PhD Thesis

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Start date: 2010Subject: search.filters.subject.Soil Science and Agricultural Chemistry

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    Residue dynamics and mobility of flonicamid and dinotefuran insecticides in soil and assimilation by rice (Oryza sativa (L.))
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani , 2024-12-19) Sakthiselvi, T.; Thomas George
    A study entitled “Residue dynamics and mobility of flonicamid and dinotefuran insecticides in soil and assimilation by rice (Oryza sativa (L.))” was carried out at the Department of Soil Science and Agricultural Chemistry and Pesticide Residue Research and Analytical Laboratory, College of Agriculture, Vellayani, Thiruvananthapuram during 20202024, with the objective to investigate the persistence, transformation and mobility of flonicamid and dinotefuran formulations in soils, loss through leachate and the uptake and dissipation of residues in rice. The experiment comprised of the following lead topics viz. determination of initial physicochemical properties of sandy clay loam soils, method validation, persistence study, mobility experiment, leachate experiment, field experiment, effect of processing operations on residues and effect of residues on soil microbial activity. Initial properties of the experimental soil were determined to relate their possible influence on insecticide residue behaviour. The soil had sandy clay loam texture (56.28 % sand, 14.30 % silt and 29.42 % clay) and was strongly acidic (pH: 5.05), non-saline (EC: 0.2 dS m-1) with high organic matter (1.59 %) content. An efficient method for extraction and estimation of residues was validated by conventional liquid-liquid extraction and QuEChERS extraction method in rice crop, soil and water matrices for flonicamid, TFNA, TFNA-AM, TFNG, dinotefuran, DN-HCl and DNurea. Conventional method showed lower recovery, however, QuEChERS method was highly efficient with recovery rates within acceptable limits of 70-120 % for both parent compounds and their metabolites. QuEChERS method further validated in terms of linearity had correlation coefficient above 0.99. Precision evaluated in terms of relative standard deviation (RSD %) and Horwitz ratio had deviations within the tolerable limits of 20 % and 2, respectively. Low to medium matrix effect was obtained for all the analytes, therefore, matrixmatched standards were used for calibration to compensate it. Sensitivity determined in terms of limit of detection (LOD) and limit of quantification (LOQ) was 0.003 and 0.01 µg g-1. Thus, QuEChERS method which was proved best in terms of validation parameters of recovery, precision, linearity and matrix effect was adopted for all the experiments for sample processing. Persistence experiment was executed under two soil moisture conditions viz. field capacity and flooded condition with four insecticide concentrations viz. 0 (control), 1, 2 and 4 mg kg-1 in the laboratory. The initial residues were higher for flonicamid in the range of 0.5531.315 and 0.514-1.153 mg kg-1, respectively, under field capacity and flooded condition, than dinotefuran in the range of 0.532-1.044 and 0.238-1.041 mg kg-1. TFNA was found to be the major flonicamid metabolite under both moisture conditions with persistence till 15th day under field capacity and 80th day under flooded condition. TFNG and TFNA-AM appeared during the first week at higher concentrations under both moisture conditions. DN-HCl and DN-urea were formed only under flooded condition whereas degradation did not happen under field capacity. Dissipation data showed that flonicamid and total flonicamid had faster dissipation under field capacity with half-lives (DT50) of 1.41-3.33 days than flooded condition with DT50 of 16.90-49.50 days, whereas dinotefuran and total dinotefuran degraded faster under flooded condition with DT50 of 11.55-106.61 days than field capacity with 138.60-346.50 days. The mobility experiment involved assessing the residues of soil cores and leachates after loading 150 µg of standards of flonicamid and dinotefuran in separate columns of 50 cm length and subsequent elution with 20, 40, 80 and 160 ml of water. Significant differences in residue retention of 61.85, 58.79, 44.15 and 25.80 % for flonicamid and 72.19, 55.65, 38.62 and 21.96 % for dinotefuran were observed in the top 20 cm layer respectively after 20, 40, 80 and 160 ml of water application. Mobility of metabolites (TFNA and DN-HCl) increased significantly with increased water application. In leachates, flonicamid and dinotefuran in the range of 0.022-1.115 and 0.032-1.393 µg, respectively, were detected after 40, 80 and 160 ml of water application. TFNA was the only metabolite found in leachates at a concentration of 0.069-0.199 µg. Leachate experiment was carried out in metallic trays of 60 x 30 x 20 cm3 volume. The trays were three-fourths filled with soil, planted with rice seedlings and were irrigated every day to