Introduction
This publication presents in abbreviated form the fertilization recommendations for agronomic crops based on soil tests performed by the UF/IFAS Extension Soil Testing Laboratory (ESTL). It contains the basic information from which ESTL soil-test reports and fertilization recommendations are generated.
General Background
Soil testing is a tool in crop fertilization management. Its successful use requires that: (1) you send the lab soil samples that best represent your field or management unit; (2) the laboratory uses legitimate methods for predicting fertility; and (3) the fertilizer recommendations are based on measured crop responses.
The ESTL extracts phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca) with the Mehlich-3 extractant and bases fertilization recommendations for those nutrients on the test results. Current interpretation of test results are presented in Table 1. Nitrogen (N) fertilization is not based on soil tests but rather is based on crop needs as documented in research literature.
Liming recommendations are based on the Adams-Evans lime requirement test, a calibration equation developed for Florida soils, and on the target pH for the crop for which the recommendation is being made. Therefore, any lime recommendation based solely on soil pH will be invalid.
Soil test reports from the ESTL are computer-generated from lab data and crop codes. If a cropping situation is not in the list of crop codes, routine soil tests may not be appropriate. In such instances, the local county agent should be consulted before soil samples are sent for testing. Reports contain the results of the tests (soil pH, ppm extractable P, K, Mg, and Ca), a rating of the P, K, and Mg (high to low), and the fertilization recommendation for the specified crop. The recommendation is composed of two parts: (1) the rates of N, P2O5, and K2O fertilizer to apply; and (2) directions (or footnotes) that give important information about fertilization management such as application timing, special crop requirements, etc.
Table 2 of this document contains crop codes, crop descriptions, target pH, N recommendation, P2O5 and K2O recommendations for each of the three soil-test rating levels, the footnotes printed for each of the crop codes, and the references for these recommendations.
The text of the footnotes referred to in Table 2 is given below.
Text of Directions (Footnotes)
102. Apply all of the P2O5, 30% of the K2O, and 30 lb N/A in a preplant or at-planting application. Four weeks after planting, sidedress the remaining 70% of the K20. Apply the remaining 120 lb N/A in two or more sidedressings, one of which should be at 4 weeks after planting.
103. When cultivating hemp for seed or flowers, the total N applications should not exceed 150 lb N/acre. When hemp is grown for fiber, total N applications should not exceed 50 lb N/acre because too much N can reduce fiber quality. When hemp is grown on plastic-mulched beds, weekly fertigation with approximately ½ to 2 inches of irrigation is recommended.
104. Apply all of the P2O5, 30% of the K2O, and 30 lb N/A in a preplant or at-planting application. Four weeks after planting, sidedress the remaining 70% of the K2O. Apply the remaining 180 lb N/A in three or more sidedressings, one of which should be at 4 weeks.
106. Apply all of the P2O5 and 30% of the K2O and N in a preplant or at-planting application. Topdress or sidedress the remaining 70% of the K2O and N. For small grains grown for grain, silage, or hay, topdress during late January or early February. For grain sorghum or forage sorghum, sidedress before plants are too tall to cultivate or approximately 4 weeks after planting.
107. Apply all of the P2O5 and 30% of the K2O and N in a preplant or at-planting application. Apply the remaining 70% of the K2O and N in one sidedressing.
108. Application of 20–30 lb N/A may give vegetative response but is unlikely to increase harvested yield.
109. If peanuts are grown for seed or if they are Virginia type, regardless of soil test, apply gypsum in a band over the potential pegging zone at early flower. Apply 400 lb gypsum/A for runner types and 800 lb gypsum/A for Virginia types. Double these rates if broadcasting granular or phosphogypsum (bulk wet). For peanuts not grown for seed, apply gypsum as recommended above only if the calcium soil-test level is below 250 ppm Ca.
110. Apply 50% of the fertilizer at or before transplanting and the other half within 3 weeks of transplanting.
111. Apply 30 lb N/A, 50% of the K2O, and all of the P2O5 fertilizer in a preplant or at-planting application. Apply 50 lb N/A and the remaining K2O after the first grazing period. Apply an additional 50 lb N/A after each subsequent grazing period.
