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Title: PREDICTING NITROGEN AVAILABILITY FROM LIVESTOCK MANURES USING GROWING DEGREE DAYS

Author
item GRIFFIN, TIMOTHY
item Honeycutt, Charles

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Animal manure can be a valuable source of nutrients for crop production. However, when animal manure is added to soil, numerous microbiological processes affect the availability of manure nutrients to plants. The activity of soil microorganisms is regulated by many factors. One key factor is often temperature. This study was conducted to see if temperature accumulated over time ('growing degree days') could be used to predict nitrogen availability from manure. Dairy, beef, poultry, and swine manures were added to soil at three different temperatures. Although nitrogen availability varied widely with temperature and time, nitrogen availability from dairy, poultry, and swine manures was closely described using growing degree days. These laboratory data indicate that growing degree days can be used for predicting nitrogen availability from a range of livestock manures. If successfully extended to the field, this predictive capability may allow improved management of nitrogen from anima manures, thereby reducing environmental risks associated with manure use in crop production.

Technical Abstract: Predictive tools are needed to better match N release from manure with crop demand. Growing degree days (GDD) have been successfully used to predict N release from crop residues and other amendments. A 112 d incubation experiment was conducted at 10, 17 and 24oC to evaluate GDD (0oC base temperature) predictions of N transformations from beef, dairy, poultry, and swine manure. Manure was incorporated at rates estimated to provide 150 kg N ha-1 (or 75 mg N kg-1 soil). Soil nitrate (NO3) and ammonium (NH4) concentrations were determined at weekly or biweekly intervals. The rate of NO3 accumulation increased with increasing temperature, and could be predicted across temperature regimes using GDD. This predictive ability could be generalized across dairy, poultry and swine manures using an exponential equation, NO3=54.10* (1-e-0.006*GDD), while N was immobilized by incorporation of beef manure. The disappearance of NH4 was a linear function of time and of GDD. A single predictive equation was sufficient for dairy, poultry, and swine manures, in the form NH4 (as % of input)=0.703-0.0021*GDD (R2=0.66), with soil NH4 reaching zero at approximately 350 GDD. These laboratory data indicate that GDD can be used for predicting NO3 accumulation and NH4 disappearance from a range of livestock manures. If successfully extended to the field, this predictive capability may allow for improved management of N from animal manures.