 News Radio 1310 KNOX AM Grand Forks. 1079 and 1033 KNOX FM. Translated on K239BG in Grand Forks and K277DN in Grand Forks. Cooler crops make higher yields. I'm Darren Hefty with Hefty Naturals. When your crops experience stress, you lose yield at harvest. And your crops are most vulnerable to heat and drought during the critical reproductive stages. Shield your crops from the worst summer can bring with a foliar application of HeatShield.