JWSS - Journal of Water and Soil Science

Organic acids play an important role in improving the bioavailability of soil nutrients. The objectives of this study were to determine the effect of oxalic acid on the release of soluble, exchangeable and non-exchangeable forms of K from micaceous minerals and potassium feldspars, and also to investigate the trend of K release by time. A laboratory study was carried out using a completely randomized design with two replicates. Biotite, phlogopite, muscovite, Zanjan and Yazd K-feldspars (< 50 &mu;m size) were treated with 0, 10 and 100 mM of oxalic acid solutions for a period of 5 hours and 20, 60 and 90 days. The amount of K was determined by flame photometer. The results indicated that most amount of soluble, exchangeable and no-exchangeable K was released by 100 mM of oxalic acid. The maximum soluble K (0.86 gKg-1) was released from phlogopite, and the maximum exchangeable and non-exchangeable K (1.5 and 29.6 gKg-1, respectively) were released from biotite. Muscovite with 0.19, 0.34 and 1.41 gKg-1 of soluble, exchangeable and non-exchangeable K, respectively, had the lowest release of K among the studied minerals. The kinetics K release from minerals consisted of two phases. The first phase was relatively rapid and then it had a slow rate until the end of the experiment. Given that the applied concentration of organic acid was high, potassium release during the experiment period did not reach the steady state. Therefore, a longer period of release experiment is suggested.

This study was done to compare K+ and NH4+ fixation in different agricultural systems in Khuzestan province. Soil samples were collected from Shushtar and Abadan. Samples were collected from depths of 0-30 and 30-60 cm in sugarcane, multi cropping, palm and uncultivated land. Then, 0-50-100-200-400-600-800-1000 mg kg-1 K+ or NH4+ concentrations were added to 0.5 gram of clay separated from these soil samples. These clay samples were kept for 24 h at room temperature. Then, they were extracted with 0.5 M magnesium acetate, and K+ and NH4+ were determined by flame photometer and micro diffusion methods, respectively. Fixed K+ or NH4+ was determined from added and extracted cations. Also, XRD studies were done in some samples. Kaolinite, palygoreskite, illite, chlorite, smectite and quartz were identified by XJRD. Statistical analysis showed that K+ or NH4+ fixation and rate were increased by increasing the concentration. Maximum K+ or NH4+ were fixed in surface layer’s clay in Shushtar multi cropping and Abadan Palm cultivation. The results showed that K+ and NH4+ fixation were increased by increasing the concentration. But, under increasing concentration for a cation, fixation decreased for others and vice versa. NH4+ fixation was more than K+. This may be due to smectite clay mineral in these samples. Smectite group tend to cause NH4+ fixation more than K+. These results can be applied for K+ or NH4+ fertilizers management.

Few investigations have been carried out on the ability of different plants to take up non-exchangeable potassium (K). The objective of this investigation was to examine the ability of different alfalfa cultivars to absorb K from phlogopite. An experiment was carried out with a completely randomized design with 3 alfalfa cultivars including Pickseed 2065 (MF), Rehnani (R) and Hamadani (H) grown in a quartz sand medium containing <53 micron sized phlogopite under complete and K-free nutrient solutions for a period of 6 months. During the growth period, the shoot was harvested 4 times. At the end of the experiment, the root was also separated from the growth medium and collected. Plant samples were extracted using the dry ash method and their K concentration was determined. Under the K-free nutrient solution, the highest shoot and root K concentration and uptake were found for the MF cultivar. The shoot and root K concentration in this cultivar were respectively 1.6 and 1.5 times higher than those in the R cultivar and 1.8 times greater than those in the H cultivar. The K uptake in the shoot and root of the MF cultivar was respectively 1.6 and 1.9 times higher than that of the H cultivar and 1.6 and 1.5 times higher than that of the R cultivar. Thus, in addition to other parameters, the type of plant variety should be taken into account when K requirement is evaluated.

Evaluation of chemical and biological indicators of soil in different land uses could be helpful in sustainable range management, preventing degradation of soil quality trend. This study was conducted in Friedan in Isfahan province in 2010 to compare chemical and biological indicators in three land uses (rangeland, degraded dry land and dry land), during two growing seasons (May and September) in three slopes (0-10, 10-20, 20-30 %). Nitrogen, phosphorus, potassium, organic matter, cation exchange capacity and microbial soil respiration were measured. Results showed that all measured characteristics except potassium decreased over an increase in the slope. Maximum values of phosphorus, organic matters, cation exchange capacity and soil respiration were obtained in pasture (28.4 mg/kg, 0.62%, 20.38 cmol/kg, 33.2 mgC/day, respectively)but potassium maximum rate was seen in dry land form (406.8 mg/kg).The effect of season on all measured parameters was significant except for N, while the highest amounts of phosphorus, potassium, cation exchange capacity and soil respiration (28.7 mg/kg, 377.3 mg/kg, 19.6 cmol/kg and 25.9 mgC/day, respectively) were seen in May and the highest organic matter rate (0.68%)in September. The results of this study showed that an increase in the slope, poor range management, and the end of the growing season could be major factors degrading the soil quality indices and soil productivity.

