Timing of Dairy Manure Applications to Perennial Grass
on Well-Drained and Poorly-Drained Soils
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D.M. Sullivan, C.G. Cogger, A.I. Bary, and S.C. Fransen
Timing of manure applications is a critical part of dairy farm plans because it affects water quality, crop production, and manure handling costs. We conducted a 2-year field study to provide information to farm planners on manure application timing for intensive grass production in the Pacific Northwest. We applied dairy manure slurry (340 kg total N ha-1 yr-1; 300 lb N acre-1 yr-1) to orchardgrass on well-drained and poorly-drained soils in western Washington, comparing early (February and May), mid-season (May through summer), and late (summer-fall) timing sequences for manure application. We also compared manure N rates ranging from 170 to 670 kg ha-1 yr-1 (150 to 600 lb acre-1 yr-1) for the mid-season application only. Forage yield, N uptake, apparent N recovery, and late-season soil nitrate-N were measured. Cumulative apparent N recovery for manure N averaged 31%, and ranged from 24 to 38% over all treatments. The early and late manure sequences on the well-drained soil had greater spring-harvest and cumulative yields than for the mid-season sequence. Timing effects were smaller and not statistically significant on the poorly-drained soil. The effect of a manure application on grass production was greatest in the first harvest following application, and declined in subsequent harvests. Residual soil nitrate was less than 5 mg N kg-1 soil for all manure timing sequences applied at the (340 kg total N ha-1 yr-1; 300 lb N acre-1 yr-1) rate.
Sullivan, D.M., C.G. Cogger, A.I. Bary, and S.C. Fransen. Timing of dairy manure applications to perennial grass on well-drained and poorly-drained soils. J. Soil & Water Conservation. (In Press) [refereed journal]