By Burton Johnson
About 81 percent of the 2016 soybean crop has been seeded as of Sunday May 22. As we are nearing the end of the planting season, producers sometimes wonder about which relative maturity (RM) will provide the best results.
Research was conducted to determine the influence of cultivar maturity rating, seeding date, and location on soybean yield. The trial was planted from north to south at, Carrington, Prosper, and Lisbon, North Dakota, in 2014. The experiment had 4 replicates with experimental units six rows wide (12-inch spacing) x 25 ft. long. The three RM’s were 00.9, 0.7, and 1.4.
At Carrington, the early maturing cultivar (RM 00.9) had a similar yield level planted late May to mid- June. The RM 0.7 cultivar had the highest yield planted by May 23 but later planting resulted in generally lower yields compared with the early maturing RM. It is risky to plant a late maturing RM (1.4) in Carrington as it may not mature before a potential frost in the fall. The yield potential of the RM 1.4 dropped off rapidly with later planting dates.plsc.kandel.2
At Prosper, the early maturing cultivar (RM 00.9) had a reduced yield potential as the planting date got later and yielded consistently lower compared to the more adapted maturity (RM 0.7) cultivar. There is an increased risky when planting a late maturing RM (1.4) during the last part of the planting season as it may not mature before a potential frost in the fall. The yield potential of the late maturing RM (1.4) dropped off rapidly with later planting dates.
At Lisbon, the early maturing cultivar (RM 00.9) had a similar yield level planted late May to mid-June. The RM 0.7 cultivar had highest yield of the three RM’s, when planted by June 10 and later. The full season RM (1.4) in this trial (with late frost in 2014) yielded higher than the 00.9 and 0.7 RM when planted late May, however the yield dropped of substantially when planted late.
At all locations, highest soybean yields generally were achieved with planting before the third week of May, with small declines with early June planting, and large declines at later planting dates in June and July.
Each season will be different and results for the 2016 season may be different than observed in 2014. If there is an early frost in 2016, later maturing cultivars will be at greater risk of not being physiological mature.