Nitrogen- vs. phosphorus-based dairy manure applications to field crops: nitrate and phosphorus leaching and soil phosphorus accumulation.
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.
Toth
John D
JD
Section for Animal Production Systems, School of Veterinary Medicine, Univ. of Pennsylvania, 382 West Street Rd., Kennett Square, PA 19348, USA. jdtoth@vet.upenn.edu
Dou
Zhengxia
Z
Ferguson
James D
JD
Galligan
David T
DT
Ramberg
Charles F
CF
D000818:Animals; D000829:Animals, Domestic; D018556:Crops, Agricultural / Q000254:growth & development / Q000378:metabolism; D003612:Dairying; D004784:Environmental Monitoring; D005308:Fertilizers / Q000706:statistics & numerical data; D008372:Manure; D009566:Nitrates / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D010758:Phosphorus / Q000737:chemistry / Q000378:metabolism*; D018517:Plant Roots / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013997:Time Factors
D005308:Fertilizers; D008372:Manure; D009566:Nitrates; D012989:Soil Pollutants; D010758:Phosphorus; D009584:Nitrogen