Root distribution and water use in a four-year old silvoarable system

Abstract

In a trial established in 1992 at Silsoe, Bedfordshire, England, soil trenches were used to examine the root distribution of 3 poplar trees (clone Populus 'Beaupre') bordered by cultivated fallow and cropped alleys. On a length basis, 60% of the tree roots were present in the 2-m wide plastic mulched strips at the base of the tree, with 36% and 4% in the fallow and cropped areas, respectively. The poor growth of poplar roots in the cropped areas is probably a result of competition for water. In the cultivated fallow areas, the root length density was greater at a depth of 30-70 cm than in the surface layer (0-30 cm), suggesting that cultivation could reduce competition between tree and crop roots. The change in soil water content around a representative tree surrounded on both sides by fallow, was monitored during the dry summer of 1996. The mulch at the base of the tree appeared to prevent early season soil evaporation. By the end of July, the tree was extracting water at a distance of 3.6 m from the base of the tree.