Forage Fertilization: Constant monitoring to ensure healthy stand

April, 2017
Jonael H. Bosques, Hardee County Cooperative Extension Service, Wauchula

Adequate forage fertilization can improve more than our finances. It can also reduce pasture grass decline and with routine soil monitoring producers can make sound decisions on when and where to invest on a given season.

Plants have some needs that are often overlooked, and low nutrients or inadequate pH can reduce their vigor favoring long taprooted plants such as broadleaf weeds. Nitrogen (N), phosphorus (P) and potassium (K) are called macro nutrients due to their high quantity requirement by plants. Secondary nutrients are sulfur (S), calcium (Ca) and Magnesium (Mg), which the plant has a moderate demand for. Micronutrients are needed in smaller amounts than macro and secondary nutrients. These are iron, zinc, copper, manganese, boron, molybdenum, chloride and nickel.

A large portion of our soils due to their nature have a limited ability to hold nutrients and oftentimes pasture weed problems and stand loss are due to deficiencies in one or more of these essential elements.

Soil acidity

Flatwoods soils are naturally acid due to climatic conditions. Undisturbed soils have a pH around 4.5. The term pH refers to the ability of the soil to exchange hydrogen and it ranges from pH 0 to 14. Normal blood pH for humans is 7.4, and perennial forages prefer a pH of between 5 and 7. A pH lower than 4 creates the potential for aluminum toxicity in the soil which can affect root growth and plant vigor. A pH greater than 7 can reduce the availability of micronutrients affecting multiple pathways involved in forage growth.

Nutrient value

Many people just lime their pastures every other year due to increasing input costs. Nevertheless, replenishing the whole nutrient profile of the soil can improve more than just your grass stand. Applications of nitrogen can increase crude protein content in the forage as well as digestibility (which will lead to more intake by livestock).

Well-nourished grass will mean less weeds

Grass stands that receive adequate nutrition and liming have the ability to survive and spread more readily. Well-nourished forages better compete for nutrients, and water. They can outcompete in most cases common broad leaf weeds and fight off diseases.

Routine monitoring

Soil analysis is performed by randomly taking core samples from your fields 4 to 6 inches in depth. These core samples will be collected and mixed together in a bucket, and a subsequent subsample free from debris (roots, twigs, stones, etc.) will be sent out to be analyzed at a soils laboratory.

At the soils laboratory, your sample will be subject to chemical extraction of nutrients (similar to the process that happens at the root level by plants when they absorb nutrients from the soil profile). The soil sample will be analyzed for macro- and secondary nutrients as well as pH. Furthermore, a soil amendment recommendation will be generated specifically for your field/pasture. Mehlich 3 is the most accurate soil extraction protocol for determining nutrient content and pH.

It is recommended that you sample your pastures and fields yearly, and give yourself enough time for the applied lime to interact with your soil. This usually takes close to four months to stabilize and reach the pH level that is recommended following adequate spreading procedures.

Soil analysis can be performed for a relatively economical price through the UF/IFAS Extension Hardee County office. Come by the office and get some soil test kits for your farm.

For adequate determination of P content on Bahiagrass pastures, a tissue sample should be analyzed as well. This tissue analysis will determine the level of P in the plant and combines the soil data to conclude if P should be applied or not. Some areas of Hardee County are rich in P, but there are pockets around that vary in levels of this nutrient.

A little extra information can go a long way when we are trying to manage a system such as our pastures in which we cannot control rain, temperatures and other variables that influence plant growth and nutrient mobility. Remember that grass is the cheapest feedstuff we have for our cows, horses, goats and other livestock. The lack of monitoring can result in a gradual depletion of healthy and profitable resource such as our perennial forages. Routine soil analysis, inspection of your grass stand, assessment of your weed populations and analysis of forage quality will be money and effort well spent.

If you would like to learn more on how to test your soil, plant fertility, forage production and other topics, please call your local UF/IFAS Extension agent.

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