Nutrient Accumulations in Corn Soil as Influenced by Poultry Litter Application Rate.

Poultry litter can be a valuable resource when applied at rates required by a given crop. However, nutrients being present in higher concentrations than needed, or not available when needed, are obvious concerns for producers when using poultry litter as a fertilizer.   During 2005-2008, silage corn plots were established under no-till and conventional till conditions with three fertility treatments superimposed over the tillage treatments.  The fertility treatments were  ½ rate of poultry litter at N rate and ½ inorganic N (PL + I), poultry litter applied at the N rate (PL), and inorganic fertilizers (I).  Soil samples were taken from 0-15 cm prior to planting, at mid-season, and at corn harvest. The harvest soil samples were analyzed for nutrient content and comparisons are as follows.  Over the four year observation, very few differences were seen between tillage treatments.  Interactions existed between tillage and fertility for available Mg and Cu,  along with organic matter and CEC.   Differences were observed between fertility treatments in the following measurements:  water pH, available P, K,  Zn, and ortho-phosphate content.  Water pH was greater in treatments receiving poultry litter than inorganic fertilizers alone.  Available P and Zn were higher in treatment PL than I.  Available K was higher in treatment PL than either PL + I or I.  Ortho-phosphate content was greater in treatment PL than in I.  Indications are that poultry litter applied at the N rate resulted in excess levels of available P, K, Zn, and ortho-phosphate in comparison to the inorganic fertilize