Manure Nitrogen Availability: Dairy Manure in Northeast and Central U.S. Soils

Abstract

ABSTRACT Accurate prediction of nitrogen (N) availability from manure is required for efficient utilization of this resource in crop production. This study was conducted to evaluate the impacts of temperature, water regime and selected soils on N availability from a liquid dairy (Bos taurus) manure. Two Maine soils [Caribou sandy loam (fine-loamy, mixed, frigid Typic Haplorthod) and ‘Newport’ loam (unnamed variant of a Bangor silt loam; coarse-loamy, mixed, frigid Typic Haplorthod)] and an Illinois soil [Catlin silt loam (fine-silty, mixed, superactive, mesic Oxyaquic Arguidoll)] were incubated in the laboratory at 11, 18 and 25°C under constant (60% water filled pore space, WFPS) and fluctuating (60 to 30% WFPS) water regimes, with and without dairy manure in a factorial arrangement. Ammonium concentrations increased immediately upon manure addition and declined thereafter as nitrate levels increased. Elevated NO3 − levels reflected nitrification of NH4 + added in the manure, with little additional net mineralization of manure organic N. Temperature strongly influenced NO3 − concentration over time, but this effect could be described with the thermal unit (degree day) concept. The fluctuating water regime had no significant impact on manure-derived NO3 − Changes in manure NO3 − over thermal time could be described with a single exponential equation. However, less manure NO3 − was observed in an Illinois soil than in two Maine soils. Separate particle size analysis and microbial community assessments indicate higher N immobilization potential in the Illinois soil. Because soil type strongly impacted N availability, it is clear that additional soils with ranges in several physical, chemical and biological properties should be investigated to quantify these relationships with manure N availability.