Abstract: Non-grain utilization of cultivated land threatens farmland ecological environment and soil health, which restricts grain production. To identify the key obstacle factors of cultivated soil under non-grain utilization, explore the changes of soil quality and function, and evaluate the effects of non-grain utilization on the health of farmland soil, we evaluated soil health of farmland under different non-grain utilization types (vegetables, bamboo-abandoned, nursery-grown plant-abandoned, nursery-grown plant-rice) by soil quality index and soil multifunctionality index method combined with sensitivity and resistance approaches. The results showed that soil organic carbon and total nitrogen (TN) in the bamboo-abandoned soil were 95.3%, 66.7%, 65.7% and 82.6%, 57.0%, 59.5% of those under vegetables, nursery-grown plant-abandoned and nursery-grown plant-rice treatments, respectively. The electrical conductivity of vegetable soil was 2.2-2.5 times that of other soils of non-grain cultivated land. Total phosphorus and nitrate nitrogen were 1.8-2.0 times and 3.5-5.5 times of other soils of non-grain cultivated land, respectively. Among different non-grain utilization types, soil quality index and soil multifunctionality index of vegetable soil were the highest. Soil quality index and soil multifunctionality index decreased significantly in bamboo-abandoned (50.2% and 22.7%), nursery-grown plant-abandoned (38.3% and 14.4%) and nursery-grown plant-rice (27.7% and 8.5%) treatments, compared with that of vegetable soil. Random forest model analysis showed that available potassium and available nitrogen (AN) were the key factors affecting soil quality index. TN, cellulase and xylanase activities that related to soil C cycle were the key factors affecting soil multifunctionality index. In addition, available phosphorus, AN, TN and enzyme activity were sensitive indices to soil change in non-grain cultivated land. By comprehensively evaluating soil quality of non-grain cultivated land, we identified the key obstacle factors and provide a theoretical basis for the healthy soil cultivation and sustainable utilization of non-grain cultivated land.

Key words: non-grain utilization of cultivated land, land use mode, radar map area method, soil multifunctionality, soil quality, soil nutrient