Tuesday, November 6, 2007 - 11:40 AM
201-8

Drainage and Sub-Irrigation Impact on Nutrient Status in a Lacustrian Soil.

Barbara A. Baker1, Norman R. Fausey1, and Khandakar Islam2. (1) USDA, ARS, 590 Woody Hayes Drive, Columbus, OH 43210, (2) Ohio State University - OARDC, OSU South Centers, 1864 Shyville Rd, Piketon, OH 45661-9749

The objective was to evaluate the impacts of drainage and sub-irrigation on soil nutrient status. Water management treatments (WTM) included both unrestricted subsurface drainage year round and subirrigation during the crop-growing season with unrestricted subsurface drainage the remainder of the year. Soil samples were collected at 0-20 and 20-40 cm, processed and analyzed for various soil nutrients by ICP analysis. A number of soil nutrient indices were calculated to evaluate nutrient availability in soil. The concentration and mass of S varied significantly in response to WTM with an interaction from soil depth. Significantly higher concentration and mass of Fe, Mn, and B was found in sub-irrigated soil compared to drained soil. There was a significant depth effect on concentration and mass of C, N, P, K, Mg, and S but not Ca. None of the nutrient indices changed significantly in response to the WTM, however, soil depth exerted consistent effects on nutrient indices. Using stepwise forward elimination of nutrients to calculate nutrient index based on minimum data-sets (MDS), the normalization of C, N, P, K, Fe, and Cu (MDS6) or C, N, and P (MDS3) gave higher values for surface depth than subsurface depth for both soils. Among the nutrients, C was found to be most important indicator to evaluate over-all nutrient availability in soil. While the MDS6 significantly accounted more than 95% variability, the MDS3 accounted more than 90% variability in Allindex. Total organic C as a single linear measure of nutrient availability significantly accounted for 87% of the variability in Allindex, 93% of the variability in MDS6, and 91.4% of the variability in MDS3. N and P as single measures of nutrient availability quadratically accounted 81 and 85% of the variability in Allindex, 87% of the variability in MDS6, and 91% of the variability in MDS3.