The purpose of nutrient management is to provide sufficient nutrients for crop production and ensure an economic response, while minimizing off-site losses of these nutrients. The agronomic and environmental objectives are met by making the most use out of available nutrients. Best use is accomplished by applying all nutrients at the optimum rate, place, time and form for crop utilization. This requires careful accounting of nutrient applications to optimize the agronomic use and minimize off-site losses.
How Does This Practice Work?
Many factors affect crop yield; nutrients are only one factor, but it is critical to determine nutrient application rates through soil testing. Soil test results will give you the appropriate nutrient application rates for all nutrients and lime. In some states, soil test results can also be used for nitrogen recommendations, whereas in other states they cannot. Both public and private labs can supply soil test results. Good soil sampling is at the heart of a reliable soil test. First, use your soil test report to ensure that the soil pH is in an adequate range. If the soil pH is too high or too low, it will reduce the crop’s ability to use P and other nutrients efficiently. Adjusting the soil pH to the agronomic optimum range with lime is therefore important. If a soil test indicates P is needed, then the soil test report will include the appropriate rate of fertilizer P to apply. In some states, starter levels of P (approximately 20 lbs P2O5 per acre) are recommended for some crops even if soil test results indicate sufficient levels of soil P. Check with your state’s Extension Service to determine if starter P is recommended.
You will also need to determine P placement as you can broadcast, dribble, or band it. Sometimes placement will depend on the form and type of fertilizer or organic material you are using, as well as the cropping system. For instance, broiler litter applied to a pasture will be broadcast. The most efficient placement of the P will depend on an interaction of climate, soil and crop. Research on commercial P sources sometimes shows a difference in crop response to P based on placement and sometimes does not. Contact your state’s Extension Service or USDA-NRCS office for the recommended placement.
Nitrogen, phosphorus, and potassium forms can either be organic or inorganic and within each major category there are multiple forms. For instance, organic materials can be compost, swine effluent, broiler litter etc. The type of organic material determines not only the nutrient content but also its solubility. Commercial fertilizers come as premixed grades based on their percentage N-P2O5-K2O (e.g. diammonium phosphate – 18-46-0), uniform blends (e.g. 10-10-10) or bulk blend (fertilizer blended to meet the specific field fertility needs). Some commercial fertilizers will be fluid and some granular. It is easier to match nutrient rates to soil test recommendations when a blended fertilizer is used, as ratios between nutrients can be changed.
Often, when organic materials are applied, P has been oversupplied and no additional P is needed on these fields. Because nutrients in most organic materials are unbalanced– that is more P is present than is needed when applied to meet crop N requirements – application rates may be determined by N, P, or even heavy metal (copper – Cu and zinc – Zn) concentrations. The rate-limiting nutrient will depend on how each state has applied the federal USDA-NRCS 590 Nutrient Management Standard (USDA-NRCS, 2019). In this code, the rate-limiting nutrient is determined by applying a P risk assessment known as the P Index or a soil test P level (agronomic or environmental) to determine if animal waste is applied on a N or P basis. Most states have chosen to use a P Index on fields receiving animal waste in order to determine the rate-limiting nutrient. Be careful when applying animal manures as they may contain Cu or Zn, which may ultimately cause excess levels that are toxic to crop production.
Where This Practice Applies and Its Limitations
Nutrient management should be used on any field to which commercial fertilizer or organic materials are applied. Not only does the practice protect the environment, but it also improves your economic bottom line by ensuring that adequate nutrients are supplied without spending extra money on unnecessary nutrients.
Nutrient management planning can be highly effective at reducing the build-up of P in soils which is important as soil test P levels are one of the most important factors determining off-site losses of P. Nutrient management also prevents over-application of N, so it can reduce unwanted N and P losses into our streams, lakes, and estuaries. Importantly, nutrient management saves money. By optimizing pH and by supplying the correct amount of nutrients placed in the soil correctly, at the right time and form, production costs will be reduced and yields will be maintained.
Cost of Implementing the Practice
Nutrient management planning generally costs money, but much more can be saved by accurately prescribing fertilizer inputs and related costs. Depending on the soil type, soil tests are needed every two to four years. In some states soil testing is free, whereas in other states it may cost as much as $15 per soil sample. State and federal agencies, as well as private consultants write nutrient management plans. If you use a state or federal agency, the service is free. Consultants generally charge between $10 and $20 per acre to write a nutrient management plan that may or may not include soil testing.
You will save money if you fertilize based on your soil test report. If you need to add more nutrients (e.g. you have manure you need to land apply), then you should increase crop productivity and increase profits. If you do not need nutrients, then you will save money by not using fertilizer. In an analysis of farmers’ fields in North Carolina, cost savings per acre using nutrient management ranged from $5 to $55 per acre, primarily by using the soil test report to determine the appropriate P rate (Hardy et al., 2003). These cost savings are based on free soil testing and nutrient management planning.
Operation and Maintenance
Nutrient management plans should be redone every five years or whenever you change crop rotations.
Hardy, D.H., D.L. Osmond, and A. Wossink. 2003. An Overview of Nutrient Management with Economic Considerations. SoilFacts, AG 439-55. NC Cooperative Extension Service, NC State University, Raleigh, NC. http://www.soil.ncsu.edu/publications/Soilfacts/AGW-439-55/SFnutmgt12-21-02.pdf.
USDA-NRCS. 2019. Conservation Practice Standard: Nutrient Management, Code 590. https://www.nrcs.usda.gov/resources/guides-and-instructions/nutrient-management-ac-590-conservation-practice-standard
For Further Information
Contact your local soil and water conservation district, USDA-NRCS or Cooperative Extension Service office. To find your local USDA Service Center, visit https://www.nrcs.usda.gov/contact/find-a-service-center.
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Gatiboni, L., D. Osmond, and R. Maguire. 2023. Nutrient Management. SERA17 Phosphorus Conservation Practices Fact Sheets. https://sera17.wordpress.ncsu.edu/nutrient-management/