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Last week we started a conversation about high fertilizer prices and ways that producers can try to stretch their soil fertility dollar. I mentioned that the first, and often most overlooked, step in a soil fertility program was to take a soil test each year on each pasture or hay meadow. Soil tests take a little time and effort to collect and submit, but they can save you money in the long run by allowing you to shop for the best fertilizer to meet your nutrient needs.

Once you receive your results in the mail from the soil lab, the real fun begins. There are about 20 nutrients known to be essential in plant growth.

Nitrogen, phosphorous, and potassium (the three main numbers reported on a bag of fertilizer as N, P and K, respectively) are considered primary nutrients and needed by plants in the largest amounts. Calcium, magnesium, and sulfur are considered secondary nutrients and are needed by plants in smaller amounts for their normal growth and development. Micro-nutrients include zinc, iron, copper, manganese, and boron (which are especially important if you plant clovers and other legumes in your pastures). 

When your soil test report arrives you will find a printout of the relative amounts of each nutrient evaluated expressed in parts per million and a rating of very low to very high.

Parts per million, when multiplied by two, provides you with pounds of nutrient per acre.

Ratings of very low, low or moderate mean that you will see a response in plant growth by fertilizing with this nutrient. Ratings of high to very high mean that you will probably not see a response to fertilizing with that nutrient and you could spend your money elsewhere.

For example, a soil test reports nitrate nitrogen at 17 ppm and a rating of moderate. This means that you have 34 pounds of nitrate nitrogen per acre and you will likely see increased plant growth from adding nitrogen to the soil.

A soil test report will also include reading for sodium, salinity and pH.

Ideally you would like to see low sodium and salinity levels in your soil. If your sodium and salinity levels are high, you could be irrigating with less than ideal water or, quite possibly, have been using high rates of commercial fertilizers for a long time.

Soil pH is a measure of the acidity of the soil and is a scale generally reported ranging from zero to 14. Soil pH greatly affects the availability of nutrients in the soil. As soil pH decreases from 7 to 0, the major nutrients - N, P and K - become less available to your plants and the plant toxic soil element aluminum becomes more readily available to plants. In general, we do not have any naturally occurring soils in East Texas with pH readings above 7. Unless you are growing a crop that likes a low soil pH, this condition is corrected through the addition of agricultural limestone.

Next week we will talk more about liming to correct soil pH and the importance of controlling pasture weeds as a part of a soil fertility program.

Speaking of weed control, the Smith County Extension office will have a private pesticide applicator training and testing course at 8:30 a.m. March 25. For more information on the course and to view how low soil pH affects nutrient availability in the soil, visit http://tceblogs.tamu.edu/mt/smith.

Brian Triplett is the Smith County Extension agent for agriculture and natural resources. He can be reached at 903-590-2980 or via e-mail at b-triplett@tamu.edu or on the Web at http://smith-tx.tamu.edu.