Taking Measure of Fertility Levels

Article by: Pamela Sherratt   With the beginning of spring it's time to start planning season fertilizer programs!   Important tasks carried out now in preparation for the season ahead may include a soil test. Conducting a spring soil test provides a historical record of the soil pH and soil nutrient status. This supplies information on how well last year’s fertility program provided for the need of the turf. It also provides information that is used to develop your fertility management plan for the current season. Soil pH and soil nutrient analyses are critical. Certain physical analyses are optional. Most physical parameters don’t change much over time, however, they should be known for the fields you manage. The chemical analyses provides information on:

 *  Soil pH

* Level of available phosphorus, potassium, calcium, and magnesium

* Level of available iron, manganese, zinc, and copper

* Cation exchange capacity and base saturation levels

* The physical analysis of soil reveals:

           - Soil texture (% sand, silt, and clay)

           - Amount of organic matter present

 

These results can then be used to determine the field’s seasonal fertilizer needs, and cultivation requirements, to diagnose/predict any turf problems, and ultimately govern turf quality.

 

A Guide to Conducting a Soil Test:

 

Perform a chemical soil analysis every 2-3 years for soil fields and at least once every year for high sand (>85% sand) fields. Take a representative soil sample - walk in a zigzag pattern from endzone to endzone. Using a soil probe, collect 15- 20 random soil cores @ 3-inch depth. Remove upper turf and thatch. Collect in a clean plastic container and mix to make a composite sample. Send one pint of soil to a reputable soil testing laboratory. Use same soil testing laboratory to ensure consistency in results.Best sampling times are spring and/or fall prior to fertilization.Best to sample the same time every year. Be consistent in your overall sampling procedure from year to year. Allow 2-3 weeks for test results.

 

It is important that the soil laboratory chosen is reputable and familiar with the sports turf industry.The lab will produce a concise report for the sports turf manager. It is worth noting that labs may report different results. This does not necessarily mean that one lab is right and the other wrong; the variation is due to the labs using different soil testing methods that can give slightly different results. For example; analysis for available nutrients in soils is not absolutely precise but this is unimportant because no one should be maintaining nutrient status on the absolute verge of deficiency. A turf manager who is concerned with lab results, or who is interested in better understanding soil test procedures should contact the lab. A general guide to the optimum soil test levels (sufficiency ranges) for sports turf surfaces can be found in Table 1. More highly managed sports fields should target for the upper end of the sufficiency range.

 

Soil Test Designations for Levels of Macro- and Micro- nutrients in Turfgrass Soils
Test Factor Optimum Level (Sufficiency Range)
Soil pH 6.5 - 7.5
LIme Test Index (Buffer pH) 68 - 70 (mineral soil and organic matter)
Soluble Salts 0-200 mhos x 105
Phosphorus 35 - 85 lbs.P / acre
Potassium  250 - 350 lbs. K / acre (with % base saturation of 2 - 7%)
Magnesium 150 - 800 lbs Mg / acre (with % base saturation of 10 - 20%)
Calcium 1,000 - 8,000 lbs. Ca / acre (with % base saturation of 65 - 85%)
Sulfur 20 - 60 lbs. SO4 / acre
Zinc 3 - 6 lbs. Zn / acre
Manganese 20 - 50 lbs. Mn / acre
Copper  1 - 5 lbs Cu / acre
Iron 50 - 150 lbs. Fe / acre
Boron  1 - 3 lbs B / acre