| Popis: |
In a rice-based cropping system soils are often subjected to different moisture regimes, which may influence desorption of adsorbed Zn and thus limit Zn availability to crops. Laboratory and greenhouse experiments were conducted to study the effect of moisture regimes with or without organic matter addition on changes in desorption of adsorbed Zn in soils and its utilization by rice and maize plants. Three different moisture regimes, flooded-dried, alternate wetting and drying and preflooding, with (50 g kg -1 ) and without (0 g kg -1 ) added organic matter were imposed in two Alfisols and two Inceptisols of West Bengal, India. Percent desorption of adsorbed Zn was significantly higher in Alfisols (64.5%) than in Inceptisols (45.5%). Desorption was also significantly higher under flooded-dried (61.4%), alternate wetting and drying (67.1%), and preflooding (47.3%) moisture treatments than in the control (43.4%). Organic matter application enhanced desorption under flooded-dried and alternate wetting and drying but decreased it under preflooding. The variation in Zn desorption among soils and moisture treatments is the result of changes in soil pH, Fe-oxides, bonding energy constants, and free energies for Zn adsorption. Greenhouse experiments showed that dry matter yield and uptake and utilization of Zn for maize were higher under flooded-dried. For rice, yield and Zn accumulation were higher under preflooding treatments compared to the control in which the soils were not subjected to these pre-plant moisture treatments. Soil-zinc data and plant response were in close agreement, except in Inceptisols for rice under preflooding with added organic matter treatment. Results indicated a more efficient use of Zn fertilizer where maize followed rice, and where rice was grown after preflooding the soils. |
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