Determination of relationships between different forms of potassium in soils and their constituents can help us to resolve some nutritional problems such as potassium fixation and release and its fertilization management in soil. This investigation was carried out to determine the contribution of soil and their constituents (clay and silt) Kex and Knex to available potassium for plants in 12 loess-like and loess-derived soil series of Golestan province in a pot experiment of corn. Total K uptake of corn in the greenhouse experiment was used as an index of soil-available K. Results showed that the contribution of Kex to plant K uptake was more than that of Knex in clay fraction of all soils. Whereas the contribution of Knex to plant K uptake was more than that of Kex in silt fraction of all soils excluding Oghchi soil series with the highest initial Kex. Therefore, the silt fraction is an important K source for supplying the plant need for K in loess-like and loess-derived soils.

The aim of this study was to assess the kinetics of nonexcheangable potassium release in surface and subsurface soil horizons, using organic and inorganic extractions, in Kohgilouye-va-Boyerahmad Province. Kinetics of K⁺ release was studied by successive extractions of K from 64 selective surface and subsurface soil samples, using 0.01 M CaCl₂ and 0.01 M oxalic acid, for 1948 h, with two replicates. Nonexchangeable K⁺ release was fitted by Elovich, Pseudo-first order, Power function and Parabolic equations. Result showed that the average nonexchangeable K⁺ released (extracted by 1M HNO₃) was 356 mg/kg, while those extracted by CaCl₂ and oxalic acid after 1948 h were only 58% and 52% of the total amount of nonexchangeable K⁺ of the soils, respectively. In all soil samples, nonexchangeable K⁺ released by oxalic acid was less than that released by CaCl2, due to the high buffering capacity resulting from high carbonates in the soils. Potassium release rate in Elovich and Parabolic equations were significantly correlated with non-exchangeable potassium and some physical and chemical characteristics.  Based on high Coefficients of determination (r²) and low Standard errors (SE), Elovich, Power function, First order and Parabolic equations were selected as the best equations for prediction of K⁺ release from the soils.

Potassium (K) fixation in soil is an important process which affects the availability of K to plants. There is limited information on K fixation capacity (PFC) of soils in Chahar Mahal & Bakhtiary province. This study was carried out with the aim of determining PFC and its relation with soil characteristics in 10 samples of surface soils in Chahar Mahal & Bakhtiary province. PFC was determined by adding six different levels of K by using KCl salt and measuring cation exchange capacity (CEC) in mineral, organic and clay fraction of soils. The results showed that the CEC in the mineral, organic and clay soils changes from 16.02-19.38, 1.71-3.27 to 29.3-39.8 cmol+/kg consequently. Potassium availability index (PAI) in the soils changes from 0.36 to 0.7 and Potassium fixation index (PFI) changes from 0.29 to 0.63. According to the results PFI and PAI showed significant correlation with whole and mineral fraction of the soil CEC, clay percent, pH and CaCO₃ percent. The results of this study also showed that fixation of K fertilizer in the studied soils plays an important role in K dynamic of soil and K availability to plants.

Salt cedar is widely spread out in most part of the country but there is lack of information about its symbiosis with arbuscular mycorrhizal fungi. Then, the main objective of this study was to evaluate the symbiosis of AMF with salt cedar and its affectability by distance from river and soil physiochemical properties. For this purpose, riparian Maroon forest width was divided to three locations including riverside area, intermediate area and the area far from river with 200-hundred-meter interval. In each site 10 salt cedars were randomly selected and soil plus hair root samples were gathered from the salt cedar rhizosphere. Our result indicated that root colonization and spore density in the intermediate distance had the lowest and highest values, respectively. These values were significantly different compared to the other two sites. The average root colonization percent in the riverside area, intermediate area and the area far from river sites were 82.37, 73.77 and 80.17, respectively. While the average spore density in the riverside area, intermediate area and the area far from river were 189, 245.5 and 188.8 in five gram soils, respectively. Root colonization had significant positive correlation with soil potassium while spore density had significant correlation with studied soil physiochemical properties. Also, soil nitrogen, organic carbon, potassium and clay showed 52.6, 51.19, 50 and 23.4% decreasing trend from the riverside area to the area far from river. Regarding this research results, salt cedar showed high level of symbiosis with arbuscular mycorrhizal fungi but this symbiosis could be affected by distance from river in riparian forest.

Potassium is the most abundant nutrition element in the surface soil but most of the potassium is unavailable to the plants. The present study was conducted with the aim of isolation of potassium solubilizing bacteria from rhizosphere soil and evaluation of quantitative ability of released potassium from different sources of silicate by strains. For this propose, laboratory and greenhouse evaluations were carried out on corn (Zea mays L. Cv. single cross 640 (as a factorial in a completely randomized design with three replications. Laboratory factors were potassium sources (four levels), incubation time (seven levels) and microbial inoculation (six strains) and greenhouse factors were potassium sources (five levels) and microbial inoculation (four strains). The results showed that among the bacterial strains KSB₁₃ had maximum dissolution diameter (25 mm) and solubilisation index (SI=3). The highest potassium content (3/32 µg/mL) was released from biotite by strains of KSB₁₀ after ten days incubation. The microbial inoculation increased root dry weight and plant height for 30 and 25 percent, respectively, compared to control treatments. Also the mean shoot dry weight and K content in microbial treatments of silicate minerals were respectively increased 3/75 and 1/57 times higher than control treatment. It can be concluded that microbial inoculation causes potassium release from silicate minerals and improved plant growth.