Ducks Unlimited has some compiled some information about how many winter wheat plants per square foot is needed to produce a profitable yield in the Prairie Pothole Region.
It says the University of Minnesota's recommendation is:
"If smaller patches have stands of 8 plants per square foot, leave the whole stand. If large areas are lost, consider destroying the winter wheat and planting spring wheat in those areas. Avoid interseeding winter winter and spring wheat as this creates a mixture of contrasting wheat classes which can result in marketing problems."
USDA ARS at Mandan, N.D., makes the following recommendation:
"The target plant population needed to optimize yields under the variable climatic conditions of the region should be about 17 plants per square foot. Our data shows that winter wheat yields are reduced progressively as plant population decreased below 11 plants per square foot. In the Northern Plains, winter wheat has a relatively short period of time for tillering to occur. Optimum grain yields in the 40 to 50 bushel per acre range cannot be obtained unless the number of head-producing tillers reaches or exceeds at least 37 per square foot. In order for the population of head-producing tillers to reach 37 heads per square foot, the plant population must be greater than 9.3 plants per square foot."
Blake Vander Vorst, Ducks Unlimited agronomist in Bismarck, N.D., says that if you have eight winter wheat plants per square foot across the field, with as low as five plants per square foot in small patches, the stand can be managed to produce a profitable yield. You will need to apply nitrogen early to enhance tillering and pay close attention to weed management in the thin stands.
Make the first spring nitrogen application as soon as the winter wheat breaks dormancy or as the soon as the soil is no longer frozen, Vander Vorst advises.
If you have applied a substantial portion of your N in the fall at seeding, or before the soil was frozen. 25 pounds of N is adequate to stimulate tillering.
"The key is get some nitrogen on as soon as possible to increase the tiller numbers," he says.
Adding a fungicide at the half rate with the herbicide application may also help to retain tillers, especially when the winter wheat was seeded into wheat stubble, Vander Vorst says.