Influence of dairy slurry manure application method, fall application- timing, and winter rye management on nitrogen conservation

Fall manure applications can lead to nutrient losses prior to spring planting. This 2-yr study evaluated effects of winter cereal rye (Secale cereal L.) crop management (cover crop versus ryelage), and fall, dairy slurry manure application method (broadcasted versus injected) and timing (September vs. November) on manure–N conservation. Nitrogen conservation was calculated from NH₃ volatilization, percentage of manure–N in aboveground rye (%ManureN-R) and soil (%ManureN-S) in spring prior to corn (Zea mays L.) planting, and subsequent corn yield. Ryelage compared to cover crop conserved more %ManureN-R (2.6-fold) and despite reduced corn yield, ryelage-corn treatments with 3.6-fold greater rye biomass produced 20% greater total harvested forage than cover crops. Compared to broadcasted manure (BM), injected manure (IM) reduced NH₃ losses and increased ryelage biomass (42%) after September (EARLY) applications, %ManureN-R (50%), %ManureN-S at multiple depths, and total harvested forage (20%). Corn silage yield with IM compared to BM was also greater after all cover crop treatments (23%), all ryelage treatments in 2015 (35%), and ryelage with a November application (LATE) in 2014 (30%). Compared to EARLY, LATE applications increased %ManureN-R in ryelage after BM (44%) and IM (50%), %ManureN-S at multiple depths in both rye treatments, and corn silage yields with IM following cover crops (21%). Following ryelage, corn yields were not larger following greater %ManureN-S in LATE IM versus BM, suggesting potential for more soil NO₃ leaching loss with LATE IM. However, multiple management options reduced fall manure–N losses and conserved manure–N for crop utilization, allowing for farm management flexibility.