Calculating Crop Development

A Little Bit Country

Growing degree days (GDD’s) are highly correlated with crop growth. Using GDDs is much better than calendar days or even average daily temperature.

DGGs for small grains are calculated using a base temperature of 32 degrees for North Dakota and are easily obtained from the North Dakota Agricultural Weather Network (NDAWN). GDDs are calculated by subtracting the base temperature for a crop from the average of the minimum and maximum for the day. For example, if the high temperature for May 1 was 70 degrees Fahrenheit and the low was 40 degrees Fahrenheit the accumulated GGDs for May 1 would be 23. (70+40/2-32 = 23)

After planting, barley requires about 176 GDDs before emergence occurs and 245 GDDs before reaching the first leaf. Factors such as depth of planting, soil blackness, and soil temperature can of course influence the actual GDDs needed before emergence. Wheat takes slightly more GDDs (180) before it emerges and reaches the first leaf stage.

According to NDAWN, there were 203 GDDs during the period of April 21 and May in the Williston area. This is 16 and 18 more GDDs than in the Crosby and Tioga areas respectively. Compared to last year, Williston experienced 59 more GDDs during the same period.

Spring wheat varieties generally require between 1445 and 1590 GDDs from planting to the completion of the flowering stage. Data over a 30 year period show 3942 accumulated GDDs from May 1 to September 1 in Williston.

A link to NDAWN can be found on our website: http://www.ag.ndsu.edu/williamscountyextension.

Tree of the Week

This week I will focus on Green Ash. I hesitate using this precious space on a tree that is the cornerstone of planting throughout the area. However, because there are many new homeowners and also because there is a looming threat to this tree, there is some value in discussing its merits.

First, I must acknowledge that Green Ash is a hardy and drought resistant tree which also has some resistance to alkali conditions. Because of this, it is one of a few trees native to this region. Since the onset of Dutch elm disease it has become even more popular as a replacement for the American Elm. My observations tell me that Green Ash might comprise approximately 50 percent of the total tree population in the county. It is well adapted to moisture stress conditions found in rural areas and responds very well to supplemented water in city plantings.

Green Ash can reach very high into our open spaces. Its mature height range of 30-60 feet will really depend on environmental and soil conditions. The branches will reach out 10-20 feet making it a good place for a lawn chair.

Now for the down-side of Green Ash, there is a tremendous amount of concern about the westward movement of an imported insect called the Emerald Ash Borer. This insect crawls under the bark where it feeds creating tunnels in the vascular portions, which prevents transfer of nutrients and eventually death. Since its accidental introduction into the United States and Canada in the 1990’s it has spread to 14 states including Minnesota. Our state foresters feel it is just a matter of time before it reaches North Dakota. Meanwhile, we can only hope people are cautious about bringing infested firewood into the state and research can develop a resistant variety and some sort of pesticide which can effectively protect the existing trees.

Other pests common to Green Ash trees include anthracnose (a wet weather disease) and the ash plant bug. Few trees succumb to these.

 

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