Browsing by Author "Durga Devi, K M"

Now showing 1 - 16 of 16

Assessment of 2, 4- D residues in the major rice soils of Kerala
(Department of soil science and agricultural chemistry, College of horticulture,Vellanikara, 2002) Durga Devi, K M; Chinnamma, N P
Effect of agrochemicals on biological activity in lateritic soil
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2018) Nisha Paul; Durga Devi, K M
In modern agriculture, agrochemicals are frequently used to boost crop production. The use of pesticides is indispensable in various crops and cropping systems, particularly under tropical climatic condition. However erratic application of these chemicals may affect soil health, which in turn change the population and composition of soil microflora and soil fertility. The land use type also play a significant role in controlling the microbial community. Hence, the present study was undertaken at College of Horticulture, Vellanikkara during 2017-2018 so as to determine the impact of three agrochemicals viz. oxyfluorfen, copper oxychloride and chlorpyriphos on the population of soil microflora and dehydrogenase enzyme activity in lateritic soil collected from two land use types. Representative soil samples were collected from two land use types viz., land under cultivated grass, Agronomy farm, College of Horticulture, Vellanikkara (LUT 1) and cocoa plantation, Cocoa Research Center, KAU, Vellanikkara (LUT 2) during August, 2017. The soil samples were analyzed to assess physical, chemical and biological characteristics before starting experiment and the data revealed that soil collected from LUT 2 was more conducive for microbial growth and dehydrogenase activity. Pot culture experiment with cowpea (variety: Bhagyalakshmi) was conducted during March to June, 2018 with fourteen treatments (3 agrochemicals at 2 different doses under each land use types + 2 controls, one each for two land use types) and three replications. Agrochemicals viz., oxyflourfen (OXY) at 0.15 and 0.30 kg ha-1 (herbicide), copper oxychloride (COC) at 0.75 and 1.50 kg ha-1 (fungicide) and chlorpyriphos (CHL) at 0.30 and 0.60 kg ha-1 (insecticide) were selected for the study. Soil samples were analyzed at four intervals viz., 7, 30, 60 and 90 days after agrochemical spraying (DAS) to evaluate the effect of agrochemicals on chemical and biological characteristics of soil. The chemical characteristics of soil viz., pH, electrical conductivity, organic carbon, available N, P, K, Ca, Mg, S and micro nutrients like Fe, Mn, Cu, and Zn followed a decreasing trend towards the harvest in all the treatments under both the land use types. The effect of agrochemical application on chemical characteristics and nutrient availability of the soil was at lower magnitude compared to their influence on biological activity of the soil. The biological characteristics of soil viz. dehydrogenase activity and microbial population (fungi, bacteria and actinomycetes) were higher in soil samples collected from LUT 2 (cocoa plantation) at all the sampling intervals. Soil samples from both the land use types registered reduction in biological activity due to agrochemical application, which was higher at 7 DAS than the other sampling intervals. The extent of reduction in biological activity after application of agrochemicals was comparatively higher in LUT 1 (land under cultivated grass). Higher doses of the pesticides showed greater decline compared to their lower doses. Biological activity increased from 7 to 60 DAS and the extent of reduction with respect to control also became lower. At 90 DAS, a declining trend in the dehydrogenase activity and microbial population (except fungi) was noticed. The adverse effect of agrochemicals on dehydrogenase activity and bacterial population at 7 DAS followed the order: CHL > COC > OXY and OXY > CHL > COC respectively. However at 90 DAS, oxyflourfen exerted minimum adverse effect on soil bacteria. The study revealed that dehydrogenase activity is highly correlated with the population of soil microflora, especially soil bacteria. The adverse effect of agrochemicals on fungal population can be ranked as: COC > OXY > CHL at both 7 and 90 DAS. The percentage inhibition of actinomycetes population at 7 as well as 90 days after agrochemical application was in the order: OXY > COC > CHL. Cowpea yield was not affected by the agrochemical application and land use types. However higher doses of all the agrochemicals under study reduced the number of root nodules in cowpea.