112. When planting on a prepared seed bed, apply 30 lb N/A, 50% of the K2O, and all of the P2O5 fertilizer in a preplant or at-planting application. Apply 50 lb N/A and the remaining K2O after the first grazing period. Apply an additional 50 lb N/A after each subsequent grazing period.
When overseeding established perennial grasses with cool-season annual grasses, apply 50 lb N/A plus all of the P2O5 and K2O after emergence. Apply an additional 50 lb N/A after each subsequent grazing period.
115. Apply all of the P2O5 and K2O fertilizer in late fall. If legumes are planted in combination with oats, rye, wheat, and/or ryegrass, apply 30 lb N/A in a preplant or at-planting application plus one additional 50 lb N/A application after the grass is well established.
118. Apply 0.75 lb boron/A in the fertilizer or 0.5 lb boron/A as a foliar spray with the first fungicide application.
119. Application of sulfur is not required if test value is greater than 6.0 mg/kg or ppm. If the soil test value is less than 6.0 mg/kg or ppm apply sulfur as recommended.
120. Fertilizer should contain 15–20 lb sulfur/A. Apply as a sulfate (e.g., gypsum, ammonium sulfate, magnesium sulfate, potassium sulfate, potassium magnesium sulfate), because elemental sulfur will react too slowly to supply the sulfur needs of the current crop.
121. Apply all of the P2O5 and K2O in spring or early summer when seedlings or regrowth are 3–4 inches tall. Species included are aeschynomene, alyceclover, desmodiums, hairy indigo, perennial peanut, and other tropical legumes.
122. Species included are all true clovers (white, red, arrowleaf, crimson, subterranean), vetches, lupines, and sweet clover.
123. Apply all of the P2O5 and 50% of the K2O fertilizer in late fall. Apply the remaining K2O in early spring. If the alfalfa is mechanically harvested rather than grazed, apply an additional 30 lb P2O5/A and 60 lb K2O/A after each harvest. An additional application of 100 lb K2O/A in June or July may increase summer survival of alfalfa. Apply 3 lb boron/A per year to alfalfa in three 1 lb/A applications. Copper and zinc fertilizer may be needed if soil pH is above 6.5. The lime requirement shown is adequate for established alfalfa. However, if the alfalfa has not yet been planted, apply and incorporate one ton of lime/A if the soil pH is below 6.6. Lime is especially important for establishment of alfalfa. It is not practical to incorporate lime once the alfalfa is planted.
124. UF/IFAS fertilization and liming recommendations are advisory in nature and emphasize efficient fertilizer use and environmentally sound nutrient management without losses of yield or crop quality. It is generally assumed the nutrients will be supplied from purchased, commercial fertilizer and the expected crop yields and quality will be typical of economically viable production. Growers should consider IFAS recommendations in the context of their entire management strategy, such as return on investment in fertilizer and the benefits of applying manure or biosolids (sewage sludge) to their land.
125. Grass species included are bermuda, star, digit, and rhodesgrass.
126. FERTILIZATION MANAGEMENT NOTES FOR BERMUDAGRASS, STARGRASS, DIGITGRASS, AND RHODESGRASS
Establishment of New Plantings
For establishment of new plantings, apply 100 lb N/A and split as follows: apply 30 lb N/A, all of the P2O5, and 50% of the K2O as soon as plants have emerged. Apply the remaining K2O and 70 lb N/A 30–50 days later.
Maintenance Fertilization of Established Pastures
For grazed, established stands, apply 80 lb N/A, all of the P2O5, and 50% of the K2O in early spring. Apply 80 lb N and the remaining K2O at midseason.
Under intensive management in central and south Florida, up to 200 lb N/A may be economically viable for stargrass and bermudagrass. In that situation, apply 80 lb N/A, all of the P2O5 and 50% of the K2O in early spring, follow with 50 lb N/A in midseason, and 70 lb N/A and the remaining K2O in mid- to late September.
