Soil is basic to all agricultural ventures including the home lawn, farming, raising livestock and the home garden. Knowing what your soil condition is in can help save money while providing adequate nutrients at the correct amounts to plants. Soil tests are simple to perform. They can be used to estimate the kinds and amounts of soil nutrients available to plants. They also can be used as aids in determining fertilizer needs. Properly conducted soil sampling and testing can be cost-effective indicators of the types and amounts of fertilizer and lime needed to improve crop yield.
There are three steps involved in obtaining a soil test:
- Obtain sample bags and instructions
- Collect composite samples
- Select the proper test, complete the information sheet and mail it to the Soil Testing Laboratory at Texas A&M.
County extension offices provide soil sample bags, sampling instructions and information sheets for mailing samples. The bags should be filled with approximately one pint of a composite soil sample. This amount is sufficient for most soil tests. Any suitable container can be used for the sample, but it is important to complete the information sheet and follow the instructions for collecting and mailing samples.
The objective in sampling is to obtain small composited samples of soil that represent the entire area to be fertilized. This composited sample is comprised of 10 to 15 cores or slices of soil from the sampling area. Fields or tracts of land with differences in past cropping, fertilization, liming, soil types or land use will require several composite samples. It is important to obtain enough subsample to ensure a representative composite sample. A greater number of cores make the sample more representative of the field. Factors that will affect results include sampling tools, number of subsamples, depth of sampling and soil compaction and moisture.
Several tools, such as a trowel, spade, sharp shooter or soil probe, can be used to collect samples, depending on soil conditions and sampling depth. Traditionally, soil samples are collected to a depth of 6 inches. This depth is measured from the soil surface after non-decomposed plant materials are pushed aside.
Several different soil tests are available. These include tests for routine nutrients, micronutrients, boron, detailed salinity, lime requirement, texture and organic matter. The routine test determines the soil pH, salinity, nitrates, and levels of the primary nutrients (phosphorous, potassium, calcium, magnesium, sodium and sulfur available to plants. The routine test will provide the basic N-P-K fertilizer recommendation for selected crops. This test meets most application needs.
The micronutrient test provides general guidelines for troubleshooting deficiencies. A detailed salinity test should be conducted when water quality is of concern or in areas where salt water spills have occurred. Texture and organic matter are specialty tests for specific applications, such as when installing a septic system.
The information form requests information about soil conditions, acreage sampled, past cropping, fertilization and an estimate of the expected yield.
Soil samples should not be stored for long periods of time prior to shipping to the lab. Air drying samples in the shade on clean brown paper is strongly recommended. However, do not oven dry the samples. Instructions for mailing are provided with the sampling instructions. A routine analysis is $10 per sample. Between 5 and 7 days are required to obtain results for routine analysis from the lab. Therefore, it is beneficial to conduct sampling early in the season.
A soil probe is now available at the extension office for checkout. For further information on this topic, contact the extension office at (940) 538-5042 or Missy Hodgin at email@example.com.