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Animal manures contain significant amounts of plant-available nutrients which could increase crop yields. They also contain heavy metals which may be exported outside soil systems by plants, animal and surface and underground water following application to soils. The effect of some animal manures on rice yield and extractability of iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) were determined in fours soils with different properties. The manures were applied at the rate of 100Mg ha-1, and rice was grown for two consecutive seasons. In the second of the two seasons, rice yield and yield components were determined. Immediately after the second season rice harvest, soils were sampled and analyzed for DTPA extractable Fe, Zn, Mn, and Cu. Averaged across the soils, the level of extractable Fe increased by between 5% in chicken manure (PM) and 71% in cattle manure (CM); Zn by between 312% in CM and 871% in swine manure (SM); Mn by between 61% in PM and 172% in SM and Cu by between 327% in PM and 978% in SM. Mixing these manures before application reduced the level of extractable trace elements. Although there was increased yield following application, the results of this study indicated a possible risk of trace element export to the environment within a year, if high levels of the manures are applied. [ABSTRACT FROM AUTHOR]

One of the measures being adopted for relieving environmental problems arising from agricultural production is to recycle animal manure and other organic products as fertilizers and soil amendment. In Japan, this is a usual practice among farmers. In this study, we evaluated the effects of chicken manure (PM), cattle manure (CM), swine manure (SM) and mixed manure (MM = PM + CM + SM) on the growth, dry matter yield, and nutrient [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)] uptake of rice (Oryza sativa Var. koshihikari). Four naturally infertile soils, andosol (A), red-yellow soil (RY), sandune soil (SD), and masatsuchi (M), were amended with 100 Mg ha-1 (dry weight) of each of the manure and allowed to stabilize for 4 weeks before rice was seeded. Changes in rice growth as indicated by plant height and number of leaves and tillers were monitored for 6 weeks, and the biomass yield was determined. Shoot samples were also analyzed for nutrient uptake. The amended A and RY soils produced the best effects on all the rice parameters studied. However, the number of rice leaves were significantly higher in RY than A. The manure effects on rice growth and biomass yield were ranked as CM > MM > SM > PM. Amending the soils with manure significantly delayed seedling emergence. Andosol amended with CM and MM produced significantly greater roots than with other manures. Masatsuchi amended with PM had lower shoot and root biomass than even the control. Among the manures, the uptake of all nutrients was highest in CM. The higher dry matter yield of rice in soils amended with CM and MM may be due to better nutrient balance and relatively lower levels of toxic factors in the material. [ABSTRACT FROM AUTHOR]