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Determining suitable planting date and soil temperature for enhanced growth and yield of soybean under no-till semi-arid condition
(Executive summary – 2020/21)
Principal Investigator: Dr. Gautam Pradhan, NDSU Williston Research Extension Center
Co-Investigators: Dr. Jerald W. Bergman and Dr. James W. Staricka, NDSU WREC
Research Conducted
Two glyphosate tolerant varieties (‘ND17009GT’ and ‘ND18008GT’), either treated with fungicide Obvious @ 6.4 oz/100 lb seed or untreated, were planted at seven different dates (2nd, 8th, 15th, 22nd, and 29th of May, and 5th and 11th of June 2020) under no-till dryland conditions.
Why the research is important to ND soybean farmers
Soybean acreage has been steadily increasing in ND, including the western part of the state, which has an exceptionally drier climate (ppt: <15 in/year) than the eastern part (ppt: >20 in/year). There is a lack of soybean production management guidelines suitable for no-till dryland producers of western ND. The determination of suitable planting dates and soil temperature is crucial to avoid abiotic and biotic stress as well as to have a sustainable higher soybean yield and farm income under no-till dryland conditions.
Final findings of the research
2020 was an extreme drought year. We received annual precipitation of seven inches, which was half of the precipitation compared to an average of the last 63 years. Also, this year, the first fall killing freeze occurred on September 8th, a month earlier than in 2019, which killed all the plants planted in June.
The effect of planting date, variety, and seed treatment was not observed on grain number and test weight. Planting soybean on or later than May 29th significantly decreased plant height, above ground biomass, thousand grain weight, and grain yield. When soybean was planted on or before May 22nd, ND17009GT and ND18008GT yielded about 11.4 bu/ac and 10.1 bu/ac of grain, respectively. When the planting was delayed to May 29th, the yield of ND17009GT decreased by 45% and that of ND18008GT decreased by 24% (Figure 1). The variety ND17009GT, when averaged across other treatments, had higher biomass, grain weight, and yield than ND18008GT.
Benefits/Recommendations to North Dakota soybean farmers and industry
The results from this year showed that under no-till dryland conditions of western North Dakota, a season long drought may result in a massive decline in soybean yield (avg trial yield: 10 bu/ac in 2020, 30 bu/ac in 2019) irrespective of the date of planting. The study also showed that under drought conditions if planting is delayed to May 29th, soybean yield may become as low as 6 to 7 bu/ac; and if the combined effect of early fall killing freeze and drought occur, planting in June may result in zero economic yields.