Impact of drying method, dietary phosphorus levels, and methodology on phosphorus chemistry of broiler manure

Abstract

Areas of intensive poultry production are prone to high phosphorus (P) losses due to excessive manure application. Historically, manure application rate has been calculated based on nitrogen (N) needs of the crops and N content of the manure with no attention to the quantity of phosphorus (P) loading. In many instances, a gradual buildup of P in soil has resulted from long-term manure application. Therefore, P input from animal manure via runoff is acknowledged as the primary factor for the eutrophication of surface water bodies. This study was conducted to evaluate (i), the impact of dietary P concentration on the broiler manure P content and the pre-analysis drying methods on the broiler manure nutrient composition with emphasis on phosphorus and (ii), to compare the use of Ion Chromatography and the Murphy–Riley method for the determination of inorganic phosphorus in the broiler manure water extract. Four drying methods were used to dry the fresh broiler manure as follows: air drying (AD), freeze drying (FD), oven drying at 65°C (OD65), and oven drying at 105°C (OD105). The results were compared with analysis of the fresh broiler manure with no drying (ND). The diet P concentration did not affect the broiler manure total N content. However, a significant decrease in total N occurred at all P levels due to drying when compared with fresh manure analysis. The diet P level had significant effect on total P and water-extractable P. Freeze drying followed by OD105 caused the most reduction in manure total P content. Drying also had a significant effect on the metal nutrient content of the broiler manure. However, the effect was inconsistent.