1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Dynamics of iron and aluminium in rice based ecosystem of detrital laterites of AEU 11and mitigation strategies(Department of soil science and agricultural chemistry, college of agriculture,Vellayani, 2023-11-11) Sreelakshmi, M M.; KAU; Aparna, BA study entitled “Dynamics of iron and aluminium in rice based ecosystem of detrital laterites of AEU 11 and mitigation strategies” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2019-2023. The major objectives of the study were to assess Fe and Al dynamics in detrital laterites derived rice tracts of Northern Kerala (AEU 11), to suggest management strategies to mitigate acidity, and to maximize the yield of rice. The investigation was envisaged in six parts viz. survey and collection of geo referenced soil samples, characterization of geo referenced soil samples, generation of thematic maps using ARC GIS software, solution culture experiment, soil column studies for assessing the nutrient release pattern, pot culture experiment to screen the ameliorant for alleviating Fe & Al toxicity, field evaluation and validation. The salient research findings emanated are summarized below. In the first experiment, 10 geo referenced soil samples were collected from surface and subsurface depths of 0-15 cm (80 nos.) and 15-30cm (80 nos.) respectively from rice fields of AEU 11 (northern laterites). After surveying the study area, the soil samples were characterized for physical, chemical and biological parameters. Kalikkadavu series recorded the highest mean value for exchangeable acidity, potential acidity, pH dependent acidity, available Al content at 0-15cm and 15-30 cm. The highest available Fe content was observed in Kalikkadavu series at 0-15 cm and Naduvattom series at 15-30 cm. The order of contribution of Fe fractions to total Fe at 0-15 cm depth was observed as follows: Fe-re>Fe-or>Fe-ox>Fe-ex>Fe-c. At 15-30 cm, the order was as follows: Fe-re>Fe-ox>Fe-or >Fe-c>Fe-ex. Regarding Al fractions, the order of contribution of various Al fractions to total Al at both depths was observed as follows: Al-re> Al-ex>Al-c>Al-ox≥Al-or.The nutrient index of detrital laterite-derived rice soils of AEU 11 was observed to be medium to high for available N, available P, low to high for available K and medium to high for organic carbon content. Micronutrients like Fe, Mn, Zn and Cu were observed in the sufficiency range in all the soil series. From paired t-test analysis, significant variations of pHKCl, bulk density, organic carbon, labile organic carbon, carbon stock, available P, available Ca, available Fe, available Al, available B, pH-dependent acidity, and potential acidity were observed at two different depths of 0-15 cm and 15-30 cm. Principle component analysis (PCA) of surface soils showed that the first eight PCs eigenvalue ≥1 accounted for 73.914% of the total variance. In PC1, EC, organic carbon, labile carbon and available K had the highest factor loadings. Bulk density in PC2, mineralizeable carbon in PC3, exchangeable acidity in PC4, available Mn, Zn, and Al in PC5 available S in PC6, exchangeable H+ in PC7 and available Ca in PC8 reported highest factor loadings. PCA of soils at 15-30 cm showed that the first six PCs eigenvalue ≥1 accounted for 75.073 % of the total variance. In PC1, EC, organic carbon, carbon stock and available K had the highest factor loadings. Bulk density and mineralizeable carbon in PC2, water soluble carbon, exchangeable acidity and exchangeable H+ in PC3, exchangeable Al and exchangeable acidity in PC4, available P in PC5, and available Fe in PC5 exhibited highest factor loadings. The hierarchical cluster analysis of 80 locations was carried for two soil depths. At 0-15 cmand 15-30 cm, among the clusters, cluster II was the largest consisting of 57 soil samples including a majority of Naduvattom, Nanminda, Kalikkadavu, Kunnathura, Kunnamnagalam, and Payalam series. Analyzing the intra-cluster distance, it was found to be highest in Cluster V whereas, the inter-cluster distance was found to be highest between clusters III and IV. Interpretation of various statistical analysis revealed that Kalikkadavu series recorded the highest mean values for available Fe (979.61 ± 969.79 mg kg-1), Al (192.5 ± 65.25 mg kg-1), exchangeable acidity (1.66 ± 0.23cmol kg-1soil), potential acidity (45.8 ± 2.57 cmol kg-1) and pH dependent acidity. Hence this series was selected for conducting further experiments. A solution culture experiment was carried out using Hoagland nutrient solution to study the response of rice seedling variety Uma to 5 different levels of Fe and Al (control, 50 ppm, 450 ppm, 850 ppm, 1250 ppm).The relative decrease in root and root length with increase in Fe and Al concentration was observed. The control showed maximum root length of 8 cm and the minimum root length of 3 cm was observed in 1250 ppm Al. A maximum root length of 9.25 cm was observed in control and lowest value of 4.5 cm was observed in the treatment 1250 ppm Fe dose. Though the effect of Al doses on shoot length was non-significant, a decline in shoot growth was observed with increase in Al concentration. To conclude a