maintain the flooded condition. Plants were sprayed with flonicamid (Ulala 50 % WG) and dinotefuran (Token 20 % SG) after 50 days of planting at the recommended dosage of 75 and 30 g a.i. ha-1, respectively and samples were analysed for residues. Dissipation data showed that flonicamid degraded with DT50 of 6.36, 1.96 and 9.49 days, whereas, dinotefuran had DT50 of 10.19, 2.81 and 6.93 days in plant, soil and leachate water, respectively. TFNA, TFNA-AM and TFNG appeared as major flonicamid metabolites in plants with DT50 of 9.49, 8.25 and 12.38 days, respectively. In soil and leachate samples, TFNA was the only major metabolite with DT50 of 22.35 and 7.62 days, respectively. However, DN-urea was the only dinotefuran metabolite formed in plants. Persistence and dissipation kinetics of insecticides under open field rice ecosystem were ascertained by conduction of supervised field trials with treatments including two formulations viz. flonicamid and dinotefuran and three application frequencies (25, 25 & 50 and 25, 50 & 75 days after transplanting). In rice leaves, higher initial residues were recorded for flonicamid of 14.80-17.38 µg g-1 than dinotefuran of 2.56-3.48 µg g-1. The residues persisted up to 20th and 10th day with DT50 in the range of 2.75-3.13 and 1.62-2.21 days for flonicamid and dinotefuran, respectively. The safe waiting period for fodder use was calculated to be around 25 days for flonicamid, however, it was found to be safe immediately after application for dinotefuran. Significant differences in the DT50 values were obtained for chemical type, however, no significant effect was observed among application frequencies. In soils, residues were not detected in any of the treatments irrespective of chemical type and application frequencies. In rice grains, initial residues of 3.02 and 1.13 µg g-1 with DT50 of 9.01 and 7.05 days for flonicamid and dinotefuran, respectively, were registered. The residues persisted till 20th day for dinotefuran, while flonicamid residues persisted during the entire study period of 25th day. The harvested field samples including straw, soil and grain samples were processed and residue occurrence was studied. Only the grain samples obtained from triple application frequencies contained flonicamid residues above LOQ which were subjected to processing operations like parboiling, hulling, milling and cooking to determine the effect on residues. Cooking was proved to be most effective followed by parboiling in the removal of residues. The human dietary risk assessment was assessed in terms of estimated daily intake (EDI) and risk quotient (RQ). The calculated EDI was less than the acceptable daily intake (ADI) value of flonicamid and dinotefuran. RQ values were worked out to be < 1, suggesting that consumption of rice grains was under acceptable level of risks. The effect of flonicamid and dinotefuran residues on soil microbes was studied through dehydrogenase activity and microbial population by analysing the treated samples of field soil from 0th to 45th day. Soil dehydrogenase activity significantly reduced after each treatment with increased application frequency showing greater reduction. Among the chemical types, dinotefuran had much impact with activity range of 67.85-77.31 µg TPF g-1 hr-1 than flonicamid with 73.37-83.25 µg TPF g-1 hr-1 on the day of application. The activity started recovering after a month of application in all the treatments. The impact of residues on the population showed that, bacteria were highly affected followed by actinomycetes and fungi were least affected. The effect was higher in plots treated with dinotefuran three times. In a nutshell, the persistence of dinotefuran was significantly higher than flonicamid which could be influenced by soil properties. The mobility and leachate study confirmed that, the chemicals have higher leaching potential, hence careful management under flooded conditions is necessary to prevent contamination of water bodies. The field study showed that, both the insecticides degraded at a faster rate with very short DT50 of within 10 days (nonpersistent) in rice and soil samples. Hence, foliar spray of flonicamid and dinotefuran at the recommended dose in repeated sprays were safe for consumption which is supported by the associated dietary RQ of < 1. Processing operations of harvested samples showed that the extent of residue reduction were observed to be cooking (82.79 %) > Parboiling (61.06 %) > Milling (42.25 %) > Hulling (26.80 %). Increased number of sprayings and dinotefuran chemical type were found to have a significant impact on soil dehydrogenase activity and microbial population for one month period which recovered to the original level presumably due to dissipation of residues. The research underscored the relatively safe nature of flonicamid and dinotefuran in rice field ecosystem under Kerala’s climatic conditions, implying the adoption of these chemicals have the potential for sustainable management of sucking insects.
