There are rules of thumb that suggest a) cutting immediately the day after frost, b) waiting two to four days or c) waiting seven to 10 days after a frost. Which rule of thumb do I follow?
Cutting before the frost would prevent the stockpiling of nitrates; cutting the crop immediately the morning after the killing frost would reduce the time allowed for the roots to store nitrates in the plant, minimizing the final level in the plant; and cutting immediately may also maximize the potential forage feed quality, again depending on the stage of maturity of the crop. b) As the survival rate of the leaves goes up, the wait period to cut the forage would go down. Therefore, consider waiting from two to four days, as there are more leaves available to utilize the nitrates. Keep in mind, though, that waiting to cut may result in reduced forage quality and a poorer feed. c) A waiting period of several days after a frost is based on the following theory: even after a killing frost, the roots of the plant will continue to absorb nitrates from the soil and store them in the stem and stalk. If a large majority of the leaves are killed by the frost, they will be unavailable to utilize
