Nitrogen- vs. phosphorus-based dairy manure applications to field crops: nitrate and phosphorus leaching and soil phosphorus accumulation

J Environ Qual. 2006 Oct 27;35(6):2302-12. doi: 10.2134/jeq2005.0479. Print Nov-Dec 2006.

Abstract

Management of animal manures to provide nutrients for crop growth has generally been based on crop N needs. However, because manures have a lower N/P ratio than most harvested crops, N-based manure management often oversupplies the crop-soil system with P, which can be lost into the environment and contribute to eutrophication of water bodies. We examined the effects of N- vs. P-based manure applications on N and P uptake by alfalfa (Medicago sativa L.), corn (Zea mays L.) for silage, and orchardgrass (Dactylis glomerata L.), leaching below the root zone, and accumulation of P in soil. Treatments included N- and P-based manure rates, with no nutrient input controls and inorganically fertilized plots for comparison. Nitrate concentrations in leachate from inorganic fertilizer or manure treatments averaged 14 mg NO(3)-N L(-1), and did not differ by nutrient treatment. Average annual total P losses in leachate did not exceed 1 kg ha(-1). In the top 5 cm of soil in plots receiving the N-based manure treatment, soil test P increased by 47%, from 85 to 125 mg kg(-1). Nitrogen- and P-based manure applications did not differ in ability to supply nutrients for crop growth, or in losses of nitrate and total P in leachate. However, the N-based manure led to significantly greater accumulation of soil test P in the surface 5 cm of soil. Surface soil P accumulation has implications for increased risk of off-field P movement.

MeSH terms

  • Animals
  • Animals, Domestic
  • Crops, Agricultural* / growth & development
  • Crops, Agricultural* / metabolism
  • Dairying
  • Environmental Monitoring*
  • Fertilizers / statistics & numerical data
  • Manure*
  • Nitrates / chemistry
  • Nitrates / metabolism*
  • Nitrogen / chemistry
  • Nitrogen / metabolism*
  • Phosphorus / chemistry
  • Phosphorus / metabolism*
  • Plant Roots / chemistry
  • Soil Pollutants / analysis
  • Soil Pollutants / metabolism*
  • Time Factors

Substances

  • Fertilizers
  • Manure
  • Nitrates
  • Soil Pollutants
  • Phosphorus
  • Nitrogen