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    Residue distribution and mobility of chlorantraniliprole formulations in soil and it's uptake by rice (Oryza sativa L.)
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2023-03-28) Greeshma Suresh.; Thomas George
    The study entitled ‘Residue distribution and mobility of chlorantraniliprole formulations in soil and its uptake by rice (Oryza sativa L.)’ was conducted at the Department of Soil Science and Agricultural Chemistry and the laboratory attached to the All-India Network Project (AINP) on Pesticide Residues, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala during 2018-22. The main objectives of the experiment were to investigate and understand the persistence, transformation, and mobility of chlorantraniliprole in soils and leachate water and the uptake and dissipation of residues in rice (Oryza sativa L.) The study was conducted in laterite and coastal alluvium soils of Kerala. The representative soil samples of laterite soil were collected from the fields located within the campus of the College of Agriculture, Vellayani and coastal alluvium soils from the wet lands of the Integrated Farming System Research Station, Kerala Agricultural University, Karamana (8.4736 ⸰N; 76.914 ⸰E). The physical and chemical properties of respective soils revealed that, laterite soil was moderately acidic (pH 5.7) and coastal alluvium soil was strongly acidic (pH 5.2) in nature. The bulk density and particle density of the laterite soil was 1.60 and 2.65 Mg m-3and 1.36 and 2.57 Mg m-3 for coastal alluvium soil respectively. The electrical conductivity was 0.27 and 0.28 dS m-1 for laterite and coastal alluvium soil respectively. The cation exchange capacity of the soil was found to be 3.41 and 5.18 cmol (+) kg-1 for laterite and coastal alluvium soils respectively. The organic carbon was high in coastal alluvium soil (1.07 %) than laterite soil (0.63 %). The estimated major primary nutrient content was, available nitrogen (203 kg ha-1 and 338.69 kg ha-1); available phosphorus (21.7 kg ha-1and 14.48 kg ha-1); available potassium (228 kg ha-1and 121 kg ha-1) respectively. The secondary nutrients such as calcium, magnesium and sulphur were found to be 250, 42 and 43 ppm for laterite soil and 230, 132, 98 ppm for coastal alluvium soil respectively. A suitable method was validated for standardizing the analytical procedures for estimation of chlorantraniliprole residues in soil, plant, water, grains and straw by QuEChERS method and liquid-liquid partitioning using dichloromethane (DCM) in water. The residues were estimated and quantified by using LC-MS/MS and the method gave satisfactory recovery values of chlorantraniliprole for soil, water, and plant with good RSD (%) for recoveries. The analytical procedures gave good recovery for the chlorantraniliprole residues when spiked with 0.01, 0.05, 0.10, 0.5 and 1.0 levels and LOQ of chlorantraniliprole was determined as 0.01 mg kg-1. The recovery percentage ranged from 90.34 - 96.12 and 84.91 - 95.57 in laterite and coastal alluvium soils respectively. Similarly, the recovery percentage ranged from 97.72 - 99.75, 94.93 - 96.16, 88.97- 95.43 and 89.63- 95.43 respectively in water, plant, straw, and grains. The studies on persistence of chlorantraniliprole in laterite (S1) and coastal alluvium soils (S2) were performed under two different soil moisture conditions viz., field capacity (M1) and flooded (M2) by spiking (1, 2 and 4 mg kg-1) under laboratory conditions. The residues were estimated and quantified by using LCMS/ MS method. The half- life of chlorantraniliprole in the laterite soil when applied at 1, 2 and 4 mg kg-1 levels under the field capacity were 10.01, 15.67 and 21.16 days and