Effect of herbicides and chemical characteristics of soil on microbial biomass carbon and enzyme activity
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2017) Amritha, K; Durga Devi, K M
Weed competition is one of the major factors limiting rice production in the tropics. Due to the scarcity and high cost of labour, weed management with herbicides is widely practiced. The problem associated with herbicides is the persistence of their residues in soil which interact with microorganisms thereby altering the microbial diversity and soil enzyme activity. Hence, the present investigation entitled “Effect of herbicides and chemical characteristics of soil on microbial biomass carbon and enzyme activity” was undertaken at College of Horticulture, Vellanikkara during 2016-2017. The objectives were: (i) to determine the impact of pre and post emergence herbicides on microbial biomass carbon and the soil enzymes namely dehydrogenase, urease, and phosphatase and (ii) to study the influence of chemical characteristics of the soil on microbial biomass carbon and enzyme activity. Representative soil samples were collected during March-April, 2016 from four sites viz., rice field of Agricultural Research Station, Mannuthy (medium organic matter soil with a history of herbicide application: S1 Control), non- cropped area of Agricultural Research Station, Mannuthy (medium organic matter soil without a history of herbicide application: S1 Absolute control), rice field of Kole land, Alappad (high organic matter soil with a history of herbicide application: S2 Control), and non- cropped area of Kole land, Alappad (high organic matter soil without history of herbicide application: S2 Absolute control). Physical, chemical, and biological characterization of the soil samples were done before starting the experiment. Pot culture experiment with rice variety Jyothi was conducted in the kharif season of 2016 with twelve treatments and six replications in factorial CRD (four herbicides under each soil type + four controls). The herbicides included pendimethalin, oxyfluorfen, bispyribac-sodium, and cyhalofop-butyl. Pre emergence herbicides (pendimethalin and oxyfluorfen) were applied at six days after sowing (DAS) and post emergence herbicides (bispyribac-sodium and cyhalofop-butyl) at 16 DAS. Soil samples were analysed at six intervals viz., on the day of herbicide application, but two hour before, then at 7, 15, 30, and 60 days after herbicide application (DAHA) and at harvest so as to evaluate the changes in the chemical and biological properties. Data on analysis of soil samples before the period of experimentation revealed that soils from rice field of Kole land recorded physical, chemical, and biological characteristics which are more favourable for the growth of microflora. The chemical characteristics like pH, electrical conductivity, and organic carbon followed a decreasing trend towards the harvest in all the treatments. Decline in microbial biomass carbon (MBC) was observed upto harvest except on 60 DAHA. Pendimethalin treatment in S1 soil (medium organic matter) registered the highest per cent reduction in MBC with respect to control at different intervals. Percentage reduction in MBC due to herbicide application was comparatively lower in S2 (high organic matter) throughout the period of study. Activity of dehydrogenase, urease, acid phosphatase and alkaline phosphatase was higher in S2 compared to S1. In all cases, the enzyme activity increased upto 60 DAHA with slight variations and declined thereafter registering a peak at 60 DAHA. Among the four enzymes studied, urease recorded maximum increase at 60 DAHA followed by acid phosphatase, dehydrogenase and alkaline phosphatase. All the vegetative and yield parameters of rice were high in S2 (high organic matter soil) irrespective of the treatment combinations. Adverse effects of herbicides on the plant characters were minimal. Whole plant analysis for major nutrients also exhibited appreciably higher values in S2 compared to S1. Out of the five biological parameters analysed, microbial biomass carbon showed the highest variation from control at all the sampling intervals. The adverse effects of herbicides on MBC and enzyme activity followed the order: pendimethalin > bispyribac-sodium > oxyfluorfen > cyhalofop-butyl. Organic carbon had highly significant and positive correlation with all the biotic components viz., MBC, dehydrogenase, urease, acid and alkaline phosphatase activity at different sampling intervals consequent to herbicide application. Further study should be focused on identification of microbial diversity, effect of rhizosphere on biological activity and analysis of biological parameters with respect to crop growth stages consequent to herbicide application.
