Root pruning reduces root competition and increases crop growth in a living mulch cropping system

In two field experiments, growth of white cabbage in pure stands was compared with that of cabbage grown in living mulch systems to reduce pest attacks. The roots of the living mulch were pruned early in the season, with the aim of reducing competition and increasing growth of the white cabbage. Root pruning was shown to increase the above-ground biomass of white cabbage, with two prunings giving higher cabbage yields than one, but there were clear differences between the living mulch species tested (red clover, birdsfoot trefoil, salad burnet, winter rye). Below-ground growth and competition were examined by measuring root distribution in minirhizotrons and uptake of N-15 placed at different soil depths. These studies showed that the ability of mulch species to compete for resources at depth was restricted by pruning, and that this was crucial for the development of the white cabbage crop.