Soybean Production On Potassium Deficient Soil.

A 3-yr nutrient study was conducted with soybean on a potassium deficient Bude silt loam in Pontotoc County, MS.  Soil samples were analyzed by public and private soil testing laboratories and recommendations were included as treatments.  Additional treatments included a fertilizer rate regime and poultry litter.  Fertilizer used in the study was potassium (K) 0-0-60, phosphorus (P) 0-46-0, and elemental sulfur (S) 90%.

Soybean was planted on May 7, 18, and 17 in 2010, 2011, and 2012, respectively.  Fertilizer treatments were applied within 10 days of planting.  The two center rows of each plot were mechanically harvested with a small plot combine.  Analysis of variance was conducted and means were separated.  An economic analysis was conducted.  Fertilizer and poultry litter prices were obtained from fertilize retailers and area farmers.  Prices utilized in calculations were K $582.50/ton, P $600.00/ton, S $0.35/lb, and poultry litter was $45/ton.  Crop sales revenue was $15/bu based on the 2012 market price.

Soil test results indicated the extractable nutrient level of K to be in the “low range”, while S and P was in the “medium range” according to both laboratories, public and private.  Average soybean yield were 39.1, 42.8, 59.1 bu/ac for 2010, 2011, and 2012, respectively.  Yield with all fertilizer treatments was greater than the no fertilizer treatment, except the lowest rate of K in 2010.  Yield was not different with any treatment in the fertilizer rate regime.  The addition of P or S did not improve yield.  The highest level of economic return (crop value less fertility cost) was achieved with poultry litter at 0.9 ton/ac, valued at $591.00/ac, K 120 lb/ac valued at $647.00/ac, and poultry litter 1.0 ton/ac, valued at $918.00/ac in, 2010, 2011, and 2012, respectively.