Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Cation Activity Ratios in Equilibrium Soil Solution and Uptake of K, Ca, and Mg by Lawn Grass

A. ISLAM
Department of Soil Science, University of Dacca

K. ANAM
Department of Soil Science, University of Dacca

S. M. IMAMUL HUQ
Department of Soil Science, University of Dacca

A. HOSSAIN
Department of Soil Science, University of Dacca

A. H. M. AHMED
Department of Chemistry, University of Dacca

Abstract/ Executive Summary:

K intensity decreased with cropping at all pH levels, reflecting that K in soil solution was absorbed by grass grown on the soils. Uptake of Ca and Mg increased progressively with increased rate of Ca and Mg application. The increase in uptake of ca and Mg was associated with decrease in K uptake. Linear relationship existed between K and aK⁄√(aCa+Mg) indicating that K uptake was largely regulated by equilibrium activity ratio of K. The uptake of ca and Mg was linearly related to √aCa⁄√(aCa+Mg) and √aMg⁄√(aCa+Mg), respectively concluding that uptake of ca and Mg was controlled by the square of the respective activity ratios. The linear relationship between the Ca uptake and √aCa⁄√(aCa+Mg)+ B.aK and Mg uptake and √aMg⁄√(aCa+Mg)+ B.aK demonstrated the existence of ion antagonism in soil.

Keywords: Catioin activity, K, Ca, Ca and Mg

Location:

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer

Objectives:

Green house and laboratory experiments were carried out to study the relationships bewteen (i) aK⁄√(aCa+Mg) in soil solution and K uptake ; (ii) √aMg⁄√(aCa+Mg) in soil solution and Mg uptake; (iii) √aCa⁄√(aCa+Mg) in soil solution and Ca uptake; (iv) √aMg⁄√(aCa+Mg)+ B.aK in soil solution and Mg uptake and v) √aCa⁄√(aCa+Mg)+ B.aK in soil solution and Ca uptake by lawn grass

Methodology:

Two soils (0-15 cm from surface) representing the Tejgaon and Karail series were collected from two rice growing areas of Bangladesh. Some of their physical and chemical properties 350 gms of air dry soil were taken in five inches diameter plastic pots arranged in a completely randomized design in triplicate. As the soils were acidic in reaction, they were limed with a set amount of CO₃ using different portions of CaCO₃ and MgCO₃ to obtain seven exchangeable Mg:Ca ratios from 2 to 40. 60 mgms of P and 57 mgms of N in the form of diammonium hydrogen phosphate were added to each pot. The soils were brought to their field capacities and then allowed to settle for a week so that the soils attained differet pH. Lawn grass was grown at the rate of 0.3 gms of seed per pot. The grasses were cut every month afterwards leaving a 2 cm stubble. NH₄NO₃ at the rate of 50 mg N pet pot was added after each cut. The harvested grasses were dried at 80⁰C for 16 hrs. The roots left in the pots were also analyzed. The soils were sampled to the full depth of each pot (four cores per pot) after each cut and equilibrium ratios were determined immediately using CaCl₂ equilibrium method of Talibudeen and Dey(13). pH of the suspensions was measured by a pye glass electrode pH meter. The activity ratios of the soils were determined by following the method of Mathews and Beckett(8). The K in the suprnatant solution was detetmined by a Unicam sp 900 flame photometer and Ca and Mg by titration with EDTA. Exchangeable K, Ca and Mg were determined before and after cropping by leaching with NH₄OAc using tube method of Mattson(9). K, Ca and Mg in the extract were measured by a unicam Sp 900 flame photometer. Mechanical analyses were done by Hydrometer method (10) and the textures were determined by the USDA(16) method. The pH of the soils was determined by a Pye glass electrode pH meter at a soil : water ratio of 1:2.5. Organic carbon was determined volumetrically by wet oxidation method (17). Plant and root analyses : Samples of plants and roots were wet digested with nitric acid and perchloric acid(10). K, Ca and Mg were measured by a Unicam sp 900 flame photometer.

Source of Information: Journal of Bangladesh Academy of Sciences, Vol. 1, No. 2, 1977

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the regression analyses it was found that the Mg concentration in the plant was proportional to √aMg⁄√(aCa+Mg)+ B.aK or per cent Mg √aMg⁄√(aCa+Mg)(I⁄I (B.aK)⁄√(aCa+Mg) ),where, aMg, aCa+Mg and aK are the initial ion activities calculated from the composition of the equilibrium soil solution and B is proportionality factor which is, in part, determined by the properties of the particular plant. The value for proportionality factor B is given by B= [K/(Ca+Mg)]plant/ aK⁄√(aCa+Mg))solution and it expresses the relative ability of K to compete with Ca and Mg - assumed to be the dominant soil cation-uptake process. The regression analyses showed that introducing the K-activity function in the denominator accounted almost quantitatively for the effects of varying soil K. The results showed that the K-Mg antagonism was the result of ionic competition in the soil solution. The expression, √aMg⁄√(aCa+Mg)(I⁄I (B.aK)⁄√(aCa+Mg) ) X Y that described Mg availability as the product of the two component terms which Salmon(12) referred to as X and Y. The term X was largely dependent upon the exchangeable Mg content of a soil and a measure of the intensity with which Mg was available in relation to the predominant soil cations. Although √aMg⁄√(aCa+Mg) was almost directly proportional to the exchangeable Mg content of a soil, the Mg concentration in grass was proportional to the square toot of the solution ratio. So, to double the Mg in grass the exchangeable Mg must, in theory, be quadrupled. The term I deals with the effect of 'antagonistic' cations which may be only a small proportional of the total soil cations, but still compete effectively with Mg in the uptake process. The competitive abilities of ions (in this case potassium) could be taken into account by appropriate proportionality factors, determined for a given set of growing conditions (K⁄√(aCa+Mg) in plant/(aK⁄√(aCa+Mg)) in solution, Term Y was independent of term X, but its effect on Mg uptake depended on the exchangeable Mg content, because increasing the value of X also increased the differences between X and XY. This explained why K decreased the Mg content of grass more when much Mg was present. Correlation co-efficients calculated between Ca uptake and √aCa⁄√(aCa+Mg)+B.aK in soil soiution ranged between 0.91 and 0.99 except fot the root in the Tejgaon soil indicating that the Ca content in grass was closely related to √aMg⁄√(aCa+Mg)+ B.aK . Linear regression analyses clearly demonstrated that there was a straight line relationship between them suggesting ionic antagonism between Ca and other cations.

Knowledge Management: Journal