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Open Access
Effect of Vermicompost on the yield and quality of tomato (lycopersicon esculentum Mill.)
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1996) Pushpa, S; KAU; Prabhakumari, P
An investigation was carried out at the Instructional Farm, attached to the College of Agriculture, Vellayani to evaluate the Effect of vermicompost on the yield and quality of tomato. The experiment was laid out in Randomised Block Design with ten treatments and three replications. Biometric observations viz. height of the plant, number of leaves and number of floweres were greately influenced by the application of vermicompost compared to farm yard manure. Yield attributes like mean fruit weight and girth of fruits were also found to be significantly influenced by the vermicompost application. Vermicompost application has got a significant influence on the yield of tomato. Plants receiving 25t vermicompost along with full dose of inorganic fertilizers produced maximum yield followed by the plants receiving 25 t farm yard manure along with full dose of inorganic fertilizers. Germination count and viability was maximum when vermicompost was used as the organic source. Maximum germination count and viability was observed when 100t ha-1 vermicompost was used. Vermicompost application has also got a significant influence on fruit qualities. Protein, and carbohydrate content were more in vermicompost treated plants compared to farm yard manure application. Chemical properties of the soil was significantly influenced by the application of vermicompost. pH, organic carbon, available N, P2O5, K2O, Ca and Mg was maximum when 25t vermicompost along with full dose of inorganic ferilizers was used. However availability of micronutrients Mn, Cu, Zn was more in 100t vermicompost applied plots. Application of vermicompost increased the uptake of nutrients by plants. Maximum uptake of all nutrients viz. N, P, K, Ca, Mg, Mn, Cu and Zn was found in plants treated with 25t vermicompost along with full dose of inorganic fertilizers. Correlation studies showed that nutrient uptake was significantly and positively correlated with availability of nutrients. Yield and nutrient uptake of plants were significantly and positively correlated with availability of nutrients and so vermicompost can be effectively used for increasing the fruit yield and quality of fruits in tomato.
Open Access
Land evaluation and suitability rating of the major soils of Onattukara region
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1998) Premachandran, P N; KAU; Subramonia Iyer, M
The need for a scientific approach in inventorying and utilizing land resources most economically and efficiently is now universally accepted. Agricultural prosperity, to a great extent, depends on judicious use of soils and rational application of soils data. A reconnaissance soil survey of Onattukara region was undertaken to study the extent and distribution of the different soils for soil classification, land capability and irrigability classification and for subsequent land evaluation. The study reveals that Onattukara region extends over an area of 40,948 ha. The soil map showing the distribution of the identified twenty soil series has been prepared. The climatological data reveals that the soil moisture regime is , ustic and the soil temperature regime is isohyperthermic. The soils have been classified as per Soil Taxonomy (U.S. Soil Survey Staff, 1975) and Keys to Soil Taxonomy( U.S. Soil Survey Staff, 1994 and 1996). Ten series were classified under Entisols, SIX under Inceptisols, three under Ultisols and one under Alfisols. Based on the inherent soil characteristics and landscape features, the soils have been grouped into three land capability classes, nine capability subclasses and land capability map prepared. The soils were classified into five land irrigability classes, eight land irrigability subclasses and land irrigability map prepared. The soils were evaluated based on principles of land evaluation and rating of productivity parameters. The productivity rating of the soil propertIes agamst the productivity index for nee, coconut, sesamum ,cassava and banana were made and conclusions arrived at. Productivity rating shows that Kottakakam series is best suited for rice, Palamel, best for coconut and banana, Artuva and Mahadevikad, for sesamum and Palamel and Vallikunnam, for cassava. On the basis of the studies carried out, a land use is proposed for the twenty soil series of Onattukara region based on crop suitability ratings and crop suitability map prepared for the five crops taken for study. A proper soil survey interpretation provides information on soil potential, productivity and limitations in their sustained use. Soil survey information forms the major basis for land evaluation. A thorough knowledge of the potentialities and limitations of every piece of land is a prerequisite in its efficient utilization. A systematic survey is essential for the evaluation and classification of the soils based on their inherent soil characteristics, land capability, land irrigability and land suitability. A systematic survey and evaluation of the soils of Onattukara region was taken up to study, interpret, classify and to show their location and extent on base maps. It is hoped that the present study would open up avenues for further investigations on land evaluation, crop suitability and other management aspects for sustained use of soil resource data to the best advantage. This will also form the basis for microlevel planning for integrated and sustainable development of the region under Panchayat raj.