the half- life 7.45, 10.25 and 12.69 days under flooded condition respectively. Similarly, the half- life of chlorantraniliprole in the coastal alluvium soil when applied at 1, 2 and 4 mg kg-1 levels were 13.84, 17.10 and 23.88 days under the field capacity and 9.18, 10.72 and 13.35 days under flooded condition respectively. The persistence was higher in coastal alluvium soil and degradation of chlorantraniliprole was faster at flooded condition than in field capacity condition for both the soils. Application of chlorantraniliprole at higher concentrations resulted in prolonged persistence compared to lower application levels. Mobility of chlorantraniliprole in laterite and coastal alluvium were assessed by analyzing the residue at different depths after loading 150μg of chlorantraniliprole followed by subsequent elution with 20ml, 40ml, 80ml and 160 ml of water equivalent to 50mm, 100mm, 200mm and 400mm rainfall. Majority of the residues were accumulated in 0- 5cm cross sections of the tube and presence of residues in lower layers were indicated by increasing the level of irrigation. The percentage of chlorantraniliprole residues in top 0 -5 cm in laterite soil was 63.73, 52.31, 31.48 and 27.77 and coastal alluvium was 73.46, 56.58, 34.48 and 25.70 on elution with 20ml, 40ml, 80ml and 160 ml of water respectively. Leaching potential was higher for laterite soil compared to coastal alluvium soil due to presence of low clay and organic matter content. Chlorantraniliprole residues were detected in leachate water for soil columns eluted with 160 ml of water for both the soils, whereas, the residues detected in leachate water was below limit of quantification (LOQ) in soil columns eluted with 20, 40 and 80 ml of water. Research data revealed that, type of soil, level of irrigation and depth of soil column influenced the mobility of chlorantraniliprole in soil The field experiment was conducted at the research fields of the Integrated Farming System Research Station, Karamana, Kerala Agricultural University. The study proposes to understand the probable side effects and residue accumulation in leaf, grains, and straw after the use of two different formulations of chlorantraniliprole viz., chlorantraniliprole 18.5 SC (Coragen ) and chlorantraniliprole 0.4 % G (Ferterra) each at 30 and 40 g a.i per ha, respectively in rice, the most important staple crop of Kerala, when applied to the treatment plots. The frequency of application was single - 25 days after transplanting (DAT), double (25 and 50 DAT) and triple (25, 50 and 75 DAT) applications. The persistence and dissipation pattern in soil and plant and the respective half-life values were calculated under field condition. The calculated half-life values of chlorantraniliprole for foliar (Coragen 18.5 SC) applications for T1 (single), T2 (double) and T3 (triple) were 6.93, 7.24, 8.9 days, respectively. Similarly, half-life for soil application of chlorantraniliprole (Ferterra 0.4 % G) T4 (single), T5 (double) and T6 (triple) were 7.63, 8.2, and 10.8 days respectively, in soil. The half-life values in plants were 9.15, 11.8 and 12.59 days for T3, T5 and T6, respectively. Chlorantraniliprole residues in straw and grains obtained from field study were also estimated. The residues detected in straw for treatments T3, T5 and T6 were 0.183, 0.076 and 0.282 mg kg-1 respectively. The residues in T1, T2 and T4 were found to be below the limit of quantification (LOQ). The residues in fresh grains and after parboiling were estimated and from which the extent of removal of residues was determined. The parboiling of grains was found to be an effective method of decontamination by higher dissipation of residues. In the case of grains, the initial residues detected