With all the talk about how big soybean yields are getting, agronomists and growers still may wonder if those high yields could be masking hidden nutrient deficiencies that might result in leaving some additional potential out in the field. I spent this season exploring that question and was able to produce results and draw conclusions that I hope to replicate in fields next year.
In my opinion, feeding soybeans begins at planting. I have seen some success in using a plant growth regulator (PGR) or biostimulant/fulvic acid product applied during the preplant herbicide application. I saw an increase in early root growth and nodulation, and even noticed nodules appearing sooner than expected.
Tissue testing is an important aspect of any proper fertility and foliar nutrition program. My rule of thumb is to tissue test early and before any planned application passes, such as herbicide or fungicide. Multiple tissue test results showed deficiencies in both macro and micro nutrients.
The beauty of tissue testing before a planned application pass is that it allows you to apply a foliar nutrient application without the cost of another trip across the field, which can save a grower $5 – $6 per acre. I suggest conducting a jar test before doing this to ensure product compatibility and prevent any potential headaches that could occur when adding a fertilizer to the mix. I’ve had a lot of success adding zinc, manganese and boron in with herbicide applications and saw a visible difference in the way that the soybean plant recovered more quickly from the herbicide application.
The next opportunity to tissue test and plan a foliar application would be around R3—before any planned fungicide or insecticide applications. In my plots, tissue testing showed deficiencies in some of the critical macro and secondary nutrients. I always like to include a product that contains some nitrogen and sulfur and have observed a resulting increase in pod set compared to an application of just fungicide and insecticide alone.
This year I did follow up with an added pass of additional nitrogen and boron to help with pod fill and am anxiously awaiting harvest to see the results from adding this additional pass into the program. I included this additional late-season application based upon excellent high yield potential and since we needed to spray for some spider mites.
I truly believe that we will continue to push soybean yields higher and higher each year as we increase genetic potential within the seed and adopt better management strategies for soybeans. With increased yield expectations we will have to continue feeding soybeans throughout the season so that yield isn’t limited. Remember to utilize tissue testing, which is both cost-effective and efficient, to ensure that plant nutrition does not become a limiting factor in high yield soybeans.