Open Access
Distribution of extractable in soils of selected major land resource area of Kerala
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1997) Sathyanarayanan, R; KAU; Abdul, Hameed
The investigation was carried out to assess the total and available micronutrients in soils of selected major land resource areas (MLRAs) of' Kerala. The micronutrients investigated in the present study were iron, manganese, zinc, copper and boron. The study was intended to establish the pattern of the distribution of micronutrients both vertically and spatially in eight MLRAs viz, Palode, Vellayani, Trivandrum, Mannar, Kottarakkara, Thakazhy, Ramankary and D-Block soil series of Kerala. Three extractables viz DTPA, EDTA and ammonium acetate were used in the analysis. The available boron content in these soils was also determined by hot water extraction method. All the micronutrients showed great variation in their distribution in the various horizons of the profiles. The micronutrients content of the soils estimated were correlated with soil properties like pH, organic carbon, CEC and clay content. They were found to be positively and significantly correlated with organic carbon, CEC and clay content while it was significantly and negatively correlated with pH. The significant correlations revealed that the micronutrient availability in these soils were influenced greatly by the soil properties mentioned above. From the results obtained, it was observed that micronutrients like iron and manganese were well supplied in all the profiles studied. The micronutrients were found to decrease with depth except in Ramankary, D-Blockand Thakazhy series where it showed an irregular trend with depth due to the peculiar hydrologic and oxidation-reduction conditions existing in these soil series. The available and total micronutrients content in the surface soils from places around the profile sites did not show any significant variation among places. In almost all the samples very high iron content was recorded.
Open Access
Leaf litter dynamics in acacia and eucalyptus plantations
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1997) Moossa, P P; KAU; Venugopal, V K
An investigation entitled “Leaf litter dynamics in Acacia and Eucalyptus plantations” was undertaken to study the leaf litter production, litter decomposition and nutrient release characteristics, and impact of Eucalyptus and Acacia monoculture plantations on the soil physico-chemical and biological characteristics during 1994-97. One hectare each of Acacia auriculiformis, Eucalyptus tereticornis and a moist deciduous forest coming under the Kulathupuzha range of Kerala Forest Department were selected for the study. Field experiment were conducted to determine the leaf litter production and decomposition characteristics of plantation and natural forest. Leaf litter collected at monthly intervals showed that highest litter production was in Acacia (9.4 t ha-1 year-1) followed by natural forest (6.67 t ha-1 year-1) and Eucalyptus (4.68 t ha-1 yaer-1). Pattern of litter production was unimodal in Acacia and natural forest while in Eucalyptus it was bimodal. Chemical analysis of litter samples of plantations and natural forest revealed that with respect to nutrient content fresh and leaf litter of Acacia and Eucalyptus is superior to natural forest whereas litter quality in terms of water soluble components, polyphenols, lignin and cellulose were superior in natural forest. Annual dry matter loss of leaf litter by decomposition followed the order natural forest > Acacia > Eucalyptus. Nutrient release pattern of major and micro nutrients were also worked out for the leaf litter during the process of decomposition and natural forest litter recorded the highest mobility for all the nutrients on decomposition. Improvement in soil physico-chemical properties were noticed due to leaf litter decomposition in the monoculture plantation and natural forest. Biological activity in terms of earthworm and nematode under monoculture plantation was significantly lower than that of adjacent natural forest. Microbial content of soil below the litter bag during different months of decomposition were low in Eucalyptus and Acacia. Chemical analysis of the profile samples of various plantations revealed lower nutrient status in respect of major and micronutrients compared to natural forest. The physical properties of the soil also recorded as unfavourable change in the monoculture plantations as compared to the adjacent natural forest. Proximate anlysis of soil organic matter and humus characterization of the soil organic matter separated from various plantations indicated a low rate of humification and condensation under Eucalyptus. Low humic acid and fulvic