What is in this article?:
- Forage crops: soil testing to manage nutrient costs
- N, P and K
- Maintain balance
- With fertilizer prices at a near record high, the admonition to base fertilization on soil tests should not have trouble being heard.
- Soil testing remains one of the cheapest practices a forage producer can use.
- For the past few years, fertilizer prices have increased significantly and have not come down much — producers must learn to manage costs and maintain optimum production.
- Fertility recommendations should be based on how much nitrogen, phosphorus and potassium, as well as secondary and micronutrients are available in the soil.
Corriher said producers should stay on top of nutrient management for consistent production and emphasized that soils should maintain a balanced nutrient profile. She said some managers might try to decrease or eliminate one nutrient to save money. “But balance is important. Leaving out either one of the three primary nutrients will affect production, if soil test recommendations call for all three.”
Proper nitrogen application rates are important to meet production goals. With improved bermudagrass for hay production, Corriher said 100 pounds of nitrogen is needed per acre for each cutting. For grazing, 60 pounds of nitrogen per acre, applied up to three times a year may be necessary.
“To establish bermudagrass, apply 40 pounds of nitrogen per acre and after sprigs are established and growing, add another 50 pounds per acre to enhance establishment for one cutting the first year.”
She said improved bermudagrass, such as Tifton 85, may have “heavier nutrient demand because of higher yield and quality potential. Common bermuda or seeded bermudagrass may have lower fertility requirements but yield and quality will be lower.”
One application per year, at planting, should be sufficient for phosphorus and potassium. She recommends a split application of nitrogen to decrease nitrogen loss. “Split application increases yield by 5 percent to 10 percent and increase nutrient use efficiency by 25 percent to 30 percent. It’s also an advantage during extreme conditions.” Split applications reduce the risk of leaching, volatization, late freeze or drought.”
Corriher said current high fertilizer prices might tempt some producers to cut back on fertility. “Don’t eliminate one specific nutrient and rely on a soil analysis to get better information about what’s available and what can be reduced. If you must cut back, do so uniformly, not just one nutrient. Don’t apply just nitrogen if the analysis calls for nitrogen, phosphorus and potassium.”
She said soil pH plays a significant role in forage production and affects fertility rates. At a pH of 7, for instance, producers need 70 pounds of nitrogen, 30 pounds of phosphorus and 60 pounds of potassium. At 5.5, that changes to 52, 15 and 45.
Producers looking to save money might also consider alternative sources, Corriher said. Animal manures may be an option, but she recommends testing to determine nutrient content.
She said beef cattle manure will average 27 pounds of nitrogen, 24 pounds of phosphorus and 36 pounds of potassium per ton. Dairy cattle manure averages 28, 11, and 26 pounds per ton. Broiler manure contains an average of 58 pounds of nitrogen, 51 pounds of phosphorus and 40 pounds of potassium per ton. Layer manure averages 30, 40 and 20 pounds per ton and swine manure provides 10, 9 and 7 pounds per ton, on average.
Corriher said these are averages and actual amounts vary. “Have it tested,” she said. “There is no guaranteed analysis.”
She said legumes may offer another nitrogen source for forage producers and provides added benefits. “Legume in forage may reduce or eliminate some commercial fertilizer,” she said. “Producers will still need phosphorus and potassium. They also get improved animal performance and may reduce winter feeding costs while improving soil tilth.”
Legumes also attract wildlife and help suppress weeds, which could reduce herbicide demand.
“But the best way to reduce cost is to soil test and calculate the cost per pound of nutrients, especially the three primary nutrients. If fertilizer and limestone are reduced, be prepared to lower stocking rates.”