Impact of mineralogy on potassium dynamics and retention behavior in Bangladesh soils used in rice cropping systems
Year: 2008
Type: dissertation
Abstract: The combination of rising population and increasing food demand has placed \ntremendous pressure on the soil resource in Bangladesh, especially floodplain soils \nwhere rice may be grown year round. Although these floodplain soils contain minerals \nhigh in potassium (K) such as micas, K deficiency in rice paddy soils is increasing \nthroughout Bangladesh. Harvesting of straw from fields exacerbates the removal of \nnutrients including K, and intensive cropping with unbalanced fertilizer has resulted in \ndepletion of "readily available" K in large areas. \nFive representative floodplain soils in rice production were sampled by horizon \nto determine physical, chemical and mineralogical properties, assess soil K, investigate \nplant available K, and understand impacts of redox on K fixation and release. \nTotal and nonexchangeable K were determined using concentrated hydrogen \nfluoride (HF) digestion and 1.0 M HNO3 digestion, respectively, along with NH4OAcextractable \nK. Cation exchange capacity under both oxidized and reduced conditions \nwas determined. Assessment of adsorption and release of K as a function of redox was done in conjunction with seven different concentrations of potassium chloride (KCl) \nsolution and three different soils. \nSignificant amounts of K were present in all fractions of silts and clays. \nPotassium concentration was greatest in the coarse clay fraction. High HNO3- \nextractable K suggested that much of the K in soils was from mica interlayers. Acidic \nsoils contained less K in all fractions than the less weathered, calcareous soils. The clay \nfractions exhibited mostly mica, vermiculite, smectite and kaolinite. The cation \nexchange capacity (CEC) of reduced soils was less under oxidized condition, due to \ncollapse of the interlayer in response to increased layer charge upon structural Fe \nreduction. \nThe adsorption of K was greater for calcareous soils under both oxidized and \nreduced conditions than for the acidic soils. Less native K was extracted under oxidized \nconditions than under reduced conditions. Less adsorption under reduced conditions may \nbe due to an increase in solution Fe2+ which can compete with K+ for exchange sites on \nclays.
Author: Sumitra Bose Biswas
Language: English
Subfield: Soil Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2271716371