View full calendar

    Fertilizer Management


    Fertilizers are generally defined as "any material, organic or inorganic, natural or synthetic, which supplies one or more of the chemical elements required for the plant growth". Most fertilizers that are commonly used in agriculture contain the three basic plant nutrients: nitrogen, phosphorus, and potassium. Some fertilizers also contain certain "micronutrients," such as zinc and other metals, that are necessary for plant growth. Fertilizers are applied to replace the essential nutrients for plant growth to the soil after they have been depleted.
    Excess amounts of fertilizers may enter streams creating sources of nonpoint pollution. Fertilizers most commonly enter water sources by surface runoff and leaching from agricultural lands. Large amounts of nitrogen and phosphorous are present in the runoff. Increased amounts of nitrogen, phosphorous, and other micronutrients can have negative impacts on public health and aquatic ecosystems.

    Handling and Storing Fertilizer

    • Follow label directions
    • Lock or otherwise secure storage container valves when not in use
    • Storage buildings should have impermeable floors (impermeable secondary containment dikes can be used)
    • DO NOT store fertilizer underground in containers or pits
    • Mix and load fertilizers at the application place when possible
    • Handle and store fertilizer away from wellheads and surface water
    • Immediately recover and reuse or properly dispose of fertilizer spills
    • Always store fertilizers in their original containers

    Application of Fertilizer

    Fertilizer application timing - Fertilizers with nitrogen present should be applied as closely as possible to the period of maximum crop uptake. Partial application of fertilizer in the spring with small additions as needed can reduce leaching and improve nitrogen uptake. Fertilizing in the fall has been shown to cause groundwater degradation.

    Application Rates and Fertilizer Types - It is necessary to sample soil every year to determine crop nutrient needs for accurate fertilizer recommendations. To calculate the optimal rate of application other sources that contribute nitrogen and phosphorous to the soil should be considered. Organic matter and manure contribute phosphorous. Crops can quickly take up nitrate forms of nitrogen, but are subject to leaching loss. Fertilizer with nitrogen should be limited when leaching potential is moderate to high. If the leaching potential is moderate to high, ammonium nitrogen fertilizers should be used because they are not subject to leach immediately. However, in warm moist conditions ammonium quickly turns into nitrate. More slowly available nitrogen fertilizers should be used in these situations. Although phosphorous is less prone to leach, loss through surface runoff is common so phosphorous should only be applied as needed and at recommended rates.

    Runoff*Fertilizer application equipment should be checked and calibrated annually.

    *Fertilizer should never be applied when the ground is frozen.

    *Fertilizer application should be limited on slopes and areas with high runoff.

    Irrigated crop production has the highest potential for water contamination because of the large quantity of water that is applied. When excess water is applied nitrogen and phosphorous can leach into groundwater or runoff into surface water. Using systems such as sprinklers, low energy precision applications, surges and drips help producers apply water efficiently and uniformly. Delivery systems such as lined ditches and gated pipes as well as reuse systems such as field drainage recovery ponds are efficient.

    Why is it important to manage fertilizer use?

    Nitrogen and phosphorous occur naturally in streams throughout Utah and are important nutrients to aquatic ecosystems. However, too much of these nutrients can cause serious problems in lakes and streams. Often times in agricultural areas, excess nitrogen enters the system from animal operations or from irrigation return flow. These added nutrients may lead to fish kills, noxious aquatic plant growth, and foul odors.

    Human Health
    Nitrogen fertilizer (organic and inorganic) can contribute to nitrates in drinking water. Pregnant or nursing women and infants are especially vulnerable to nitrate related potentially very serious health problems. To test your water for nitrates you may purchase a kit at your local hardware store for approximately $10-20. You may use the following table to help you interpret your results. For more information about nitrates, click here.
     Nitrate Level, ppm  (parts per million)  Interpretation
     0 to 10

     Safe for humans and livestock. However, concentrations of more than 4 ppm are an indicator  of possible pollution sources and could cause environmental problems.

     11 to 20  Generally safe for human adults and livestock. Not safe for infants because their digestive  systems cannot absorb and excrete nitrate.
     21 to 40  Should not be used as a drinking water source but short-term use is acceptable for adults and  all livestock unless food or feed sources are very high in nitrates.
     41 to 100  Risky for adults and young livestock. Probably acceptable for mature livestock if feed is low in  nitrates. 
     Over 100   Should not be used as drinking water for humans or livestock.