Poultry Manure N Availability to Summer and Winter Crops.

Several poultry manure types are produced and applied to NC field crops assuming 50% of the total N is available to the first crop when surface applied, and 60% when incorporated.  However, this assumption might not hold constant for different crops, environments, and tillage practices.  We report on short-term studies with winter wheat, and long-term studies with corn and cotton in NC. The objectives of this study were to calculate N availability coefficients based on crop yield responses (fertilizer nitrogen equivalence, FNE) or plant N uptake (plant available N, PAN) for the 1^st crop; and for the long-term experiments also for the 2^nd, and 3^rd crops.  Experiments were established in better drained Coastal Plain and more poorly drained Tidewater region sites during 2008-2011. Yields and plant N uptake from poultry manure treatments were compared to N responses modeled from inorganic fertilizer rates and the check plot (no N applied). For winter wheat, calculated FNE and PAN coefficients ranged from 0.2 to 0.5, with most values <0.4. For corn planted in 2009, the FNE and PAN values exceeded 0.5 (50%), while in the 2^nd year following application FNE values ranged from 0.16 to 0.29, and in the 3^rd year FNE values ranged from 0.17 to 0.47. Lack of response to inorganic N fertilization prevented calculation of coefficient values for cotton. Poultry manure N availability appeared to be lower for the winter crop, possibly due to cooler temperatures. Long-term data from the summer crop study suggests some contribution of residual N to future crops is likely.