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Nutrient Management - Field Application

Cooperative effort to protect Kentucky’s water resources from nutrient and pathogen pollution originating from manure and fertilizer applications

Tibor Horvath, Nutrient Management SpecialistBy Tibor Horvath, Nutrient Management Specialist for NRCS in Kentucky

The USDA Natural Resources Conservation Service (NRCS) along with the Kentucky Division of Conservation and the University of Kentucky Cooperative Extension Service is helping Kentucky growers develop and implement a Nutrient Management Plan that can greatly reduce the nutrient runoff and leaching to surface and ground water from field applications of animal manure and fertilizers and the same time improve the farm’s profitability.

What is the KentuckyAgriculture Water Quality Act?

The Kentucky General Assembly passed the Kentucky Agriculture Water Quality Act in 1994 (KRS. 224.71-100 through 224.71-140). The goal of the act is to protect surface and groundwater resources from pollution as a result of agriculture and silviculture (forestry) activities.

Whom does the Kentucky Agriculture Water Quality Act affect?

The Agriculture Water Quality Act requires all landowners with 10 or more acres used for agriculture or silviculture operations to develop and implement a water quality plan based on guidance from the Kentucky Agriculture Water Quality Plan. It is the sole responsibility of each landowner to develop, implement and revise when needed, a water quality plan for their individual operations.

To develop your Kentucky Agriculture Water Quality Plan online, go to the following website:

The Nutrient Management Plan portion of the Kentucky Agriculture Water Quality Plan will assess the current nutrient levels in all crop fields through soil sampling and based on the planned crops nutrient need will develop a manure and fertilizer spreading schedule to match the nutrient needs of the subsequent crop. The three most important macro nutrients are Nitrogen (N), Phosphorus (P) and Potassium (K). When animal manure is used as fertilizer, the manure also needs to be tested for available N, P and K to determine the needed manure application per acre to match the crops nutrient requirements.

Spreading manureUsing only animal manure as fertilizer creates a challenge because the N, P and K content of the manure usually does not match the crop’s nutrient needs. In most cases, if the manure application is planned to match the crop’s Nitrogen need, then the Phosphorus and Potassium will be over applied, causing P and K buildup in the soils. For this reason, the Kentucky Ag Water Quality Authority established soil-Phosphorus level thresholds to prevent Phosphorus over applications and the risk for surface water pollution by Phosphorus runoff from crop fields (Table 1).

Phosphorus runoff causes major water quality degradation in lakes and rivers, including the Mississippi river and the Gulf of Mexico Hypoxia problem. Phosphorus runoff is also related to nutrients such as Nitrogen that could be originating from crop field runoffs.

Soil Phosphorus level <400 lbs./acre

Manure can be applied based on the Nitrogen need of the crop

Soil Phosphorus level is between

401 - 600 lbs./acre

Manure can be applied based on the Phosphorus need of the crop

Soil Phosphorus level is between

601 - 800 lbs./acre

Manure can be applied based on half of the Phosphorus need of the crop

Soil Phosphorus level > 801

No manure or Phosphorus fertilizer application allowed.

Table 1.Soil test Phosphorus level thresholds and Phosphorus application limitations.

The right nutrient application timing and the right application method also can reduce nutrient pollution.

Nitrate leaching to ground water is also a great concern that can present a serious threat to our public water supply. The NRCS is using a Nitrogen Index Tool that can assess the risk of Nitrate leaching based on the field’s soil type, the crops grown, and the fertilizer materials used, and can be utilized to choose different crops or nutrient sources to alleviate the Nitrate leaching rate to the ground water.

The NRCS is offering financial assistance to producers to hire a Technical Service Provider (TSP) to develop a Nutrient Management Plan that will address all water quality concerns related to nutrient applications.

If the Nutrient Management Plan is completed, the producers can seek financial assistance for the implementation of the plan through the Environmental Quality Incentive Program of NRCS.

Please visit your local NRCS field office for further information and for any technical or financial assistance related to water or soil quality to improve our environment and to enhance your farming operation: