Nitrogen Transformations in a Poultry Manure Amended Soil: Temperature and Moisture Effects

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Abstract
Efficient agronomic management of poultry manure requires information on its contribution to the N budget of the soil‐crop system. Of primary importance in this regard is the timing of N mineralization from the organic fraction of the manure. As manure applications are frequently made year round, it is also essential to understand how environmental variations will alter the rate and extent of N mineralization. Consequently, a laboratory study was conducted for 150 d to measure the effects of temperature and moisture on net N mineralization from three poultry manures. Each manure sample was incorporated with an Evesboro loamy sand (mesic, coated typic Quartzipsamments) and changes in soil inorganic N (NH+4‐N and NO−3‐N) and pH were determined at 30, 90, and 150 d. Although variations were noted between manure types, most of the net mineralization (Nm) observed at 25 °C and 40 °C occurred within the first 90 d. Mineralization was reduced at 0 °C but, by the conclusion of the study, considerable accumulations of inorganic N (18–76 mg/kg) were detected at this temperature. Thirty to 60% of the organic N added to the soil in manures 1 and 3 was mineralized, when moisture was not limiting. Inconsistent mineralization patterns obtained with manure 2 were attributed to microbial immobilization of N. Accumulations of NH+4‐N under cold or dry conditions resulted in elevated soil pH levels. Conversely, considerable soil acidification occurred under warm, moist conditions due to rapid nitrification of NH+4‐N added in the manures.

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