[Effects of Plastic Mulch Film on Soil Nutrients and Ecological Enzyme Stoichiometry in Farmland]

Ecological enzyme stoichiometry can be used to evaluate the limit of soil microbial energy and nutrient resources. To illustrate the effects of plastic mulch film on soil ecological enzyme stoichiometry in farmland, this study collected soil with different amounts of mulching film residual and used the fluorescence analysis to determine the activities of key enzymes for the carbon, nitrogen, and phosphorus cycle processes including β-1,4-glycosidase (BG), β-1,4-N-acetyl amino glycosidase (NAG), and phosphatase (ACP) activity. This study investigated the effects of plastic mulch film on soil nutrient cycling and supply in farmland. The results showed that in the soil with chemical fertilizer, plastic film mulching decreased soil Olsen-P and NO₃^--N contents to 48%-62% and 16%-24% of those in the soil without plastic film mulching, respectively. In the soil with the combined application of organic-chemical fertilizers, plastic film mulching increased Olsen-P and NO₃^--N contents by 144%-203% and 1.9-5.1 times, respectively. In the organic-chemical fertilization soils, plastic film mulching decreased SOC:TN in soils by 6.6%-25.8%, whereas it increased SOC:TP and TN:TP significantly. MBC, MBN, and MBP contents in the soil with plastic film mulching were significantly lower than that in non-plastic film mulching farmland, and there were no significant differences in MBC:MBN and MBC:MBP between soil with and without plastic film mulching. The MBN:MBP was reduced by 36.6% and 23.8% in S1 and S2, and 5.4 and 1.3 times in S3 and S4 by plastic film mulching, respectively. The change pattern of NAG:ACP in soil was similar to that of the corresponding elements ratio in microbial biomass. In the soil from plastic film mulching, the ratio of BG:NAG was 1.3-15 times higher in organic-chemical fertilization soils than that with only chemical fertilizer. In conclusion, plastic film mulching reduced the availability of soil nutrients, and organic-chemical fertilization alleviated the limitation of soil nutrients to a certain extent. This study deepened the understanding of the response of soil microorganisms to nutrient cycling after plastic film mulching. It provides a theoretical basis for optimizing the farmland management in the use of plastic film.