Bahiagrass Fertilization at Springtime

May 2005
Dr. Martin B. Adjei - Range Cattle Research & Education Center

Pasture fertilization is one of the most expensive costs in beef production. With the escalating fertilizer costs and concerns of over-fertilization on water quality there has been a need to re-evaluate fertilizer recommendations for pasture grasses. Our research findings have shown that we can eliminate phosphorus and potassium fertilization for grazed bahiagrass without reducing yields or affecting quality (both digestibility and protein content) of the grass. The reasons that phosphorus and potassium can be eliminated are that when pastures are grazed a substantial percentage of nutrients are actually recycled back to the plant. Additionally, most perennial grasses like bahiagrass have deep roots which can reach the hard pan that is naturally rich in plant nutrients. This has led to major revisions in the IFAS fertilizer recommendations for grazed bahiagrass, resulting in cost savings of millions of dollars to Florida ranchers. In addition, this has had a positive impact on surface and ground water quality.

Bahiagrass is one of the most popular perennial grasses grown in Florida for cattle production. It makes up 75% of improved pastures statewide. The main reasons are that it is a low maintenance grass that is fairly easy to establish from seed and maintain. For the past 10 or so years we have emphasized the economic advantage of applying no P and K to grazed bahiagrass in south Florida.

However, producers should know that there are currently three nitrogen options to choose from for bahiagrass forage production. These options are based on the amount of forage one wants to obtain. Fertilizer for the various options should be applied in early spring to maximize the needed spring forage.

A summary of the current revised IFAS fertilizer recommendations for bahiagrass are as follows:

  • Low Nitrogen Option (for grazed pastures only): Apply 50 to 60 pounds of nitrogen per acre and no phosphorus and no potassium.
  • Medium Nitrogen Option: Apply 100 pounds of nitrogen per acre. When adopting this option it is also suggested to apply 25 pounds P2O5 per acre if the soil tests low in P and 50 pounds K2O per acre if the soil tests very low or low in K. No K should be applied if the soil tests medium or high in K.
  • High Nitrogen Option: Apply 160 pounds of nitrogen per acre. This must be split into two 80 lb per acre applications, one in spring and one in late summer. It is also suggested that one applies 40 pounds of P2O5 per acre if the soils tests low in P and 20 pounds of P2O5 if the soil tests medium. It is also currently recommended to apply 80 pounds of K2O if the soil tests low in K and 40 pounds of K2O per acre if the soil tests medium. No K should be applied if the soil tests high in K.

It should be noted that there are currently no micro nutrient recommendations for perennial grasses grown in Florida. The reason for this is that it has never been demonstrated that addition of micronutrients produce economic increases in forage grass production in south Florida.

In conclusion, the University of Florida currently recommends that phosphorus and potassium not be applied to bahiagrass that is grazed in southern Florida. This is because all studies conducted to date in south Florida show no economic advantage from the addition of phosphorus, potassium or micronutrients to bahiagrass pastures. There still is the question as to how long bahiagrass can go without phosphorus and potassium and we don't have enough information to answer that question at the present time. Thus it may be necessary to periodically apply small levels (25 pounds per acre) of phosphorus and potassium just as an insurance policy against deficiencies. The reductions in phosphorus and potassium fertilizations should result in great cost savings to ranchers in these tough economic times. Please note that when making hay, nitrogen, potassium and some phosphorus must be applied after every cut. For other details, get into the habit of contacting your county agents. They are there to help you decide.

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