Soil test P levels between 50 PPM and 150 PPM (or P Risk Index of Medium to High)

Soil test phophorus (STP) is a good indicator for the potential of phosphorus movement off site, though other mangement and soil conditions can result in higher or lower actual measured losses. As STP values increase, the elevated soil solution levels are exposed to loss through tile or surface water with water movement. Fields at the 50 PPM (100 lbs/A) to 150 PPM (300 lbs/A) Bray P1 level can have a wide range of annual edge-of-field losses depending on field management and soils. As STP values increase, the elevated soil solution levels are exposed to loss through tile or surface water with water movement. Edge-of-field testing has shown dissolved reactive phosphorus (DRP) concentrations of 0.02 to 0.4 PPM and 0.1 to 2 lbs of DRP load per acre. Agronomic crop needs are met by current soil-available nutrients.

Continued phosphorus application at this STP level on livestock farms would be due to the use of application timing to use manure-nutrient content to replace purchased fertilizer, limited land base, or emergency application due to weather or storage capacity concerns.

Farmers and other professionals should closely watch soil test reports for elevated STP levels. STP is highly buffered by soil phosphorus reserves, and STP levels do not change quickly. If elevated phosphorus levels exist, the field should be evaluated for potential phosphorus contributions through tools such as the Ohio P Risk Index to see if further use of BMPs would benefit water quality.

Fertilizer rate determination and application practices

If manure or other organic nutrient sources are applied

NRCS 590 NRCS 590 Criteria on rate should be applied to determine rate limits and is outlined in the table below. Additionally field P index, soil water holding capacity, slope conditions and other outlined criteria should be evaluated using NRCS 590 standards to decrease the risk of manure movement. Permitted facilities need to follow guidelines established in their permit.

STP Level Bray P1

Application Criteria

40-100 PPM

Organic nutrients applied based on N needs of next crop or P needs of rotation based on manure nutrient content whichever is less.

Plus >30% cover or incorporation within one week.

100-150 PPM

Organic nutrients applied based on N needs of next crop or P needs of rotation based on manure nutrient content whichever is less.

Plus >50% cover or if <50% cover incorporation within 7 days

And one of the following:

  1. No application setback of 100 feet between application and sensitive area
  2. Vegetative filter (33 feet minimum ) is present between application and sensitive area
  3. Incorporation within 24 hours.

Best Management Practices