Nitrogen- and Phosphorus-Based Manure Application Strategy Effects On Corn Yield and Soil Phosphorus.

Dairy manure applied at rates to meet corn (Zea mays L.) nitrogen (N) requirements usually causes accumulation of phosphorus (P) in soils.  Applying manure at rates equivalent to crop P removal can avoid soil P buildup and control potential P runoff losses.  This study evaluated the effects of using N- or P-based manure application strategies on corn growth and yield and soil P status.  Three fertilization procedures were applied annually for 5 yr (2002 to 2006) and included fertilizer N, manure applied to meet crop N needs, and manure applied to supply anticipated grain P removal supplemented with fertilizer N to equal the N supplied in the fertilizer N treatment. Fertilizer N only was applied to all treatments for an additional 4 yr (2007 to 2010) to study the residual effects of manure applications on corn production and soil P.  During the 5-yr manure application phase, the N-and P-based manure treatments had higher yields than the fertilizer N treatment in only one year.  During the 4-yr residual phase, manure treatments had higher yields than the fertilizer N treatment in 2009 and 2010.  After 4 yr of manure application, soil test P increased from an initial value of 89 mg kg^-1 to 114 and 135 mg kg^-1 in the P-based and N-based manure treatments, respectively, while the fertilizer N treatment declined to 77 mg kg^-1.  In 2009, soil test P was 68 and 87 mg kg^-1 in the P-based and N-based manure treatments, respectively, and the fertilizer N treatment declined to 50 mg kg^-1.  Manure applied annually for 5 yr at N- or P-based rates maintained or increased corn yields, and yields were significantly increased by the residual effects of manure additions.  Using a P-based manure application strategy maintained lower soil P levels during both application and residual phases.