Agronomy Talk

Agronomy Update

Soybean Tissue Sampling and Corn Disease Watch

Published on Monday, July 20, 2015

With the next round of treatments for soybeans happening soon, tissue samples are critical to ensure the plant is getting what it needs and confirming that we are applying nutrients that will benefit the crop. This week, sales intern Christy Kettler takes us through some best practices when it comes to tissue testing and some updates on the corn diseases she has been seeing throughout central Indiana. 


Soybean Tissue Sampling

Christy Kettler | Sales Intern | Central Indiana


When tissues testing soybeans, the best time to sample is just before or right when the first flowers open. As long as the sample is taken before the first pod fills, the sample will be valid. The sample needs to be taken from the most recent fully developed trifoliate leaf at the top of the plant. Do not use a trifoliate that is not fully developed.

To get a sample from a plant, select the correct trifoliate and carefully pinch off the most fully developed leaf. Do not include the petiole. Place the sample in a paper bag labeled with which sample it is. The samples should be put in a paper bag for transport as plastic bags will hold moisture and can cause mold or skew results of tissue sample. Leave the bag open to allow air drying. This will usually take between 24-48 hours. Then, close the bag and mail or deliver the sample. When evaluating the best way to treat an entire field, be sure to take between 30 and 50 samples from different areas of that field for the most accurate read.

The results from a lab will indicate levels of nutrients in the plant. Typical values tested are N, P, K, Ca, B, Mg, Mn, Cu, Mo, and Zn. Values lower than the critical value indicate a lack of that particular nutrient. Soybeans will sometimes respond to fertilizer at the point after the flowers have opened. The results are more useful for management practices for the coming seasons. High values are usually not going to harm the crop but should be noted as an unusual condition in the area that sample was taken. High values could indicate that there was not enough tissue to dilute the nutrient that was taken up by the roots. 

Northern Corn Leaf Blight and
Gray Leaf Spot Concern in Corn

Continued rain and moderate temperatures are enabling the spread of northern corn leaf blight and gray leaf spot. Continue scouting for the progress of the diseases and consider all factors when making a management decision. These factors may include price of inputs thus far, price of grain at market, yield potential, projected losses and other yield factors. The Purdue University Extension has information available to assist in projecting yield and making management decisions.

The traps throughout north central Indiana have shown the next wave of European corn borer moth flight action. I have found eight moths this week and expect those to be laying egg masses soon for the next generation to attack the fields. Japanese beetles have also made an appearance in corn as well as in the traps. Be sure to reference the Purdue University’s Entomology and Agronomy updates for more information. 


If you have any questions about these findings or would like more information, please reach out to myself or your seed advisor. 


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Denny Cobb

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