Making Hay, Silage, or Green Chop
Apply 80 lb N/A and all of the recommended P2O5 and K2O in early spring. Apply an additional 80 lb N and 40 lb K2O/ A after each cutting, except the last in the fall. Include 20 lb of P2O5 in the supplemental fertilizer if the soil tested low or medium in P.
Special Note If Applying Manure or Biosolids
A different set of economic factors are usually considered when waste materials rather than purchased fertilizer are supplying the nutrients. Additionally, it is often impractical to follow the application timings discussed above when using waste materials from other operations.
127. Apply all of the P2O5, 50% of the K2O, and 40 lb N/A at planting. Topdress the remaining N and K2O in late January. On land which lacks clayey soil within the top 6 to 8 inches of the surface, apply 5 to 10 lb sulfate-sulfur/A at planting and 10 lb sulfate-sulfur/A in the topdressing. Wettable or other elemental forms of sulfur will react too slowly to supply the sulfur needs of the current crop. On flatwoods soils with pH above 6.1, apply 10 lb manganese/A. On better-drained sands with pH above 6.5, apply 6 to 10 lb manganese/A.
128. The recommended rates of fertilizer are sufficient to produce soybean yields in the 60 bu/A range. If yields from this field have never exceeded 40 bu/A under current management, reduce P2O5 and K2O recommendations by 20 lb/A. If yields from this field have never exceeded 25 bu/A, reduce P2O5 and K2O recommendations by 40 lb/A. Often this adjustment will mean that you will achieve your yield potential without any P or K fertilizer additions.
129. These recommendations are made assuming adequate soil moisture will be available either from rainfall or irrigation. In south Florida, lack of adequate rainfall during the cool season frequently causes stand failure or limits growth. Under nonirrigated conditions in south Florida, the probability of inadequate moisture is high, and the likelihood that the crop will benefit from applied fertilizer is low, especially on the drier soils.
130. For grazing or hay production of perennial peanuts, apply all of the P2O5 and K2O in early spring. For hay production, make an annual application of 20 to 30 lb sulfur/A. Apply as a sulfate (e.g., gypsum, ammonium sulfate, magnesium sulfate, potassium sulfate, potassium magnesium sulfate). After each hay harvest, apply an additional 15 pounds of P2O5 and 40 pounds of K2O per ton of hay removed, unless the soil tested high.
131. FERTILIZATION MANAGEMENT NOTES FOR GRAZED BAHIAGRASS
Bahiagrass is probably the most widely used planted forage grass in Florida. It responds well to grazing management and inputs such as fertilization. However, it also can persist and give satisfactory yields under low inputs. Because of the wide range of possible use and management levels, recommendations for bahiagrass fertilization differ with the level of management and the economic inputs. Management decisions concerning liming and fertilization of bahiagrass pastures are very sensitive to cattle productivity and prices.
Liming
In order to obtain maximum fertilization efficiency, soil pH should be maintained at 5.5 or higher. If soil pH tests below 5.3 or lower, a lime requirement test will be conducted and a recommendation for lime application will be made. Optimal use of lime is to apply at least 3–6 months prior to fertilization to provide adequate time for the lime reaction to occur and the soil pH to adjust to the desired level. Soils should be tested for pH every 2–3 years.
Phosphorus Fertilization
In order to receive phosphorus fertilizer recommendations for established bahiagrass, soil and tissue samples should be submitted to the ESTL at the same time. As per the preliminary research findings, soil tests alone were not found to be adequate to determine bahiagrass P needs. A companion tissue test has therefore been added to the testing procedures along with the soil test to determine the P fertilization needs. Producers are strongly encouraged to simultaneously test soil and tissue samples if bahiagrass pastures have not received P fertilization for long periods. Phosphorus should not be applied if tissue P concentrations are at or above 0.15%, even if soil tested Low in P. For Medium and High soil P levels, P application is not recommended since there is no added benefit of P fertilization on bahiagrass yields.