in T3, T5 and T6 were 0.143, 0.283 and 0.382 mg kg-1 and on parboiling, this was reduced to 0.045, 0.106 and 0.159 mg kg-1 respectively. The per cent dissipation after parboiling were 68.53, 62.54 and 58.37 per cent for T3, T5 and T6, respectively. The studies on metabolism/ transformation products of chlorantraniliprole revealed that, no toxic metabolites were detected in soil or any plant parts. The soil enzyme activity tests were used as a measure of metabolic activity of micro-organisms in soil from field application. The residual effect of chlorantraniliprole formulations on soil microbes were also assessed indirectly using enzyme assays viz., dehydrogenase and urease activities in soil. The soil samples were collected from field experiment plot, at 0th, 15th, 30th, 45th and 60th day after application of chlorantraniliprole. In coastal alluvium soil, the dehydrogenase as well as urease activity was reduced due to the residual effect of chlorantraniliprole. Granular formulation (Ferterra 0.4 G) had more impact on activity of soil microbes, compared to foliar formulation (Coragen 18.5 SC). The frequency of application also influenced the soil microbial activity and the enzyme activities approached to control conditions by the 75th day after the last application for all the treatments except T6. Leachate study was conducted in tray by application of Ferterra 0.4 % G in two soils viz., laterite and coastal alluvium soil under cropped condition and collection of leachate water as well as soil for residue analysis. The dissipation pattern showed higher persistence of chlorantraniliprole in coastal alluvium soil than laterite soil, but residues detected in leachate water was more in laterite soil. In brief, laterite soils had higher dissipation potential than coastal alluvium soils. The persistence of chlorantraniliprole under field capacity condition was higher than flooded condition for both the soils. The mobility of chlorantraniliprole was found to be slightly higher in laterite soil compared to coastal alluvium soil and indicates its moderate mobility behavior. There exists a possibility of groundwater pollution with the application of higher concentration of chlorantraniliprole or due to heavy rainfall. The application of chlorantraniliprole formulations on crops in laterite soil may cause higher risk of groundwater contamination than coastal alluvium soils. The presence of higher amount of organic matter content in coastal alluvium soils is responsible for reducing the downward flow in soil profile to an extent. Field study revealed that, foliar application had lower residual effect than soil application of chlorantraniliprole. The frequency of application and type of formulation also affect the residual activity in soil and plants. Soil microbial activity was reduced initially but shifted to normal conditions within 60 days after application for single and double application, and by 75 days in the case of triple application of chlorantraniliprole (Ferterra 0.4 % G). The present findings may be used for modelling the environmental fate of chlorantraniliprole in laterite and coastal alluvium soils under different moisture levels and field conditions. The optimum use of chlorantraniliprole with recommended dosage on crops and soil along with field application of organic matter can prevent the ground water contamination significantly. Detailed study in undisturbed soil column is recommended in future studies to give better insight on leaching and mobility of chlorantraniliprole in soil.
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    Influence of soil characteristics and fertility management practices on nutrient and antinutrient accumulation in amaranth (Amaranthus tricolor L.)
