USING COVER CROPS TO ESTABLISH WHITE AND BLACK SPRUCE ON ABANDONED AGRICULTURAL LANDS

Vegetation control is a critical factor in reforestation. On abandoned agricultural lands, an alternative to herbicide application is the us e of cover crops to compete with the weeds a nd to improve survival an d growth rates of transplanted species. A factorial experiment was car ried out on four sites to test this hypothesis. The experiment include d three factors. The first factor consisted of lime versus no lime app lication. The second factor included four cover crop combinations and a control. Cover crop combinations were winter barley (Hordeum vulgare ) underseeded with either birdsfoot trefoil (Lotus corniculatus), Kent ucky bluegrass (Poa pratensis), ladino clover ( Trifolium repens), or a mixture of Kentucky bluegrass and ladino clover. The third factor co nsisted in planting either white (Picea glauca) or black (Picea marian a) spruce seedlings. Winter barley did not establish as rapidly and vi gorously as expected. Nevertheless, the cereal reduced weed population s in the establishment year. For broadleaf weeds, this reduction was n ot large enough to allow a carryover during subsequent years. In contr ast, subsequent increase of the grassy weed populations was slowed dow n in the presence of cover cro ps. The establish ment of the other cov er crops was poor and highly variable from site to site. It is not cle ar whether this relative failure was due to growing conditions, poor e stablishment of the cereal cover crop, or to other factors. Liming and cover crops had little effect on spruce growth but black spruce seedl ings grew taller than white spruce seedlings at two out of four sites, and basal diameter of white spruce reached larger values than did bla ck spruce. For white spruce, this might constitute an advantage in old fields where seedlings are prone to lodging under weed pressure. Fina lly, it was noted that seedling survival was exceptionally high in all treatments.