Effects of organic alternatives for weed control and ground cover management on tree fruit growth, development and productivity

Organic fruit production in the US, especially the western regions, is expanding. The increase is occurring for both economic and ecological reasons. Current market conditions dictate that organic apple growers produce large, flavorful, high quality fruit. Large, high quality fruit receive price premiums and market acceptance whereas small fruit can be difficult to sell, even at lower prices. To grow large fruit, trees must be unstressed and provided with adequate water and nutrition. Weeds can compete with fruit trees for both water and nutrients. Research has demonstrated that weed competition in young fruit trees reduces tree growth and efficiency, and therefore decreases fruit production and fruit size (Merwin and Stiles, 1994). Reduced tree growth reduces tree volume and potential production. Thus, it is a standard orchard practice to control weeds during the establishment and early growth of an orchard. However, the effect of weed competition on production and fruit size of mature fruit trees has not been studied. Most experiments are conducted on young trees so that blocks can be established solely for the purpose of the experiment. Most commercial fruit, both peaches and apples, is produced on mature trees. Thus it is important to understand the effects or lack of effects that weeds may have on a mature tree. This information could have significant impact on how orchards are managed.