Using Plant Tissue Testing to Identify Problems

Using Plant Tissue Testing to Identify Problems and Improve Yields

BY DEREK EMERINE

The 2020 crop is well under way. Depending on the environmental conditions and fertilization practices, there could potentially be some nutrient deficiency symptoms showing up. Historically supplemental nitrogen applications have been the “go to” solution. It is also important to understand that many other plant nutrients may be deficient in season. Using visual symptomology to identify these deficiencies can be very difficult. This is especially true if there are multiple deficiencies. The best way to identify these deficiencies is by acquiring plant tissue samples. In South Texas, nitrogen deficiency may be present. However in many situations nutrients like potassium, sulfur, zinc, and manganese are also showing up as deficient. Although nutrients like sulfur, zinc, and manganese are not macronutrients, they can definite ly impact yield if they are deficient.

Having realistic expectations is very important when pulling tissue samples in problem areas. There may already be yield loss and the later in the plants life cycle the deficiency is iden tified the chance of improving the problem in this growing season lessens. There is still value in plant tissue testing though because the information can be used the following year to change fertility management. It is also very important to always pull two plant tissue samples. One from the problem area and one from an area of the field that looks better. Sometimes both samples may come back “sufficient” but there may be signifi cant differences between the “good” and “bad” sample that will illustrate clearly what is causing the problem.

Proactively pulling tissue samples can also be very important to improve yields. This does not mean getting on a weekly tissue sampling program. Planning out 2-3 sampling dates for your crop around strategic growth stages will suffice. In cotton, most nutrients are taken up in great quantities from early to midbloom. Pulling a tissue sample just after first square makes a lot of sense. If nutrient levels are not optimum or greater at this stage, the crop will most likely have deficiencies during peak nutrient uptake. Plant tissue testing prior to flowering in grain sorghum and at around V5-V8 in corn would be the best time to identify if future problems are a possibility. The subsequent samples can come at early and mid-bloom in cotton, bloom stage in grain sorghum, and just prior to tasseling and R1 in corn.

Once a deficiency is identified, a debate can be had on how to correct the deficiency. Deficiencies found very early in the season will benefit more from dry or liquid fertilizer applications. Deficiencies found mid or late season can be alleviated from foliar applications. Foliar applications are not a silver bullet. They will never replace dry or liquid fertilizer applications, but they can be great supplements and improve yields if deficien cies are present.

Collecting the correct plant part and proper care of the sample are extremely important to ensure accurate results. Pulling samples from the wrong part of the plant or not handling the samples correctly will lead to erroneous results. Lastly, if there is confusion about the sample results get input from an agrono mist or input provider that you trust.