acid content in humus and dominance of fulvic acid over humic acid was also noticed in Eucalyptus plantations. Functional group analysis of humic acid and fulvic acid showed that humic material separated from natural forest contained higher quantity of total acidity, contributed by COOH and phenolic group compared to plantation soils. UV, IR, DTA and TGA analysis of humic acid and fulvic acid separated from various plantations showed no variation with respect to natural forest. Allelopathic effect of fresh leaf and leaf litter extract of various plantations on the germination and growth of rice and cowpea followed the order Eucalyptus > Acacia > natural forest and as the concentration decreased from 1: 2 to 1: 10, the allelopathic inhibition also decreased significantly. Allelopathic effect of soil extract also followed the order Eucalyptus > Acacia > natural forest. Thus it can computed that though the leaf litter production and litter quality of monoculture plantations are comparable with that of natural forest, leaf litter decomposition and nutrient released were significantly lower than that of natural forest. Soil physico-chemical properties, soil fertility and biological activities were also adversely affected by monoculture plantations.
Open Access
Characterisation of the gravels in the major soil series of Trivandrum district
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1996) Suraj, John; KAU; Subramonia Iyer, S
Soil gravels are different in their morphological, physical, chemical and mineralogical features; as well as in their origin. In the major soil series of Trivandrum district, soil gravel inclusions make up a considerable part of the soil mass. Presence of soil gravels interferes with the cultivation operations, reduce soil volume and quantity of available water. In soil textural determinations and the soil fertility evaluation, presence of soil component greater than 2mm is usually disregarded and ignored. In order to gather information on the nature and properties of soil gravels, their genesis and distribution and their specific contribution to soil fertility; an integrated and systematic morphological, physical, chemical, mineralogical and micromorphological characterisation and interpretation of soil gravels of the representative profiles of the major soil serious of Trivandrum district namely Palode, Nedumangad, Varkala, Thonnackal and Trivandrum series were attempted. All the series except Thonnackal were gravelly throughout; Palode, Varkala, and Trivandrum series showed an increase in gravel content with depth but no specific profile pattern was observed at Nedumangad and Thonnackal. Palode series is unique with all the different gravel fractions (2mm to 2.5 cm, 2.5 to 7.5 cm and 7.5 to 25 cm). Another uniqueness of the Palode series is the presence of gneissic cobbles. Cobbles were absent in all the other series. Combination of grayels different in morphology and genesis are present at Palode and Trivandrum series. Gravel consolidation and soil hardening were observed maximum at Varkala series and least at Thonnackal series. Higher total phosphorus and potassium content of gravels indicate that gravels are the potential source of phosphorus and potassium for crop production. Acid insoluble content of gravels are in the increasing order Varkala< Trivandrum Quartz content of the finer gravels are in the increasing order at Varkala Palode and Nedumangad series contain multiglaebular microgravels and multimicrogravelly coarse gravels and cobbles. The gravels of Varkala are dominantly nodular than concretionary. The uniqueness of the Thonnackal series is the presence of rubefied less hard kaolinitic gravels. The gravels of the Trivandrum series are nodular, plinthic to petroplinthic with bigger angular skeletons. The preponderance of gravels with geodic internal morphology in the lower horizons and pseudomorphic in the surface horizons are direct expressions of geogenic and pedogenic origin of gravels. The observation of nucleic type of gravels in the last horizon of Thonnackal series is indicative of its detrital origin from microgravels of nearby landscapes. The preponderance of quartz both in the soil and gravels is obviously due to the acid igneous and metamorphic parent material. The hardened plinthite gravel ie., the petroplinthite gravel is proposed in the soil taxonomy to differentiate Entisols and Inceptisols from Oxisols and Ultisols. The comparative gravel contribution to available nitrogen content of the soil is in the increasing order Palode A multilocational field experiment based on the information gathered in the present study is desired to be taken up to reveal the effect of gravels on the performance of crops in the actual field situation.
