How to Assess the Level of Frost Damage

To evaluate a field, walk an X or W path across the field and note all plants that will survive in a 1/4 m2 (3 ft2) area every 20 paces. This should be 50 to 100 samples. Record an observation from each sample. Calculate the percentage of the field that has adequate plant recovery. The frost may thin the stand only, especially in low lying areas. As a guide, a reasonable plant population early in the season is three to four plants/ft2. However, one to two plants/ft2 across the majority of a field can be adequate if managed carefully with today’s herbicide tolerant systems. Thin stands such as these can yield up to 90% of a normal stand seeded at an early date but will be later in maturity. Crops re-seeded late in the season typically yield less than earlier seeded that had thin stands. For example, one case study by the Canola Council of Canada showed a 7.4 bushel/acre advantage when a crop was not re-seeded after a frost. It likely will be better to leave a thinner stand (provided it is reasonably uniform) than take the risk of late re-seeding because maturity/early fall frost becomes a concern.