Drought conditions and extreme heat throughout Kansas are forcing farmers to consider harvesting soybeans for forage, rather than grain. Many factors should be considered when making this decision and some are discussed in a K-State Agronomy eUpdate,electronic newsletter that comes out every Thursday. Drought and heat stress in Kansas soybean fields.

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Herbicide applications made during the growing season are an additional concern that has been raised by farmers. The herbicide label is the law, and many herbicide labels do restrict the use of soybeans as a forage. It will be critical to know the waiting period that must be followed between the application of a given herbicide and the grazing or harvesting of the soybeans for use as a forage. 

The list of herbicides with a brief summary of restrictions for grazing/haying soybeans treated with various herbicides is on our web site www.cottonwood.ksu.edu  It is a quick read but to long to list in this article. 

Here is an excerpt from the article Drought and heat stress in Kansas soybean fields. 

• Cutting for hay – Prolonged heat and drought stress can cause considerable leaf area loss and soybean yield reduction. If the crop is so drought-stressed that it’s losing leaves or not setting pods, it may be time to cut it for hay. This might appeal to livestock producers who are facing dry pastures and supplemental feed costs. The decision depends on the stage of growth and condition of the plants. If possible, it’s best to hold off on making any decisions about cutting soybeans for hay until the plants are moving into seed fill (the optimal time to cut beans for hay to retain digestible nutrients). 

However, holding off until this stage of growth may not be possible if plants in the vegetative stage are dropping half or more of their leaves already. If too many leaves have dropped, the crop has a  reduced value as a hay crop. Producers may need to make the decision to cut for hay while the plants are still in the vegetative stage, before the beginning seed fill stage, and before the soybeans lose too many leaves. Soybean plants that still have 30% of their leaves can produce 0.75 to 1.25 tons dry matter of hay per acre, with about 13% protein and 48 percent in-vitro dry matter digestibility. The more leaves a plant has, the more hay tonnage it will produce.

The “grey area” is where there are plants with 30 to 50% of leaves remaining since those leaves have the capability of filling pods if it rains and of making a soybean harvest that is worth more than the price of the hay.

• Final considerations – Scout your acres for drought and heat stress so you can make timely decisions. Beyond yield reductions due to pod abortion, further yield impact can be expected also due to poor seed-filling conditions that may reduce the seed weight.

Stacy Campbell is an agriculture and natural resources agent for Cottonwood Extension District. Email him atscampbel@ksu.edu or call the Hays office, 785-628-9430.