Open Access
Evaluation of maton rockphosphate in the acid rice soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1997) Suja, Thomas; KAU; Sushama, P K
A study conducted at College of Horticulture during the period 1994 – 96 so as to assess the effectiveness of Maton rockphosphate (MTRP) as a source of P compared with single super phophate (SSP), diammonium phosphate (DAP) and Mussoorie rockphosphate (MRP). In addition to the above sources a control treatment (with no P fertiliser) and another treatment with SSP at the rate of 45 kg P2o5 ha-1 given twice (conventional practice) were also included. The P release from all the sources were monitored with an incubation experiment. In order to evaluate the response of fertilisers two continuous pot culture experiments were undertaken using Jaya variety of rice. Two acid rice soils of Kerala, viz., Kuttanad alluvium and laterite were used for the study. The variations in pH of the soil types indicated that there was increase with advancement of periods under waterlogging irrespective of the treatments including the control. Available N was high in Kuttanad alluvium as compared to laterite and was found to decrease with periods of incubation. The content of available P gradually increased with period of incubation, reached a peak at 120 days for water soluble phosphates (SSP and DAP) and 180 days for rockphosphates, irrespective of the soil types. Comparing the two extractants, Mathewstriacid extracted more available P than that of the Bray solution in both the soil types. Available K decreased with periods of incubations. In general, Kuttanad alluvium recorded higher content of available nutrients as compared to laterite. In both the soil types the most dominant P fraction was Fe – P followed by AI – P and Ca – P. While evaluating the pot culture experiment it was observed that available nutrient content decreased with advancement of crop growth. Even after the harvest of second crop, the residual effect of MTRP was recorded to be high. There was maximum uptake of P at the second crop season as compared to the first crop irrespective of the soil types. The leachate loss decreased with crop growth in both the soil types. But the maximum leachate loss was recorded for N followed by K and P. The grain yield as well as the relative yield was found to be maximum for the laterite soil on comparison to Kuttanad alluvium for the first and second crop of rice. In Kuttanad alluvium, DAP and MTRP yielded better in the first and second crop respectively. While in laterites SSP was found to be better in grain yield as compared to other sources, The source, DAP was superior to others in straw yield for both the soil types with increase in levels of P application, there was increase in grain and straw yield.
Open Access
Increasing the geranoil content of palmarosa oil by chemical methods
(Department of Soil Science and Agricultural Chemistry, Horticulture College, Vellanikkara, 1997) Mullakoya, C P; KAU; Samuel, Mathew
Palmarosa, Cymbopogon martinii (Stampf) var. motia is an important essential oil crop grown commercially in various states of peninsular India. Palmarosa oil finds extensive use in flavouring, cosmetics and toiletry. The oil is valued for the principal constituent geraniol, present in the oil to the extent of 75-82%. Besides being a high grade perfume, geraniol is the starting material for a number of synthetic aroma chemicals. Next to geraniol, the most abundant chemical component of the oil is geranyl esters, predominantly geranyl acetate. Most oils contain about 2 - 12% geranyl acetate. Several factors like the genotype, season, harvest stage, method of oil extraction etc. influence the ratio of geraniol to geranyl acetate in the oil and it is found that a reciprocal relationship exists between the geraniol and geranyl acetate content of the oil. At most times, the geraniol content of palmarosa oil produced by cultivators fall short of requirements of the user industry. The availability of an inexpensive and efficient method of hydrolytic conversion of geranyl acetate to geraniol will facilitate the farmer to undertake an on-farm quality upgradation of his product which will fetch him better price. A laboratory investigation was carried out at the Aromatic and Medicinal Plants Research Station, Odakkali, Kerala during 1994-96 to develop a method for upgrading the quality of palmarosa oil by the conversion of geranyl acetate in the oil to geraniol. Four treatments were tried for the hydrolysis of geranyl acetate, with essential oil of palmarosa type ODP-3 as the test material viz., methanolic sodium hydroxide, methanolic sodium