If P recommendations are not desired and the producer is only interested in either the test for soil pH and lime requirement recommendations, or the test for soil pH, lime requirement, K, Mg, and Ca recommendations, the soil sample alone can be submitted to the ESTL. In this case, the soil test report will notinclude P fertilizer recommendations.
Both the consolidated representative soil and the tissue samples should be collected simultaneously from each field of up to 40 acres.
The testing procedures and the recommendations for P for bahiagrass may be adjusted as field research data become available.
Maintenance Fertilization of Established Bahiagrass Pasture
Four fertilization options are presented below for bahiagrass pastures. Choose the option that most closely fits your fertilizer budget, management objectives, and land capability. If you will only be grazing your bahiagrass, you should carefully consider the potential for economical return on your investment in fertilizer before using the Medium-Nitrogen or High-Nitrogen options described below. The added forage produced for grazing animals may not be worth the added cost.
Low-Nitrogen Option. Do not use this option if you cut hay, because nutrient removal by hay is much greater than by grazing animals. This option results in the lowest cost of purchased fertilizer. Apply 50 to 60 lb N/A in the early spring to maximize much-needed forage. Do not apply K recognizing that N will be the limiting nutrient in this low-cost option. Apply 25 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Do not apply P if tissue P concentration is at or above 0.15%, even if the soil tests Low in P. For Medium and High soil P levels, neither P application nor tissue analysis is recommended because there will be no added benefit of P fertilization on bahiagrass yields.
Medium-Nitrogen Option. Apply 100 lb N/A in the early spring. Apply 25 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Do not apply P if tissue P concentration is at or above 0.15%, even if the soil tests Low in P. For Medium and High soil P levels, neither P application nor tissue analysis is recommended because there will be no added benefit of P fertilization on bahiagrass yields. Apply 50 lb K2O/A if your soil tests Low in K and none if it tests Medium or High.
High-Nitrogen Option. Apply 160 lb N/A in two applications of 80 lb N/A in early spring and early summer. Apply 40 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Do not apply P if tissue P concentration is at or above 0.15%, even if the soil tests Low in P. For Medium and High soil P levels, neither P application nor tissue analysis is recommended since there will be no added benefit of P fertilization on bahiagrass yields. Apply 80 lb K2O/A if your soil tests Low in K and 40 lb K2O/A if it tests Medium. No K should be applied if your soil tests High in K. The fertilization rates suggested in this option are high enough to allow bahiagrass pasture to achieve well above average production. Management and environmental factors will determine how much of the potential production is achieved and how much of the forage is utilized. A single cutting of hay can be made without need for additional fertilization.
Bahiagrass Cut Sometimes for Hay
For a Single Cut per Year from Pastures. If you used the Low-N option of pasture fertilization, apply 80 lb N/A no later than six weeks before the growing season ends. Apply 50 lb K2O/A if your soil tests Low in K and none if it tests Medium or High. Apply 25 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Do not apply P if tissue P concentration is at or above 0.15%, even if the soil tests Low in P. If you used the Medium-N option of pasture fertilization, apply an additional 80 lb N no later than six weeks before the growing season ends. Apply 50 lb K2O/A if your soil tests Low in K and none if it tests Medium or High. Apply 25 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. If you used the High-N option of pasture fertilization, you do not need any additional N fertilization to make one cut of hay. Apply 80 lb K2O/A if your soil tests Low in K and 40 lb K2O/A if it tests Medium. Apply 40 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%.
Bahiagrass Grown Only for Hay
For Multiple Cuts of Hay. Apply 80 lb N/A in early spring. Also in spring, apply 80 lb K2O/A if your soil tests Low in K and 40 lb K2O/A if it tests Medium. Apply 40 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Apply an additional 80 lb N and 40 lb K2O/A after each cutting, except the last in the fall. Include 20 lb of P2O5/A after each cutting if the soil tested Low in P.
