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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
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
Prediction of potassium fertilizer requirement of banana, musa (AAB Group) 'nendran'
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1997) Sindhu, J; KAU; Korah, P A
A study was undertaken in the field of a local farmer from May, 1995 to January, 1996 to assess the effect of application of different doses of potassium on the growth, yield and quality of bananacv. Nendran. The experiment also envisaged standardisation of the index plant part of K status and determination of K level in index plant part and soil for maximum and economic yield. The experiment was laid out in RBD with five levels of K (0,150, 300, 450 and 600 g K 2O per plant ) as treatments replicated four times . The soil , low in N,P and K status belonged to the taxonomic class Loamy Kaolinitic Isohyperthermic Rhodic Haplustox. All the biometric characters studied namely height of plant , girth of pseudostem, number of functional leaves , total leaf area and leaf area index showed an increasing trend with increase in the dose of K application from 0 to 600 g K2O per plant and the effects were more pronounced from the shooting stage of the crop after it had received the full dose of K supply.
Open Access
Suitability of sul-po-mag as a potassium cum magnesium fertilizer for banana in Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1997) Anila Mathew; KAU; Chinnamma, N P
The present investigation was carried out in the Department of Soil Science and Agriculture Chemistry, College of Horticulture, Vellanikkara during the period of September 1994 to August 1995. The study was aimed to bring to light the suitability of Sul-Po-Mag as a potassium cum magnesium fertilizer for banana in Kerala. The treatments included Sul-Po-Mag substitutes of potassium to the extend of -25, 50 and 100 per cent in the normal recommended dose of NPK as urea, diammonium phosphate and muriate of potash at the rate of 190 g N, 115 g P205 and 300 g K20 per plant per year. Treatments of muriate of potash supplemented with magnesium and sulphur separately and with magnesium and sulphur together were also included and they were compared with the recommended practice. The experiment was laid out in randomised block design with three replication. During the early stages of growth, the treatments failed to influence the morphological characters such as height, girth and number of leaves of the plant. But at the later stages, the girth and the number of leaves differed significantly and the application of Sul-Po-Mag showed a favourable influence on these characters. No significant difference was observed in characters like total number of suckers, days to flower, days to mature and total duration of the crop among the treatments. Among the bunch characters, numbers of hands, length and girth of fingers and bunch weight were influenced by the difference in treatments while the number of fingers per bunch and weight of fingers remained unaffected. The maximum yield was given by the treatment where potassium was supplied by Sul-Po-Mag and muriate of potash in half doses. Though the treatments differed significantly in yield from the control, where no fertilizer was applied, the treat- ments of muriate of potash and Sul-Po-Mag are on par indicating that Sul-Po-Mag is as good as MOP for its capacity to meet potassium requirement of the crop. The treatments did not differ significantly in quality parameters such as reducing sugars, total sugars, sugar acid ratio, weight of pulp and peel and pulp peel ratio. But significant difference was observed with total soluble solids, ascorbic acid content, non reducing sugars and acidity. High value of these characters were recorded with Sul-Po-Mag except for the reducing sugars and total sugars. Treat- ments with magnesium and sulphur were found to decrease the sugar content of fruits. High pulp peel ratio of Sul-Po-Mag treatments showed increased storage quality. The nitrogen, phosphorus and sulphur contents of leaves remained unaffected both at vegetative and harvest phases, while potassium, calcium and magnesium differed significantly between the treatments. The contents in leaf of N, P, K, Ca, Mg and S were decisively influenced by the treatments at the time of shooting. Nutrient contents of leaves were found to increase till shooting and a drastic reduction was observed thereafter. Calcium, magnesium and sulphur contents in the fertilizer increased their availability in soil and the plant content. Treatments with Sul-Po-Mag and magnesium showed high content of potassium in leaves. The contents of potassium, calcium, magnesium and sulphur were found to be the highest in the pseudostem followed by leaves. Rhizome and fruit also showed appreciable amount of these nutrients. The total uptake of potassium, calcium, magnesium and sulphur ranged between 365.26-221.06, 73.57-57.97, 4.45-14.5 and 3.71-4.94 g plant-1 respectively. Only the total uptake of magnesium was decisively influenced by the treatments. The maximum values of uptake of magnesium found in treatment which was supplied with Mg equivalent to that present in half dose of Sul-Po-Mag. Available P, available K and available S contents of the soil were found to be nonsignificant both at vegetative and harvest stages. The sulphate containing treatments were found to decrease the pH of the soil. Maximum electrical conductance was found with Mg supplied treatments. Organic carbon content was found to be significant only at harvest stage. Calcium, magnesium and sulphur contents in the fertilizer were found to increase the soil content of these elements.
Open Access
Inter-relationship of potassium with other soil fertility parameters in two major wetland rice soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1997) Naveen Leno; KAU; Thomas Varghese
A study was done at the College of Agriculture, Vellayani during 1994-95 to quantify the different forms of potassium and to investigate the inter-relationships of these forms with other soil fertility parameters. Soil samples were collected from ten locations each, of the two major wet land rice soils of Kerala selected for the study viz., lateritic alluvium of Pattambi (brown hydromorphic) and Onattukara sandy soil (greyish Onattukara) of Kayamkulam. Incubation studies were also carried in both soil types, with and without applied potash, for a period of two months. The study revealed that considerable variation existed in the physico-chemical properties of the two soils. The lateritic alluvium of Pattambi was clayey, high in chloride, organic matter, active iron, CEC, ECEC, exchangeable Ca, Mg and sum of bases and was low with respect to coarse sand and available phosphorus contents and was less acidic as compared to the Onattukara sandy soils of Kayamkulam. The latter was loamy sand in texture with a high content of coarse sand fraction, more acidic, high in phosphorus content and low in clay, chloride, organic matter, active iron, CEC, ECEC, exchangeable Ca, Mg and sum of bases in comparison to the former. Fractionation studies revealed that the Pattambi soils had a higher content of total K, HN03K and fixed K as compared to that of Kayamkularn soils. The high positive correlation of exchangeable K with the available K fraction in both the soil types justifies the existence of a dynamic equilibrium between the two fractions. The .negative correlation of exchangeable and available fractions of K with active iron observed in Pattambi soils was contrary to earlier observations in this regard. Though comparatively high in organic matter, the effect of soil reaction on the available K status was not considerable in Pattambi soils as compared to Kayamkulam soils. This led to the conclusion that management of organic matter in tropical soils is important to maintain the available K status for sustainable farming. The positive inter correlation obtained between lattice K and total K indicated that the major portion of soil potassium existed in the lattice form. The positive and significant association of other forms of potassium was indicative of the existence of a dynamic equilibrium between these forms of K. Potassium fixation was found to be a constraint in Pattambi soils especially with the addition of potassic fertilisers. Hence this should be given due consideration while formulating cost-effective and efficient potassium management strategies since the major chunk of potassic fertilisers are imported in our country.
Open Access
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; KAU; Rajendran, P
The 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.

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