Updated December 2, 2016:
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Title: Utilizing soybean maturity class and planting date evaluation to improve soybean production in West and Central ND.

Principal Investigator: Jasper M Teboh, NDSU Carrington Research Extension Center;
Co-Principal Investigators: John Rickertsen, NDSU Hettinger Research Extension Center; Szilvia Zilahi-Sebess, NDSU Carrington Research Extension Center

Executive summary_________________________________________________
Producers and stakeholders have interest in expanding soybean production and productivity beyond Central ND, to non-traditional production areas, west of the Missouri River. Dry summers with low available moisture at critical growth stages, and short growing cycle are some of the limiting factors. The goal of this project is to enhance the farmer’s understanding of how maturity classes/groups (MG) and planting dates may be used to minimize soybean production risks. This research was conducted to determine optimum yielding maturity classes of soybean under dryland conditions in Western ND, and under irrigation in Central ND, to determine if early or late planting has any significant impact on soybeans.

Field trials were conducted in Hettinger (HREC), where irrigated soybean from three MG was established under rain-fed conditions, and in Carrington (CREC), where four MG were grown under irrigation. Seeds were planted at four planting dates from May 5th (early planting) to June 9th (late planting). The soybean MG were, 0.2, 0.4, 0.6 at both sites, including 0.7 at CREC. Maturity groups 0.2 to 0.4 would be considered early at HREC, while they are generally considered suitable at CREC. Each planting date was about one week from the previous date at HREC, and varied between 10 days and 2 weeks from the previous date at Carrington. Maturity groups 0.2, and 0.6 were RoundUp Ready varieties, while 0.4 and 0.7 were conventional varieties.

Average yield at the HREC was 31 bu compared to 41 bu/a at CREC. At HREC, yields were significantly greater for MG 0.6 and 0.2, than MG 0.4 when averaged across planting dates. This suggests that yield differences among MG may be due to influences from some other factors, besides being an early or a late variety. It must be noted that the 0.2 and 0.6 varieties were both RoundUp Ready varieties, and the other(s) conventional. Protein followed similar trend as yields, while oil was lower for any MG with a higher yield. Planting on May 19th produced the highest yields (averaged at 35 bu/a), followed by May 27th (31 bu/ac). Yield differences for MG 0.6 showed more stability showing less differences between planting dates. Despite yield dependency of early MG on planting date, this was not consistent. Overall, later maturing varieties had better yields. At CREC, yield differences were not significant. Average yields varied between 44 bu (MG 0.7) and 41 bu/a (MG 0.4) at this irrigation site. Planting on June 1st gave the highest yield, even though yields and protein were not significantly different. Results in 2015 indicated that early planting can produce similar yields as a later planting date, depending on the maturity group used.