Bahiagrass for Seed Production
Apply 60–80 lb N/A in February or March. At the same time, apply 80 lb K2O/A if your soil tests Low in K and 40 lb K2O/A if it tests Medium. Apply 40 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Graze until May, June, or July, depending on variety. Remove cattle before seed heads start to emerge and apply an additional 60–80 lb N/A.
If the bahiagrass is not grazed, do not apply fertilizer in February or March because this may stimulate excessive top growth. Mowing from February to April may be needed to remove excessive top growth. Apply 60–80 lb N/A before seed heads first appear. Apply 25 lb P2O5/A if your soil tests Low in P and tissue P concentration is below 0.15%. Do not apply P if tissue P concentration is at or above 0.15%, even if the soil tests Low in P. For Medium and High soil P levels, neither P application nor tissue analysis is recommended. Apply 50 lb K2O/A if your soil tests Low in K and none if it tests Medium or High. Fertilize Pensacola in March/April and Argentine and Paraguay in May/June.
132. HAY OR SILAGE (PERENNIAL GRASS)
For Multiple Cuts
Apply 80 lb N/A and all of the recommended P2O5 and K2O in early spring. Apply an additional 80 lb N and 40 lb K2O/A after each cutting, except the last in the fall. Include 20 lb of P2O5/A in the supplemental fertilizer if the soil tested low or medium in P.
For a Single, Late Season Cut from Pastures:
If you have not applied N in the past two months, apply 80 lb N/A and the soil-test recommended amount of P2O5 and K2O. If you have applied N in the past two months, do not apply any N now, but do apply the soil-test recommended amount of P2O5 and K2O. Any application of fertilizer should be made no later than six weeks before the growing season ends.
Special Note If Applying Manure or Biosolids:
A different set of economic factors is usually considered when waste materials rather than purchased fertilizer are supplying the nutrients. Additionally, it is often impractical to follow the application timings discussed in this footnote when using waste materials from other operations.
133. FERTILIZATION MANAGEMENT NOTES FOR LIMPOGRASS (Hemarthria)
Establishment of New Plantings
For establishment of new plantings, apply 100 lb N/A and split as follows: apply 30 lb N/A, all of the P2O5, and 50% of the K2O as soon as plants have emerged. Apply the remaining K2O and 70 lb N/A 30–50 days later.
Maintenance Fertilization of Established Pastures
For grazed, established stands, apply 60 lb N/A and all of the P2O5 and K2O in late winter or early spring. Apply an additional 60 lb N in late summer or early fall. For a minimum fertilization alternative, ignore the P and K recommendation and apply only 60 lb N per year.
Making Hay, Silage, or Green Chop
Apply 80 lb N/A and all of the recommended P2O5 and K2O in late winter or early spring. Apply an additional 80 lb N and 40 lb K2O/A after each cutting, except the last in the fall. If the soil tested Low in P, then include 20 lb P2O5/A in the fertilizer applied after each cutting, except the last in the fall.
Special Note if Applying Manure or Biosolids:
A different set of economic factors is usually considered when waste materials rather than purchased fertilizer are supplying the nutrients. Additionally, it is often impractical to follow the application timings discussed above when using waste materials from other operations.
134.BAHIAGRASS, ESTABLISHMENT OF NEW PLANTINGS
Apply 80 lb N/A for establishment of new bahiagrass plantings in two split applications. Apply 30 lb N/A and all of the recommended P2O5 and 50% of the recommended K2O as soon as the plants have emerged. Apply the remaining 50 lb N/A and the remaining K2O between 30 and 50 days after the initial application. If manure or biosolids are used as the main source of nutrients, apply the entire annual application once the plants are large enough to withstand physical damage from the application.
Tables
Table 1. Current Mehlich-3 soil test interpretations used for agronomic crops.
Table 2. Target pH, and recommended annual N, P2O5, and K2O fertilizer rates for agronomic crops. Phosphorus and K rates are based on interpretation of a Mehlich-3 soil test.
Table 3. Interpretation for bahiagrass soil and tissue test.