Assessment of soil property in the Guyuan region from Ningxia Province of China and prediction of pepper blight.

Soil quality is an important determinant of soil-use efficiency in the Loess Plateau. However, there is no in-depth study on the soil quality of the Loess Plateau. The present study compared the quality of the 0-20 cm soil layer (T0-20) and the 20-40 cm soil layer (T20-40) from the Guyuan region located in the Loess Plateau. The analysis revealed that T0-20 had a higher content of total N, total P, available P, and organic matter, and the activities of microbial enzymes, especially β-grape-glycosidase (β-GC) and sucrase (SC), than T20-40, indicating that soil quality in T0-20 was better than T20-40. Amplicon sequencing found that Pseudombrophila from Ascomycota was the most abundant microbial species and significantly differed between T0-20 (34.2%) and T20-40 (48.7%). This species and another 19 microbial species, such as Ceratobasidiaceae and Mortierellaceae, determined the diversity of soil microorganism. Further analysis of the phenotype and other parameters of pepper seedlings subjected to P. capsici infection isolated from test soil revealed that decreased organic matter content in deep soil layer is related to happening of pepper blight, and 3 h after infection was the critical time point for infection. The peroxidase (POD) activity increased after P. capsici infection and was positively correlated with infection time, suggesting this enzyme may be an indicator of pepper blight occurrence. These findings provide a theoretical foundation for planning pepper blight management and crop cultivation strategies in the Guyuan region.