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Cropping System Effect on Soluble and Sediment-Bound Phosphorus Losses

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  032076,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14942) @2003
Authors:   Joseph D. Grande, K.G. Karthikeyan, John C. Panuska, Mark Powell
Keywords:   Phosphorus transport, best management practices, corn silage, dairy manure, nutrient management, residue cover

There is a growing interest in corn silage utilization due to changes in animal farm dynamics and favorable economics compared to alfalfa. The extent of residue cover influences runoff production and soil losses, and hence, these changes will affect the off-site migration of phosphorus (P). Since high-cut silage will increase residue cover, this method could conceivably minimize water quality degradation that would otherwise result from harvesting corn for silage. We examined cropping system effects on sediment and P losses from no-till fields planted in corn. Treatments included conventional corn grain (CG) and silage (CS-L) and non-conventional, high-cut (24-26) silage (CS-H). Each treatment received one of three manure treatments: no manure, application in fall or spring. Simulated rainfall (76 mm/hr; 1 h) experiments were performed in spring and fall 2002, runoff from 2.0 m x 1.5 m plots collected and a sub-sample analyzed for total sediments, dissolved reactive phosphorus (DRP), and total phosphorus (TP).

Compared to CS-L, CS-H was effective in reducing sediment and P losses; the reductions were greatest in fall runoff and were enhanced by manure addition. Runoff depth, sediment load, DRP load, and TP load were reduced by 50% when no manure was added and by 85% with manure applied in either season. Although sediment, DRP, and TP concentrations were higher under manure application, the secondary effect of enhanced infiltration resulted in lower values on a load basis. Reductions were smaller following spring rainfall. DRP concentration was sensitive to manure application timing while TP concentration was not. Compared to the no manure treatment, DRP concentrations in runoff from all crop treatments were five times greater following spring manure application, while TP concentrations were highest under no manure. Preliminary data on particle size distribution in transported sediments reveal an increased concentration of fines (< 2 m) on manure-applied plots. Recently applied spring manure protected the soil the most, but leads to the preferential selection of finer particles.

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