significant reduction in root length and shoot length of rice seedlings was observed with increasing doses of Fe and Al. The representative Fe and Al rich soil samples from Kalikkadavu series were collected for setting up the soil column experiment. The treatments include KAU PoP, NPK as per PoP+ double dose of potassium (K), Phosphogypsm @ LR +NPK as per PoP, Phosphogypsm @ ½ LR + Lime @ ½ LR +NPK as per PoP, Calcium silicate as per LR+ NPK as per PoP, Rice husk ash + NPK as per PoP, Rice husk Biochar + NPK as per PoP, Vermicompost + NPK as per PoP and Absolute control. From the soil analysis, the lowest values for exchangeable acidity were noticed in rice husk ash (RHA) in the 21st week of sampling. The highest mean value for total Al was observed in control during the 1st, 7th, and 14th weeks of sampling while calcium silicate recorded the highest in the 21st weeks after sampling. Rice husk biochar (RHB) and RHA reduced the total Al content during the later stages of sampling. The lowest values for available Fe were noticed in RHA during the 1st and 7th week of sampling and RHB during the 14th and 21st weeks of sampling. A significant effect of RHB on lowering the available Al content was more pronounced during 1st, 14th, and 21st week while the lowest available Fe during the 7th week was exhibited by the treatment RHA. Regarding water analysis, the absolute control exhibited the highest value for exchangeable acidity at all the sampling periods while the lowest values were noticed by RHB treatment. A decrease in total Fe of water has been observed in all the treatments but the significant variation was observed only during 7th week. The significant effect of RHB in reducing total Al was noticed during 21stweek of sampling (0.267 mg kg-1).From the above results, a profound effect of rice husk ash, rice husk biochar, vermicompost and double dose of potassium on exchangeable acidity, Fe content and Al content was been noticed and thus these treatments were selected for conducting pot culture experiment. A pot culture experiment was conducted to evaluate the effectiveness of treatments to alleviate Fe and Al toxicity using rice as the test crop. From the experiment, the effect of RHB was found superior in reducing the Fe availability at growth stages. At active tillering stage, RHA recorded the lowest exchangeable acidity and at the harvesting stage, the effect of RHB was prominent. The highest dry matter yield of 126.83 g plant-1, grain yield of 48 g plant -1 and straw yield of 86.67 g plant-1, harvest index of 0.356 was noticed by RHB. From the interpretation of the results of pot culture experiment and by considering the potential ability of rice husk ash and rice husk biochar to reduce exchangeable acidity, available Fe and available Al content in soil under study, the aforesaid treatments were considered for field evaluation and validation. From the field experiment, the lowest value for available Fe was noticed in RHB (144.55 mg kg-1) at harvest stage. A highly significant and positive correlation was observed between available Fe and exchangeable Fe, oxide bound Fe, residual Fe and with total Fe content. With respect to available Al, lowest mean value was observed in RHB at panicle initiation and harvest stage. At harvest, the effect of RHA as on reducing exchangeable acidity was more pronounced. Available Al maintained highly significant and positive correlation with exchangeable Al, oxide bound Al, residual Al, and total Al content. The total Fe content of shoot, root and grain at active tillering and harvest were significantly low in plants treated with RHB. The total Al content of shoot at AT was significantly lower in plants treated with RHB while in roots; KAU PoP recorded the lowest value. At harvest, RHB outperformed by exhibiting the lowest value for Al content in shoot and root. In shoots, the highest Fe uptake was noticed by farmer’s practice. A significantly lower mean value was noticed by RHB. Regarding the Fe uptake by grain, RHB recorded the highest mean value. In shoot and root, a significantly lower Al uptake was noticed by farmer’s practice. The highest mean value for Al uptake in shoot and root was noticed in absolute control. Regarding plant observations, a significantly higher value of plant height, productive tillers was noticed by RHB at all stages. RHA recorded a significantly higher value for filled grains per panicle which was found statistically on par with RHB. A significantly higher value of grain yield, straw yield, and dry matter yield was observed in RHB which was found statistically on par with RHA. The significant mean value for Fe-deposited roots was found low in RHB. The highest lignin content, chlorophyll content, total sugars, and root spread were noticed in RHB. Also, RHB recorded a significant lower value for proline content. From the above results of the field experiment, the effect of application of rice husk biochar at 5 tha-1 on alleviating Fe and Al toxicity was more pronounced. Though the effect of RHB on soil nutrient status, crop nutrient content, nutrient uptake, plant growth characters and crop yield was found on par with the application of rice husk ash 2 tha-1, superior effect of rice husk biochar was more pronounced. From the above experiments, it can be concluded that the most common yield-reducing factors of rice production in northern laterites are high soil acidity preceded by Fe and Al toxicity. From the investigation, basal application of rice husk biochar at 5 tha-1 along with urea, rajphos, and muriate of potash can be recommended to alleviate Fe and Al toxicity, augment soil fertility, and enhance rice productivity in detrital-derived rice fields of northern KeralaItem Dynamics of pesticide residues in cardamom growing soils of Iddukki district.