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1975 - 19792
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Subject: Soil Science and Agriculture Chemistry × Author: KAU × End date: 1979 × Start date: 1975 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Morphological and physio chemical properties of Karapadom soils of the Kuttanad region of Kerala State
    (Division of Agricultural Chemistry, College of Agriculture, Vellayani, 1975) Santhakumari, G; KAU; Aiyer, R S
    A study was mads on ths morphological and physico-chemical properties of 3 profiles of the Karapadom soils of the Kuttanad region. The study revealed many salient features of Karapadom soils The main conclusions drawn from the results obtained are summarised as follows 1. The soils can be texturally classified as clay, loamy sand, silt and silty loam* Maximum percentage of clay was recorded by the top layer of Vettikaripadom, lowest layer of Mathurpadom and sub-surface layer of Mathurvadakke padom profiles. 2. In Mathurpadom and Mathurvadakke padom absolute specific gravity Increased with increase in depth and there is no general trend in the value of apparent density. 3. Mathurpadom and Mathurvadakke padom profiles are strongly acidic when compared to Vettikaripadom which is situated on the western most boundary of Kuttanad near Punnapra. 4. Electrical conductivity increased as depth of the profile increased in Mathurpadom and Mathurvadakke padom profiles. 5. In the three profiles, the organic carbon varies from 0.79 to 4.09 per cent and nitrogen varies from 0.11 to 0.3 per cent. She carbon nitrogen ratio of the profiles varies from 6.58 to 18.33
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    ThesisItemOpen Access
    Evaluation of available phosphate reserve of soil by chemical methodes
    (Department of soil science and agricultural chemistry, College of Horticulture, Vellanikkara, 1979) Mathew, Jacob K; KAU; Jose, A I
    A laboratory study including a pot culture experiment was carried out using 18 lateritic soil to evolve a suitable laboratory chemical method as an index for the estimation of available phosphate reserve (Ra-value). The total plant removable phosphorus of the soils was determined growing rice (variety IR-8) continuously in soils taken in pots, till the content of phosphorus in plants became below the critical level. The pot culture experiment was designed in completely randomized design with 18 treatments (soils) and 3 replications. To evolve a suitable extractant for the estimation of “Ra-value” H2SO4 and HCI at different concentrations and combinations were tried. Out of the 29 extractants employed, 17 were selected based on their consistence in the pattern of phosphorus release and the amount of phosphorous extracted. From a pilot study, in which different organic acids at different concentrations were screened, oxalic acid at the strength of 0.05 N was selected as the best chelating agent to be employed with the 17 mineral acid combinations. The results showed that compared to Bray No.1, the performance of HCI was very poor and had only a little pronounced influence on the extraction of phosphorus. Sulphuric acid at analogous concentrations extracted higher quantities of phosphorus and obtained better correlations with phosphorus uptake values at the end of 6th crop. Combinations of mineral acids extracted higher quantities of phosphorus from soil than the individual acids, with a pronounced influence at lower concentrations. The pattern of release of phosphorus fluctuated widely when the mineral acids were used individually, but the degree of fluctuation was considerably less when employed in combination. In all the above cases the major part of phosphorus was extracted within 30 minutes and thereafter the release was very slow. The pilot study employed in the selection of organic acids for chelated system, to prevent the resorption of phosphorus into the soil from the solution, revealed that resorption of phosphorus from the solution can be effectively prevented by employing organic acids; the amount of phosphorus extracted by the mineral acids can be increased by the presence of organic acids notably oxalic acid and acids at the strengths of 0.05 N were as good as 0.10 N in their effects on the extraction of soil phosphorus. A period of equilibration not less than 30 minutes was considered critical and optimum. The extractant No.10 (0.06 N H2SO4 & 0.06 N HCI in 0.05 N oxalic acid) was found to be superior to the remaining combinations and gave better correlation with “Ra-value” of the soil. Phosphorus extracted by Bray No.1 failed to correlate significantly with phosphorus uptake by crops in soil groups in which the percentage phosphorus content of plants were below 0.025, 0.05 and 0.2 showing that Bray No.1 is not an efficient extractant for the estimation of “Ra-value” of the soil. Thus the present study recommend the extractant 0.06 N H2SO4 and 0.06 N HCI in 0.05 N oxalic acid with an equilibration period of 30 minutes and soil solution ratio 1 : 10 as a better method for estimating the “Ra-value”. Regression equation between phosphorus extracted by this method and “Ra-value” of the soils selected was rather narrow, the application of this equation in predicting the possibility of skipping phosphorus application in soils appeared very much limited.