Soybean and Corn Tissue Testing - Managing Unseen Nutrient Deficiencies

Take Home Message

• The optimal time to take a plant tissue test is at tasseling for corn and R2 for soybean
• Collect leaf samples and place them in a dry bag to be delivered to the  Penn State Ag Analytical Services Lab (avoid leaves affected by disease or insect damage)
• Fill out this submission form to send in samples
• Plan to conduct tissue sampling across multiple years to observe trends in nutrient uptake and fine tune your fertility programs
• Combine these results with soil test results to better manage crop fertility.

Several growers are considering more high yield management strategies for their soybean and corn crops. There are several foliar fertilizer products with ideal levels of numerous micronutrients, but our research indicates tremendous variation in crop response to these products. Yield enhancement is tied to whether the plant is actually deficient in micronutrients or not.

Since some micronutrients are mobile in the soil, especially boron, sulfur, manganese, chlorine, (and molybdenum, cobalt, nickel, calcium to a lesser extent) the soil samples growers usually take every couple of years do not provide an accurate assessment off which to base micronutrient fertility recommendations. The best way to determine hidden hunger is with a simple $24.00 plant tissue test. A few growers last season enjoyed 90 bu/A soybeans and 290 bu/A corn plus while managing for high-yield crops. The first step is to take an accurate soil test (at the correct sampling depth) and maintain optimum levels of Phosphorus at 30 to 50 ppm and Potassium at 100 to 150 ppm.

Soybean Considerations

Once the plant begins to flower, make sure to gather samples over the next two weeks. Immediately send the samples via overnight mail to gain quick results. This will allow for adequate time to determine a nutrient strategy before peak growth at R3 when pods are being filled.

Soybeans and Other Beans

 
Collect the uppermost trifoliate for leaf tissue testing. Image credit: Del Voight, Penn State Extension

Soybean plant tissue levels

Corn Considerations

Collect the corn tissue samples from the leaf feeding the ear (also called the ear node leaf) and send in immediately. This will allow for adequate time to determine a nutrient strategy before peak growth at grain fill.

Corn

*Sampling after silking occurs is not recommended.

Silks shown with leaf feeding the base of the silk. This is the ear leaf to collect for tissue testing. Photo credit: Del Voight, Penn State Extension

Corn plant tissue levels

Once results of the samples are returned, compare nutrient values to the chart to interpret the results. The Ag Analytical Lab will provide this upon delivery in most cases.