Saturday, 15 July 2006

Organic Production Systems for Pecans.

Joe Bradford, USDA-Agricultural Research Service, 2413 East Highway 83, Harlingen, TX 78596

Mainstream or conventional farming systems are accelerating the degradation of our soil and water resources, and are creating both food and farmer safety issues due to excessive use of tillage, synthetic fertilizers, pesticides, and fungicides. To overcome these problems, both growers and consumers are looking more to the production and consumption of organically growth food products. Growth of sales of organically grown products has increased at an annual rate of 20% per year since 1992 and sales are presently a $12 billion per year industry in the United States. Today the production of food carrying the USDA organic label is based primarily on a trial-and-error approach conducted on small family farms and is not as based on the scientific approach of hypothesis testing as warranted. Furthermore, starting from October 2002, the USDA has implemented national organic labeling standards for the sale of all organic foods. Guidelines, based on scientific research and economic analysis, for developing farming systems that meet organic standards would greatly minimize the risk of converting from conventional to organic farming systems. Therefore, in 2003 an organic farming systems research unit was established at the USDA-ARS Subtropical Research Center in Weslaco, Texas; and research was initiated to develop organic production systems for selected fruits and vegetables. Among the research projects, an organic pecan production project was begun on an 800-tree pecan orchard, divided into conventional and organic managed areas. Treatments within the five pecan variety orchard include various soil and foliar applications. Partial control of insects and diseases was accomplished through release of beneficial insects and application of foliar sprays, including compost tea. The pecan nut casebearer (Acrobasis nuxvorella) was controlled with beneficial insects, the pecan weevil (Curculio caryae) with compost tea, and aphids (Monellia caryella and Monelliopsis pecanis) with insecticidal soap. Yet to be controlled is pecan scab (Cladosporium caryigenum). For each tree in the 422 tree organic orchard, number of nuts, total nut and kernel weight, and kernel quality was determined for the last 3 years. In 2005 the best soil amendment in terms of yield was poultry litter plus mycorrhizae; the second, poultry litter plus compost. The yield increase for the poultry litter/mycorrhizae treatment was nearly double the conventional synthetic fertilizer treatment. The effect of soil nutrient management on nut yield differed among the five varieties. Diversity of the soil food web was greater for the organic treatments; and microbial counts on leaves were greater when compost tea was foliar applied. Nutrient uptake in leaves was not different for conventional and organic soil treatments in 2005. Evaluation of soil amendments and search for methods for improved insect and disease control will be continued for three additional years. The paper will include also a discussion of systems approach versus components research for developing organic production systems.

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