Some winter kill is to be expected in Minnesota. This past winter was relatively mild but bare by Minnesota standards. The warm conditions at the end of March allowed dormancy to break early but cool weather that followed has meant that fields have been slow to green up and have just started to put on new leaves and tillers, especially north of Interstate 94. This past week was probably the first time that evaluating surviving plant density was fairly straightforward.
Winter survival in all likelihood will variable within a field and depending on topography (windblown hilltops having less stand than protected areas of the field). If stands are reduced uniformly across the field, stands of 17 plants/ft2 can still produce near maximum grain yields. Even stands as low as 11 plants/ft2 can still produce a 40 bu/A yield.
To do a stand count, use one of the following two methods:
- Count the number of plants in a foot of row at several locations in the field. Take an average and convert in plants per acre using Table 1.
- Take a hula-hoop, let it fall, and count the number of plants inside the hoop. Repeat this at random several times across the field and calculate an average. Use Table 2 to convert the count to an approximate population per square foot or acre.
Table 1. Average number of plants per foot of row for different row spacing and plant densities per acre.
Table 2. Adjustment factors to multiply the number of plants inside a hoop and convert the number in to number of plants per acre.