(Department of Soil Science and Agricultural Chemistry,College of Agriculture, Vellayani, 2011) Siji N Nath; Thomas GeorgeItem Influence of organic matter and moisture on adsorption of chloroacetanilide herbicides in laterite soil.(Departmental of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2011) Hasna, K; Durga Devi, K MItem Calcium dynamics in substrate - wormcast - mushroom - plant continuum(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 2010) Bindhu, C J; Sushama, P KThe study on Calcium dynamics in substrate-wormcast-mushroom-plant continuum was conducted at College of Horticulture, Vellanikkara during October 2006 to May, 2010 with the objectives, to select a suitable organic enrichner for calcium rich wormcast production, to standardize the protocol for calcium rich wormcast production, to test the suitability of wormcast as a casing material and substrate for milky mushroom production, to evaluate the spent mushroom as source of nutrition in tomato (Lycopersicon esculentum Mill.) and to explore the contributions of different calcium rich nourishing media to soil health in a sustainable way. In order to attain the objectives, the different experiments were done in a phased manner. In experiment 1, the different animal and bird manures such as those of cow, pig, rabbit, goat, poultry and quail were characterized for their physico-chemical properties especially the calcium. The screening process was carried out as a rapid exploratory trial. Based on calcium content, cowdung and goat manure were selected as the promising organic enrichners for calcium rich wormcast production. In order to standardize the protocol for calcium rich wormcast production, an incubation experiment was carried out with banana pseudostem as the substrate. Along with different levels of organic enrichners, the inorganic materials such as phosphate rock and lime were tried. The biotic agent, Eudrilus euginiae was introduced after 10 days of incubation. The temperature of the compost pile was monitored daily. The samples were drawn at fortnightly intervals and examined for various properties like pH, microbial count and earthworm biomass. Along with the determination of physico-chemical properties of compost material, the wormcast was also fractionated into humic and fulvic acids of organic matter. Based on the calcium content, the wormcast produced in the treatment that received 50 per cent level of cow dung was selected for the succeeded experiment. In order to evaluate the best casing material, a study was undertaken in a suitably designed mushroom shed, using the mushroom strain, Calocybe indica. The trial was carried out with different casing materials, wormcast, coirpith compost, termite mud dune and soil, viz., 10, 20, 30, 40 and 50 per cent of the substrate, paddy straw. Samples were drawn at harvest for recording the morphological characters, growth attributes, yield, keeping quality, biochemical constituents and physico-chemical properties. Based on calcium content, the spent mushroom produced by the treatments with 20, 40 and 50 per cent wormcast was selected as the nutritional source for tomato. A pot experiment was done with tomato variety, Anagha. The spent mushrooms were mixed with potting mixture at levels, 25, 50, 75 and 100 per cent of the recommended dose of vermicompost for tomato (4.5 kg pot-1). From the pot culture, it was inferred that spent mushroom at levels, 50 and 75 per cent were superior to others in terms of nutrient uptake and yield in tomato. The calcium use efficiency in terms of physiological efficiency, agronomic efficiency, recovery efficiency and factor productivity was also computed for the treatments that yielded comparatively better. The important salient findings are as follows: 1. Cow dung is the best substrate for the production of calcium rich wormcast 2. The wormcast, coirpith compost and termite mud dune are not suitable as substrate For milky mushroom but are suitable as casing materials. 3. Wormcast at a level of 20 per cent of substrate is the best casing material for milky Mushroom as compared to coirpith compost, termite mud dune and soil. 4. Spent mushroom at a level of 50 per cent of recommended dose of vermicompost is sufficient for a mean yield of 0.770 kg pot -1 in tomato. 