Reference for Paste Analysis

 Based on 6” depth samples.  Percentages and values will vary based on Sample depth, pH, compaction, and stress factors.
Download Quick Reference for Turfgrass Soil Paste and Analysis
 

Paste Extract Guidelines

These guidelines help identify what is happening in the soil short term. It's a great tool for determining what nutrients are soluble in soil solution, including sodium and salt levels and in identifying solubility of calcium. When interpreting a paste extract test, it is important to understand that there is a need to maintain both strategic nutrient levels as well as a balanced ratio of nutrient levels.

 

Several factors can influence a paste extract soil test and need to be considered when interpreting results:

•   Weather conditions; including the direction of storms, amount of rainfall, and influence of acid rainfall

•   Irrigation

•   Poor water quality

•   Recent fertilization applications (i.e. water soluble nutrients may be in solution)

•   High bicarbonate levels

•   Compaction layers

•   Plow pan

•   Black layer

•   Improper aerification and/or topdressings

•   Very low exchange capacities/no buffering capacity

 

Testing protocol:

These tests should not be done as a stand-alone test; instead, they should initially be done in conjunction with a standard soil test on the same site. As a monitoring tool, these tests can be run on a 6-8 week schedule.

 

REFERENCE           DEFINITION/RESULTS

pH                               Levels may or may not be the same as standard soil tests.

Soluble Salt                High levels are undesirable and can harm turfgrass. Excessive concentrations can be leached from the root by extreme irrigations. This can only be accomplished with good subsoil drainage and exceptional soil permeability.                                                               

                                    < 960 ppm (same guidelines as soil test)

Chlorides                    Chloride concentrations contribute to the total soluble salt concentration and are readily leached from soils with good drainage.  High levels will reduce biological activity.

Bicarbonate               High levels will cause calcium to precipitate in the soil forming calcium carbonate causing a serious reduction in permeability of the soil when sodium is present. Soil will tighten if there are high levels of bicarbonate an indication of poor drainage and improper watering practices.

                                    < 50 ppm

ANIONS

Sulfur (S)                   Sulfur deficiencies are most prevalent on sandy soils subject to leaching, soils with low organic matter content, high nitrogen use, and when clippings are removed.

            5 – 10 ppm

Phosphorus (P₂O₅)    Not very soluble; high levels of aluminum & iron tie-up phosphorus.

                                    1 – 3 ppm

MAJOR ELEMENTS

 

Calcium (Ca)             Calcium should always be greater than the combination of Mg & K.

                                    The percentage ration of Ca: Mg should be 3:1 or a ppm ratio of 5:1.

                                    40 – 60 ppm   (ideal range 55 – 60%)

Magnesium (Mg)       Magnesium plays a key role in chlorophyll production. Deficiencies are often associated with low CEC, acidic (ph<5.5) soils subject to leaching, high inputs of Ca as lime or gypsum, and high K fertilization.

                                     8 – 12 ppm   (ideal range 18 – 20%)

 

Potassium (K)            Should always be higher than sodium (Na) as a percentage, especially when bicarbonate levels are high.  Potassium is very soluble and is easily fixed in the presence of certain clay types.

15 – 20 ppm   (ideal range 9 – 10%)

Sodium (Na)               Should always be less than K as a percentage. The negative effects of sodium are critical where there is heavy traffic. Compaction of clay soils results in a decrease in aeration, water infiltration and percolation of soil water. As results rise above the optimum level, soil biology is weakened.

< 20 ppm (8 – 2%)

MINOR ELEMENTS

Boron (B)                   A water soluble, essential micro-nutrient for plant growth. While turfgrasses are generally tolerant of boron, soil accumulation can be problematic because boron can form chemical complexes that do not easily leach from the soil. Availability is reduced when soils have been recently limed to pH > 6.5 or in calcareous soils with high Ca content.

                                    0.1 ppm

Iron (Fe)                     High levels can tie-up phosphorus, while deficiencies are often associated with poor rooting or root viability conditions, pH > 7.0, high P levels at high pH, excess thatch, and low organic matter soils.

                                    0.3 ppm

Manganese (Mn)       Availability is reduced on high pH soils, calcareous soils, acid and heavily leached sands, peat and muck soils at pH > 7.0, and during dry, warm weather.

                                    0.1 ppm

Copper (Cu)              Deficiencies are most common on organic soils, heavily leached sands, high pH, and with high levels of P, Fe, Mn, Zn and N.

                                    0.08 ppm

Zinc (Zn)                    Deficiencies are most common on alkaline soils, during cool, wet weather, on highly weathered acid, coarse textured soils, and with high levels of N, P, Fe, Cu and Mn.

                                    0.08 ppm

Aluminum (Al)          High levels can tie-up phosphorus.

Please note: With all trace nutrient levels, an acceptable range of variability for the ideal levels would run plus (+) or minus (-) 0.02 ppm.