Rapid Method for Evaluation of Available Nitrogen in Poultry Manures

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  • 各種鶏ふんの窒素無機化量の簡易評価法
  • カクシュ ケイフン ノ チッソ ムキカリョウ ノ カンイ ヒョウカホウ

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Abstract

o develop a rapid method for evaluation of available nitrogen in poultry manures, extraction of uric acid into phosphate buffer was studied. 1) We used 11 samples of poultry (caged layer) manures: their total nitrogen, C/N ratio, inorganic nitrogen released after 7 d and after 28 d of incubation with soil at 30℃ were, 22-46 g kg^<-1>, 5.7-11.6, -0.3-16.8 g kg^<-1> and 1-24 g kg^<-1>, respectively. 2) For the determination of uric acid from the manures, we found it satisfactory to extract 0.5 g air-dry sample with 200 mL of phosphate buffer (PB) solution (pH 7.0) at 60℃ for 60 min with occasional shaking. 3) The forms and concentrations of nitrogen in PB extracts were almost similar to those in aqueous extracts. Since ammonia may be lost by volatilization from the aqueous extracts of higher pH, we preferred the PB solution for the extraction. 4) Nitrogen, regardless of the forms, extracted into the PB solution correlated well with the inorganic nitrogen released after the incubation with soil. Uric acid in the extracts was especially high in the incubation, and we think it good to determine it for the evaluation of the nitrogen availability. 5) The differences in absorbance at 260 and 290 nm of the PB solution (after being diluted to 10 times) had significantly high correlations with uric acid contents in the extracts; therefore, we propose the measurement of the ultraviolet absorbance in phosphate buffer extracts as a rapid method for evaluating the available nitrogen in poultry manures.

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