Root Growth and Nitrogen Utilization of a Leek Crop and an Undersown Catch Crop

Summary

After its late harvest a leek (Allium porrum) crop will normally leave large quantities of nitrogen (N) in the soil which may be subject to leaching. A possible method to reduce N leaching losses is to establish a catch crop before the harvest of the leek crop. It was the aim of this study to investigate the effects of incorporating a catch crop in a leek crop with minimal competition and to monitor how root growth affected N availability across soil depths at different distances between catch and leek crop rows. To reduce competition between both crops leek was planted at 0.5 and 0.75 m row distances and chicory (Cichorium intybus) as a catch crop at an interrow spacing of 0.75 m. Minirhizotron glass tubes were inserted in the middle of the interrow spaces (with or without catch crop established in mid July) and in the leek row. Leek roots grew to a depth of about 0.4 m by mid October with a high root density directly below the leek row but did not extend growth to the centre of the 0.75 m interrow. At the same time the catch crop had extended its roots to a depth of at least 1.25 m and was exploring the full width of the 0.75 m interrow with some roots even below the leek rows. The results show that it is possible to establish a catch crop in leek thereby depleting soil N and reduce the risk of N leaching without jeopardising crop yield.