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture ,Vellanikkara, 2024-05-18) Dharmendranaik, E.; Beena, V I
    The research programme entitled “Influence of soil characteristics and fertility management practices on nutrient and antinutrient accumulation in amaranth (Amaranthus tricolor L.)” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, Kerala Agricultural University during 2017-2023. The study was programmed to determine the extent of accumulation of antinutrients viz., nitrate and oxalate in vegetable amaranth under different fertility management practices and to elucidate the relationship between soil characteristics and antinutrient accumulation. The investigation was carried out in three phases viz., (i) pot culture experiment with nine fertility management practices and two soil types, (ii) field experiment involving the best three fertility management practices selected from pot culture study and two varieties of amaranth viz., red (Arun) and green (CO-1) (iii) an evaluation of antinutrient status in the amaranth samples collected from farmer’s field. Initial steps included the characterization of electrochemical properties and nutrient status of soils collected from two different locations: (i) Chittur, Palakkad (Vertisol - alkaline soil: Typic Haplusterts) and (ii) Vellanikkara lateritic soil (Instructional Farm, Vellanikkara,very strongly acidic soil: Kandic Paleustalfs). A pot culture experiment was conducted from January to May 2019 in CRD with red amaranth variety “Arun” and 18 treatment combinations viz., nine fertility management practices and two soil types. The nine fertility management practices included in the experiment were: T1: Organic manure alone (Organic KAU-POP: FYM @ 25t ha-1); T2: KAU-POP (N: P: K -100:50:50 kg ha-1 + FYM + foliar spray of 1% urea); T3: T2 with foliar spray of amino acid-methionine 200 mg L-1 (instead of urea spray); T4: N: P: K - 100:75:75 + FYM + foliar spray of 1 % urea + lime as per soil test; T5: T4 with foliar spray of amino acid-Methionine 200 mg L-1 (instead of urea spray) + lime as per soil test based recommendation; T6: N: P: K -100:50:50 kg ha-1 in the form of Factamfos (basal), urea (top dress) and MOP +FYM +foliar spray of 1% urea; T7: T6 with foliar spray of amino acid -methionine 200 mg L-1(instead of urea spray); T8: Soil test based application of nutrients + foliar spray of 1%urea; T9: T8 with foliar spray of amino acid-methionine 200 mg L-1 (instead of urea spray). In all the treatments except T6 and T7, N and P were applied in the form of urea and superphosphate. In the treatments, T6 and T7, basal dose of 50: 50 kg ha-1 N and P were applied as Factamfos and the remaining 50 kg N as top dress in the form of urea. Potassium was applied in the form of MOP in all the treatments. In all the treatments,FYM was applied @ 25t ha-1 as per POP. The top-performing three fertility management practices were selected from the pot culture experiment based on two criteria viz., yield and antinutrient content (nitrate and oxalate). The field experiment was carried out in RBD with six treatment combinations from January to May 2022 at Agronomy Farm, College of Agriculture, Vellanikkara. For the evaluation of antinutrient status in the samples from farmers’ fields, fifteen amaranth samples each from two locations namely, Chittur and Madakkathara panchayat were collected. Fifteen soil samples pertaining to the sampled area were also collected. Soil and plant analysis for macro and micronutrients as well as antinutrients were also carried out. The data revealed that amaranth yield is comparatively lower in the first harvest. The second and third cuttings gave comparable yields. The total yield data from the three cuttings showed that the plant yield of amaranth did not differ significantly with soil type for the first and second harvests. However, Chittur soil exhibited a significantly higher yield than Vellanikkara soil for the third harvest. The total amaranth yield from the three harvests was significantly lower in organic manure alone treatment (109.16 g plant-1) and KAU POP (167.89 g plant-1) compared to the other treatments irrespective of the stage of harvest. Methionine spray gave a comparatively lower yield than urea spray. Soil test based application of nutrients performed better than KAU POP treatment. The treatments T4 and T6 (100: 75: 75 NPK and Factamphos treatments with urea