Foliar-applied potassium triggers soil potassium uptake by improving growth and photosynthetic activity of wheat and maize

Foliar fertilization is an important agricultural practice. How crop plants considerably response to small amounts of foliar-applied minerals is not fully understood. In this study, we tested whether foliar-applied potassium (K) stimulates soil K uptake by plant roots. Firstly, K uptake from nutrient solution by wheat seedling was investigated with and without foliar application of K. To dissect net K uptake, quantified amount of foliar-applied K (∼19.2 mg pot−1), and K uptake by non-foliar-fertilized plants was subtracted from whole plant K uptake (foliar-treated). In the second set of experiment, maize was grown in soil, and 2% K2SO4 (∼45.4 mg K pot−1) was foliar-applied to dissect soil indigenous K uptake. In addition to elevated K level in both crops, the net K uptake via wheat and maize roots quantified ∼23% and 55%, respectively higher with foliar application of K. It is coupled with improving phenotypic observations, comprising root biomass (32–56%), root-to-shoot ratios (7–38%), and water contents (13–15%) by plotting multivariate analysis. Further, the elevated leaf gas exchange measurements and chlorophyll contents by 10% in wheat and 14% in maize ensured the optimum photosynthetic activity in foliar-applied seedlings. Notably, after crop harvesting, ∼10% lower biological available K in the soil of foliar-applied maize was found. In sum, our findings provide scientific basis that foliar K fertilization improves soil K uptake by wheat, maize, and probably, closely related to cereal crops. It also suggests a novel aspect for further investigation to understand the underlying signaling pathway(s).