Effect of water management and lime on iron toxicity and yield of paddy
(Kerala Agricultural University, 1996) Durga Devi, K M; Gopi, C S; Santhakumari, G; Prahhakaran, P V
A field experiment was conducted during rabi and summer seasons of 1991-92 in paddy fields of Chalakudy Command Area, in order to study the effect of a single top dressing of lime on iron toxicity and yield of paddy under different water management practices. Considerable reduction in Fe' * concentration could be noticed in soil as well as plant during the period of panicle initiation when lime was applied entirely as one top dressing (at 20 days after transplanting or 30 days after sowing). Application of lime 9 500 kg ha' as single top dressing resulted significantly higher grain and straw yields of paddy as compared to lime >8> 300 kg ha ', 900 kg ha ' and no lime application. The economic level of lime for getting maximum profit from grain and straw was 568 kg ha ' and 635 kg ha1 for the rabi and summer crops respectively.
Evaluation of available phosphorus and potassium in soil using a common extractant
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1986) Durga Devi, K M; Jose, A I
A laboratory evaluation and an uptake study using Neubauer seedling technique was carried out for evolving a single extractment suitable for extracting both available P and available K, so as to simplify the process of extracting these available plant nutrients in soil testing works. Eighty seven soil samples from different parts of the State were used to evaluate the performance of the selected number of extractants based on a 3 step evaluation i.e., (i) an initial study consisting one soil, 18 extractants at a single soil solution ratio (1:10) and two equilibration periods (30 and 60 min); (ii) a preliminary screening consisting of 9 soils, 15 extractants at a single soil solution ratio (1:10) and 5 equilibration periods (5, 10, 15, 30 and 60 min). An uptake study was also conducted using Neubauer seedling technique and correlation coefficients were worked out between the amount of P extracted by the various extractants and the P and K uptake by rice; (iii) a final selection of the common extractant consisting of 10 extractants with suitable equilibration periods, at 1:10 soil solution ratio and 87 soils. In combination of NH4 F and DTPA, increasing concentration of NH4 F retarded the extraction of both P and K and they extracted much smaller quantities of P and K as compared to that of Bray No.1 and neutral normal NH4 OAC. Use of ammonium acetate along with Bray No.1 inhibited the release of P drastically. Mathew’s triacid extractant viz., 0.06 N H2 SO4 + 0.06 N HCL + 0.05 N oxalic acid extracted relatively large amounts of P and K. The pattern of P and K release when examined together as a function of period of equilibration found that the equilibration period for different extractants was varying. The suitable equilibration period for 0.1 M NH4F + 0.001 M DTPA, 0.1 M NH4F + 0.003 M DTPA, 0.5 M NH4F + 0.005 M DTPA, 0.05 M NH4F + 0.05 M acetic acid, and Dray No. 1 is 5 min. for 0.3 M NH4F + 0.001 M DTPA combination and Bray No.1 + 0.005 M DTPA an equilibration period of 10 min is found to be the optimum. An equilibration period of 30 min is suitable for Mathew’s triaced extractant, Olsen’s extractant and neutral normal ammonium acetate. Since the initial and preliminary studies established the suitability of Bray No.1 for available P and the neutral normal ammonium acetate for available K and because the coefficient of correlation between the amount of K extracted by the extractants and the K uptake by rice were highly significant at all the equilibration periods the final selection of the common extractant was based on the correlation of the P and K values of the selected extractants with that of Bray No. 1 P and neutral normal ammonium acetate extractable K. The correlation coefficients with Bray No.1 P established by the various extractants have shown the following decreasing order of efficiency. 0.5 M NH4F + 0.005 M DTPA > 0.05 M NH4F + 0.05 M acetic acid > NH4OAC > Olsen > Mathew’s triacid > Bry No.1 + 0.005 M DTPA > 0.3 M NH4F + 0.001 M DTPA > 0.1 M NH4F + 0.001 M DTPA > 0.1 M nH4F + 0.003 M DTPA. All the extractants were not significantly and positively correlated with NH4 OAC (std) K. The three extractants viz., Mathew’s triacid, 0.1 M NH4F + 0.001 M DTPA and Olsen’s extractant have given significant positive relationship with NH4 OAC (std) K. Highest correlation was obtained with Mathew’s triacid followed by 0.1 M NH4F + 0.001 M DTPA and Olsen’s extractant. Thus it is confirmed that Mathew’s triacid extractant is the best common extractant for available P and available K. No analytical difficulty in the determination both P and K was observed while using this extractant. Inter-correlations worked out between the various soil properties have cleared the following facts. Mathew’s triacid P and Bray No.1 P were significantly and positively correlated with total P and negatively correlated with P fixing capacity. NH4 OAC (std) K and Mathew’s triacid K gave significant positive correlation with total K as well as CEC. Mathew’s triacid extractant viz., 0.06 N H2SO4 + 0.06 N HCL + 0.05 N oxalic acid with a soil solution ratio of 1:10 and an equilibration period of 30 min is recommended as a commom extractant for available P and available K by the present study, since it saves considerable time and materials in soil testing.
