Desert dust as a plant fertilizer in an ambient and elevated CO2

Desert dust, volcanic ash and fire ash are the most abundant natural atmospheric particles. These particles considered as an important nutrient source that controls the long-term productivity of infertile terrestrial ecosystems, by replenishing soil nutrient stocks. However, currently we do not know whether atmospheric deposition can act as a direct, alternative source for nutrients. These are particles enriched with phosphorus (P) and other essential macro and micronutrients such as: K, Ca, Mg, Zn, Cu, Fe, Mn, Zn, and Mo. These nutrients are vital for plants and support their growth.

The current research shows that elevated CO₂ (eCO₂) in the atmosphere has positive and negative effects: On the positive side, increase of CO₂ levels is predicted to result with an increase in photosynthesis leading to improved primary biomass production and thus enhancement of CO₂ capture. On the other hand, at eCO₂ plants show decreased concentrations of mineral nutrients in most of their organs, suggesting downregulation of the activity of the membrane transporters involved in root nutrient uptake; a decreased ability to assimilate nutrients from the roots system.

Preliminary results of recent studies had shown that plants can utilize P via foliar nutrient uptake mechanism, directly from dust that settled on the plant’s leaves. Since the efficiency of roots to assimilate nutrients is projected to decrease in future eCO₂, foliar nutrient uptake may be a significant alternative pathway for plants to gain needed nutrients. In this work, we used atmospheric fertilization experiments – where we deposited dust directly on plant leaves – to show that atmospheric deposition boosts plant growth and fertilizes them through direct foliar nutrient uptake pathway. The foliar nutrient uptake mechanism was shown both in an ambient and eCO₂ levels for the three primary atmospheric particles mentioned above. We saw that volcanic ash had significantly increased biomass at eCO₂ compared with ambient CO₂ levels. Our results demonstrate that foliar nutrient uptake is a significant mechanism at immediate timescales. Furthermore, that the direct alternative pathway of foliage nutrients assimilation has a potential to regulate carbon sink processes in a terrestrial ecosystem in a future climate.