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.