Soil profile characteristics of high-productivity alluvial cambisols in the North China Plain

The North China Plain (NCP) is one of major breadbaskets in China. Crop growth and grain yield differ significantly with spatial variations of soil properties. This study aims to identify the key soil properties in relation to the grain yield for the winter wheat (Triticum aestivum L.)-maize (Zea mays L.) cropping system in a high-productivity farmland of the NCP. The field trials were conducted in three fields with different grain yield levels in Tai'an City, Shandong Province, China, during the 2009–2012 period. Consistent field management strategies were applied in the three fields. Fifty-one physical and chemical indicators of the soil profile as related to grain yield were evaluated. An approximate maximum of 17.8% annual average grain yield difference was observed in the fields during the period of 2009–2012. The soil indicators were classified into three clusters with specific functions using cluster analysis, and three key indicators were extracted from each cluster to characterize the different soil properties of three fields. The first cluster represented soil water retention capacity, and the key indicator was available soil water (ASW), which ranged from 153 to 187 mm in the 1.2 m profile and was correlated positively with grain yield. The second cluster represented soil water conductivity, as measured by saturated hydraulic conductivity (Ks). The higher yield field had a greater capacity to retain topsoil water for its lower Ks (1.9 cm d−1) in the 30–70 cm soil layer as compared to the lower yield field. The third cluster represented nutrient storage and supply, as indicated by the ratio of nutrient content to silt+clay content of the top soil layer. The ratio of soil organic matter (OM), total nitrogen (TN), available P, exchangeable K+ to silt+clay content in the 0–20 cm soil layer were 19.0 g kg−1, 1.6 g kg−1, 94.7 mg kg−1, 174.3 mg kg−1 in the higher yield field, respectively, and correlated positively with the grain yield. By characterizing the differences in soil properties among fields with different yield levels, this study offers the scientific basis for increasing grain yield potential by improving the soil conditions in the NCP.