Management of Manure Nitrogen Using Cover Crops

The experiment was conducted to determine whether cover crops reduce N losses of fall‐applied liquid hog manure and whether sequestered N by cover crops is “transferred” to subsequent corn (Zea mays L.). Two locations (Elora and St. Mary's) in southern Ontario from 2003–2004 were used consisting of six cover crop treatments (red clover [RC] [Trifolium pratense L.] fall‐killed, RC spring‐killed, oat [Avena sativus L.] fall‐killed, oilseed radish [Raphanus sativus L.] fall‐killed, perennial ryegrass [Lolium perenne L.] spring‐killed, and no‐cover crop), and three target manure rates (0, 100, and 200 kg N ha−1). Non‐legume cover crops positively responded to fall manure application, where biomass increased by 50 to 130%. Red clover biomass increased 0 to 25% at higher manure rate application. A similar trend was found with plant N uptake. Generally applied manure N recovery was low (0–25%) in all the cover crops. Ammonia losses from manure applications to RC was higher than other cover crops due to inability to incorporate manure. During the period corresponding with corn N uptake, non‐legume cover crop impact on soil mineral N did not differ from the no cover control. When non‐legumes were used as cover crops following manure application, corn biomass, grain yield, and N uptake were equivalent to no cover crop treatment. However, when RC was used as a cover crop, above corn parameters were equivalent for all manure application rates and greater than the no‐cover crop treatment, so “transfer” of manure N could not be confirmed.