Document Type : Research Paper
Authors
1
M.Sc. Student of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
2
Professor of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
3
Associate Professor of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan, Iran
Abstract
Potassium is an essential element for plant growth thatis mostly supplied by K-bearing minerals in soils. The role of these minerals, which are mostly mica, in K supply for plants is well known. However, little information is available on the rate of K release from micaceous minerals with time.The objective of this study was to investigate the temporal changes of concentration and uptake of potassium from phlogopite by alfalfa. A pot experiment was conducted under greenhouse conditions. Growth medium was a mixture of quartz sand and phlogopite. The experimental design was a completely randomized factorial with 3 replicates. During 200 days of alfalfa cultivation, plants were irrigated with either a complete or K-free nutrient solution and distilled water as needed. At 40, 75, 110, 140, 165 and 200 days after cultivation, 3 replicates of each treatment were harvested and their K concentration and uptake were measured by flame photometer following dry ash extraction. Results indicated that the K concentration in plant tissues significantly decreased with time. In addition, phlogopite was able to maintain plant potassium concentration for more than 110 days in the sufficient range. Also, the parameters of growth and uptake rates showedsignificant changes with time. At the early stage of plant growth, both growth rate and K uptake were low.These parameters increased with time as the ability of root to extract potassium increased. At the end of the experiment, because of the plant age and also decline in potassium source, root power for potassium uptake diminishedand, thus, the amounts of plant growth rate and K uptake rates also decreased.
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