Browsing by Author "Singh, M.M."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Determination of Active Root Distribution of Hevea brasiliensis using Radioactive Phosphorus
    (1971) Soong, N.K.; Pushparajah, E.; Singh, M.M.; Talibudeen, O.
    Phosphorus uptake by Hevea seedlings from nutrient solution and by mature Hevea trees from the soil was studied using P32 tracer. The usefulness of leaves and latex for detecting PM uptake by Hevea was compared. Latex assay was found to be more convenient and reliable than leaf assay and was used to determine the relative distribution of active roots of Hevea in three different soil zones under study. Maximum root activity was found to be in the first 12 feet from the trees, reflecting past cultural practices. Injection of P32 into the trunk of a mature rubber tree showed translocation into the leaves and latex but no radioactivity could be detected in the roots or in the surrounding soil indicating that trunk injection was unsuitable for estimating the distribution of active roots in soil.
  • Thumbnail Image
    Item
    K-A1 Exchange Equilibria in Acid Soils of Malaya and the Use of Thermodynamic Functions to Predict the Release of Non-exchangeable K in Soil to Plants
    (1971) Singh, M.M.; Talibudeen, O.
    A thermodynamic treatment of cation exchange equilibria was used to interpret K.-AI exchange equilibria in 0.01N chloride solutions for 9 common acid soils of Malaya. In 7 of the 9 soils, K. was adsorbed more strongly than Al while for the remaining 2, the reverse was the case. The standard free energy for formation of K-soil from Al-soil varied from —2550 to 900 calories!mole. In all soils, the activity coefficient of the adsorbed K ions, fK , first increased and then decreased with decreasing K-satura-tion, while fAit the activity coefficient of the adsorbed Al ions, decreased continuously with decreasing Al-saturation. Between soils, changes in J'K with K saturation varied much more than changes in /A1. Excess free energy functions for.. AI-+K. exchange calculated from ( fK,fAl ) values for the soils showed distinct differences between all soils. For soils containing micaceous minerals, these differences in the surface chemistry of the soils were related to the release of initially non-exchangeable potassium in the soil to Pueraria phaseoloides in glass-house experiments.