The invention relates to nutrient compositions for agricultural applications, and methods for plant or crop growth and care. The nutrient composition comprises a potassium-based nutrient solution enriched by electrochemical treatment. In various embodiments, the potassium-based nutrient composition comprises hypochlorous acid. The present invention involves the use of the nutrient compositions or solutions, among other things, in pre-harvest and post-harvest treatments and in environmental and soil disinfection.