Development of a phosphorus index for pastures fertilized with poultry litter--factors affecting phosphorus runoff

J Environ Qual. Nov-Dec 2004;33(6):2183-91. doi: 10.2134/jeq2004.2183.

Abstract

Currently, several state and federal agencies are proposing upper limits on soil test phosphorus (P), above which animal manures cannot be applied, based on the assumption that high P concentrations in runoff are due to high soil test P. Recent studies show that other factors are more indicative of P concentrations in runoff from areas where manure is being applied. The original P index was developed as an alternative P management tool incorporating factors affecting both the source and transport of P. The objective of this research was to evaluate the effects of multiple variables on P concentrations in runoff water and to construct a P source component of a P index for pastures that incorporates these effects. The evaluated variables were: (i) soil test P, (ii) soluble P in poultry litter, (iii) P in poultry diets, (iv) fertilizer type, and (v) poultry litter application rate. Field studies with simulated rainfall showed that P runoff was affected by the amount of soluble P applied in the fertilizer source. Before manure applications, soil test P was directly related to soluble P concentrations in runoff water. However, soil test P had little effect on P runoff after animal manure was applied. Unlike most other P indices, weighting factors of the P source components in the P index for pastures are based on results from runoff studies conducted under various management scenarios. As a result, weighting factors for the P source potential variables are well justified. A modification of the P index using scientific data should strengthen the ability of the P index concept to evaluate locations and management alternatives for P losses.

MeSH terms

  • Animals
  • Fertilizers*
  • Manure
  • Phosphorus / analysis*
  • Poultry
  • Rain
  • Reference Values
  • Soil Pollutants / analysis*
  • Water Movements
  • Water Pollutants / analysis*

Substances

  • Fertilizers
  • Manure
  • Soil Pollutants
  • Water Pollutants
  • Phosphorus