Schultz Bruce, Blanchard, Tobie M., Gould, Frances I.
Brenda Tubaña, LSU AgCenter soil scientist, continues to work on a project to evaluate proper rates of potassium and phosphorous in combination with lime in a corn and soybean rotation.
“We want to make sure our fertilizer recommendations are correct,” she said. “This study is long-term. It gives us an overview of the dynamics and fate of applied P and K fertilizer in the soil.”
Tubaña said corn tends to use a large amount of phosphorous, while soybeans take up more potassium. Soil pH has to be in the 6.5 to 7 range to ensure that plants have access to balanced amounts of nutrients, she said. Soil that is too low in pH, which indicates excessive acidity, can be corrected by liming.
“The data we get from this long-term study thus far clearly show that the benefits of P and K applications are magnified if the pH is optimal,” she said. “Also, with the proper pH, crops can avoid micronutrient deficiencies and toxicities.”
From soil samples, lab testing determines available P and K level in the soil, and a recommendation will be made if levels are low, usually in the range of 60 to 90 pounds each.
Soil types can affect potassium recommendations, but soil type is not a consideration for phosphorous, she said.
She said stubble can be plowed back into a field after harvest to reintroduce potassium and phosphorous to the soil.
The LSU AgCenter and the LSU College of Agriculture