Effects of catch crop type and root depth on nitrogen leaching and yield of spring barley

Summary

Catch crop root growth and nitrogen (N) uptake from both shallower and deeper soil layers is important for N management in arable farming system particularly in climates where excess winter precipitation induces N leaching. We simulated the root growth and biomass yield of three common catch crops [chicory (Cichorium intybus L.), fodder radish (Raphanus sativus L.) and perennial
ryegrass (Lolium perenne L.)] and their effect on soil mineral N in different soil layers by using the FASSET model. The simulated results of catch crops root growth and mineral N in the soil profile were validated against two years (i.e. 2006 and 2007) of observations taken in Foulum and Flakkebjerg, Denmark. Fodder radish had the deepest root system and depleted N from deeper soil layers than
chicory and ryegrass. The effect of these three catch crops on N leaching and grain yield of spring barley was simulated for 30 years using the FASSET model. The simulations showed that the system with ryegrass catch crop
had a smaller amount of N leaching from 1 m depth than the system with other catch crops and without catch crops. However, estimated total N leached from 2 m soil depth was the smallest in the system with fodder radish followed by the system with chicory, indicating that these catch crops are capable for taking soil N also from below 1 m depth. On average, the system with fodder radish was estimated to decrease N leaching from 2 m depth by 79% compared with the system without catch crops, resulting in an average spring barley grain yield increase of 2%. Chicory and ryegrass
correspondingly contributed to reducing N leaching from 2 m soil depths by 71 and 67%, but with the cost of decreasing spring barley yield by 3 and 5%, respectively, when compared with the system without catch crop. Termination of catch crop use slightly increased the spring barley yield, but also increased N leaching by about 17%. Inclusion of catch crop in the system increased the total N and C content in the soil in all cases but the increase was largest with ryegrass.