Nitrous oxide emissions and nitrate leaching in an arable rotation resulting from the presence of an intercrop

The effects of cereal legume intercropping on nitrogen dynamics and losses from an arable rotation are reported. The main hypotheses were that: (a) intercrops can reduce nitrous oxide (N2O) emissions relative to those from cereal monocrops; (b) the choice of legume cultivars can change N losses from a system and also influence soil available-N. Two field experiments were established in the east of Scotland. The treatments in 2006 consisted of either component monocrops (barley, oat, pea or clover) or cereal-legume intercrops. Spring oats were planted in 2007 and perennial ryegrass in 2008 on both sites. Nitrate leaching was reduced under legume intercrops when compared with the barley monocrop (cumulative values of 0.67 and 3.80 kg NO3−–N ha−1, respectively) in 2006. Nitrous oxide losses were significantly different between the treatments and especially the two barley/pea cultivar (cumulative values of 6.02 and 2.14 kg N2O–N ha−1 for intercrops cv. Nitouche and cv. Zero 4, respectively) in 2006. The leguminous intercrops increased the soil available-N during the first growing season and in the subsequent crop. Thus intercrops may reduce N losses and this work highlights the need to choose suitable cultivars, taking into account the effects upon the growth of the main crop and the wider environment effects.