1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Phosphorus dynamics in an ultisol(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2005) Smitha, M S; Sureshkumar, PA pot culture experiment was carried out at Radiotracer laboratory of College of Horticulture, Vellanikkara, using laterite soil (Ultisol), from the main campus of Kerala Agricultural University with the objectives to trace the fate of fertilizer P and to study the dynamics of P by the addition of amendments. The experiment included 13 treatments of three levels of P and four amendments and an absolute control. Amendments were added to the respective treatments and kept for wetting and drying cycles for two weeks 32P labelled KH2PO4 (32P @ 0.4mCig-1 P) was added as per the treatments. Seeds of cowpea @ 3 seeds pot -1 were sown. Application of Phosphorus at different levels significantly contributed to available P status different P fractions i.e. non occluded Al-P and Fe-P, P sorbed by carbonate, occluded P and Ca-P in a linear fashion at all the stages of crop growth i.e. just before sowing, flowering and harvesting. The amendments also contributed to the above pools. Among the amendments Pongamia leaves was found to have better influence in contributing to the above pools except for Ca-P, where lime was found to have a better influence. This was supported by the data on plant P content, where the increasing levels of P and amendments improved the plant P content at 15 DAS, flowering and at harvest. Further Ca-P fraction was dominantly contributing to the available P suggesting that applied P might get transformed to non occluded Al-P and Fe-P, occluded P as well as P sorbed by carbonate, which might be slowly transformed to Ca-P fraction probably Ca (H2PO4)2, the soluble form which is contributing to available P. It was observed that, non occluded Al-P and Fe-P was contributing to plant P as time proceeded due to solubilisation of this fraction. Application of P at increasing level and amendment significantly increased the dry weight of pods and haulm. Radioactive 32P labelled with the applied phosphorus could be traced out in the available pools and fractions of P only at just before sowing, flowering. Percentage of P derived from applied P were the highest for higher level of P and amendment sodium silicate.Item Effect of vermicompost on the electro-chemical properties and nutritional characteristics of variable charge soils(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1997) Bijulal, B L; Rajendran, PThe study entitled "Effect of vermicompost on the electrochemical properties and nutritional characteristics of variable charge soils" has been carried out during 1994-95 which comprised of two experiments, viz., an incubation study and a pot culture experiment. The incubation experiment was carried out at the laboratory attached to the Department of Soil Science and Agrl. Chemistry, College of Agriculture, Vellayani which was intended to study the effect of vermicompost (VC) in comparison with two other organic manures, viz., FYM and ordinary compost, on the electro-chemical properties and nutritional characteristics of a low activity clay soil taken from Vellayani. The pot culture experiment was conducted using the same soil used for the incubation study, to compare the agronomic effectiveness of various organic manures including vermicompost using cowpea as a test crop. Both the experiments were laid out in Completely Randomized Design. The incubation experiment was conducted with nine treatments consisting of various organic manures with and without rock phosphate. Periodical sampling and analyses of soil incubated with various treatment materials were done at 30 days' interval to study the comparative effect of treatments on the electo-chemical properties and nutritional characteristics of the soil. The pot culture experiment was conducted with eleven treatments containing different organic manures with and without chemical fertilizers, to study the comparative effect of different treatments on crop growth using cowpea. Observations on various biometric and yield parameters have been recorded and analyses of plant samples were done at three stages of growth of the plant, viz., 20 DAS, maximum flowering and at harvest. The nutrient status of the soil after the experiment was also analysed. From the incubation experiment it was made clear that the effect of various organic manures differed significantly in influencing the electro-chemical and nutritional properties of variable charge soils. In general, vermicompost maintained its superiority over other organic manures, especially in the presence of chemical fertilizers, in influencing various soil properties. The effects were statistically significant in the order vermicompost > FYM> ordinary compost. From the experiment it was proved that lower doses of vermicompost could be equated with higher doses of FYM and ordinary compost. Vermicompost established its superiority over other organic manures by influencing many of the soil properties favourably. The major effects were the reduction in P-fixation and increased P solubility in presence of vermicompost. The increased mineralisation of other major and secondary nutrients in the presence of VC caused an enhancement in the availability of these nutrients on an equivalent weight basis. A substantial increase in base status and pH, caused by vermicompost improved the overall plant nutrient status and soil environment compared to other organic manures. The organic matter fractions and other colloidal fractions were found to be favourably influenced by vermicompost. Organic colloids, being the most active and reactive phase of the soil, its contribution towards the total base exchange capacity and cation protection was more pronounced in the case of vermicompost. Biometric observations at critical stages of growth of the crop and yield parameters recorded when analysed statistically have proved the superiority of VC over other organic amendments studied. Vermicompost application in combination with chemical fertilizers was proved to be the best among treatments tested. Lower doses of VC (10 t ha-1) with lime and fertilizers was equally effective as higher doses (20 t ha-1) of other organic manures studied. Analysis of plant samples at critical stages of growth also revealed the same effect. Soil analysis data after the pot experiment has further established the superiority of VC over other treatments. This is indicative of the ability of VC to sustain a higher level of soil fertility for a sufficiently longer period of time. However, the present study being an experiment under controlled conditions, further research involving detailed field experimentation with selected crops is needed for drawing final conclusions.