Loss of yield or lower fruit quality due to iodine deficiency in tomato and sweet pepper crops under heat stress can be prevented by application of potassium nitrate with iodine

Under a newly proposed definition of plant nutrients, the element iodine qualifies as such due to its unique perception by the crop and its binding to 82 regulatory plant proteins. Next to its positive effects on root, shoot, fruit and seed growth and development, and time of flowering, iodine can also support the ability of plants to maintain vegetative growth and development of fruits in the face of abiotic stress. This is inferred from the benefit of iodine in the radical oxygen scavenging metabolism of the plant in scientific trials. To extrapolate from laboratory or small scale pot trials to farm practice, iodine must be applied in a comparable manner to other micronutrients in a practical nutrient program. In this paper, eight case studies from farm practices are presented, in tomato (Solanum lycopersicum L.) and sweet pepper (Capsicum annuum L.). These show how iodine can be applied in micronutrient dosages in commercial cropping systems by using potassium nitrate as carrier. Fertigation of fruit and vegetable crops enables crop production in arid areas where heat stress is a dominant cause of yield loss. Potassium nitrate is a common source of potassium and nitrate to apply in these systems. In comparison with the -iodine deficient- control that received the same macro- and micronutrients without additional iodine, the application of iodine with potassium nitrate increased fruit yield in crops exposed to heat stress with 11% (range: 6-17%). These observations illustrate a suggested mode of action of iodine for stress resilience in plants, based on published scientific evidence.