Evaluation of the effect of phlogopite mineral application in a sandy growth medium on the barley yield and potassium uptake under drought stress

Drought is the most important known abiotic stress which strongly affects the growth and yeild of different crops worldwide. Among all the mineral nutrients, potassium (K) plays a particularly critical role in plant growth and metabolism, and also contributes to the survival of plants and adequate biomass production under various biotic and abiotic stresses, especially under drought stress. Under drought stress conditions, K regulates the stomatal opening and helps plants adapt to water deficits. In this study, the effect of phlogopite, as a potassium-rich source and a soil chemical conditioner, to help moderate the adverse effects of drought stress on barley growth and yield under greenhouse conditions was evaluated.

This study was conducted as a completely randomized design with factorial arrangement and 3 replications in the hydroponic greenhouse of the Isfahan University of Technology. The growth medium was a mixture of quartz sand and phlogopite and different levels of drought stress were applied. Plants were supplied with either a complete or a potassium-free nutrient solution during the five-month growth period. At the end of the experiment, shoots and roots were harvested separately and their dry weight recorded. The amount of potassium in the extract prepared by the dry ash method was determined by a flame photometer. The percentage of potassium release from phlogopite in potassium-free nutrient solution was calculated and elemental analysis (XRF) was performed on several selected samples.

The shoot and root dry weight and potassium uptake of plants grown in the phlogopite containing media were higher than those in the control media. These two parameters were also higher in plants received complete nutrient solution as compared to those supplied with the K- free nutrient solution. Drought stress reduced yield and potassium uptake. The highest levels of loss of dry weight and potassium uptake were observed in plants supplied with the K-free nutrient solution under severe drought stress. There was a significant positive correlation between the shoot dry weight and K uptake and also between the root dry weight and K uptake. The results of the elemental analysis of phlogopite particles before and after application in the growth medium were consistent with the amount of potassium uptake by the plant. The highest percentage of potassium removal was observed under no drought stress conditions. In general, it looks like that the application of phlogopite alleviates the negative effects of drought stress by releasing its interlayer potassium, due to the important role of potassium in regulating stomatal opening and closing, increase photosynthesis rate and water retention in plant tissues.

The results of this study showed that the application of phlogopite was useful as a natural and low-cost source to supply K requirement in plant growth medium to reduce the effects of the drought stress, especially in the greenhouse.