Early February is the time to determine whether to apply additional nitrogen for spring production of small grain forage or grain. In early winter, producers frequently ask our soil fertility specialists how much of the nitrogen applied the previous fall to small grain pastures is available for spring forage or grain production. The question is difficult to answer, even with information about the planting date, soil, variety, rainfall, fall growth, and amount of forage used by cattle.
Data that may help estimate nitrogen availability come from a fourteen-year study conducted at the Noble Research Institute Red River Research and Demonstration Farm near Burneyville, Oklahoma. The data indicate that there could be a relationship between fall nitrogen rates and the amount of nitrogen available for spring production. Remember that we derived this information from only one location (or microenvironment), clipped all the forage, and removed it from the research plots. The figure indicates (follow dashed line) that, on average, if 150 pounds of nitrogen were applied in the fall, 50 pounds of nitrogen would be available for spring production; if 100 or 200 pounds were applied, 28 or 75 pounds would be available, respectively.
Results from this study could be used to estimate the carry-over of nitrogen for spring production.