Site Variability, Soil Quality and Crop Performance.

Crop yield is often associated with site variability. Composite soil cores at 0-10, 10-20, and 20-30 cm depth, respectively were randomly collected from replicated (n=4) consistently higher (Good) and poor (Poor) crop stands (continuous corn) at the Ohio State University Waterman Farm, Columbus, Ohio. The field moist soil samples were processed, and analyzed for total microbial biomass (SMB), metabolic quotients (qR), pH, total, active and particulate C and N, available P and S, exchangeable K, Ca, Mg, Fe, Mn, Cu, Zn, B, Mo, moisture content, bulk density, saturated hydraulic conductivity (ks), and aggregate stability (WSA). The measured and calculated soil properties with crop yields (2003-2007) data were integrated to calculate soil quality for evaluating site variability impact on crop yields. The SMB (more than 50%) and qR, as a measure soil biological quality indicators, were significantly higher in Good site than in Poor site. The active C content was also higher in Good site than in Poor site. Soil pH, particulate organic C and N, total C and N did not vary significantly between Good and Poor sites. The Poor site had Ca and K but lower Fe and B contents than in Good site. The ks and WSA varied significantly between Good and Poor sites. Both ks and WSA were higher in Good site than Poor site. The values of soil quality properties decreased significantly with increasing soil depth. The calculated soil quality indices showed a significant difference between Good and Poor sites. Good site had higher soil quality than Poor site. Likewise, temporal crop yields were higher (more than 50%) in Good site than in Poor site. Results suggest that both inductive (soil properties) and deductive (crop yields) indicators can be used to consistently detect site variability effects on crop yields.