Nutrient management


Nutrient management is the science and practice directed to link soil, crop, weather, and hydrologic factors with cultural, irrigation, and soil and water conservation practices to achieve optimal nutrient use efficiency, crop yields, crop quality, and economic returns, while reducing off-site transport of nutrients that may impact the environment. It involves matching a specific field soil, climate, and crop management conditions to rate, source, timing, and place of nutrient application.
Important factors that need to be considered when managing nutrients include the application of nutrients considering the achievable optimum yields and, in some cases, crop quality; the management, application, and timing of nutrients using a budget based on all sources and sinks active at the site; and the management of soil, water, and crop to minimize the off-site transport of nutrients from nutrient leaching out of the root zone, surface runoff, and volatilization.
There can be potential interactions because of differences in nutrient pathways and dynamics. For instance, practices that reduce the off-site surface transport of a given nutrient may increase the leaching losses of other nutrients. These complex dynamics present nutrient managers the difficult task of achieve the best balance for maximizing profit while contributing to the conservation of our biosphere.

Nutrient management plan

A crop nutrient management plan is a tool that farmers can use to increase the efficiency of all the nutrient sources a crop uses while reducing production and environmental risk, ultimately increasing profit. Increasingly, growers as well as agronomists use digital tools like SST or Agworld to create their nutrient management plan so they can capitalize on information gathered over a number of years. It is generally agreed that there are ten fundamental components of a Crop Nutrient Management Plan. Each component is critical to helping analyze each field and improve nutrient efficiency for the crops grown. These components include:
;Field map: The map, including general reference points, number of acres, and soil types is the base for the rest of the plan.
;Soil test: How much of each nutrient is in the soil profile? The soil test is a key component needed for developing the nutrient rate recommendation.
;Crop sequence: Did the crop that grew in the field last year fix nitrogen for use in the following years? Has long-term no-till increased organic matter? Did the end-of-season stalk test show a nutrient deficiency? These factors also need to be factored into the plan.
;Estimated yield: Factors that affect yield are numerous and complex. A field's soils, drainage, insect, weed and crop disease pressure, rotation and many other factors differentiate one field from another. This is why using historic yields is important in developing yield estimates for next year. Accurate yield estimates can improve nutrient use efficiency.
;Sources and forms: The sources and forms of available nutrients can vary from farm-to-farm and even field-to-field. For instance, manure fertility analysis, storage practices and other factors will need to be included in a nutrient management plan. Manure nutrient tests/analysis are one way to determine the fertility of it. Nitrogen fixed from a previous year's legume crop and residual effects of manure also affects rate recommendations. Many other nutrient sources should also be factored into this plan.
;Sensitive areas: What's out of the ordinary about a field's plan? Is it irrigated? Next to a stream or lake? Especially sandy in one area? Steep slope or low area? Manure applied in one area for generations due to proximity of dairy barn? Extremely productive—or unproductive—in a portion of the field? Are there buffers that protect streams, drainage ditches, wellheads, and other water collection points? How far away are the neighbors? What's the general wind direction? This is the place to note these and other special conditions that need to be considered.
;Recommended rates: Here's the place where science, technology, and art meet. Given everything you've noted, what is the optimum rate of N, P, K, lime and any other nutrients? While science tells us that a crop has changing nutrient requirements during the growing season, a combination of technology and farmer's management skills assure nutrient availability at all stages of growth. No-till corn generally requires starter fertilizer to give the seedling a healthy start.
;Recommended timing: When does the soil temperature drop below 50 degrees? Will a N stabilizer be used? What's the tillage practice? Strip-till corn and no-till often require different timing approaches than seed planted into a field that's been tilled once with a field cultivator. Will a starter fertilizer be used to give the seedling a healthy start? How many acres can be covered with available labor and equipment? Does manure application in a farm depend on a custom applicator's schedule? What agreements have been worked out with neighbors for manure use on their fields? Is a neighbor hosting a special event? All these factors and more will likely figure into the recommended timing.
;Recommended methods: Surface or injected? While injection is clearly preferred, there may be situations where injection is not feasible. Slope, rainfall patterns, soil type, crop rotation and many other factors determine which method is best for optimizing nutrient efficiency in farms. The combination that's right in one field may differ in another field even with the same crop.
;Annual review and update: Even the best managers are forced to deviate from their plans. What rate was actually applied? Where? Using which method? Did an unusually mild winter or wet spring reduce soil nitrate? Did a dry summer, disease, or some other unusual factor increase nutrient carryover? These and other factors should be noted as they occur.
When such a plan is designed for animal feeding operations, it may be termed a "manure management plan." In the United States, some regulatory agencies recommend or require that farms implement these plans in order to prevent water pollution. The U.S. Natural Resources Conservation Service has published guidance documents on preparing a comprehensive nutrient management plan for AFOs.
The International Plant Nutrition Institute has published a 4R plant nutrition manual for improving the management of plant nutrition. The manual outlines the scientific principles behind each of the four R's or “rights” and discusses the adoption of 4R practices on the farm, approaches to nutrient management planning, and measurement of sustainability performance.

Nitrogen management

Of the 16 essential plant nutrients, nitrogen is usually the most difficult to manage in field crop systems. This is because the quantity of plant-available nitrogen can change rapidly in response to changes in soil water status. Nitrogen can be lost from the plant-soil system by one or more of the following processes: leaching; surface runoff; soil erosion; ammonia volatilization; and denitrification.

Nitrogen Management Practices that Improve Nitrogen Efficiency

Nitrogen management aims to maximize the efficiency with which crops use applied N. Improvements in nitrogen use efficiency are associated with decreases in N loss from the soil. Although losses cannot be avoided completely, significant improvements can be realized by applying one or more of the following management practices in the cropping system.

Reduction of greenhouse gas emissions

Nitrate is the form of nitrogen that is most susceptible to loss from the soil, through denitrification and leaching. The amount of N lost via these processes can be limited by restricting soil nitrate concentrations, especially at times of high risk. This can be done in many ways, although these are not always cost-effective.
''Nitrogen Rates''
Rates of N application should be high enough to maximize profits in the long term and minimize residual nitrate in the soil after harvest.
''Conservation tillage''
Short-term changes in the plant-available N status make accurate seasonal predictions of crop N requirement difficult in most situations. However, models that use soil, weather, crop, and field management data can be updated with day-to-day changes and thereby improve predictions of the fate of applied N. They allows farmers to make adaptive management decisions that can improve N-use efficiency and minimize N losses and environmental impact while maximizing profitability.

Additional measures to minimize environmental impact

Conservation Buffers