carbonate, ammonia and aqueous sodium hydroxide. Mixing of essential oil with 5% methanolic NaOH reagent in the ratio of 1 : 4 and keeping undisturbed at ambient conditions for 30 min were the optimum conditions for the complete hydrolysis of geranyl acetate in the oil. The product of reaction analysed 90.5% geraniol and the process yielded geraniol to the extent of 78.74% of the oil taken for processing. However, treatment of the oil with methanolic sodium carbonate or ammonia did not result in hydrolysis of geranyl acetate. In the case of aqueous sodium hydroxide method of hydrolysis, refluxing the essential oil with an equal volume of 20% aqueous NaOH solution for 30 min was optimum for the complete hydrolysis of geranyl acetate in the oil. The product contained 89.35% geraniol and the quantity of geraniol yielded by the process was estimated at 86.67% of the oil taken for processing. Comparison of the methods of hydrolysis studied -revealed that in terms of geraniol content of the product, geraniol yield from the process and time: required for '\ .' .. the reaction, the aqueous sodium hydroxide method was found to be the best. The efficiency of the method for quality upqradation was tested on essential oils of different Cymbopogon types viz., ODP-1, ODP-3, C-3, OD-455 and Jamrosa. All the oils were characterised by low level of geraniol and high level of geranyl acetate and none of them conformed with ISI specifications for palmarosa oil. In case of all the oils, the treatment resulted in complete conversion of gerariyl acetate to geraniol with commensurate increase in the level of geraniol, bringing about a vast increase in their quality. By the process, oils of ODP-3 and Jamrosa were upgraded to meet the specifications for palmarosa oil. Verification of the sodium hydroxide hydrolysis method on pilot plant scale showed that it can be employed on large scale for the quality improvement of . palmarosa oils which contain appreciable amount of geranyl acetate.
Open Access
Morphological, physical and chemical characterization of the soils of North Kuttanad
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1997) Manorama Thampatti, K C; KAU; Jose, A J
An investigation was carried out at the College of Horticulture, Vellanikkara during 1992 to 1995 to evaluate the morphological, physical and chemical characteristics of soils of North Kuttanad and to assess the extent of toxic factors that pertained in the soil due to restricted movement of water under the influ- ence of Thanneermukkom regulator. The study was carried out in three parts, viz., (1) Morpho- logy and physicochemical characteristics, (2) Fertility characteristics and (3) Toxicity chara- cteristics. Fifteen soil profile were drawn from North Kuttanad to study the morphology and physicochemical characteristics of the area. The fertility characteristics were studied by collecting 97 surface soil samples (0-15 cm depth) from 27 padasekharams of the area during rainy and summer seasons (before and after the closure of Thanneermukkom regula- tor). Toxicity characteristics of the area were studied by collecting bulk soil samples (0-25 cm depth), surface water and ground water from the above sites during the same period. Morphological and physicochemical properties of the soils showed great degree of variation. Soils were dark brown to black in colour, sticky and plastic, subangular blocky in structure and sandy to clayey in texture, with random deposits of lime shells and humus. Presence of faint to prominent reddish yellow or brown mottles, rice roots and root canals were some of the special characteristics observed in the soil profiles. Soils of the area were highly acidic and mildly saline. Both soil acidity and salinity increased with depth. Organic carbon, CEC and ECEC of the area were higher compared to other parts of Kerala, but the base saturation was comparatively lower. The area was rich in almost all the essential nutrients except P. Fe, Al and S were present in toxic concentrations. Potential acidity of the area was very high and more than 70 per cent of it was contributed by hydrolytic acidity and the rest by exchangeable acidity. All the acidity characteristics increased with depth. The profile IX was grouped under order Inceptisol and all others under order Entisol. On evaluating the fertility characteristics of the area it was observed that the area experienced an increase in soil acidity and availability of N, P, Fe and Zn and a decrease in salinity, CEC, ECEC and available K, Ca, Mg, \.10 and Cu. However, the availability of all nutrients except P was above the deficiency level. Fe was present in toxic