Evaluation of available phosphorus and potassium in soil using a common extractant
(Kerala Agricultural University, 1986) Durga Devi, K M; Jose, A I
A laboratory evaluation and an uptake study using Neubauer seedling technique was carried out for evolving a single common extractant suitable for extracting available P and available Kso as to simplify the process of extracting these available plant nutrients in soil testing work. The study was conducted in three phases, viz., an initial study, preliminary screening and a final selection using different extractants. The triacid (0.06 N H2S04 + 0.05 N HCI + 0.05 A/ oxalic acid) with a soil solution ratio of 1 :1 0 and equilibration period of 30 min was found to give very good correlation with Bray No. 1 P and NH4OAc (std) K and this extractant can be recommended for different soils of the state.
Evaluation of phosphogypsum as an ameliorant in acid soil under wetland ecosystem
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikara, 2023-04-20) Anusree T.; Durga Devi, K M
The present investigation entitled “Evaluation of phosphogypsum as an ameliorant in acid soil under wetland ecosystem” was conducted at the Dept. of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur during 2018-2022. The study aimed to assess the suitability of phosphogypsum and its combination with liming materials or rock phosphate and organic manure, for the amelioration of soil acidity, management of iron and aluminium toxicity, enhancement of nutrient availability, and finally to increase rice productivity under wetland conditions. The investigation was conducted in four experiments viz., a soil characterization study, a pot culture experiment, an incubation study, and a field experiment. The first three experiments were conducted at the College of Agriculture, Vellanikkara, Thrissur and the field experiment was carried out in a farmer’s field at Elavathur in Mullasseri Kole land of Thrissur district. Initially, ten soil samples were collected from Pavutai Padashekharam of the Mullasseri panchayath before the cultivation of the crop and were characterized for its major physical, chemical, and biological properties. The pot culture experiment with rice as a test crop was carried out on the acid soil collected from Pavutai padashekharam to study the effect of phosphogypsum and its combination with liming material or rock phosphate and organic manure, on soil acidity and availability of nutrients with 13 treatments comprising T1 (PG), T2 (RP), T3 (Lime), T4 (Dolo), T5 (PG+lime+VC in the ratio 1:8:1), T6 (PG+Dolo+VC in the ratio 1:8:1), T7 (PG+RP+VC in the ratio 1:8:1), T8 (Dolo+RP+VC in the ratio 5:4:1), T9 (PG+lime in the ratio 1:3 ), T10 (PG+Dolo in the ratio 1:3), T11 (PG+RP in the ratio 1:3), T12 (Dolo+RP in the ratio 1:1 ) and T13 (Control). The combinations of amendments in different ratios were based on the Ca requirement of the soil. These treatments were applied to the soil for providing the required Ca quantity of 140 kg Ca ha-1 which is decided based on the soil pH and the added quantity of different amendments was decided based on the Ca content of the amendments. Phosphogypsum @ 823.09 kg ha-1, rock phosphate @ 605.68 kg ha-1, lime @ 197.07 kg ha-1 and dolomite @ 466.46 kg ha-1 were supplied in treatments with their sole application.
