Developing a growing degree day model for North Dakota and Northern Minnesota soybean

The predicted values were used to create a model that allows producers to select the MG of their cultivar, date of planting, and the nearest North Dakota Agricultural Weather Network (NDAWN) station. The output provides the predicted maturity date, as well as the average first day of occurrence of select threshold temperatures (36°, 32° and 28 °F) at 50% probability level. This model will help growers to judge the risks of certain frost occurring before the selected cultivar's projected maturity date. The projected maturity date is based on two parts. The first part is the observed period from the planting date to the date the model is queried and is based on daily maximum and minimum temperatures. The second part is the forecast period that is based on normal (1981-2010 average) daily maximum and minimum temperatures from the queried date through the end of the select growing season. The growing degree days (GDD) values are accumulated from the planting date through the end of season based on these daily maximum and minimum temperatures. Input into the model should be for adapted MG soybean for the region and for planting dates between May 15 and 31. Farmers and agriculturist in North Dakota and northwest Minnesota can use the model before planting to determine if a MG would mature before the frost with varying temperature thresholds and monitor the accumulation of GDD and development of the crop during the season and estimated date of maturity.