A Novel Test for Measuring and Managing Potential Phosphorus Loss from Dairy Cattle Feces

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• 作者：Zhengxia Dou ; Charles F. Ramberg ; Jr. ; Lydie Chapuis-Lardy ; John D. Toth ; Yu Wang ; Robert J. Munson ; Zhiguo Wu ; Larry E. Chase ; Richard A. Kohn ; Katharine F. Knowlton ; James D. Ferguson
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：June 15, 2007
• 年：2007
• 卷：41
• 期：12
• 页码：4361 - 4366
• 全文大小：151K
• 年卷期：v.41,no.12(June 15, 2007)
• ISSN：1520-5851

文摘

Pollution of waters resulting from phosphorus (P) runofffrom agricultural land receiving long-term manure applicationis one of the most serious threats to water quality inmany regions of the world. Of various approaches to alleviatethe problem, reducing P surplus on animal farms throughoptimizing P intake and minimizing P excretion in manureoffers a great opportunity. Here, we present a fecal P testmethod that has the potential to identify over-feeding ofP in dairy cattle. Previous research has suggested that water-extractable P in dairy cow feces closely reflects dietaryP changes and may indicate the animal's P status (adequatevs excessive). However, the notion was somewhatconfounded when a subsequent study found other factors(pH and Ca content as well as sample handling method)also affecting P extractability in water. In the present work,we hypothesize that the impact of those factors on Pextractability can be overcome by selecting dilute acidsolutions to replace deionized water as the extractant. Usingsamples from 25 commercial dairy farms, we tested anarray of acid solutions (including HCl, citric acid, and aceticacid) and found that 0.1% HCl is the most suitableextractant. Inorganic P (P_i) released in 0.1% HCl closelyreflected dietary P changes among the farms (R² = 0.69) andwas independent of pH, Ca, or sample handling method.Knowledge of P metabolism and partitioning in dairy cowsand our experimental data suggest that excess P intakeby the animal leads to greater amounts of bioavailable butunabsorbed P, which is excreted in feces. Its relativemagnitude may be estimated by measuring P_i extractablein 0.1% HCl. This novel and simple fecal P test couldpotentially be used as an indicator of the animal's P supplyutilization status and thus serve as a screening tool forthe presence of P over-feeding on dairy farms.