Poultry Manure Fertilizer Nitrogen Equivalence and Plant Available Nitrogen Sensitive to Crop and Application Rate.

Fertilizer nitrogen equivalence (FNE) is a factor that represents the proportion of the total nitrogen in an organic material that contributes to yield while plant available nitrogen (PAN) is the fraction of plant N absorbed from organic manure.  These factors are controlled by both intrinsic crop growth characteristics and extrinsic soil and environment conditions.  Crop nitrogen demand along the growth continuum has a profound effect on yield and plant N uptake.  A cotton-corn-cotton rotation experiment was established in an upper coastal plain site (UCPRS) on Norfolk loamy sand, Typic Kandiudults and in a tidewater site (TRS) on Portsmouth fine sandy loam Aquic Paleudults soil for three years.  The FNE and PAN values of three poultry manure N sources were determined under conservation and conventional tillage by comparison to an inorganic fertilizer, 30% urea ammonium nitrate yield and plant N uptake response curves.  Results indicate poultry manure FNE for corn production ranged between 0.18 – 0.83 and PAN 0.26 – 0.65 wider than cotton 0.22 – 0.35 and 0.18 – 0.31 respectively.  This suggesting that the soils might have had large residual N or much of the N absorbed by cotton did not improve yield.  Also, the FNE and PAN factors varied with source and rate of poultry manure application.  In addition, corn yields were higher with conservation than with conventional tillage in both sites.  However, mixed yield pattern was observed in cotton in both sites under the two tillage systems.