spray) showed superiority over the other treatments in producing higher amaranth yield. Nitrate and oxalate contents in amaranth were significantly lower in Vellanikkara soil as compared to Chittur soil at all the three stages of harvest. Organic manure alone treatment registered the lowest value for nitrate as well as oxalate in both soils. Methionine treatments exhibited nitrate and oxalate levels similar to that of urea spray. While examining the nitrate and oxalate levels across the different harvest stages and treatments, it was found that nitrate and oxalate concentration in amaranth ranged from 953.58 (T1 second cut) to 4486.66 mg kg-1 (T8 third cut) and 2791.24 (T1 and T6 second cut) to 3843.66 mg kg-1 (T2 first cut) respectively. In order to understand the extent of reduction in nitrate and oxalate concentrations due to cooking, fresh amaranth samples from the first cut were steamed for 3-4 min., air dried and the analysis of nitrate and oxalate was carried out. It was found that the cooked amaranth samples had nitrate levels in the range of 931.33 (Organic KAU POP) to 1793.66 mg kg-1 (KAU POP) and oxalate levels in the range of 2301.00 (Organic KAU POP) to 3211.42 mg kg-1 (Factamphos treatment) across the different fertility management treatments. However, in the raw amaranth samples from the first cut, nitrate content ranged from 1202.66 (T9) to 2044.00 mg kg-1 (T3) and that of oxalate ranged from 2881.28 (T1) to 3843.36 mg kg-1 (T2). Higher values of antinutrients were observed in KAU POP treatment even after cooking. Among the integrated nutrient management practices, significantly lower values of nitrate and oxalate were recorded in soil test-based nutrient (T8 and T9) treatments. The percentage reduction in nitrate and oxalate due to cooking ranged from 9.59 to 21.67 % and 15.50 to 36.05 % Total antioxidant activity was higher in Vellanikkara soil at the second and third harvest stages and its content decreased with advancement of harvest time. Higher values were observed in the first cutting and the values ranged from 3570.50 mg kg-1 (T1 – OM alone) to 3146.39 mg kg-1 (T5 - high P and K). However, all the treatments were on par. The same trend was obtained for the second and third harvests. Beta carotene content was lower in Vellanikkara soil as compared to Chittur soil and its content also decreased with harvest time. Organic manure alone treatment was significantly inferior to INM treatments, especially soil test-based application of nutrients at first and third harvest. The data on soil nutrients indicated that ammoniacal nitrogen decreased with harvest stages in both soils. Even though nitrate nitrogen decreased with the advancement of crop growth in lateritic soil, it showed an increasing trend in Chittur soil indicating no leaching loss of this nutrient in this soil type. Both the soils were inherently rich in nutrients and cattle manure is a source of key nutrients including N, P, K, S, Mg, and Ca as well as certain micronutrients. This would have been the reason for the lack of significant variation among the fertility management treatments.Based on the yield performance and antinutrient content (nitrate and oxalate) in amaranth the best three treatments were selected from the pot culture study so as to assess their performance under field condition. The field experiment was conducted at Agronomy Farm, College of Agriculture, Vellanikkara with two varieties of amaranth viz., Arun (red amaranth) and Co-1 (green amaranth) and the three treatments selected from the pot culture study. . The selected treatments were : T1 - N: P: K - 100:75:75 kg ha-1 + FYM+ foliar spray of 1% urea + lime as per soil test-based recommendation, T2 - N: P: K -100:50:50 kg ha-1 in the form of Factamfos (basal), urea (top dress) and MOP +FYM + foliar spray of 1% urea and T3 - Soil test based application of nutrients + foliar spray of 1% urea. Data on the effect of treatments on amaranth yield indicated that the varieties differed significantly. At the first and third harvests amaranth var: Co-1 had a significantly higher yield (9.19 and 8.43 t ha-1 respectively) than Arun (4.98 and 5.73 t ha- 1 respectively). However, there was no significant difference in yield between the varieties at the second harvest (9.20 and 8.08 t ha-1 respectively). The impact of various fertility management practices on amaranth yield was not significant. However, there were significant