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ThesisItem Open Access Influence of soil texture on potassium availability, fixation and uptake by rice in laterite soils(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 1991) Jessymol, A S; KAU; Mariam, K AThe present investigation was carried out m order to assess the influence of various proportions of clay on the potassium dynamics in s oil on application o f potassium fertiliser and its effect on the uptake o f nutrients by rice Sixty surface samples were collected from the major rice growing areas of Thrissur district Based on their particle size analysis and organic carbon content, twenty samples were selected for studying the various physico-chemical characteristics related to the potassium availability In order to find out the transformations of applied potassium, a laboratory incubation experiment was carried out in five selected soils for a period of three months Mineralogy of the fine sand fraction was also carried out in these soils A pot culture experiment was carried out in four selected soils to determine the uptake of nutrients. The soils collected from the three locations showed wide variations in their clay content and majority o f them were grouped under the textural classes, sandy loam and sandy clay loam The single value constants were showing variations depending on the clay content and organic carbon The content and uptake o f N, P, and K was found to increase with increasing levels o f K application Calcium did not show significant difference with applied K and in the case of Mg a decreasing trend was observed The water-soluble and ammonium acetate extractable K were decreasing with advancement o f the crop growth and these fractions were found to be maximum correlated with the dry matter weight at i the flowering and tillering stages respectively Nitric acid soluble fraction was found to contribute towards the later stages of crop growth Maximum correlation was obtained for the gram yield and straw yield with this fraction Even though the positive effect of potassium application on the yield of paddy is very conspicuous, the response varied with the textural composition In more clayey soils more o f potassium fertilisers hast to be recommended to get maximum response as revealed m the present studyThesisItem Open Access Taxonomy and fertility capability assessment of the soils in the command area of Edamalayar Project(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 1991) Krishnakumar, P G; KAU; Venugopal, V KIn the present investigation attempt has been made to evaluate the morphological, physical and chemical characteristics of eight soil series occupying in command area of Edamalayar irrigation project. Out of these eight soil series selected for study, three were located In uplands consisting of well drained soils represented by Thodupuzha, Punnamattom and Velappaya series. The remaining five soils characterised by imperfectly drained paddy lands, occupy the valley between the undulating laterite hills namely, Mulamthuruthy, Kothamangalam, Ikkanadu, Ayyanthole and Konchira. Profile pits were dug at these different locations ' and examined for their morphological features. Soil samples representing the different horizons were collected for laboratory. studies. The physico-chemical characteristics of the soil profiles were investigated with a view to study the interrelationship between the various properties and to relate these characteristics to the genesis of these soils. Surface samples collected from different locations under each series were also analysed for available nutrients and other fertility parameters to arrive at fertility capability classifications.ThesisItem Open Access Sulphur status of major uplands of south Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1991) Sheeba, S; KAU; Korah, P AA study has been made to determine the different forms and distribution of sulphur, and its relationship to relevant soil parameters in the major upland soils of South Kerala representing sandy, redloam, laterite midland, laterite midupland and forest soils. An attempt was made to study the plant available sulphur by conducting Neubauer technique using paddy as the test crop. Available sulphur in the soils was also estimated using different extractants. The results of the experiments were summarised and appropriate conclusions drawn. The study revealed that the forms of sulphur varied considerably from soil to soil. The soils in general were not deficient in this element. The content of different forms of sulphur was maximum in the forest and minimum in sandy soils. Sulphur content decreased from forest to sandy soils through laterite midupland, laterite midland and redloam soils. Organic sulphur registered more than 90 % while sulphate sulphur less than 10 % of the total sulphur in all the soils. The leaching loss of sulphate sulphur in the humid tropical soils may be accounted for the lower contribution of sulphate sulphur to total sulphur. In all the soil types both total and organic sulphur decreased with increasing depth. Except for sandy soils sulphate sulphur also showed the same trend in distribution in all the soils. Accumulation of sulphate form in the subsurface layers of sandy soils may be attributed to its coarse textured nature. Of the four extractants used for the determination of available sulphur in soils, Morgan’s reagent was proved to be the best extractant followed by neutral normal ammonium acetate, normal hydrochloric acid and water in the descending order in all the soils. Sulphur uptake as determined by Neubauer technique recorded the highest value in forest and lowest in sandy soil, laterite midupland, laterite midland and redloam coming in between in the descending order. Neubauer values reflected the actual amount of sulphur in the soils. The significant correlation between the Neubauer values and available sulphur determined by the different extractant was also established. The different forms of sulphur were positively and significantly correlated with the soil characteristics viz. silt, clay, organic carbon, total contents of nitrogen, phosphorus, calcium, magnesium and sesquioxides and negatively correlated with soil pH. The relationship among the various forms of sulphur was also found to be significantly positive.ThesisItem Open Access Nutrient uptake efficiency of cassava (Manihot esculenta Crantz) as influenced by vesicular arbuscular mycorrhizal (Vam) association and rock phosphate application(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1991) Narayanan, S; KAU; Saifudeen, NAn experiment was conducted under pot culture in Fine Loamy Mixed Isohyperthermic Khaplic Haplustafs soil of Vellayani series at College of Agriculture, Vellayani, Trivandrum ; during Sep. to Dec. 1989. Sixteen treatment combinations with four levels of Rock phosphate (0, 50%, 75% and 100% recommended dose), VAM inoculation and control, and soil sterilisation and non – sterilisation was applied to cassava (cultvar M – 4). Biometric observation and chemical analysis of plant parts were undertaken for three mouths of thirty days interval. The results indicated no significant variation in soil nutrient status due to the effect of applied treatments during the three months. Dry matter production of cassava was increased by inoculation of VAM and phosphate nutrition. Application of 37.5 kg P2O5/ha in non – sterilised soil along with VAM inoculation was found to be the best treatment combination. Inoculation of VAM fungi resulted in better uptake of major, secondary & micro nutrients during the active vegetative phase of the crop. Effect of soil sterilisation was not conclusive. Phosphate nutrition of the crop resulted in better uptake of all major nutrients. Field experiments are suggested to establish the present findings and to relate the effects of treatments with tuber yield.