Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2014
Publication Date: N/A
Technical Abstract: Oat (Avena sativa L.) shows promise as a fall-forage option for dairy producers in Wisconsin, and potentially opens a window of opportunity for manure spreading that is not associated with production of corn (Zea mays L.). Our objectives were to assess the effects of summer applications of bedded-pack manure containing wood shavings or commercial N fertilization on the DM yield, N uptake and recovery, and nutritive value of fall-grown oat forages. Research plots were fertilized with either bedded-pack manure (23 or 45 Mg/ha, wet basis; 22.9% DM; 1.9% N, DM basis), or commercial urea (46-0-0) at application rates of 0, 20, 40, 60, or 80 kg N/ha, and then seeded to two oat cultivars (Ogle or ForagePlus). Plots were harvested on two dates (early October or November), which simulated grazing and silage applications, respectively. Climatic conditions differed sharply across years, with growth responses limited somewhat by drought during 2012. During both years, DM yield increased linearly (P = 0.034) with commercial N fertilization, and yields following applications of urea exceeded (P = 0.003) forages receiving bedded-pack manure during 2011, but not during 2012 (P = 0.845). Overall DM yields were greater in early November compared to early October during both 2011 (3991 vs. 2257 kg/ha; P < 0.001) and 2012 (2753 vs. 1997 kg/ha; P < 0.001). Apparent N-recoveries by oat forages increased linearly (P = 0.007) with urea application rate during 2011, and increased with both linear (P = 0.005) and quadratic (P = 0.003) effects during 2012. However, apparent N-recoveries following applications of bedded-pack manures were essentially nil for both years (overall range = -6.2 to 2.6% of N applied). For 2011, concentrations of water-soluble carbohydrates (WSC) were inversely related to urea application rate, declining from 12.4 to 10.1% as fertilization rate increased from 0 to 80 kg N/ha, which was explained by both linear (P = 0.009) and quadratic (P = 0.004) effects of application rate. Similar effects were observed for 2012, when WSC declined from 19.3 to 16.3% across the same urea fertilization treatments. Calculated energy density of fall-oat forages remained very high across all treatments; overall means were 67.0 and 70.1% TDN for 2011 and 2012, respectively. These results indicate that fall-grown oat is an energy-dense forage option, but bedded-pack manures containing wooden shavings provide little immediately available N to support forage production.