LAWN & GARDEN TESTING

Parts per million (ppm):

Results for the major and minor elements are reported in parts per million (ppm) on an elemental basis. An acre of mineral soil 6 to 7 inches deep weights approximately 2,000,000 pounds. Therefore, to convert parts per million readings to pounds per acre, multiply by 2.

ME/100 g (milliequivalents per 100 grams):

Total exchange capacity is expressed in milliequivalents per 100 grams of soil. To determine this soil cations, such as calcium, magnesium, hydrogen, potassium, and sodium are expressed in terms of their relative ability to displace other cations. The unit, ME/100 g serves this purpose.

Millimhos/cm (mmhos/cm):

Electrical conductivity measurements are often used to measure the amount of soluble salts in the soil. Conductivity is generally expressed in mmhos/cm. The conductivity increases with increasing soluble salts, and most plants typically begin to struggle when the conductivity reading of the saturation extract reaches 2.0 mmhos/cm.

Total Exchange Capacity (TEC):

Measures the capacity of the soil to hold nutrients. The higher the TEC reading, the greater the capacity. Peat or muck soils will have TEC’s in excess of 35, heavy clay type soils have TEC’s ranging from 15 to 35, loamy soils from 6 to 15, and sandy soils are often below 6. Although high TEC soils can hold more nutrients, it does not necessarily imply that they are more productive. Much depends on good soil management (such as drainage, tillage, nutrient ratios, etc…).

Soil pH:

Total exchange capacity is expressed in milliequivalents per 100 grams of soil. To determine this soil cations, such as calcium, magnesium, hydrogen, potassium, and sodium are expressed in terms of their relative ability to displace other cations. The unit, ME/100 g serves this purpose.

Buffer pH:

This measurement is an index value used for determining the amount of lime to apply on acid soils with a pH of less than 7.0. A value of “NA” is given on soils with water pH’s greater than 7.0.

Organic Matter:

Measures the amount of plant and animal residues in the soil after initial decomposition. The color of the soil is often closely related to the organic matter content. Light colored soils generally have 1 to 3.5% organic matter, while dark colored soils often range from 3.5 to 7.0% or higher. The organic matter serves as a reserve for many essential nutrients, especially nitrogen. During the growing season, a part of this reserve nitrogen is made available to the plant through soil microbial activity.

Estimated Nitrogen Release:

This is a calculation estimating the amount of potential nitrogen to be released in a growing season to the plants. The calculation is based off of the organic matter content of the soil.

Soluble Sulfur:

The soil test measures several forms of sulfur that can be readily available. Higher sulfur levels can occur when soils have reduced internal drainage, high soil pH, or are irrigated with water that his naturally high in sulfur. Optimum levels of sulfur in soil often depend on soil organic matter level content, soil texture, drainage, and yield goal. Generally, whenever the following conditions exist, the need for sulfur will be increasingly important for optimum plant growth:

• Well drained, low TEC soils
• Soils low in organic matter
• Low soil pH (below 6.0)
• Use of high analysis, low sulfur fertilizers
• High application rates of nitrogen fertilizers
• High sulfur demand crops

Overall the effectiveness of sulfur fertilizers is related to how fast the product becomes water soluble in the soil so that it is available for plant uptake.

Phosphorus:

We offer several different phosphorus tests. The most common is the Mehlich 3, which is included on all our standard packages. It gives an estimate on the amount of plant available P in the soil. Ideal levels are around 30 to 35 ppm, but may be higher for specialty crops, fruits, and vegetables. The Bray II phosphorus test is included on some reports too. The Bray II also measures plant available phosphorus, but it is a little stronger extraction and estimates some of the active reserve phosphorus in the soil (the portion that would become plant available once the plant available pool is used up by actively growing plants). A level of 40 to 60 ppm is good for most crops. Other P tests are available, but most are related to specific soil conditions/situations. These values in ppm can be multiplied by 4.58 to change units into pounds per acre of P2O5, which may make fertilizer recommendations easier.

Exchangeable Cations (Calcium, Magnesium, Potassium, and Sodium):

The amount of cations found on soil exchange sites (TEC). Levels of each nutrient vary between crops, soil types, soil textures, etc…

Base Saturation Percent:

Percent saturation refers to the proportion of the TEC occupied by a given cation (an ion with a positive charge such as potassium, sodium, calcium, magnesium, and hydrogen). The percentage saturation for each of the following cations for optimum crop performance will usually be within the following ranges:

• Potassium: 2 to 5%
• Magnesium: 12 to 18%
• Calcium: 65 to 75%
• Hydrogen: 0 to 12%
• Sodium: Less than 1% and/or less than the % potassium

Extractable Minors:

This category includes boron, iron, manganese, copper, zinc, and aluminum. Aluminum in this situation is only used if one would want to calculate a phosphorus index. The other extractable minors are needed by plants for proper physiological growth. Recommendations for these nutrient elements can be tricky because they can often vary quite a bit between different plant species. However, most mineral soils are adequately supplied with them, especially if large amounts of organic materials have been worked into the soil. Below are ideal levels for most plants:

• Boron: 0.8 ppm
• Iron: 100+ ppm
• Manganese: 35 to 75ppm
• Copper: 2 ppm
• Zinc: 5 ppm

If minor nutrient elements are needed, purchase a soluble micronutrient fertilizer material at a lawn and garden store and follow the manufacturer’s directions for applications. Be careful with application of minor elements because over-applying these can lead to serious growth issues due to toxicity.

Nutrient Recommendations:

The key here is to make sure that you are selecting the proper fertilizer materials. If you are dealing with a small area; an acre or less, you will be dealing with very small amounts of fertilizer and it is often more convenient to apply all nutrients as a single mixed fertilizer. On larger areas, it may be more economical to use a combination of fertilizer materials. In order to determine which blend fits your needs you will need to have an understanding of a fertilizer label.

A fertilizer label will contain 3 numbers which indicate the nutrient content of the material. The first number indicates the % nitrogen, the second is % phosphate (or P2O5) and the third is % potash (or K2O). For example, 100 pounds of 12-12-12 fertilizer would contain 12 pounds of nitrogen, 12 pounds of phosphate and 12 pounds of potash or a 20 pound bag would contain 2.4 pounds of each nutrient.

Example:

The following example describes how to calculate the amount of fertilizer needed from the soil analysis report. A recommendation is for 100 pounds of N, 20 pounds of P2O5, and 60 pounds of K2O. Thus the ratio of nutrients needed is 5:1:3. You can use any number of materials, but something like 25:5:15 which has the same ratio is easy to work with. To determine the amount of the 25:5:15 blend needed to meet your recommendation follow the steps below.

1. Divide your recommendation by 44 to get from pounds per acre to pounds per 1000 square feet. 100/44 = 2.3; 20/44 = 0.5; 60/44 = 1.4; now you have 2.3-0.5-1.4
2. Multiply the above answer by 100 to get 230-50-140
3. Now divide the answer in step 2 by the N or P2O5 or K2O content of the fertilizer to get 9. Therefore, it requires 9 pounds of 25-5-15 per 1000 square feet to deliver 2.3 pounds of N, 0.5 pounds of P2O5 and 1.4 pounds of K2O, which matches your recommendation.

Note: Organic amendments can be used and they will deliver micronutrients too. If buying organic amendments from a garden store there will likely be an analysis on the bag (5-3-2 or something of that nature) that can be used to determine the amount of material needed to satisfy your recommendation. If you are not buying the organic waste and are using manure, it may be wise to have the manure tested so you can put down the right amount of material. Years of over application of manure can lead to nutrient imbalances in the soil, which could cause productivity issues.