RT Journal Article SR Electronic T1 Timing of dairy manure applications to perennial grass on well drained and poorly drained soils JF Journal of Soil and Water Conservation FD Soil and Water Conservation Society SP 147 OP 152 VO 55 IS 2 A1 D. M. Sullivan A1 C. G. Cogger A1 A. I. Bary A1 S. C. Fransen YR 2000 UL http://www.jswconline.org/content/55/2/147.abstract AB 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 two 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-1yr−'; (300 lb N ac-1 yr−1)I 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 through fall, timing sequences for manure application. We also compared manure N rates ranging from 170 to 670 kg ba−l yf−1 (150 to 600 lb at−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 yf1 (300 lb N at−1 yr−1) rate.