Evaluation of water hyacinth co- composts for nutrient retention in lateritic soil
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Anisha, V A; Durga Devi, K M
Water hyacinth is a serious menace in low land ecosystems and it’s spread has threatened water quality and aquatic life. Various biological, chemical and physical methods that have been employed to control the weed has yielded minimal results. Hence management through utilization is a viable strategy. It can be effectively utilized in many ways to support crop production. Co-composting has been proved as a promising technique for safe and quick disposal of the weed by utilizing the co-substrates viz., poultry manure, sawdust, biochar, glyricidia, paddy straw, dried leaves and cattle manure. As the weed accumulates N, P, K and other essential nutrients, compost made from water hyacinth can be utilized for improving soil fertility and crop production. Hence, the present investigation entitled “Evaluation of water hyacinth co-composts for nutrient retention in lateritic soil” was under taken in the Department of Soil Science and Agricultural Chemistry at College of Agriculture, Vellanikkara during 2020-2021. The objectives were; (i) To find out the suitable combination of water hyacinth and co-substrates for enhancing the quality of water hyacinth composts (ii) To assess the nutrient retention capacity of different co-composts in lateritic soil. Different co-substrates were collected from nearby areas and water hyacinth was collected from Kole lands of Thrissur. Water hyacinth and co-substrates were characterized prior to composting. Water hyacinth co-composts (vermi compost) were prepared using the aforesaid substrates in concrete tanks. The physical and chemical properties of the composting mixtures were recorded at 40 days interval starting from 20 days of composting until 100 days. The yield of water hyacinth co-composts was estimated and the various co-composts were characterized for their physical and chemical properties. Incubation study was conducted to evaluate the nutrient retention capacity of different water hyacinth co-composts in lateritic soil during December 2020 with eight treatments and three replications (soil+ 7 co-composts and soil alone as absolute control). The lateritic soil for study was collected from Instructional Farm, Vellanikkara and analysed for chemical properties. Compost amended soils were incubated for a period of 28 days and nutrient retention capacity (N, P, K, Ca, Mg, S, B, Zn) was estimated at 4 different time periods after incubation (7, 14, 21, 28 days). Data on characterization of co-substrates revealed that substrates vary in their chemical properties and nutrient content. Among the co-substrates, poultry manure possessed many favourable characteristics. Changes in physical and chemical properties of composting mixtures at different intervals indicated the progress of composting process and stage of compost maturity. All the co-substrates gave reasonably good yield of water hyacinth co-composts. A notable increase in compost yield to an extent of 159.7 per cent was realized in the biochar treatment. Addition of co-substrates improved the bulk density and porosity of water hyacinth co-composts. Application of co-substrates improved the pH of final compost. Highest increase was noticed in the treatment with paddy straw. Addition of paddy straw had significant adverse effect on the electrical conductivity of final co-compost (170.6 % increase in EC over water hyacinth sole treatment) and all the other treatments showed EC below maximum permissible limit for plant growth. The total carbon content of all the co-composts was higher than water hyacinth sole compost. Nitrogen content of the co-compost was improved to a greater extent by the application of paddy straw and poultry manure. Co-composts with sawdust, biochar and dried leaves had significantly lower quantity of nitrogen compared to water hyacinth sole compost. Glyricidia and poultry manure were highly effective in improving total phosphorus content of the co-compost. Total potassium content of water hyacinth compost was significantly improved with the addition of co-substrates like paddy straw and biochar, the extent of increase being 192 and 170 per cent, respectively. Carbon to nitrogen ratio of water hyacinth co-compost was significantly lowered by using poultry manure as a co-substrate. Addition of poultry manure improved all the three secondary nutrients viz., Ca, Mg and sulphur to a higher magnitude. No favourable effect was noticed on the boron content of co-compost by the addition of different co-substrates. However, Fe and Mn levels of final co-composts were considerably lower than the water hyacinth sole compost. This could be considered as a favourable effect of co-composting of water hyacinth with different substrates. Zinc content of the co-compost was significantly improved by the inclusion of co-substrate particularly with the use of poultry manure and dried leaves. Copper content of the co-compost was significantly higher with the addition of poultry manure as co-substate. The addition of co-compost to lateritic soil, improved retention of nutrients particularly nitrogen. The only exception was co-compost with paddy straw (0.9 per cent decrease in the nitrogen retention capacity). Irrespective of the treatments, cocompost retained all the phosphorus and boron present in the co-compost amended soil. The soil’s potassium, magnesium, sulphur and zinc retention capacity could be improved when amended with water hyacinth co-compost. In general, soil with biochar co-compost showed significantly high retention capacity with respect to plant nutrients particularly nitrogen. Further study should be focused on field experiments to test the agronomic efficiency of different water hyacinth co-composts, testing suitability of various crop residues and organic wastes as co-substrates and to derive suitable substrate combinations and ratios to eliminate the adverse effects of co-substrate on compost quality.