5. There is very promising complimentality among the different calcium rich nourishing media such as substrate, wormcast, spent mushroom and soil. 6. There is much addition of calcium from the different sources both to the exchangeable and non-exchangeable pool of soil calcium. Effective management of animal manures for enriched compost production, use of spent mushroom as organic manure and the utilization of wormcast for milky mushroom culture are some of the practical utilities of the study. Moreover, the vermiculture may be extended to further agripreneurship programmes.Item Synerigistic effect of Na and K on yield and nutrient uptake in Coleus (Coleus praviflorus L)(Department of Soil Science & Agricultural chemistry, College of Agriculture, Vellayani, 2004) Neenu, S; Sudharmai Devi, C RA field experiment was carried out in College of Agriculture, Vellayani during September 2003 to January 2004 to study the “Synergistic effect of Na and K on yield and nutrient uptake in coleus (Coleus parviflorus L.)”. The treatments included were 50 and 100 per cent of the recommended dose of K alone and in combination with 50, 75 and 100 per cent of Na of common salt to equalize the same amount of recommended dose of K. The experiment was conducted in Randomized Block Design. The plant growth characteristics like plant spread, number of functional leaves and LAI showed significant variation due to treatments. The highest values for these parameters were registered by K and Na at 50:50 proportions, showing the synergistic interaction of the two elements at this combination. Leaf water content varied significantly due to treatments. The 50 per cent K plus 75 per cent Na treated plants showed highest value of RLWC. Even though the chlorophyll content did not show significant difference between treatments, it increased with Na application along with 50 per cent K, revealing a role of Na in chlorophyll biosynthesis Tuber yield did not show any significant difference due to treatments. Even then the 50:50 combinations of Na and K treatment gave the highest tuber yield followed by 100 per cent K plus 50 per cent Na treated plants. The yield attributes like number of tubers, weight of tubers and tuber index did not vary significantly. Among the quality attributes, starch content varied significantly due to treatments. The treatment with 100 per cent K plus 75 per cent Na gave the highest value of starch followed by the 50:50 combinations of Na and K. The cooking quality of treatments T3 (100 per cent K alone), T4 (50 per cent K plus 50 per cent Na) and T5 (50 per cent K plus 75 per cent Na) were similar. The shelf life of 100 per cent K plus 100 per cent Na treated tubers were found to be the highest. There was an increase in the content of N, K, Ca and Mg in the plants when Na was also supplied as treatment. Consequently the uptake of nutrients increased with the application of different levels of Na along with 50 per cent K. This shows that Na has a stimulative effect on uptake of nutrients. Application of Na did not affect any soil properties like pH, EC and organic carbon. The available nutrients like N, P, Ca and Mg increased in Na treated plots Yield of tuber was positively and significantly correlated with the dry matter production and uptake of Ca. Yield was positively correlated with the uptake of all nutrients under study. From the above points, it can be concluded that a combination of 50 per cent K and 50 per cent Na is optimum for getting the maximum yield. From the present study it also became evident that the efficiency of nutrient uptake increased at this combination. By adopting this practice, it was seen that the quality of coleus tubers improved and they became nutritionally more rich. This practice was found to be economically more feasible. Considering all these aspects, this fertilizer practice can be recommended to the farmers for getting a higher profit. From this investigation we can clearly establish a synergistic interaction of the two monovalent nutrient ions, K and Na on the growth and yield of coleus.Item Impact of organic farming practices on soil health,yield and quality of cowpea (Vigna unguiculata subsp. sesquipedalis (L.) Verdcort)(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2005) Devi Krishna; Usha, P BItem Zinc and boron availability in soils and impact of carriers on crop productivity(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2005) Jyolsna, V K; Usha MathewA study entitled “Zinc and boron availability in soils and impact of carriers on crop productivity” was carried out at College of Agriculture, Vellayani 2003-2005 to monitor the effect of moisture levels with and without FYM on the availability of B and Zn in three types of soil viz., red, laterite and Onattukara sandy and the influence of carriers of Zn and B on tomato. The experiment consisted of two parts viz., incubation study and separate pot culture experiments with B and Zn. The physico-chemical analysis of soils used for incubation study was done using suitable analytical procedures. Incubation study was conducted at the laboratory to monitor the availability of B and Zn in red, laterite and Onattukara sandy soils. Two kg of each type of soil was taken in earthern pots of uniform size and incubated for two months at three moisture levels viz., air dry, field capacity and full saturation with and without FYM. The experiment was laid out in CRD with six treatments. They were, T1 – Air dry, T2 – Field