Evaluating long-term nitrogen- versus phosphorus-based nutrient management of poultry litter.
Environmental concerns are driving manure management in many areas from a traditional nitrogen (N) basis toward phosphorus (P)-based nutrient management plans. We investigated how changing nutrient management from an N to a P basis affected crop yields and soil properties in high P soils over a 7-yr period. Three sites were established on farmers' fields, and at each site the same six treatments were applied for 6 or 7 yr. These treatments were (i) no P; (ii) poultry litter applied on an N basis; (iii) inorganic P, equal to the P applied in treatment 2; (iv) poultry litter applied on an estimated annual crop P removal basis; (v) inorganic P, equal to the P applied in treatment iv; and (vi) poultry litter applied once every 2 or 3 yr at a 2- or 3-yr crop removal P rate. All treatments received the same rate of plant-available N. Yields, P balance, soil pH, Mehlich 1 P, and water-soluble P (WSP) were monitored during the experiment. Over the course of the experiment, litter had the beneficial effect of raising soil pH relative to the inorganic treatments. After 7 yr, Mehlich 1 P and WSP were greatest in soils under the N-based treatments, smallest in the no P treatment, and intermediate in the P-based treatments. For example, at the Shenandoah site, Mehlich 1 P decreased by 35 mg kg(-1) under the no P treatment and increased by 36 mg kg(-1) under the inorganic N-based treatment. There were no significant differences between inorganic fertilizer and poultry litter nutrient sources. The results of this study show that soil test P can be decreased in high-P soils over a few years by changing from an N-based to a P-based nutrient management plan or stopping P applications without negatively affecting yields.
Maguire
Rory O
RO
Dep. of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA. rmaguire@vt.edu
Mullins
Greg L
GL
Brosius
Mike
M
D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D018556:Crops, Agricultural; D004784:Environmental Monitoring; D005308:Fertilizers / Q000032:analysis; D005430:Floors and Floorcoverings; D006799:Housing, Animal; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*; D011200:Poultry; D012987:Soil / Q000032:analysis; D013997:Time Factors; D014867:Water / Q000737:chemistry
D005308:Fertilizers; D012987:Soil; D014867:Water; D010758:Phosphorus; D009584:Nitrogen