By Jerry Clark
With a lot of attention directed at corn production and prices over the past year, soybeans seem to be playing second string. Similar to the way the middle reliever pitcher is to the "closer" on a major league baseball team. The middle reliever, often called the "set-up man" keeps their team in the game until the "closer" can come in and save or win the game, gathering all the attention. Even though corn and soybeans are commonly used together in a crop rotation system, soybeans seem to be the "set-up man."
Since soybeans "set up" corn in the corn/soybean rotation, it is important to give soybeans attention. Just as a good "set-up man" in baseball usually has good command of several pitches, it takes management of several factors to increase the yield potential of soybeans.
The fastball is probably the most common pitch which pitchers have most control. Similarly, variety selection and genetics is one management factor soybean have control over. Variety selection and genetics can't be overlooked when attempting to increase yields. In fact, variety selection can be the most important factor in maximizing soybean yields. All things being equal, variety selection can influence yield more than 30%.
Planting date to soybeans is kind of like what the umpire is to the pitcher. You never know what the call is going to be. The weather and soil conditions will most likely influence planting date. However, delayed soybean plantings can cost as much as 0.4 bushels per day when delayed past the optimum planting date. Optimum planting dates are usually within the first two weeks of May depending where you are located in Wisconsin.
In addition to planting date, another factor is row spacing. Home plate and the strike zone for the "set-up man" are 17 inches. Narrowing soybean rows to something less than this can often lead to increased yield. The reason for this is because yield of soybeans grown in Wisconsin are largely limited by the short growing season. In general, production practices that encourage the greatest use of the sun's heat and light provides the best opportunity to maximize yields. One such practice is narrow row spacing (less than 30 inches).
University research results indicate narrowing rows from 30 inches to 10 inches can result in a 3% to 8% increase in yield. This yield benefit is generally can be more in the northern part of the state where the short growing season is an even larger factor in soybean yield capacity. The main benefits of narrow row spacing is early canopy closure
Early canopy closure increases crop growth rate, dry matter accumulation, and seed yield. Canopy closure of 15-inch rows will often happen 15 days earlier than 30-inch rows. This is critical since canopy closure is needed by the start of pod set (R3). Often soybeans grown in 30-inch rows fail to achieve canopy closure by this critical yield-determining growth stage. Early canopy closure will benefit weed control as the canopy shades out competing weed seedlings. Another benefit is reduced soil moisture loss as the canopy reduces evaporation and more water is available to the plant. The best time to think about moving to narrower rows is when equipment needs to be replaced or purchased.
Although split-row technology is more expensive, the return on investment is relatively high considering the yield advantage with narrow row planting and use of the planter for corn and soybeans.
A good "set-up man" usually has a change-up in his pitching arsenal to confuse the batter. For weed management it is important to consider using several weed management strategies to get good weed control and reduce the risk of herbicide resistance. Reducing or eliminating weed competition early, typically by the V2 growth stage, maximizes early-season crop growth rate, which quickens the time to full canopy closure and in turn maximizes intercepted light converted to soybean yield.
Using all the "pitches" available in the management of early season soybeans can lead to the "set-up" man having an MVP type season.
Clark is the Chippewa County Extension agriculture agent.