capacity, T3 – Full saturation, T4 – T1 + FYM, T5 – T2 + FYM and T6 – T3 + FYM. Soil samples were drawn at fortnightly intervals and analysed for the available content of boron and zinc following standard analytical procedures. Separate pot culture experiments were conducted to study the influence of B and Zn using laterite soil on growth, yield and quality of tomato. They were laid out in CRD with treatments viz., T1 – fertilizers alone as per POP, T2 – fertilizers and FYM as per POP, T3 - T1 + B/Zn @ 0.5 /2.5 kg ha-1, T4 – T1 + B/Zn @ 1.0/5.0 kg ha-1, T5 – T1 + B/Zn @ 1.5/10 kg ha-1, T6 – T2 + B/Zn @ 0.5/2.5 kg ha-1, T7 – T2 + B/Zn @ 1.0/5.0 kg ha-1 and T8 – T2 + B/Zn @ 1.5/10.0 kg ha-1. Observation on various biometric and yield parameters had been recorded. Soil, plant and fruit analysis were done using standard analytical procedures. From the incubation study, it can be seen that B availability was more at full saturation condition than at air dry and field capacity moisture regimes in all the three soils. It was minimum at air dried state of soil. Available Zn recorded maximum value at air dried state than at field capacity and full saturation moisture regimes. The influence of B and Zn on the growth, yield and quality of tomato can be clearly understood from the pot culture experiments. Plant height and number of primary branches showed significant increase with B and Zn application. Yield, B : C ratio and quality parameters were higher in the treatments which comprise B/Zn along with FYM. Available K in soil after pot culture increased with increase in levels application of boron. The same trend was shown by DTPA-extracted Zn and Cu. Available Fe and Mn decreased by B application. Soil B increased with increase in level of B application. Plant content of these nutrients showed the same trend as that of soil content. Available P, Fe, Mn and Cu decreased with increase in levels of Zn application in the pot culture experiment with Zn. Soil available Zn increased with increase in level of application of Zn. Plant nutrient content showed considerable variations. There was an increasing trend for uptake of nutrients from T1 to T8 as there was an increase in total dry matter production in both the experiments. From the results cited above it can be confirmed that B and Zn fertilization has an important role in improving yield and quality of tomato. The highest yield, quality and B : C ratio were obtained when B was applied @ 1.5 kg ha-1. This indicates that further experiments may be conducted by raising the level of B above 1.5 kg ha-1 to verify its effect on contributing to further increase in yield. In the experiment with Zn, though the yield was the highest in T8, the B : C ratio was higher in T7 than in T8 . This indicates that economic yield was obtained when Zn was at 5 kg ha-1. For the purpose of formulating recommendations on application of B and Zn, more field studies need to be conducted.Item Soil properties and produce quality of cardamom(Elettaria cardamomum Maton) under organic farming(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2004) Arun, G; Saifudeen, NAn investigation was conducted at the Upputhara panchayath of Peermede taluk, in Idukki district of Kerala with the objective to compare the soil properties, crop nutrient concentrations and quality of cardamom (Elettaria cardamomum Maton) under organic and conventional farming.' Nine certified organic farms, that follow IMO and Skal International certification standards and eight adjacent conventional cardamom farms following recommendations of Spices Board were selected for investigation. Fifty samples each of soil and cardamom leaves were drawn from both organic and conventional farms. Cured cardamom samples were collected from each farm under study. A proforma was developed in accordance with the standards fixed by IFOAM for documenting farming practices of the study area Biometric parameters and yield attributes of cardamom plants were observed directly and yield data for the organic and conventional cardamom farms were collected from farm records during the survey. The orgaruc farms selected for the study did not follow strict package of practices and there were variations among individual farms, but within the purview of certification procedures. Conventional and organic farming practices of the study area differed mainly on fertilization policy, plant protection strategy, weed control and land management. Soils of the organic cardamom farms were found to have better aeration than conventional farms, evident from the significantly lower bulk density of soils of the organic farrns. Another significant effect of organic agriculture in cardamom was the improvement of soil electrochemical properties. The rich organic soils of the study area resulted in insignificant difference in organic carbon and organic matter content of the soils of the two farming systems. The ranges of major nutrients in soils were medium to high and hence the difference between organic and conventional cardamom farms with respect to major nutrients was also not consistent. Microbes were proliferating in the organic farms resulting in better decomposition of