The payoff of a year’s worth of planning, planting and preparation is finally getting started with soybean harvest this fall.
The soybean yield at harvest is affected by several factors starting before planting occurs. Although most are focused on late season rainfall and preparing for the upcoming harvest, it is always important to review current management practices and ways to improve for next year’s crop.
The highest yielding soybean fields start by selecting the best varieties for your geographic area, soil types and planting conditions. There are numerous varieties to choose from and multiple sources of information, but first it is important to understand your fields and the traits that are needed to maximize yields. Do you have soybean cyst nematode or other diseases? Look for varieties that are consistently in the upper yield tier in multiple tests like the state trials. Understand that statistics may show that the performance of many varieties can’t be separated in the results due to variation at the testing sites.
In most cases, narrower row widths will produce better yields than wider rows, especially when planting is delayed, on soil types with limited water holding capacity or where plant growth is restricted. Generally in Ohio, 15-inch rows provide a yield boost over 30-inch row widths, while the difference between drilled soybeans and 15-inch rows is not significant. Narrower rows work better for lighter textured soil types and, when planting late, especially for double-crop planting. Yield response to seeding rates has been more difficult to ascertain, as soybeans have a tremendous capacity to compensate for lower seeding rates or gaps caused by problems at emergence. This doesn’t mean that higher seeding rates don’t pay, but it does mean that personal experience is important to consider when selecting a seeding rate.
It is not possible to consider seeding rate without discussing seed treatments. Advances in seed treatments mean that the advantages often go beyond protecting the seed prior to emergence. Newer seed treatments can help seedlings be more vigorous, help control seedling blights, nematodes and insect damage, improve nodulation and enhance nutrient availability.
Soil fertility is a key component for high yielding soybeans. Phosphorus and potassium levels should be maintained at levels adequate for all crops in the rotation. A 60-bushel crop of soybeans removes approximately 1.5 times the amount of K2O compared to a 200-bushel crop of corn, but about 33% less phosphorus than 200 bushels of corn.
Proper pH is of primary importance to soybeans, as the pH of the soil affects all other nutrients and impacts nodulation. Soybeans perform best when pH is between 6.3 and 6.8. Nitrogen is critically important to soybean production, as each bushel of grain removes between 3.5 to 4.0 pounds of nitrogen. Much of this demand is produced by N fixation, with the balance generally supplied by residual N and soil N mineralization.
Progressively higher yields may expose a need for additional nitrogen for soybeans, but experiments to date have not shown consistent results. Micronutrients are important for high yielding soybeans as well, but it can be difficult to determine if an economic response occurs from applying micronutrients to the soil or as a foliar application in-season. Manganese can be limiting in certain high pH or high organic matter soils and foliar applications work well to manage those fields. Tissue testing is helpful in monitoring nutrient levels since soil tests for many micronutrients can be difficult to interpret.
An additional practice to consider is the use of foliar fungicides to control diseases when varietal traits and weather conditions indicate a risk. Studies have been conducted in recent years comparing fungicide applications to untreated checks, and yield results indicate positive responses occur a majority of the time. Some of these tests also included an insecticide with the fungicide, and data indicated a larger response for the combined application than either one alone. Your own comparison data is a valuable tool to help make those decisions. Pod feeding insects can attack soybeans late in the season and reduce yield and quality, so monitor fields through all pod fill stages to prevent loss.
Finally, the basics are still important, including weed management, crop rotation and tillage. Weed resistance management requires a multi-faceted approach, and this will mean using herbicides with differing modes and sites of action along with proper timing. Starting with a clean seedbed is key, and that may require a fall herbicide application to control winter annual weeds and then following up with a timely residual herbicide application. Timely post emergence applications of the correct herbicides and rates can help maintain control throughout the growing season. Further advances in technology may provide some answers for resistant weeds in the near future, but basic weed control principles are still important.
In summary, high yielding soybeans require an intensive approach to management and will likely require some experimentation on your part, but each step in the learning process is valuable.