In this newsletter we present very useful information from Steve Frack, Vice President of AgSource Laboratories in Lincoln, Nebraska.

Soil Characteristics
Soil pH is a measurement of the hydrogen ion concentration in the soil.  Soil with a pH of < 7.0 is acidic and if > 7.0 is alkaline.  Soil pH impacts nutrient availability.  If extremely acid, limestone is required to neutralize the H concentration.  Different grass species differ in ability to tolerate acidic conditions.
 

Grass Species                               Optimum pH range
Fescue, Bentgrass, or Rye Grass                   5.6 – 6.6
Bluegrass or Bermudagrass                          5.8 – 6.8
 

Buffer pH is a laboratory method specifically designed to determine the amount of limestone required to raise the soil pH on acid soils.  This test is only ran when the soil pH value is below 6.5.  In addition, it is also used to estimate the total amount of hydrogen reported on the soil test.

Soluble Salt is measured by the soil’s ability to conduct electricity.  The more electricity conducted the higher the salt content in the soil.  Soluble salts are mobile in the soil solution and will move up and down with the soil water.  High soluble salt levels will affect plant growth.  On this report soluble salt is analyzed as a 1:1 soil water ratio.  The optimum range for Soluble Salt values is 0.2 to 1.5 mmhos/cm.

Cation Exchange Capacity (CEC) is reported as an index of a soil’s ability to hold cations.  It is an estimated value based on the extracted cations from the soil analysis (calcium Ca++, magnesium Mg++, potassium K+, sodium Na+ and hydrogen H+).   Since the clay and organic sites in the soil have a negative charge, the positively charged cations bond with these sites.  Therefore, CEC is closely related to soil texture.

Percentage of base saturation is calculated by dividing each individual cation by the total CEC.  Below is a table representing the optimum ratings.

Sodium provides information for reducing saline and/or alkaline conditions.  Whenever the base saturation of sodium exceeds 5%, water infiltration rates can be reduced.  When correcting soils with high sodium, check and rate drainage conditions.  To reduce the salt load it is important to improve percolation rates.  If appropriate, select one of these soil amendments: gypsum, epsom salts or elemental sulfur.
 
Soil nutrients 
Potassium is a cation held on soil’s exchange sites.   The form of potassium extracted is readily available for plant uptake.  The table below provides a generalized interpretation.   
As noted, soil texture influences availability.  Sandy textures do not have enough holding sites; resulting in high leaching rates.  Heavier textures will hold onto increasing amounts of K.  Therefore, high application rates are not advisable on sand based greens, unless using a slow release source of K.
Potassium is necessary for the translocation of sugars and the process of starch formation.  It is also required for the opening and closing of the stomata.  Potassium is contained in the plant cells and tissues, therefore, it is removed in large quantities when vegetative growth is removed (removal of clippings).
Magnesium is contained in the chlorophyll molecule, making it essential for photosynthesis.  It is also used as an activator for many enzymes required in growth processes.
Calcium is used in the structural stability of the plant.  It is part of the cell walls and membranes and needed for the formation of new cells.  Calcium deficiencies can be associated with alkaline or high pH soils as the solubility of calcium can be quite low.

Phosphorus has two types of extraction that are used in this report; if soil pH < 7.2 Bray I, if soil pH > 7.1, Olson P.  To avoid confusion, P is always reported as a Bray I  value.  In the plant, phosphorus stimulates early growth and root formation.  Its primary usage is in storage and transfer of energy throughout the plant.  The optimum Phosphorus range is 30 - 37 ppm, and the warning rage is < 30 ppm or > 50 ppm.

Micronutrients
Zinc is an essential component of several enzyme systems affecting plant growth.  If deficient, terminal growth areas will be affected resulting in decreased stem elongation, malformed or decreased terminal buds and leaf development.
Manganese serves as an activator for enzymes utilized in growth processes and assists iron in chlorophyll formation.  Deficiencies will appear as chlorosis on new plant tissue.
Copper is an activator of several plant enzymes involved in protein synthesis.
Iron is required for the formation of chlorophyll in plant cells and serves as an activator for processes such as respiration and photosynthesis.  A deficiency will occur as chlorosis of new (young) tissue.
Boron is used by the differentiation process of meristem cells.  A deficiency will cause the death of terminal growth, stimulating lateral buds to develop.
Sulfur is a component of three amino acids, which are involved in the synthesis of protein.
 

Nutrient             Optimum range
Zinc                           1.2 – 3.5
Manganese               5.0 - 20
Copper                      0.3 – 1.0
Iron                           5.0 - 20
Boron                        0.5 – 1.0
Sulfur                        7.0 - 12