Impact of glyphosate and chlorpyriphos on chemical and biological properties of lateritic soil
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2014) Shitha, C R; Durga Devi, K M
The thesis entitled "Impact of glyphosate and chlorpyriphos on chemic I a d biological properties of lateritic soil" was done in the year 2012-2013 in the Dep rt e of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikara. The programme consisted of laboratory experiment viz., avoidance behaviour of earth orm, pot culture study on survival of earthworm and soil micro flora under the different pesticide treatments and two field experiments viz., application of (1) glyphosate and (2) chlorpyriphos in cropped area and lawn respectively. The laboratory and pot culture studies consisted of seven treatments. The treatme ts included two levels of application (recommended and double the recommended dose) of t 0 formulations of glyphosate (1.2 and 2.4 kg a.i. ha") and single chlorpyriphos formulati n (400 and 800 g a.i. ha") and an absolute control. Glyphosate formulations namely Roundup® and Glycel® were applied at 6 and 12 mL L-I respectively and chlorpyriphos formulation Dursban® was applied at 4 and 8 mL L-I. The main observations included in this research programme were biological properties of soil viz., earthworm count, total microbial count, dehydrogenase activity and chemical properties of soil viz., pH, organic carbon, available P, K Ca, Mg, Fe, Zn, Cu and Mn. Both laboratory and pot culture experiments were done with native earthworms. The laboratory experiment was done to understand the avoidance behavior of earthworm to t e two glyphosate formulations and chlorpyriphos. This study showed that all the chemicals were avoided by earthworms and the maximum avoidance was obtained with the application of Roundup® (12 mL L-I) followed by Glycel® (12 mL L-I) and Dursban® (8 mL L-I). Earthworm avoidance test done by two methods of application (mixing as well as spraying) showed similar trends. However, higher net response was obtained by mixing the pesticides in soil. Spraying on the surface imitated the field situation, in which the avoidance response ranged from 20.0 to 46.7 %, while in the case of mixing the pesticides with the soil, the avoidance response ranged from 33.3 to 73.3 %. When the soil was mixe with the chemicals, the earthworms had direct contact with the pesticides throughout the treated soil section and thus they had shown greater tendency to avoid the area. Pot culture studies on the survival of earthworms revealed that neither glyphosate nor chlorpyriphos had deleterious effects on their multiplication. The study also showed that both soil fungi and bacteria were affected by application of glyphosate and chlorpyriphos. The adverse effect of chemicals on the soil fungi followed the order Roundup 12 mL i.' > Dursban 8 mL r.:' > Glycel 12 mL r.:' > Dursban 4 mL i.' > Roundup 6 mL i.' > Glycel 6 mL r.'. Percent decline in the fungal population was 10.1 to 70.5 at one week and 5.8 to 62.9 at one month after application. It was noticed that Roundup and Glycel at the recommended rates of application did not cause adverse effect on soil fungi at one month after spraying, indicating that the effect was temporary. However, chlorpyriphos formulation caused a significant decline in the fungal population at both the sampling intervals. In the case of bacteria, percentage decline over control followed the order Roundup 12 mL i.' > Glycel 12 mL i.' > Roundup 6 mL r.' > Dursban 8 mL i.' > Glycel6 mL Cl> Dursban 4 mL i.', at one week after spraying and the extent of decline ranged from 14.3 to 71.6%. At one month, the effect of chlorpyriphos (Dursban) on bacteria was comparatively lower than that of glyphosate formulations at both the concentrations. Two field studies were conducted to find out the effect of application of glyphosate in cropped area (banana field) and chlorpyriphos in the lawn. Experiment in the banana field was conducted with five treatments namely Roundup® and Glycel® each at 6 and 12 mL i.' and an absolute control. The treat~ents were replicated four times. Studies with chlorpyriphos were carried out in the established lawns of the College of Horticulture, Vellanikkara with three treatments viz., Dursban® at 4 and 8 mL L-land seven replications. Both biological and chemical properties were studied. It was found that application of . glyphosate caused short term inhibitory effect on soil fungus up to 30 days after spraying, where as application of chlorpyriphos caused short term inhibitory effect on soil bacteria (up to 30 DAS). Population of soil micro flora did not vary between treatments at 60 days after spraying glyphosate and chlorpyriphos formulations. Dehydrogenase activity and available nutrients in the soil were unaffected by the application of glyphosate and chlorpyriphos formulations used in the study.
