Effects of lime supply on the uptake of potassium and iron released from phlogopite by alfalfa

Abstract

Understanding the influence of carbonates on nutrient release from minerals and their availability to plants is necessary for the management of calcareous soils. This study was conducted to investigate the effects of various levels of lime on the release of potassium (K) and iron (Fe) from the phlogopite mineral in the rhizosphere and their uptake by alfalfa. The experiment was conducted using a completely randomized design with a factorial arrangement. Alfalfa was grown in media containing a mixture of quartz sand, phlogopite, and different levels of lime (0, 20, 50, 120, and 250 g kg−1) under four types of nutrient solution (complete, Fe-free, K-free, and Fe and K free) with three replicates for six months. Alfalfa shoots and roots were harvested and their K and Fe concentrations were measured. The results showed that the biomass of both shoots and roots was significantly affected by lime. The presence of lime in the rhizosphere resulted in an increase in available Ca, thereby reducing the absorption of both K and Fe. The presence of lime was also found to change the K/Ca balance in the growth media. This appears to be the reason for the increased shoot K concentration in plants grown in the media containing less carbonates. It seems that at high concentrations in the soil solution, Ca competes greatly with Fe, reducing its availability to plants. In general, the rates of K and Fe release from phlogopite were adversely influenced by the level of carbonates in the root zone.