Availability of phosphate throughout the year and the effect of continuous application of cattle manure in the paddy fields derived from an allophanic andosol
2007
Saito, K.(Utsunomiya Univ. (Japan)) | Matsuno, S. | Hirai, H. | Kato, H. | Maeda, T.
In the paddy fields derived from an allophanic Andosol, continuous application experiments of cattle manure and the chemical fertilizer were performed in order to 1) monitor the annual change of the phosphate availability throughout two years and 2) investigate the relationship between the phosphate contents of the rice plants and the soil characteristics. As a result, the following findings were observed; 1) the phosphate availability in the paddy fields examined tended to decrease gradually during the flooded condition (under reductive condition), while it tended to increase drastically after harvest (under oxidic condition). 2) The available phosphate contents were continuously larger in the soils developed under the cattle manure-based organic farming than in the soils developed under chemical fertilizer-based ordinary cultivation. 3) The phosphate contents of the ears in the ripening stage were significantly correlated (p0.001) with the values of the available phosphate extracted from the field-moist soils taken at the late stage of the paddy soil flooding (the panicle formation stage of the rice plant). 4) Based on the observation of the soil profiles, some distinct thready iron mottles were observed in the plow layer of the soils developed under the organic farming, while no thready iron mottle was observed but the alpha-alpha' dipyridyl reaction was positive in the plow layer of the soils developed under the chemical fertilizer based cultivation. Thus, it was suggested that the continuous application of the cattle manure in the organic farming should keep the soil rhizosphere relatively oxidic and increase phosphate availability as compared to the soils developed under the continuous application of the chemical fertilizer.
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