Timing of dairy manure applications to perennial grass on well drained and poorly drained soils

ABSTRACT:

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.