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Title: Soil changes after four years of organic vegetable production

Author
item ROBERTS, B - Oklahoma Agriculture Experiment Station
item SHREFLER, JAMES - Oklahoma Agriculture Experiment Station
item TAYLOR, MERRITT - Oklahoma Agriculture Experiment Station
item Webber Iii, Charles

Submitted to: Southern Region of the American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/17/2010
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: In 2002, scientists at the Lane Agricultural Center in southeastern Oklahoma began a study to explore the potential for organic agricultural production. Land was certified as organic according to the guidelines of the National Organic Program. At the beginning of the study, soil samples were taken in 2002. Lime was added based on soil test recommendations. For four years, vegetable crops were grown in the summer and cover crops were grown in the winter. In most years, crimson clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L.) were grown as cover crops. During the spring, the cover crops were plowed under, and four vegetable crops [tomatoes (Solanum lycopersicum L.), sweet corn (Zea mays L.), southern peas (Vigna unguiculata (L.) Walp.), and watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai var. lanatus)] were planted. The vegetables were rotated within the plots each year, so that a different crop was grown in each location each year. Poultry litter was applied to the soil five times over the four year period. The total amount of litter applied was approximately 11.5 t/a, and the analysis of the litter was approximately 2% of N, P, and K. After the four year rotation was completed, soil samples were taken to determine if changes to the soil had occurred. Organic matter did not change over the length of the study. Soil pH increased. Potassium and calcium levels in the soil approximately doubled. Neither nitrogen nor magnesium changed substantially. Copper and zinc levels more than doubled. Phosphorus increased by approximately seven times. Sulfur and iron decreased, and boron increased by about 50%. In general, the use of poultry litter and cover crops for four years improved the nutrient status of the soil. Many of the nutrients that were formerly deficient are now at recommended levels. No nutrients are currently present at excessively high levels. However, if the former poultry litter fertilization practices are continued, we anticipate that levels of P and perhaps other nutrients could soon reach excessive levels.