Variations in Corn Yield and Nitrogen Uptake in Relation to Soil Attributes and Nitrogen Availability Indices

Identification of soil attributes most determinant to crop yield is still a matter of debate. The main objective of the present study was to relate the variations in corn (Zea mays L.) yield and N uptake to 16 soil attributes. Samples were collected in 2005 and 2006 from a long-term experiment. Soil organic C (SOC), total N (TN), potential mineralizable N (PMN), NO3 extractable with KCl (NO3-KCl) and CaCl2 (NO3-CaCl2), NO3 absorbed on anion exchange membranes (NO3-AEM), N extracted with NaHCO3 read at 205 nm (N-NaHCO3-205) and 220 nm (N-NaHCO3-220), N present in fulvic acid (FA-N), humic acid (HA-N) and non-humified fractions (NHF-N), mean weight diameter of aggregates (MWD), total, macro- and microporosity, and bulk density (D-b) were measured. Principal component analysis (PCA) was conducted with the measured soil attributes, and the principal components (PCs) were used in a stepwise regression with corn yield and N uptake. In both years, a maximum of 88% of the total variance was explained. The stepwise regression analysis indicated that the first two PCs explained 78 to 91% of the variability in corn yield and N uptake. Based on the PCA, TN, HA-N, NO3-KCl, NO3-CaCl2, NO3-AEM, and PMN appeared as primary indicators of corn yield and N uptake, whereas MWD, FA-N, and NHF-N appeared as secondary indicators. When the variability in corn yield and N uptake explained by each N availability index was assessed, NO3-KCl and NO3-CaCl2 appeared as the best predictors of corn yield because of their ease of measurement and reliability across years.