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Fertilizing Summer Hay Fields

Fertilizing Summer Hay Fields— Fertilizer costs account for a high percentage of the inputs associated with hay production. A properly fertilized hay field will result in high yields, good quality and good cattle performance. Poorly fertilized hay will be of poor nutritional quality, yield poorly and cause cattle to be unthrifty resulting in a loss of body condition during the hay feeding season.
High-yielding hay removes large amounts of nutrients. The most common nutrients used in fertilizers for hay production are nitrogen (N), phosphorous (P), potassium (K) and sulfur (S). Table 1 shows the amount of nutrients removed in one ton of hybrid bermudagrass and bahiagrass hay.Table 1. Nutrient removal in hay
——————lbs/ton of hay——————
Nutrient Hybrid Bermuda Bahia
N 46 43
P2O5 12 12
K2O 50 35
S 6 6
Source: Potash and Phosphate Institute
The amount of nitrogen to be applied is determined by the yield goal, the forage species and whether the forage will be used for grazing or hay. The amounts of phosphate (P2O5) and potash (K2O) needed are determined by soil test results and will be discussed in detail further into the article. Soil testing is strongly encouraged to determine lime and fertilizer needs. A good soil testing program can identify problem areas in fields, save money on unnecessary fertilizer use and improve yields and quality through efficient fertilizer use. A soil testing program is only as good as the sample collected. Learn more about sampling soil for nutrient analysis by conducting a quick Google search for LSU AgCenter publication #2890 “Sampling Poultry Litter & Soil For Nutrient Analysis”. Nitrogen is the element which is usually most limiting in hay production. It is an important constituent of protein. Proper rates of nitrogen increase growth rate and photosynthesis. Nitrogen deficiencies are characterized by a light green color and poor growth. If grass does not “green up” after a nitrogen application, the problem could be sulfur deficiency because sulfur deficiency looks much like N deficiency. Hybrid bermudagrass hay requires high rates of nitrogen to maximize yields. If a good stand of grass is present and adequate rainfall occurs, hay yields rise proportionately to the amount of nitrogen applied. Protein also increases, assuming the grass is harvested at the proper stage of growth. Table 2 shows the effect of N rates on hybrid bermudagrass hay yield and protein content
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Table 2. Effect on N rate on hybrid bermudagrass hay yield and crude protein (5-year average)
N Rate Hay Yield (lbs./A) Crude Protein (%)
100 5,807 9.9
200 8,628 11.1
300 11,562 11.5
400 13,067 12.6
500 15,345 13.4
100 pounds N per acre applied per harvest as ammonium nitrate
Source: Effect of Fertilizer Nitrogen Rates and Sources on Coastal Bermudagrass Grown on Coastal Plain Soil. LAES Bulletin No. 797

Bahiagrass also responds positively to nitrogen applications, assuming adequate rainfall occurs and the stand is properly managed (Table 3).
Table 3. Effect on N rate on Pensacola bahiagrass hay yield and crude protein (5-year average)
N Rate Hay Yield (lbs./A) Crude Protein (%)
0 3,461 10.3
200 10,664 12.1
300 12,722 12.5
400 14,081 13.4
100 pounds N per acre applied per harvest as ammonium nitrate
Source: Responses of Bahiagrass to Applied Nitrogen, Phosphorous and Potassium, LAES Bulletin No. 701

The LSU AgCenter recommends the following N rates for summer hay fields:
 Hybrid bermudagrass 300-400 pounds per acre
 Common bermudagrass 200-300 pounds per acre
 Bahiagrass 300-400 pounds per acre
Use these rates in split applications with no more than 100 pound N per acre applied at any one time. With the high rates of nitrogen used in hay production (up to 400 pounds of N/acre), it is usually not advisable to apply all the N at one time. Losses may occur because of heavy rainfall, or the applied N may not be fully used because of insufficient rainfall. A better alternative is to apply 100 pounds of N per acre at green up, then apply 100 pounds of N per acre after each hay cutting.

