Cover crop by irrigation and fertilization improves soil health and maize yield: Establishing a soil health index

Cover crop can reduce the intensity of land use, and improve soil fertility and productivity in multiple-cropping systems. However, only a few studies have comprehensively evaluated soil health after cover crops in terms of management goal and soil multi-functionality. In this study, different minimum data set (MDS) methods were used to establish a soil health index (SQI) model to evaluate soil health of the winter smooth vetch-summer maize cropping system in southwest China. We analyzed thirty-five soil parameters (representing soil physical, chemical and biological properties) connected with the soil functions as potential soil health indicators in the phase of smooth vetch and maize under six management treatments (CK (control), N (N fertilizer), P (P fertilizer), NP (N and P fertilizer), NPW (N and P fertilizer + irrigation), CF (fallow)). Those managements were set in the smooth vetch phase (as a cover crop). The MDS using correlation analysis (cMDS), principal component analysis (pMDS) and random forest analysis (rMDS) from the total data set (TDS) were selected and then used for SQIs calculation, respectively. Cover crop by different management of irrigation and fertilization affected each soil property in different ways. All three SQIs were significantly correlated with SQI-TDS, validating the SQI models developed by three MDS methods ( P < 0.05). Further, the SQI based on rMDS was the most accurate and sensitive, suggesting the RFA-based SQI reflects soil functions more adequately than the CA and PCA-based SQI. Cover crop by the management of fertilization or/and irrigation will not only improve soil health, but also enhance maize yield compared with fallow treatment, especially for NPW treatment. Fertilization treatments (N, P, NP and NPW) had higher soil health index, which was related to the better performance of soil in sustaining biological activity, physical stability and supporting function. In summary, the SQI model developed by the RFA method can provide a practical and robust tool for assessing soil health based on the management goal. • Cover crops can improve soil health index and maize yield. • Cover crops with balanced irrigation and fertilizer have better soil health. • Increasing soil health index significantly enhances maize yield. • Soil health index developed by random forest analysis had the most accurate ability.