Are you in the habit of treating soybeans as the underdog on your farm?
In the Midwest, soybean are often viewed as JUST a rotational crop when compared to its competitive counterpart, corn. But why is this? Some may argue that they prefer to plant corn and that it is easier to consistently grow higher yields, but why do growers not have the same mentality for soybeans? Since the early 1920s the United States has used soybeans as an important forage and grain crop, and since then soybean yields have increased nearly 5-fold. But we still feel that soybeans don’t yield high enough compared to corn. A large proportion of this increase has been contributed to better breeding and trait selection, but there also has been important agronomic discoveries that contribute to higher soybean yields—not all of which are routinely being practiced.
Producing higher soybean yields should be a fairly simple task when calculating soybean yield as a function of the yield components: pod number per acre multiplied by seed per pod, and then multiplied by the average weight per seed. Research by the University of Illinois Crop Physiology lab has shown that it only takes one more soybean pod per plant to increase yield by two bushels per acre when grown at standard planting densities. This seems like a relatively simple task, but how can it be achieved? The following are important production areas where soybean growers should focus more attention in order to achieve higher yields.
Row Spacing: I can’t began to recall the vast number or articles, journals publications and research papers I have encountered indicating the best row spacing for soybeans is narrower rows. In case you have been lost in the dark, I will clue you in that nearly every single publication indicated that narrower rows (i.e., those less than 30 inches) is an easy way to increase soybean yield. Most data indicates that you lose a couple of bushelswhen using wider row spacing. This couple of bushels year-in and year-out can add up quick, especially in years like 2014 when we saw an average of a seven-bushel increase in response to narrow rows.
I realize that there is a hesitation to adopt narrow rows as they are associated with buying expensive new pieces of iron, or the occasional year of increased disease pressure, but this shouldn’t dissuade growers from managing soybeans to their full potential. I bet that a majority of farmers reading this won’t say to themselves “I am going to buy a soybean planter and use it for corn,” but the opposite is probably true when using a corn planter for soybeans. If this mentality were to switch and planters could use the same degree of precision for seed placement on the two crops, both corn and soybean management systems could benefit from narrower rows.
Better Fertility: Early on the adoption of soybeans was referred to as “‘hard on the land’ … and would be classified as a crop that rapidly depletes soil bases” (Hammond et al, 1951). This recognized that soybeans have a strong requirement for adequate fertility—actually, not that much different than corn. However, based on USDA-ERS data, only 20 percent of soybean acres are fertilized annually. This does not take into account fertilizer that was applied to the previous corn crop and that is supposed to be left over for soybeans, but it is likely that that fertilizer placed more than 18 months prior to the soybean crop is less available than hoped.
Potassium often has been considered the most important nutrient for soybean because of its much higher concentration in the seed than corn (up to five times higher). But I argue that there is another nutrient that deserves more attention: phosphorus. Unlike potassium, phosphorus has the highest harvest index of all the mineral nutrients, where 80% of what the plants takes up over the course of the season ends up in the grain, and as such gets removed from the field at harvest. This, in addition to the complex interactions where phosphorus can be immobilized in the soil, make it a key candidate for producers to consider as a component of their annual soybean fertilizer program. And I did say annual—soybeans should be fertilized separate from corn.
Variety Selection: How do you select your soybean variety? Do you base it off of maturity group, disease package or trait package, or do you simply state that if you’ve got a Roundup Ready® soybean seed, it is good enough for me? Soybean varieties often are selected with much less forethought and homework than the corn hybrids being grown. University variety trials often show 15-bushel differences between soybean varieties. As a producer I would hate to select the lowest performing variety and leave 10 bushels on the table.
Some of the difficulty of confidently choosing a soybean variety is to know what to be selecting for, and if the information is available for your region? There is much more information on how corn hybrids respond to different soil types, fertility levels and their responsiveness to other agronomic factors such as disease and pest pressure, than there is for soybean, but this does not mean that it is not available. The other challenge is brand loyalty and a reluctance to jump to another brand and number to get greater yield. There can be a lot of information to process, but as a producer, I would likely be able to better position my soybean for success if I were to have access to this kind of information and take the time to process it.
Summary: Growers, agronomists, seed salesman and researchers need to devote more attention to soybean management. No one technology will be a silver bullet for increasing soybean yields on a consistent basis, but instead it will take the adoption of integrated practices in a systems approach and the inclusion of technology to overcome particular limiting factors. When seed, traits, fertility, protection and agronomics work together as a team, soybeans can become an award-winning crop!