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Soil Characteristics and Behavior of Potassium Under Various Moisture Regimes

Harunor Rashid Khan
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh

Syed Fazl Elahi
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh

M. S. Hussain
Department of Soil Science, University of Dhaka, Dhaka-1000, Bangladesh

Tadashi Adachi
Faculty of Agriculture, Okayama University, Okayama, 700 Japan

Abstract/ Executive Summary:

Soil characteristics and behavior of potassium in four soils under different incubation times and moisture regimes were studied in the laboratory. Structural K which was the principal source of K in the soils accounted for 91 to 99% of the total K, while exchangeable K (0.26-0.57%) and non-exchangeable K (1.20-8.33%) accounted for a small percentage of the total K. The exchangeable K⁺ IMg²⁺ ratio of the soils ranged from 0.06 to 0.14. The amounts of exchangeable K in the soils increased gradually with the lapse of time and the increment was most pronounced in the Belabo and Domar soils followed by the Baliadangi soil. The difference in the moisture regimes slightly but not consistently affected the exchangeable and non-exchangeable K status in the soils. Only the Domar soil was found to release non-exchangeable K but the net fixation was also maximum (0.70 cmol (+) kg^-1) in this soil. The maximum net fixation of K was 0.10 cmol (+) kg^-1 in the Belabo, 0.37 in the Farabari and 0.60 in the Baliadangi soils, throughout the period of incubation. Illite in the soils could be considered to act as a release mineral and vermiculite as a fixation mineral. The amounts of non-exchangeable K varied considerably with the extractant used. The fixation of K in the soils was found to fluctuate with the lapse of time, regardless of soil moisture regimes. These trends were more pronounced when the sulfuric acid system was used, while the nitric acid system was found to be slightly more stable compared with the sulfuric acid system.

Keywords: Exchangeable and non-exchangeable K, Fixation and release, Illite and vermiculite, Incubation times, Moisture regimes.

Location: Department of Soil Science, University of Dhaka, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil fertility

Objectives:

To determine the soil characteristics and behavior of potassium under various moisture regimes in Bangladesh

Methodology:

The study area was in bangladesh; located between latitude 24º2'N and longitude 89º8'E. The site was selected on the basis of the differences in the parent materials and hydrological conditions of the soils. Regarding the distribution of the temperatures over the year, the study area showed two distinct seasons, cool and warm. Mean annual temperature (MAT) of the area was 25.3ºC..Temperature regime thus classified (Soil Survey,1975) as hyperthermic (MAT ≥ 22.52ºC). The mean winter (December to February) and mean summer (April to July) temperatures were 19.0 and 28.8ºC, respectively. The summer maximum in the study area ranged from 33 to 36ºC in April and the minimum temperature of 6ºC in January. Bulk soil samples (0-15 cm depth) of Belabo, Domar, Baliadangi, and Farabari series were collected for these studies. The sampled soils had not been subjected to K fertilizer application for at least 1 year. The samples were air-dried and gently crushed to pass a 2 mm sieve. After treatment with 300 g kg^-1 H₂O₂, particle size distribution was determined by the pipette method (Day 1965). Moisture at field capacity was determined by the gravimetric method after oven-drying at 105ºC (Black 1965). Organic matter content was determined by wet combustion with K₂Cr₂O₇ (Nelson and Sommers 1982). Soil pH was measured in air-dried soils from soil-water (1 : 1) and soil-1 M KCI (1 : 1) suspensions using a Corning pH meter (Model 7) as outlined by Jackson (1973). Cation exchange capacity was determined by saturation with 1 M CH₃COONH₄ (pH 7.0), ethanol washing, NH₄⁺ displacement with acidified 100 g kg^-1 NaCI, and subsequent analysis by Kjeldahl distillation (Chapman 1965). Exchangeable Na⁺ Ca²+, and Mg²⁺ were extracted with 1 M CH₃COONH₄ at pH 7.0. An incubation study was conducted using 4 surface soils, to investigate the effect of the incubation time on the fixation and release of K in the soils under wetting (field capacity) and drying (26-29°C) cycles as well as constant field-moist and constant waterlogging (under 5 cm water) conditions. The soils were prepared for the studies after addition of 2.0 cmol K (0.78 g K from KCl) kg^-1 soil. To 5 g portion of each air-dried (< 2 mm size) soil sample in an opaque plastic pot, a required amount of distilled water was added to raise the water content to the desired levels of the given moisture regimes.

Source of Information: Soil Sci. Plant Nutr., 40 (2), 243-254, 1994

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present investigation provided the evidence that, the fixation and release behavior of K in the soils mainly depended on their mineralogical and hydrological conditions. The amounts of clay and percentage of base saturation of the soils were also related to the behavior of soil K,

Knowledge Management: Journal