2008 Joint Annual Meeting (5-9 Oct. 2008): Impacts of a Perennial Pasture on Organic Matter and Nitrogen in a Rainfed Crop Rotation.
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683-14 Impacts of a Perennial Pasture on Organic Matter and Nitrogen in a Rainfed Crop Rotation.



Tuesday, 7 October 2008
George R. Brown Convention Center, Exhibit Hall E
Andrés Quincke, Alejandro Morón and Jorge Sawchik, INIA La Estanzuela, Ruta 50 km 11, Colonia, Uruguay
Soil degradation and erosion take place during years with annual crops, especially if soil is subjected to tillage. If a perennial pasture follows, soil organic matter and soil structure may recover again. In Uruguay, before the advent of no-till farming, mixed crop rotations were widely adopted (i.e. 3 years of cash crops followed by 3 years of a perennial pasture), with average erosion rates that were considered tolerable. Long-term, well managed no-till systems also allow for successfully controlling soil erosion and improving soil quality. Therefore, would a perennial pasture still provide improvements in soil organic matter when soil is under no-till?
A long-term experiment was started in 1996 on a silty clay Vertisol in southwestern Uruguay to study the effects of tillage and crop rotation on total and labile soil organic matter. Treatments are no-till vs. reduced tillage and mixed vs. continuous cropping rotations. The design is a 2x2 factorial, with three staggered replications. The basic sequence has 5 crops and lasts 3 years: wheat – oats and maize – barley and sunflower. In the continuous cropping rotation the same sequence is repeated indefinitely, while in the mixed rotation a 3-yr perennial pasture (composed of white clover, lotus, and fescue) follows the basic crop sequence. Data from the last 10 years were analyzed as a factorial design with repeated measures and with year as a random effect. No-till had significantly higher soil organic matter than reduced tillage in the 0-7.5cm soil. However, under continuous cropping, the increase due to no-till was of lower magnitude than in the mixed rotation. Potentially mineralizable nitrogen had a 5–fold increase that coincided with the pasture. Residual effects of the pasture were of higher magnitude under no-till than with reduced tillage.
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See more of: S06 Soil & Water Management & Conservation