IMPACT OF HERBACEOUS COMPETITION AND DRAINAGE CONDITIONS ON THE EARLYPRODUCTIVITY OF WILLOWS UNDER SHORT-ROTATION INTENSIVE CULTURE

The productivity of trees under short-rotation intensive culture is in fluenced by herbaceous competition and drainage conditions. During the first year of establishment of Salix discolor Muhl. and Salix viminal is L., four weed-suppression treatments were applied to two sites show ing different drainage conditions, one well drained and the other is p oorly drained. On the well-drained site, the productivity of the trees increased in all the plots under treatment, whereas on the poorly dra ined site, only the use of a plastic mulch increased the biomass produ ction. The mean productivity on the well-drained site was always super ior to the productivity measured on the poorly drained site except whe n the vegetation was controlled by the use of a plastic mulch. The ana lyses related to nutrition revealed that the trees on the well-drained site absorbed more nutrients than those on the poorly drained site. S alix discolor showed a higher uptake of potassium and S. viminalis, a higher concentration of calcium. Our results indicate that weed suppre ssion is essential to the establishment of trees in short-rotation int ensive culture and that the use of a plastic mulch proved to be partic ularly profitable on marginal sites.