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Title: Mineralization of N in Soils Amended with Dairy Manure as Affected by Wetting/Drying Cycles

item Watts, Dexter
item Torbert, Henry - Allen
item Prior, Stephen - Steve

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2006
Publication Date: 10/1/2007
Citation: Watts, D.B., Torbert III, H.A., Prior, S.A. 2007. Mineralization of N in soils amended with dairy manure as affected by wetting/drying cycles. Communications in Soil Science and Plant Analysis. 38:2103-2116.

Interpretive Summary: The use of manure in agricultural practices can be a valuable N fertility source for crop growth. Thus, a laboratory study investigated how soil moisture, and temperature affect N released from dairy compost when applied to different soils. In this study, Alabama soils were compared to a soil from Illinois. Soils that received dairy compost generated more plant available N than soils without added dairy compost. More N was released from Illinois soils compared to Alabama soils, probably due to native climatic conditions of the soil. Temperature also influenced plant available N with more N being produced at higher temperatures. Soil wetting and drying did not impact N release. Therefore, to maximize the N used by plants from manure-amended soils, different regions and temperatures need to be considered.

Technical Abstract: Interest in manure management and its effects on nitrogen (N) mineralization has increased in recent years. The focus of this research was to investigate the N mineralization rates of different soil types in Coastal Plain soils and compare them to a soil from Illinois. Soils with and without dairy composted manure addition were subjected to different wetting/drying cycles (constant moisture at 60% water filled pore space (WFPS) and cycling moisture from 60 to 30% WFPS) under laboratory conditions at three different temperatures (11ºC, 18ºC, and 25ºC). Samples were collected from three different soil types: Catlin (Mollisols), Bama (Ultisols), and Goldsboro (Utilsols). Soil chemical and physical properties were determined to help assess variations in N mineralization rates. Addition of composted manure greatly impacted the amount of N mineralized. The amount of manure-derived organic N mineralized to inorganic forms was mainly attributed to the soil series, with the Catlin (silt loam) producing the most inorganic N followed by the Goldsboro (loam) and then Bama (sandy loam). This was probably due to soil texture and the native climatic conditions of the soil. No significant differences were observed between the constant and cycling moisture regimens, suggesting that the imposed drying cycle may not have been sufficient to desiccate microbial cells causing a flush in N mineralization upon rewetting. Nitrogen mineralization responded greatly to the influence of temperature with the greatest N mineralization occurring at 25ºC. The information acquired from this study may aid in predicting the impact of manure application to help increase N use efficiency when applied under different conditions (e.g.; climate season) and soil types.