Cultivar, Harvest Date, and Nitrogen Fertilization Affect Production and Quality of Fall Oat

Previous research has shown that oat ( Avena sativa L.) has promise as a fall‐forage option for dairy producers. In addition, dairy producers often have a recurring need to identify opportunity windows for manure hauling other than before or after production of corn ( Zea mays L.). Our objectives were to evaluate the effects of N fertilization, cultivar selection, and harvest date on dry matter (DM) yield, N uptake, N recovery, and the nutritive value of fall‐grown oat forages fertilized with either urea (46–0–0) or bedded‐pack manure obtained from a dairy‐heifer facility. Two cultivars of oat (ForagePlus and Ogle) were planted in August 2011 and 2012, fertilized with bedded‐pack manure (23 or 45 Mg ha –1 , wet basis) or commercial urea (46–0–0) at rates of 0, 20, 40, 60, or 80 kg N ha –1 , and then harvested on two dates. Climatic conditions differed sharply across years, with growth responses limited by droughty conditions during 2012. During both years, DM yield increased linearly with commercial N fertilization, although the magnitude of these responses was relatively small. Yields of DM following applications of urea exceeded those of forages receiving bedded‐pack manure during 2011. Apparent N recoveries increased linearly with application rate for urea during 2011 and increased with both linear and quadratic effects during 2012, but N recoveries following applications of bedded‐pack manures were minimal during both years (overall range = –6.2 to 2.6% of N applied). These results indicate that bedded‐pack manures containing wood shavings provided little immediately available N to support production of fall‐grown oat.