Application of manure to no-till soils: phosphorus losses by sub-surface and surface pathways |
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Authors: | Peter J A Kleinman Andrew N Sharpley Lou S Saporito Anthony R Buda Ray B Bryant |
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Affiliation: | (1) USDA, Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, University Park, PA 16802, USA;(2) Department of Crop, Soil and Environmental Sciences, Division of Agriculture, University of Arkansas, Fayetteville, AR 72701, USA |
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Abstract: | The acceleration of surface water eutrophication attributed to agricultural runoff has focused attention on manure management
in no-till. We evaluated losses of phosphorus (P) in sub-surface and surface flow as a function of dairy manure application
to no-till soils in north-central Pennsylvania. Monitoring of a perennial spring over 36 months revealed that dissolved reactive
P (DRP) concentrations increased 3- to 28-fold above background levels whenever manure was broadcast to nearby field soils.
A study conducted with 30-cm deep intact soil cores indicated that incorporation of manure by tillage lowered P loss in leachate
relative to broadcast application, presumably due to the destruction of preferential flow pathways. More P was leached from
a sandy loam than a clay loam soil, although differences between soils were not as great as differences between application
methods. In contrast, rainfall simulations on 2-m2 field runoff plots showed that total P (TP) losses in surface runoff differed significantly by soil but not by application
method. Forms of P in surface runoff did change with application method, with DRP accounting for 87 and 24% of TP from broadcast
and tilled treatments, respectively. Losses of TP in leachate from manured columns over 7 weeks (0.22–0.38 kg P ha−1) were considerably lower than losses in surface runoff from manured plots subjected to a single simulated rainfall event
(0.31–2.07 kg TP ha−1). Results confirm the near-term benefits of incorporating manure by tillage to protect groundwater quality, but suggest that
for surface water quality, avoiding soils prone to runoff is more important.
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Keywords: | Phosphorus Runoff Leaching No-till Dairy manure |
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