Romanya(後のaの頭に`),J. and Rovira,P.(2009): Organic and inorganic P reserves in rain-fed and irrigated calcareous soils under long-term organic and conventional agriculture. Geoderma, 151, 378-386.

『長期的有機農業および旧来農業下の降雨および灌漑を受けた石灰質土壌における有機と無機リンの蓄積量』


Abstract
 In low input farming systems the reserves of organic and inorganic P may be a significant source of P to crops. To clarify this we investigated organic and inorganic P reserves in an array of irrigated and rain-fed calcareous soils of grassy crops, with long term organic or conventional farming practices. Organic P (Po) reserves appeared to be more sensitive than inorganic P reserves to changes in soil fertilisation regime. Organic P reserves were sensitive to the quantity of P added, rather than to the quality of the input. In soils receiving manures, there was nocorrelation between organic P reserves and soil organic C and N or soil carbonate content. In contrast, inorganic P reserves in soils receiving manure were positively linked to soil total N and to organic C (in irrigated organic soils) and negatively to carbonate content. This suggests that the accumulation of inorganic P pools in calcareous soils receiving manure may be enhanced in soils with high organic matter content. As indicated by changes in the N/Po ratio, soil carbonates protected total organic P pools from mineralisation in soils receiving adequate amounts of P fertilisers. In contrast, in soils receiving low amounts of manures we observed low amounts of organic P even in soils with a high carbonate content. Therefore, in conditions of P starvation, organic P reserves protected by carbonates may be slowly mobilised. Despite this mobilisation, in soils receiving low amounts of P, no relationships were observed between labile Pi pools and organic P reserves. In contrast in soils in soils receiving sufficient amounts of P we observed a relationship between organic P reserves and labile Pi pools. In irrigated soils inorganic P reserves were positively correlated with labile P reserves and labile Pi pools. In irrigated soils inorganic P reserves were positively correlated with labile P pools, even when fertilisation was moderately low. The application of manure to these latter soils favoured the links between organic P reserves and labile P forms.

Keywords: Soil fertility; Soil mining; P balances; Use of manures; Low input farming systems; N/Po ratio』

1. Introduction
2. Material and methods
 2.1. Study area and management practices
 2.2. Experimental design and soil sampling
 2.3. Soil analysis
 2.4. Statistical analyses
3. Results
 3.1. Soil P reserves
 3.2. Soil properties and P reserve
 3.3. Relationships between labile P forms and P reserves
4. Discussion
 4.1. Farming practices and soil P reserves
 4.2. Regulation of P reserves
 4.3. Contribution of P reserves to the availability of P
 4.4. Pathways and factors of regulation
5. Conclusions
Acknowledgements
References


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