Background Jiashi county in Xinjiang is a typical cotton-growing area and is also famous for its fruit product of Jiashi melon. This paper aims to explore the rotated-cropping mode of these two agricultural products to investigate how it affects soil chemical properties and compare it to the cotton continuously-cropping mode, and also to provides theoretical support for optimizing agricultural production and planting mode.

Methods Soil chemical properties index under cotton continuously-cropping (abbreviated as continuously-cropping) and cotton-Jiashi melon rotated-cropping (abbreviated as rotated-cropping) were compared and analyzed based on field soil sampling. The soil samples were collected from two kinds of cropping soil in the surface (0-20 cm), middle (20-40 cm), and bottom (40-60 cm) layers. Soil chemical indices were measured through indoor index analysis, and the distribution characteristics of soil organic matter, total salinity, pH, and salt base ions between the two cropping modes were compared based on t-test and homogeneity test. The variation trend of soil chemical properties and nutrients was explored.

Results 1) The soil organic matter content distribution characteristics under the two cropping modes differed in the study area. The average organic matter content in the different layers of the rotated-cropping soil showed as middle > surface > bottom layer. In the continuously-cropping soil, the average organic matter content showed as surface > middle > bottom layer. 2) The organic matter contents in both modes showed a decreasing trend with the increase of cropping years. Among them, there was a low organic matter content in the continuously-cropping soil, and the variation was small. There was a high organic matter content in the rotated-cropping soil, but the variation was considerable. 3) With the increase of planting years, the total salt content in the soil surface and middle layers of the rotated-cropping showed a decreasing trend, while the continuously-cropping soil showed an increasing trend.

Conclusions The results indicate that the organic matter content in the soil surface and middle layer increases in the rotated-cropping mode, and the content shows a decreasing trend with the increase of years. There is little difference in soil salt ion content between the two cropping modes, but the total salt content of the rotated-cropping soil was higher than that of the continuously-cropping soil. The results provide a scientific reference for optimizing the soil organic matter and the content of each salt base ion through the Jiashi melon and cotton rotated-cropping pattern.