Compost and Manure Effects on Fertilized Corn Silage Yield and Nitrogen Uptake under Irrigation

Dairy manure increases the yields of dry bean (Phaseolus vulgaris L.) and spring wheat (Triticum aestivum L.) from eroded, furrow-irrigated soils and may increase corn (Zea mays L.) silage yield from steeper eroded areas under sprinkler irrigation. In a 2-year field study in southern Idaho on Portneuf silt loam (coarse silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid), the effects of a one-time, fall application of 29 or 72 Mg ha of dry manure or 22 or 47 Mg ha of dry compost on subsequent silage yield and nitrogen (N) uptake from previously eroded, sprinkler-irrigated hill slopes were evaluated. In October 1999, stockpiled or composted dairy manure was disked to a depth of 0.15 m into plots with slopes from 0.8 to 4.4%. After planting field corn in 2000 and 2001, a low-pressure, six-span traveling lateral sprinkler system was utilized to apply water at 28 mm h in amounts sufficient to satisfy evapotranspiration to 6.436.6-m field plots. Yields in 2000 were 27.5 Mg ha, similar among all rates of all amendments and a fertilized control. In 2001, compost applied at oven-dry rates up to 47 Mg ha increased yield compared to controls. Silage yield in 2001 increased initially then decreased with increasing manure applications. Where compost or manure was applied, regardless of rate, 2-year average N uptake was 15% greater than controls. Regardless of treatment or year, yields decreased linearly as soil slope increased.