Effects of in-situ returning solanaceous vegetable straw on comprehensive quality of facilities soil

Soil as an important natural resource is crucial for plant growth. However, rapid soil degradation has been found in recent years, due mainly to some unreasonable management measures, such as the abuse of chemical fertilizers and pesticides, as well as the long-term continuous cropping. The degraded soil with the lower soil quality can also result in lower crop productivity. The soil quality can be characterized by the loss of soil organic carbon. In view of the crop straw with the high carbon content, in-situ returning straw has the great potential for high soil quality and crop productivity. A large amount of vegetable straw has been produced in China at present, particularly with the ever-increasing cultivation area and output of vegetables. It is very necessary to promote the utilization rate of vegetable straw, in order to reduce the serious resource waste and a series of environmental issues after directly discarding or burning. The continuous removal of vegetable straw from the farmland ecosystem can also cause the loss of soil nutrients and the attenuation of the organic carbon pool. Fortunately, in-situ returning vegetable straw can serve as an effective resource utilization. This study aims to clarify the effect of in-situ returning solanaceous vegetable straw on the comprehensive quality of facilities soil in the fields. The calcium cyanamide and microbial agents were also applied to the vegetable straw during in situ returning. Taking the tomato, eggplant and pepper straw as test materials, a field experiment was performed on the four treatments: non-straw returning (CK), in-situ straw returning (SR), in-situ straw returning+calcium cyanamide (SR+C), and in-situ straw returning+microbial agent (SR+M). A systematic investigation was then conducted to determine the effects of different treatments on the soil chemical properties, microbial community, and degradation rate of straw. The soil quality was fully evaluated to calculate the soil quality index (Q). The results showed that better performance was achieved in the SR, SR+C and SR+M treatments, compared with the CK. There was an increase in the cation exchange capacity, and organic carbon pool, and nutrient conditions in the soil, indicating a better change in the soil bacterial and fungal community structure. The addition of calcium cyanamide inhibited the degradation of pepper straw, but there was no effect on the tomato and eggplant straw. By contrast, the microbial agent promoted the degradation of the three vegetable straws. Furthermore, the improved Q of facility vegetable fields was achieved after in-situ returning straw treatments. Specifically, the Q values of SR, SR+C, and SR+M treatments increased by 15.8%-32.5%, 8.8%-56.8%, and 21.8%-51.4%, respectively, compared with the CK. Therefore, the in-situ returning straw combined with the application of calcium cyanamide or microbial agent can be expected to serve as an effective resource utilization for the high comprehensive quality of the facility soil in the facility cultivation of solanum vegetables. Among them, the application of calcium cyanamide greatly contributed to the comprehensive quality of facility tomato soil, whereas, the microbial agent was for the facility eggplant and pepper soil. The finding can provide the theoretical reference for the resource utilization of solanum vegetable straw in the sustainable production of facility vegetables.