Saturday, 15 July 2006

Alum WTR Amendments to Field Plots Having Soils with High Soil Phosphorus Test Levels.

Lee W. Jacobs and Brian J. Teppen. Michigan State Univ, Dept of Crop and Soil Sciences, East Lansing, MI 48824-1325

Two sites were established each year for amendment with alum WTR (water treatment residuals) in the 1998, 1999 and 2000 growing seasons. The six sites had Bray P1 Soil Test P (STP) levels of about 300, 575, 550, 550, 310 and 180 ppm. Alum WTR from Holland, MI were applied to the 1998 sites at rates of 38 and 114 dry Mg/ha and to the 1999 sites at rates of 45 and 134 dry Mg/ha. In 2000, alum WTR from Grand Rapids, MI was used at rates of 74 and 222 dry Mg/ha. WTR each year had oxalate-extractable Al levels of 3.4%, 5.4% and 2.0%, respectively. Soils were disked twice at each site following application to mix the WTR with soil. Subsequent tillage for mixing and seedbed preparation prior to planting varied from site to site. All six sites were rototilled in April/May, 2000 prior to planting to achieve a more thorough mixing of WTR and soil. Field corn (Zea mays L.) was planted at each site for most years, except soybeans (Glycine max L.) were planted at two sites in some years. Diagnostic leaf tissue samples and yield measurements of crops were taken during each growing season, until five years of crop data were accumulated. Surface soils were sampled each year and soil samples to 90 cm were collected in 2001, 2003 and 2005 to evaluate changes in Bray P1 STP and CaCl2-extractable (water-soluble) P levels with time. Results of soil tests for this seven-year field project will be presented.

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