the soil fertility index of returning farmland (RF) and adjacent cultivated plots (CK) by constructing a fuzzy comprehensive evaluation model, and to perform the soil quality evaluation of RF to Manas River irrigation area under the conditions of the “Three Red Lines” strategy. The results show that: (1) The salt content of treatment RF is 10.84% higher than that of CK. Both treatments are moderately saline soil. The salt of treatment RF is mainly accumulated at 40-100 cm. (2) The soil nutrients of RF treatment were lower than CK treatment as a whole, and the difference in alkali hydro nitrogen was the largest, 22.15% lower. (3) The soil fertility evaluation index of the two treatments ranged from 0.49 to 0.77, and the soil quality was above the middle level. The average fertility index of the CK treatment was 6.67% higher than that of the RF treatment. The research results can provide a basis for implementing the land withdrawal scheme under the constraint of the total amount of water resources in the irrigation area and the protection of soil quality.

Key words: reducing water consumption by returning farmland, soil quality, fuzzy comprehensive evaluation method, soil fertility index, Manas River irrigation area