Soil Reserves of Potassium: Release and Availability to Lolium perenne in Relation to Clay Minerals in Six Cropland Soils from Eastern China

Abstract

An 8‐month greenhouse experiment with ryegrass (Lolium perenne L.) examined the relationship between the dynamics of potassium (K) reserves in soil and changes in clay minerals, using X‐ray diffraction. The capacity of soil to release K was consistent with its ability to supply it and was the highest in the soil samples collected from Laiyang (H1T2a), Harbin (H1T1) and Beibei (H2T4), followed by the sample from Jiangyan (H1T2b), and the lowest in the samples from Gao'an (H2T3a) and Wangcheng (H2T3b). Removal of soil K decreases the intensity of reflections for illite and increases that for interstratified clay minerals. The centre of gravity values of the clay fractions was significantly negatively correlated to the depletion of soil K reserves, as ascertained through chemical extraction or through plant action. The quantitative regression equations between the centre of gravity values and the dynamics of soil reserves of K can be used for predicting the release and plant availability of K even without growing a crop. Copyright © 2017 John Wiley & Sons, Ltd.

Potassium-Fixing Clay Minerals as Parameters that Define K Availability of K-Deficient Soils Assessed with a Modified Mitscherlich Equation Model

“…Recently, Moterle et al (2016) using X-ray decomposition methods found that the removal of K from the illite interlayers transformed the clay mineral into vermiculite, a fact that had a positive effect on soil exchange capacity. The above was also confirmed by Li et al (2017) using the same X-ray curve decomposition techniques.…”

“…Potassium (K) is an essential macronutrient for higher plants and although has been studied extensively, the complexity of K release and fixation in soils is the main reason that the mechanisms that control K availability to plants remain as yet unclarified. K dynamics is considered as a dynamic chemical equilibrium that connects the three distinct forms of K in soils (soil solution K, exchangeable, and non-exchangeable K) that are assumed as plant available (Huang 2005), while the presence of 2:1 clay minerals influences the ability of the soil to release non-exchangeable K and therefore determines K availability (Li et al 2017).…”

“…Consequently, since the replenishment of water-soluble and exchangeable pools from the non-exchangeable K (Knex) pool is affected by the presence of K-fixing clay minerals in the soil, like illite and vermiculite (Barré et al 2007), their consideration on K fertilization recommendations could be proven very useful. Therefore, the quantification of available K contents of soils with respect to the contribution of both exchangeable and non-exchangeable K, in conjunction with the study of possible relationships between them and the respective modification of clay minerals, could become an essential K management tool (Li et al 2017). The above becomes even more important for soils under intensive cropping, which are expected to have higher fixation capacities and therefore, conventional extraction methods like ammonium acetate (NH 4 OAc) are proven inadequate in explaining K availability (Das 2019;Islam et al 2017;Jalali 2007).…”

Potassium Bioavailability in a Tropical Kaolinitic Soil

“…However, in this study, except for unfertilized pots, diagnostic leaf analysis did not reveal insufficient levels of any nutrient (data not shown) that could explain the decrease in dry matter production. Despite plant uptake of K from fractions that are less soluble than exchangeable K, uptake and removal of soil K over successive crop cycles can eventually lead to a decrease in K and dry matter production [43][44][45]. The use of ruzigrass to deplete soil exchangeable K was very effective (Figure 2A), as observed in previous studies [34].…”

Phosphorus and Potassium in Aggregates of Degraded Soils: Changes Caused by Biochar Application

“…[ 1 ] The exhaustion of available nutrients in the soil is among the main factors that can aggravate the degradation process, thus, increasing nutrient availability to plants in degraded areas is a key factor for restoration. [ 2 ] Phosphorus (P) and potassium (K) are two of the most limiting nutrients for plant growth and their concentrations in degraded areas are usually below plant demand. [ 3 ] Degraded soils are generally acidic, with low nutrient availability, low cation exchange capacity (CEC), and high anion adsorption capacity; [ 4 ] in other words, these areas have low agricultural aptitude and even with periodic fertilization, significant losses of P and K can occur.…”