Fertilization and Liming of Limpograss (Hemarthria) for Summer Grazing

March 2000
Jack Rechcigl - Range Cattle Research & Education Center, Professor, Soil & Environmental Quality

Limpograss (Hemarthria) is a popular grass grown for cattle in Florida. When managed correctly, limpograss can be a high yielding and good quality grass. Few studies have been conducted to evaluate the fertilizer and limestone requirements for limpograss. Thus, growers were forced to guess as to how much fertilizer and lime to apply to limpograss pastures. It is essential that we carefully evaluate how much to spend on pasture management in the hope of obtaining a profit. Pasture fertilization is one of the most expensive costs in beef production. It is no longer realistic to apply high rates of fertilizer on pastures and expect greater profits from increased pasture and cattle production.

Over the past five years the Range Cattle Research & Education Center evaluated the fertilization and lime requirements for limpograss. Results indicated that limpograss can respond to small amounts of either phosphorus (P) or potassium (K). The results show that approximately 15 to 20 pounds of P2O5 and 30 to 40 pounds of K2O should be applied per acre in a one time application in early spring. Our nitrogen (N) studies show that limpograss will respond to as high as 300 pounds of nitrogen per acre. Our results indicate that nitrogen be applied in two or three applications throughout the growing season. Higher limpograss production was also obtained with ammonium sulfate as compared to ammonium nitrate fertilizer. This increase in production is probably a result of the ammonium sulfate supplying needed sulfur for the limpograss.

Limestone is important for crop production by increasing soil pH and providing calcium (Ca) and /or magnesium (Mg). The majority of soils in Florida are acid, coarse-textured sands. These soils tend to be low in calcium and magnesium, both are required for plant growth. Acid mineral soils found in Florida can contain toxic aluminum which stunts plant root systems and reduces nutrient and water uptake. Addition of limestone can also affect nutrient availability to crops. It is important to take soil samples to determine pH and lime requirements prior to applying limestone. The amount of limestone needed depends upon the initial soil pH, soil texture and the crop to be grown. Whenever it is cost effective one should use dolomitic limestone. Ordinary calcitic limestone only increases soil pH and calcium, while dolomite limestone provides magnesium in addition to increasing soil pH and calcium.

Results of a field trial evaluating the lime requirements of limpograss showed that there is a yield response from a one-time application of one ton of limestone per acre which increased the soil pH to 5.0. Addition of one ton of limestone per acre increased average annual limpograss production by as much as 0.8 tons of dry matter per acre over three years. The application of two and four tons of lime per acre increased the soil pH to 5.9 and 6.5 respectively but did not increase limpograss yield.

Assuming you need summer grazing this research suggests that one should apply about 300 lbs/A of a 20-5-10 fertilizer in the spring with an additional 50 pounds of nitrogen applied one or two times during the growing season, and apply approximately one ton per acre of limestone to limpograss when the soil pH is less than 5.0. In new plantings of limpograss, limestone needs to be applied at least six months prior to planting to allow ample time for the soil pH to increase.

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