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.