Table 3. Effect of split N application on hay yield (3-year average)
N Application Method Hay Yield (lbs./acre)
Single spring application 9,848
4-way split 12,432
N rate was 400 pounds per acre. 4-way split involved 100 pounds per acre at green up, then 100 pounds per acre following the next 3 hay cuttings.
Source: Effects of Fertilizer Nitrogen Rates and Sources on Coastal Bermudagrass Grown on Coastal Plain Soil, LAES Bulletin No. 797

Phosphorous is shown in fertilizer rates as phosphate (P2O5). All rates discussed here will be in pounds of P2O5 per acre. Phosphorus is critical in establishment of a root system. It is essential in the storage and transfer of energy and is a component of several biochemicals that control plant growth and development. Phosphorus deficiency in warm season grasses is exhibited as small, unthrifty plants. In winter grasses and legumes, P deficiency is exhibited as a reddish-purple color on leaves and stems. Phosphate is used in much smaller amounts by hay than are nitrogen and potash (Table 1). For this reason, it can all be applied in the spring, or it can be split-applied. Phosphorus does not leach from the soil. It is lost through crop removal and soil erosion. Phosphorous availability to plants depends largely on soil pH. It is most available when the soil pH is 5.5—7.0, with the optimum pH for P availability of 6.2. When the soil pH is below 5.5, P is tied up by iron and aluminum. When the pH is above 7.0, P is tied up by calcium. Phosphate rates should be based on soil test results. Recommended rates of phosphate range from 0-140 pounds P2O5 per acre, depending on soil test level. Potassium is shown in fertilizer rates as potash (K2O). All rates discussed here will be in pounds of K2O per acre. Potassium is indirectly related to many plant cell functions. Some 60 enzymes require the presence of K. Plants sufficient in K are much more “winter-hardy” than are deficient plants. Potassium deficiency inhibits the ability of plants to use available water and results in plants prone to drought stress. Potassium-deficient plants are also much more susceptible to certain diseases. Potassium deficiency is exhibited in bermudagrass as Helminthosporium disease. The symptoms begin as small black spots on the leaves. If the deficiency progresses, the spots widen to form dead patches on the leaves. Then the grass begins to die out in small clumps. These empty spaces are usually quickly occupied by weeds. In severe cases of K deficiency, the stand may be lost. Bermudagrass hay removes tremendous amount of K2O and bahiagrass also removes relatively large amounts (Table 1). There-fore, the recommended rates of K2O are high for these crops. Potash rates should be established by soil test results. Recommended rates of K2O range from 40-300 pounds per acre, depending on soil test levels. At the higher recommended rates of potash, it is not advisable to apply all of the material in one application. On sandy soils, potassium can leach. For best results, split potash applications so that no more than 120 pounds K2O are applied at one time. Using the recommended rates of potash is essential in maintaining hay fields. Potassium deficient fields will lose both yield and stand (Table 4).

Table 4. Effect of K2O rate on yield and stand of hybrid bermudagrass (6-year average)
———bermudagrass stand %——
K2O Rate Hay Yield (lbs./A) Year 1 Year 6
0 8,919 57 29
100 12,399 47 84
200 13,583 45 89
400 14,341 41 88
Soil test K very low
Source: Effect of Fertilizer Potassium Rates on Coastal Bermudagrass Grown on Coastal Plain Soil. LAES Bulletin No. 782

When establishing (seeding or sprigging) new summer hay fields, It is important to fertilize properly. Too much fertilizer at the wrong time will encourage weed growth. Too little fertilizer will prevent the grass from growing and spreading properly. When planting into a prepared seedbed, apply nitrogen (along with all the recommended phosphate and potash) at the rate of 20-40 pounds per acre before the final tillage operation. If heavy weed pressure exists, use the lower rate. After the planted grass emerges and begins to cover, apply 40-60 pounds of nitrogen per acre. This will help the grass cover quickly. Do not apply nitrogen if the weeds are outgrowing the grass. It may be necessary to control (clipping or spraying) broadleaf weeds and annual grasses to reduce their competition for sunlight and nutrients before this application of nitrogen. Wait until desirable grass begins to cover before applying the second application of nitrogen.—Source: LSU AgCenter publication #2612