The Effect of Long-Term Application of Phosphorus Fertilizer and Manure On Micronutrient Availability.

 Micronutrient availability is important to crop production and can be affected by long-term application of phosphorus (P) fertilizer and other amendments.  This study was conducted to determine the effects of the long term application of inorganic and variably sourced organic P on micronutrient availability and the relationship between extractable micronutrients and uptake of micronutrients by winter wheat. Extractable (DTPA-sorbitol) and total micronutrients were determined from sites that had long-term application of beef manure, swine effluent, biosolids, or commercial fertilizer across Oklahoma.  Plant tissue and wheat grain samples were digested with nitric acid and analyzed for micronutrient content by an ICP-AES. Soil properties including organic matter, pH, and Mehlich 3 P were also determined. Different relationships were observed between DTPA-extractable micronutrients and total P for different P sources. Significant relationships (p < 0.01) were found between DTPA-extractable Cu, Zn, Fe, and Mo and total P applied in the biosolids amended plots.  For the beef manure plots, significant relationships existed between DTPA-extractable B, Fe, Zn, Cu, and Mn and total P applied. Significant relationships were also found between extractable B, Zn, and Cu and total P applied for the swine effluent plots. However, significant relationships were not found between the vast majority of inorganic commercial P fertilizer treatments and DTPA-extractable micronutrients. Long-term application of organic fertilizer increased micronutrient availability, but long term application of inorganic P had no effect on micronutrient availability.