In this study, the phosphorus (P) speciation of poultry-manure biochars (PMBs) and the effects of PMB application to rice paddy soils on the P availability in the soils were investigated. Poultry manure consisting of only fecal droppings (i.e., no additional water and bedding materials) was collected from a layer hen housing and subsequently pyrolyzed at 350 and 550°C under oxygen-free conditions. The PM and PMBs were then applied to soils to grow rice plants and the soil P availability to rice plants was observed. With increasing pyrolysis temperature, the total P content of PMBs increased while the corresponding content of soluble P decreased. The results of sequential extraction showed a significant decrease of H2O-P and an increase of H2SO4-P with increasing pyrolysis temperature. The 31P-NMR spectra for the solutions obtained from NaOH-EDTA extraction revealed that inorganic-ortho P was the predominant species in PM and PMBs and the relative content of monoester-P in the materials decreased with increasing pyrolysis temperature. Thus, pyrolysis process converted organic P to inorganic P. P K-edge XANES results showed an increase of apatite with increasing pyrolysis temperature. Based on these results, the effects of PMB application on the P availability in rice paddy soils were explained with respect to the P speciations in the applied materials. It was suggested that the application of 350°C PMB has the best result for reducing the amount of P application while improving soil P availability to rice plant.

Effects of poultry-manure biochars on the soil phosphorus availability to rice plant

255th National Meeting (2018)

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