Effective indicators and drivers of soil organic matter in intensive orchard production systems

Soil organic matter (SOM) is critical for the sustainable development of intense agroecosystems such as orchard production systems. Nevertheless, the status and drivers of SOM are indecipherable in different orchard systems due to the perennial anthropogenic influences and complex multicollinearity of soil properties. Thus, the present work aimed to address these issues using indicator transformation, data dimension reduction, and geostatistical method. We selected two orchard systems (open field and plastic shed) with similar mean SOM contents (approximately 15 g kg(-1)). Our results revealed that the average stratification ratio of SOM was significantly greater in open field orchards (2.20 +/- 0.93) than in plastic shed orchards (1.75 +/- 0.71) (p < 0.05). Likewise, the SOC/clay ratio in open field orchard soils (0.096 +/- 0.051) was significantly higher than that in plastic shed orchards (0.088 +/- 0.025) (p < 0.01). The variance analysis of these two indicators suggested a greater soil fertility in open field orchards than plastic shed. The main drivers of SOM in different orchard systems were different. In open field orchards, the terrain (q=0.36), soil ion processes (q=0.34), and soil types (q=0.31) were the dominant factors of affecting spatial variability of SOM, while the soil texture (q=0.44), soil types (q=0.32) and terrain (0.30) mainly explained the spatial heterogeneity of the SOM in plastic shed orchards. Outputs of this research provide a guidance for training the farmers to improve orchard SOM, as well as a reference for investigators to further explore the SOM influencing factors.