Saturday, 15 July 2006

Soil Physical and Chemical Properties in Age Chronosequence of Organic Farms.

Yoshiaki Ikemura, New Mexico State Univ, Agronomy and Horticulture Dept, Las Cruces, NM 88003 and Manoj K. Shukla, Dept of Agronomy and Horticulture, New Mexico State Univ, MSC 3Q, P.O. Box 30003, Las Cruces, NM 88003.

Organic farming is an ecologically based system which eliminates all the synthetic chemical use in crop production and antibiotics and hormones in livestock production. Organic faming is getting populer in the U.S. and around the world. More than 26 million hectares of farmland are under organic management around the world and organic farmlands have kept expanding at fast pace. According to USDA, 2.3 million acres of croplands and pasture lands are managed under organic farming in the U.S. and about 42,113 acres in the NM by the year 2001. Use of organic manures in place of synthetic fertilizers can improve soil physical and chemical properties, reduce groundwater contamination, and recycle the dairy/poultry wastes. However, noticeable changes in soil physical and chemical properties can occur only after several years. Therefore, we have selected three organic fields located in the Dona Ana County of NM, which are under organic farming for different amounts of time (3, 6, and 9 years). Our objective was to evaluate the effect of organic faming on soil physical and chemical properties under an age chronosequence of organic farms. Core and bulk soil samples were collected in triplicate for 0-10 and 10-20 cm depths from three organic and one conventional farm (Control). Sand was lower but silt content higher in conventional than other organic farms for both depths. The EC was lower for conventional than other organic farms for both depths. However, no significant differences were obtained among soil bulk density, soil pH, saturated hydraulic conductivity for either depth, and total biomass yield among organic fields and control. However, total cotton biomass yield was higher in conventional than the 3 year old organic farm, largely due to the high spatial variability of cotton in the organic farm. The analysis for soil organic C and soil N upto one meter depth is underway and these results will be included in the talk. Soil EC was lower than 4dS/m and soil pH was about 8.4 for both depths in all organic farms, therefore, soil quality was favorable for plant growth.

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