UF/IFAS Nutrient Management Series: UF/IFAS Standardized Nutrient Recommendation Development Process for Successful Crop Production and Environmental Protection
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UF/IFAS Nutrient Management Series: UF/IFAS Standardized Nutrient Recommendation Development Process for Successful Crop Production and Environmental Protection

   

UF/IFAS Nutrient Management Series: UF/IFAS Standardized Nutrient Recommendation Development Process for Successful Crop Production and Environmental Protection1

Rao S. Mylavarapu2

Interpretation of soil test results based on research and best collective scientific judgment is the primary and sole educational objective of offering soil testing service through UF/IFAS Extension Soil Testing Laboratory (ESTL) in Gainesville. Fertilization recommendations, if any, are included in soil test reports along with the soil test results and are based on such interpretations.

Soil Testing

The Extension soil testing program is a three-step process involving soil testing, interpretation and nutrient application (i.e., fertilization) recommendations (Hochmuth et al. 2000.). First, soil testing establishes the levels of nutrients in the soil. The next step, the interpretation of these soil test results, is the most crucial component of the program. The amounts of nutrients that the soil can supply for a specific crop are ranked by adequacy: Very Low, Low, Medium, High and Very High. Each rank is categorized by a range of nutrient concentrations determined in parts per million (ppm) (Table 1 ) (Hochmuth and Hanlon. 2000 ; Kidder et al. 1998 ; Kidder et al. 2000 ). These ranges determine the amount, if any, of a particular nutrient that should be applied for successful crop production based on the Crop Nutrient Requirement (CNR). Crop requirements for various nutrients have been determined based on lab and field research on crop response. The critical soil test level of a nutrient is the maximum amount of nutrient that, when applied to the soil, would produce an optimum yield or quality increase. Nutrient additions above this maximum amount will not produce a yield increase. The third step, recommendation, is based on the rank of nutrient adequacy for specific crops. For example, a High or a Very High category does not require any nutrient additions and therefore application of that nutrient is not recommended.

Soil testing involves collecting a representative soil sample(s) from a uniform field up to 40 acres that will be managed similarly. The soil sample is analyzed at the ESTL using specific standard soil test procedures. First the sample is subjected to an extraction procedure using an appropriate solution. In Florida, different extractants have been adopted based on the type of soil. For all acidic soils the extractant used is Mehlich-1 (dilute double acid) and for all calcareous soils in the state with a pH of >7.4, the extractant adopted is Ammonium Bicarbonate-DTPA (AB-DTPA). For organic soils, either water extraction or ammonium acetate extraction procedure is used depending on the nutrient in question. The suitabilities of these extractant solutions for specific soils have been determined based on multi-year field calibration studies. The extraction procedure is expected to mimic release of nutrients from the soil and therefore provide an estimate of the amount of nutrients that the soil can supply. Lime requirement is also determined using Adams Evans buffer solution (pH 8.0) for a particular crops target pH for optimum crop response.

Standardized Nutrient Recommendations

Researcher(s)/specialist(s), through the Unit administration, must approach the UF/IFAS Plant Nutrient Oversight Committee (PNOC) with proposals and documentation for new recommendations and revisions in existing ones. The PNOC meets quarterly and is presided over by the Dean for Extension. The Dean for Research and several Unit Heads comprise the active membership of the Committee. The Committee will approve or disapprove each recommendation after a review of the materials and once all the questions/comments are addressed by the researchers/specialists to its satisfaction. Any revisions and updates to the existing recommendations go through the same procedure as described above. Once approved, the recommendations are forwarded to the ESTL for incorporating into the soil test reports to the clients. Causes to approach the PNOC with proposals for new or modified recommendations may include new crops, new varieties, and new or modified soil extractants and analytical procedures.

State and local agencies have identified IFAS standardized soil testing procedures and nutrient recommendations for various commodities as the basis for developing and implementing Best Management Practices (BMPs), which are designed to sustain and improve the economic profitability of crop production while minimizing the deleterious environmental impacts from cropping practices. This is becoming more important in nutrient-sensitive regions of the state, like the Everglades, Lake Okeechobee, the Suwannee, St. Johns River, and so on. BMPs add a relatively new dimension to the already-complex process of soil testing and nutrient recommendation, hence the need for fine-tuning.

Any IFAS researcher/specialist who needs to approach the PNOC for reviewing a nutrient recommendation -- including both fertilization recommendations and BMPs -- should submit a proposal, along with any documentation and other supporting material, as an agenda item for the meetings. Proposals should be submitted to Dr. Larry R. Arrington, Dean for Extension and Chair of the Plant Nutrient Oversight Committee, UF/IFAS, P.O. Box 110210, Gainesville, FL 32611-0210, Tel: 352-392-1761/SUNCOM 622-1761, FAX 352-392-3583, email lrarrington@mail.ifas.ufl.edu.

References

Footnotes

1. This document is SL189, a fact sheet of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: February 2002. Please visit the EDIS Website at http://edis.ifas.ufl.edu.

2. R.S. Mylavarapu, Assistant Professor, Nutrient Management Specialist and Director of UF/IFAS ARL/ESTL, Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611-0290.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.


Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.