Responses of Soil Physicochemical Properties and Microbial Communities to Phosphorus Slag Amendments in a Simulating Cropping System

Comprehensive utilization of phosphorus slag (PS) is crucial to achieve sustainable resource utilization. However, only few systematic studies have been conducted on returning PS to fields. In this study, effects of PS on the soil microenvironment and planting were investigated in detail using simulations of returning PS to fields. The results showed that returning PS to fields would not cause heavy metal pollution in the soil. At the end of the experiment, the soil physicochemical properties revealed that PS addition (5% and 20% mass ratio) resulted in a slight increase in soil pH, which indicated that PS amendment decreased the acidity of the soil sample. Compared with a control sample, the available nitrogen decreased (about 10.64% to 25.53%) in the amended soil, and which was positively related to the added content of PS. Conversely, the available phosphorus content increased (from 87.64% to 192.43%) with the increase of PS content added to soil. Moreover, the PS addition to the soil altered the microbial composition. The top six genera in soil microbial community were Bryobacter (1.59%), Geobacter (1.54%), Haliangium (1.51%), Nitrospira (1.19%), Candidatus Udaeobacter (1.14%), and Sphingomonas (1.12%). The activity of urease, phosphatase, and cellulase increased, and the abundance of functional genes related to nitrogen (ureC, amoB, nirS, and nirK) and phosphorus (ppx, pqqC, and phoD) also increased after PS addition. In a pot experiment, the addition of PS to soil promoted the growth of crops. In summary, proper addition of PS to agricultural soil is beneficial for both the soil environment and the growth of crops.