Update:
First wheat harvest moisture content averaged 19% (2016) and 17% (2017). Average final harvest dates were July 16 and July 12, for the two years, respectively. Average yield for the three 2016 sites at first harvest date was 81 bu/acre, while for the first harvest date in 2017 it was 70 bu/acre. Wheat yield declined 39% during 2016 between first and last harvest dates. During 2017, wheat yield declined only 12% between those dates. Weather had a major influence on the change in yield over the harvest period during the two years; there was > 3 .5 inches rainfall (2016) while 2017 received <2.5 inches. There was nearly a 10% loss in yield between the first two harvest dates in 2016 while there was no change in yield until after the fourth harvest date in 2017. Test weight decline averaged 7 lb/bu (2016) and 6 lb/bu (2017) between first and last harvest dates with ~2 lb/bu of that loss occurring between the first two harvest dates.
Similar to responses observed for other maturity group research for double crop soybean, during 2016 yield was 9% greater for mid-late MG 4 varieties over early-mid MG 3 varieties. This yield improvement was even greater during 2017; 25% more yield for mid-late MG 4 varieties compared to early-mid MG 3 varieties.
Recommendations from this research for the wheat-double crop soybean, production system are quite simple. 1) To attain maximum yield and test weight for wheat, harvest as soon as possible at approximately 20% grain moisture. 2) To maximize double crop soybean production following wheat, plant a mid-late MG 4 soybean variety or varieties following early harvest of wheat.
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Recommendations from this research for the wheat-double crop soybean, production system are quite simple. 1) To attain maximum yield and test weight for wheat, harvest as soon as possible at approximately 20% grain moisture. 2) To maximize double crop soybean production following wheat, plant a mid-late MG 4 soybean variety or varieties following early harvest of wheat.