organic matter with concomitant solubility of major nutrients in the soil. But dehydrogenase enzyme activity of the soil didn't differ significantly. Conventional farming with chemical inputs enhanced morphological make up of cardamom plants. Leaf length, leaf breadth, plant height and number of tillers per clump were significantly low in organic cardamom plants. A reverse trend was seen in the case of petiole length. Panicle length, number of panicles per clump, number of racemes per panicle and number of capsules per raceme were significantly lower in organic farms contributing to lower yields, which of course are expected to improve as farming practices stabilize in due course. Since the morphological make up of the cardamom plants in the organic farms was relatively smaller, the minerals taken up were not diluted resulting in higher concentrations of major nutrients in organically managed plants. The effect of high levels of Ca in the exchange complex is also reflected in low uptake of Fe and Mn by organic cardamom plants. Size of fresh cardamom capsules, colour, and litre weight were higher in the organically produced cardamom samples. However, the number of seeds per capsule was lower in organic cardamom. Both oleoresin and volatile oil contents were found significantly superior in the organic to that of conventional cardamom.Item Dissipation of chlorpyrifos in red loam soil and its effect on soil organisms(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2005) Rekha, P R; Thomas GeorgeItem Heavy metals in fertilizers in relation to their accumulation in soils due to continuous fertilizer use(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Sathyaprakasan, S; Abdul HameedThe possible heavy metal pollution through continuous use of chemical fertilizers for the last several years, has become a topic of grave concern in recent times. It is possible that such heavy metals if present in soil in sufficient quantities, may enter the food chain and endanger animal and human life. The present study was taken up with a view to establishing whether the accumulation of heavy metals in soils and plants is appreciable so as to pose any health hazards. With a view to achieve the above aim soils and rice plants grown in four major rice soils of Kerala which were receiving high doses of fertilizers for the last several years, and also eight common fertilizers used in these areas were collected and analysed for the heavy metal content with emphasis to cadmium. Soils from plots receiving organic manures, chemical fertilizers and a combination of both from one permanent manorial experiment with tall’ , india rice (25 years under same treatments) and soil, plant and grain from another permanent manorial experiment with dwarf Jeponica rice (13 years old) were collected and analysed for their heavy metal content. A pot culture with added cadmium alongwith fertilizers as per package of practices was also conducted incorporating rice, amaranthus and guinea grass to study the plant to plant variation in the uptake and accumulation of heavy metals in their tissues. The result of the studies showed that the phosphatic fertilizers contained the highest amount of heavy metals and among the phosphatic fertilizers maximum amount of Cd was found in factomphos while Ni and Pb were highest in mussoorie rock phosphate. Among the four soil types investigated viz. the Karappadam, Kayal, Kari and Trivandrum sandy loam the highest content of total Cd Ni and Pb were observed in Karappadam, Kayal and Kari soils respectively. The content of extractable Cd and Pb was highest in Kari soil while the extractable Ni was highest in Kayal soil. The mean Cd and Ni content of rice straw from karappadam soil was found to be the highest where as the rice straw from Kayal soil registered the maximum content of Pb. The results obtained from the Permanent Menurial Experimental trials revealed that the continuous use of organic matter alone or organic matter and chemical fertilizers in combination increased the heavy metal content in soils and plants. In the pot culture experiment with rice there was no significant variation in the total as well as the extractable Cd in the soil after harvest among treatments with 0, 10, 20 and 30 g Cd ha-1. The same trend was observed in the straw and grain as well. The Cd content in amaranthus also was not having significant variation among treatments. But in guinea grass the Cd content was significantly higher in the pot which received the highest dose of Cd viz. 30 g/ha. Since the doses viz. 10, 20 and 30g Cd per heactre were fixed on the basis of annual addition through fertilizers the impact could be much less and therefore the results presently obtained cannot be’,said to be conclusive. Correlation studies revealed that the soil total Cd was positively and significantly correlated to plant Cd content. The extractable Cd was also positively and significantly correlated to soil P. Applied N and P fertilizers were seen to significantly influence plant Cd content. The applied K fertilizers on the other hand were seen to positively enhance plant Cd, Ni and Pb contents.
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