Effects of Dairy Manure on Phosphorus Concentrations and Losses in Tile Effluent1
- G. W. Hergert,
- S. D. Klausner,
- D. R. Bouldin and
- P. J. Zwerman2
Dissolved phosphorus concentrations and losses in effluent from a tile-drained silt loam were compared before and after manuring. Effluent samples were collected from 0.33-ha tile-drained plots for 4 years before and 3 years during consecutive annual dairy manure applications of 35 or 200 wet metric tons/ha. Plots had received fertilizer P in years prior to manuring. More than 95% of the effluent samples had dissolved molybdate reactive P (DMRP) concentrations < 30 ppb before manuring. During the 3 years the manure was applied, 53 and 92% of the effluent samples contained < 30 ppb P for the 200- and 35-metric-ton applications, respectively. The flow-weighted DMRP concentrations in tile effluent were 116, 441, and 97 ppb for 200 metric tons of manure/ha per year, and 22, 10, and 9 ppb for 35 tons/ha per year, respectively, during the 3 years manure was applied.
The tile flow accounted for about 40% of the drainage water lost from the plots, but the P contents of tile flow were 10% of total dissolved P losses in surface runoff. P additions from 30 to 40 wet metric tons/ha of manure would be adequate to meet crop needs but should not produce excessively high P concentrations in tile flow.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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