quantities. On a general comparison with that of pre-barrage period, the area experienced a reduction in salinity and an enhancement in soil acidity and availability of K, Ca and Mg. The Na content was reduced considerably in response to the reduction in salinity. The exchangeable and water soluble cations followed the same trend as that of available cations. Among the exchangeable cations Ca was the dominant basic cation instead of Na which occupied the same place during pre-barrage period. Acidity characteristics of surface samples behaved similar to that of profile samples. Pot- ential acidity and hydrolytic acidity recorded higher values during rainy season while exchangeable acidity was greater during summer. Among the components of exchange- able acidity exchangeable Al3+ dominated during rainy season, and exchangeable H+ dur- ing summer. The overall influence was greater for exchangeable A13+ as evidenced from the higher correlation coefficient (0.862**). The general soil properties and acidity characteristics of the bulk soil samples were similar to that of surface samples, showing a reduction in pH, EC, CEC and available, exchangeable and water soluble cations during summer compared to the rainy season. Among the different fractions of Fe, free and available forms were present in large quantities while exchangeable and water soluble forms were present in negligible quantities. All the fractions expressed a higher concentration during summer indicating more chances for severe Fe toxicity during that period. Mn was also present in large quantities. Compared to Fe, the concentration of different fractions of Mn were very small. The availability of Cu and Zn were also above the critical levels. The area was rich in AI. Reverse to that of Fe the different fractions of Al showed a lower concentration during summer. The free Al content was three times lesser than that of free Fe, while in exchangeable form Al expressed a higher concentration. The water soluble AI was very low. Surface water and ground water of the area were mildly acidic and saline during rainy season and they showed an increase during summer. The acidity exceeded the permissible maximum but the salinity was maintained below the permissible limit for agricultural and domestic purposes. Among the various elements present in water, Na and Cl- were the dominant ions expressing greater concentrations during summer in both surface and ground water. Based on SAR they were rated as moderately unsafe for irrigation during summer. The concentrations of K, Ca and Mg were within the permissible maximum for agricultural and domestic purposes. P was present only in traces. The Fe content was greater for ground water than surface water and it exceeded the permissible limit for drinking water. Though Mn was absent in ground water, it has already reached up to the permissible maximum in surface water. Al content exceeded the permissible maximum for domestic purposes. Cu, Zn, Cd and Pb were not detected in water. SO4-S, NH4-N and NO2+NO3- N contents of both surface and ground water were well below the critical levels suggested, but Cl' contents of both were sufficient to cause specific toxicity effect. The chlorinated hydrocarbon pesticides identi _ fied in the area were (X-HCH, y-HCH and DDT. They showed higher concentration during summer. Among the chlorinated hydrocarbons, DDT was present in larger quantities, though it was banned for agricultural uses, followed by (X-HCH. The concentration of y-HCH was comparatively small. The accumulation of fertiliser residues in the area was not so negligible. The highest concen- tration was observed for NH4-N during addi- tional crop season, at the time of basal dressing, both in soil and water. During punja season, a decrease of 55 to 60 per cent in soil and 10 to 12 per cent in water for NH4-N was observed. The content of N02+N03-N was comparatively low in soil due to continuous submergence. In water it was not as low as that of soil, indicating a major portion of N02+NOrN retained in water. P content of the area was very low. Its loss through drainage water was nil. A sizable quantity of K was also subjected to loss through drainage water, though the extent of loss was well below the level of N. Here also highest concentration was noted during additional crop season at the time of basal dressing both in soil and water. The study indicated that the area is subjected to severe pollution due to the accumulation of native toxic factors as well as residues of pesticides and fertilisers. The closure of Thanneermukkom regulator aggravates the situation by restricting the water movement.
