Producers who pay close attention to soil fertility fundamentals will help ensure desirable forage production and nutritive value, a management tool that is especially important with introduced forages. This, in turn, can decrease the purchase of off-farm feed and forage, increase animal performance and increase profitability of a forage-livestock enterprise. When written as a list, the proper order for warm-season grass fertilization is as follows:
- Conduct a soil test
- Lime as recommended
- Apply phosphorus and potassium as recommended
- Identify a reasonable yield goal
- Apply nitrogen fertilizer ahead of moisture based on yield goals
The first step in the soil fertility program is to obtain a soil sample for analysis. A soil analysis is used to determine the levels of nitrogen, phosphorus and potassium in the soil, as well as the soil pH level. Under certain circumstances, analyses for other nutrients also may be required. Based on the yield goal for specific forage crops, written recommendations for the level of each fertilizer nutrient required are usually furnished by the laboratory conducting the analysis.
After correcting the soil pH level to greater than 5.7 and meeting the phosphorus and potassium needs, there are only two basic fertilization principles required for introduced, warm-season grasses. The first principle is that nitrogen fertility is required for grass growth; the second is that nitrogen fertilization should be based on a reasonable yield goal for the region of production, explains Daren Redfearn, associate professor of forages with the OSU department of plant and soil sciences.
"The first nitrogen application should be in early May, just as the grass is beginning to grow and ahead of late-spring rainfall," he said. "Properly timed fertilization can result in better utilization of late-spring rainfall. Remember, by default, producers who use introduced forages have decided to provide the necessary fertility inputs."