Phosphorus distribution in dairy manures

Area of Science:

• Environmental Chemistry
• Soil Science
• Agricultural Science

Background:

• Phosphorus (P) in animal manure is crucial for bioavailability and environmental runoff.
• Understanding the distribution of various P forms in manure is essential for nutrient management.
• Dairy manure P composition varies significantly, affecting its environmental fate and agricultural utility.

Purpose of the Study:

• To investigate the distribution and chemical forms of phosphorus (P) in dairy manure.
• To identify correlations between total P and specific P fractions in manure.
• To evaluate efficient methods for assessing plant-available P in animal manure.

Main Methods:

• Sequential fractionation of P was performed on 13 dairy manure samples.
• Orthophosphate-releasing enzymatic hydrolysis was used to characterize organic P forms.
• Analysis included water-extractable, NaHCO(3)-extractable, and NaOH-extractable P fractions (inorganic and organic).

Main Results:

• Water-extractable inorganic P (P(i)) and NaOH-extracted organic P (P(o)) showed significant correlations with total manure P.
• Phytate-like P was the dominant enzymatically hydrolyzable organic P form in the analyzed fractions.
• A single extraction using sodium acetate buffer effectively estimated the sum of P across sequential fractions, indicating plant availability.

Conclusions:

• Manure P composition, particularly water-extractable P(i) and NaOH-extractable P(o), is strongly linked to total P content.
• Sequential fractionation provides detailed characterization of manure P forms, with phytate-like P being prevalent.
• Sodium acetate buffer extraction offers an efficient and reliable method for evaluating plant-available P in animal manure.