Open Access
Vermicompost as a potential organic source and partial substitute for inorganic fertilizers in sweet potato (Ipomoea batatas (L.) Lam.)
(Department of Soil Science and Agricultural Chemistry,College of Agriculture, Vellayani, 1998) Suresh Kumar, S N; KAU; Ushakumari, K
An investigation entitled "Verrnicompost as a potential organic source and partial substitute for inorganic fertilizers in sweet potato (Ipomoea batatus (L) Lam)" was carried out at the Instructional Farm, College of Agriculture, Vellayani during the period December 1995 to April 1996. The main objectives of the study were to study the efficiency of vermicompost as an organic manure, the extent to which inorganic fertilizers can be substituted when vermicompost was used as an organic source and the feasibility of reducing the dose of vermicompost. The experiment was laid out III randomised block design with seven treatments and four replications. The treatments consists of package of practices recommendations of Kerala Agricultural University for sweet potato (cattle manure + inorganic fertilizers) and vermicompost as organic source with graded doses of inorganic fertilizers. The growth parameters like vine length and number of branches did not show any significant variation. However highest vine length and number of branches are noticed in treatment which received vermicompost as a sole source of nutrient. Significant difference was observed in vine yield and highest vine yield was obtained when vermicompost was given as a sole source of nutrients. Yield attributing characters like length and girth of tubers and number of tubers did not show any significant variation. With respect to mean tuber weight and tuber bulking rate, the treatment differed significantly and maximum effect was observed when vermicompost was applied along with half the recommended dose of inorganic fertilizers. Significant treatment effect could be observed in total tuber yield and marketable tuber yield. Vermicornpost with half or 3/4th NPK produced highest yield. From this it could be deduced that by using vermicompost as organic manure in sweet potato, it is possible to bring down the usage of chemical fertilizers. Half or 3/4th dose of vermicompost along with recommended dose of inorganic fertilizers was equally effective as that of package of practices recommendations of Kerala Agricultural University (cattle manure + recommended inorganic fertilizers) in yield and yield attributes of sweet potato. The nitrogen and phosphorus content in the leaves and vmes did not show any significant difference by applying various treatments. But in tubers the nitrogen content was maximum when 1/2 inorganic fertilizers + organic manure as vermicompost was applied. The phosphorus accumulation in tuber was maximum in the combination of full inorganic fertilizers + organic manure as cattle manure was given. The treatment combination of full inorganic fertilizers + organic manure as vermicompost resulted m maximum accumulation of phosphorus in leaves, vines and tubers. Regarding calcium, magnesium and iron contents of leaves, vines and tubers there was no significant difference among various treatments. The application of full inorganic fertilizers + organic manure as vermicompost produced maximum manganese concentration in leaf and tuber. The starch content of tubers showed a decreasing trend with the reduction in the quantity of inorganic fertilizers. But by reducing inorganic fertilizer levels, the reducing sugar percentage increased. The crude protein, crude fibre and carotene contents showed the same trend as that of reducing sugar. The plant uptake of nitrogen, phosphorus and potassium was maximum when 112 inorganic fertilizers + organic manure as vermicompost was applied. The organic carbon level after the crop showed significant difference among various treatments. The maximum organic carbon percentage was noticed when nitrogen as vermicompost + organic manure as vermicompost was given. The growth characters like vine yield, number of branches were negatively correlated with yield. The yield components like number of tubers per plant, tuber weight, uptake of nitrogen, phosphorus and potassium showed positive correlations with yield. The economics worked out show that the highest net profit was obtained when 1/2 inorganic fertilizers + organic manure as vermicompost was given. The cost of cultivation while applying this treatment was minimum and it showed a B C ratio of 2.53.

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