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 M
Influence of weed management practices on the soil quality attributes of ultisol
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2017) Shridhar, N; Durga Devi, K M
Persistence of selective herbicides in rice -rice system
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2003) Muthu Kannan, M; Durga Devi, K M
Soil test based fertilizer recommendation for ozhalapathy watersheds
(Kerala Agricultural University, 1993) Durga Devi, K M; Rajan, K C; Latif, P H
Standardisation of procedure for residue analysis of 2, 4-d in soil
(Kerala Agricultural University, Vellanikara, 2001) Durga Devi, K M; Abraham, C T; Chinnamma, N P
Standardization of bioassay technique for determining butachlor residues in kole soils of Kerala
(Kerala Agricultural University, 1999) Durga Devi, K M; Abraham, C T; Prabhakaran, P V
Different plant species were grown in pots containing soil fortified with known quantities of butachlor and based on the response to the herbicide amaranth was selected as the indicator plant for the herbicide. Among the several growth parameters tested for assessing the plant response to soil residues of butachlor, CSGR (compound shoot growth rate) proved to be the best for quantitative determination of butachlor residues in kole soils of Kerala.
Utilisation of potassium rich crop residues for retention of potassium in lateritic soil
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Sreelakshmi, P; Durga Devi, K M
Potassium is a versatile vital nutrient for regular plant and animal growth and development. It is regarded as a "quality nutrient" because of its multifunctional role in metabolism. Kaolinite clay minerals prevalent in lateritic soils of Kerala, have lower activity and prevent the retention of available forms of potassium. Potassic fertilisers are often overlooked in fertiliser schedules due to their high unsubsidized cost. There are some K rich organic sources that are ignored by the farmers and are left or burnt in the soil. The utilisation of organic K resources like rice straw and plantain compost made from banana wastes are regarded good alternatives for synthetic potassic fertilisers. The present investigation consisted of three experiments viz., (i) assessment of decomposition dynamics of rice straw and its K release, (ii) K adsorption study on rice straw and prepared plantain compost and (iii) an incubation study in lateritic soil with different sources of potassium. The decomposition rate of rice straw has increased with the period of its incubation and it showed only a partial decomposition of 51.9 % at 90 days due to the presence of more amount of lignin, cellulose and hemicellulose content which takes more time for its degradation. The potassium release rate increased to 84.28 % at 90 days of its decomposition. The adsorption study on rice straw with different levels of KCl solution at different periods of decomposition revealed that as the solution concentration increased, the quantity of K adsorbed on rice straw also increased along with the increase in incubation period. Similarly, plantain compost that was prepared using vermi technology also showed an increased trend in the value of quantity of K adsorbed on compost as the KCl concentration increased. Because of its smaller particle size and larger surface area, plantain compost has stronger adsorption and buffer power than rice straw. Rice straw with potash (T1), plantain compost with potash (T2), wood ash, FYM with potash (T3), rice straw with lime and potash (T4), plantain compost with lime and potash (T5), wood ash, FYM with lime and potash (T6), lime and potash (T7), potash alone (T8), and absolute control (T9) treatments were used in the incubation study. The physico-chemical characteristics of soil such as pH, EC, organic carbon, available N, P, Ca, Mg, S, Fe, Cu, Zn, and Mn were determined at initial and final days of incubation. Data on the different fractions of soil K indicated that the treatment containing rice straw with lime and Muriate of potash (T4) showed the higher value of total K, exchangeable K and non-exchangeable K after 90 days of incubation. The reason might be that the presence of more inter planar sites in rice straw has trapped the K+ ions in fixed form since the material is not completely decomposed. At the same time incorporation of rice straw has enhanced the CEC of the soil thus enhancing greater adsorption of exchangeable K from unavailable forms by mass effect. The current study showed that combining organic K resources with lime and K fertilisers resulted in significant increases in soil K fractions. Integrated application of rice straw with lime and K fertiliser can be considered as the best method for long-term cultivation because it has the ability to retain and release more K, particularly nonexchangeable, exchangeable, and total K, allowing for continuous uptake of K by the crops for normal growth and development. The usage of plantain compost in combination with lime and Muriate of potash has resulted in increased availability of K as well as micronutrients by maintaining favourable pH.