The transition from vegetative to reproductive growth in indeterminate soybeans depends on the detection of night length, or number of hours without sunlight as the season continues. As soybeans are planted later into the growing season, they do not have as much time to develop biomass. They also miss the opportunity for longer days and intercepting additional sunlight, to
drive photosynthesis towards production of pods – which could decrease yield. The general hypothesis is a longer growing season, and therefore greater photosynthesis, could increase soybean yields. If there is a benefit to early planting, it should be either time savings for the farmer, maybe shifting planting of soybeans before or during corn planting to get it completed earlier, or the benefit should be a financial one, either through increased grain yield or decrease seed cost or both, ideally. Research from across the US has demonstrated soybean yields can be maintained while decreasing planting population, ultimately decreasing seed costs. Therefore, the potential for increased farmer profitability exists.
With the interest in pushing planting dates earlier, we acknowledge that other management decisions must be changes to accompany the earlier planting date; farmers cannot plant soybeans earlier without making other management changes to maximize yields. While nationally research has not demonstrated a clear trend to shifting maturity groups with shifting planting dates, generally, it has been shown that an earlier maturity variety should be used for earlier planting, to ensure flowering while
daylight is lengthening, and reproductive development takes place before the hottest temperatures of the summer. This management scenario presents risks though, as earlier harvest may be necessary to prevent yield losses from shattering or grain damage due to lower moisture content. While early- to mid-MG 4 soybeans generally yield well in Maryland, a shift to a MG 3 soybean may be necessary in this early planting scenario. Therefore, we will evaluate MG 3 varieties in this study, to hone in on where in the MG 3 continuum would yield be optimized at early planting across multiple populations.
We are proposing a multi-year study, with funds requested annually per MSB’s funding cycle, whereby we begin our evaluation under narrowed parameters (MG 3, two planting dates, three populations) in full season soybeans at multiple locations in MD, then shift our focus to double crop soybeans in a similar evaluation. The overall goal of this multi-year study is to provide MD farmers with updated planting recommendations when shifts in planting date must be made.