differences in nitrate and oxalate levels between the varieties . Red amaranth variety Arun registered higher levels of nitrate as well as oxalate. Analysis of nitrate and oxalate contents after cooking showed lower values. Nitrate and oxalate concentrations recorded in cooked amaranth var: Arun were 3190 .00 mg kg-1 and 3331.48 mg kg-1 respectively. Corresponding values noticed in Co-1 were 861.66 and 2783.73 respectively. The magnitude of reduction in nitrate and oxalate contents after cooking were in the range of 58.02 to 68.14 % and 10.38 to 12.19 % respectively. The potential toxic concentration of nitrate nitrogen in amaranth is 2100 mg kg -1 and that of oxalate is 2-5 g day-1. Therefore, it may be concluded that nitrate and oxalate concentration in cooked amaranth is not a serious issue if the fertilizers are applied along with organic manure as per the recommendations of Kerala Agricultural University Analysis of amaranth samples collected from farmer’s fields of Chittur taluk and Madakkathara panchayat revealed significant differences in nitrate and oxalate contents among the plant samples. The mean nitrate content in Chittur plant samples was 29148.94 mg kg-1, while in Madakkathara plant samples, it was notably higher at 39112.20 mg kg-1 indicating a significant variation in nitrate content between the two locations at a 0.05 % significance level. Similarly, the oxalate content (3595.95 mg kg-1) in plant samples from Chittur was found to be significantly higher than that of Madakkathara panchayat (2911.29 mg kg-1). Application of high doses of nitrogenous fertilizers without appropriate levels of organic matter, phosphorus and potassium would have been the reason for the accumulation of nitrate to extremely high level in amaranth cultivated by farmers. Considering the harmful effects of nitrate and oxalate and the benefits of the major nutrient potassium for human health, it was found that indicators viz., potassium nitrate ratio and potassium oxalate ratio in amaranth leaves may be used to assess amaranth nutritional quality. Among the two varieties tested, var. Arun displayed K/NO3 -and K/oxalate ratios of 5.24 and 9.54, respectively. Corresponding ratios for the Co-1 variety were 11.27 and 12.09, respectively. The present investigation revealed that Amaranthus dubius (Green amaranth var. Co-1 ) has higher nutritional value and lower levels of antinutrients viz., nitrate and oxalate as compared to Amaranthus tricolor L.( Red amaranth var. Arun ). Organic POP recommended by Kerala Agricultural University is a good practice to reduce antinutrients in amaranth. However, the yield and nutritional value of amaranth were higher under integrated nutrient management than in KAU organic POP in both the soils under study. Nitrate accumulation in both red and green amaranth could be reduced to a certain degree by the adoption of appropriate fertility management practices.
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    Phosphorus transformation in acid sulphate rice soils of Kerala
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture , Vellanikkara, 2024-09-29) Amrutha, K K; Beena, V I
    Acid sulphate soils are lowland soils situated below the mean sea level along the coastal tracts of Kottayam, Alappuzha, Thrissur and Malappuram districts of Kerala, spread in two agro-ecological units namely Kuttanad (AEU 4) and Kole lands (AEU 6). These soils are characterised by high levels of organic matter, low pH and toxicity of iron (Fe) and aluminium (Al) with wide variability in available phosphorus (P) content. Acid sulphate soils generally contain substantial quantities of Fe sulphide minerals or the oxidation reaction products of these sulphidic minerals and the protonated/non-protonated surfaces of Al/Fe hydroxides and oxides, resulting in P sorption and formation of the complexes, thus decreasing P availability in soil. However, the recent fertility evaluations across the state showed high available P status due to solubilization of the accumulated applied P. To develop an economically viable phosphorus nutrient management strategy, a pioneer study on P transformations in acid sulphate soils is highly required. The study aimed to understand seasonal variation of nutrients and transformations of phosphorus in acid sulphate soils. The investigation was conducted at Radiotracer laboratory, College of Agriculture, Vellanikkara, with four experiments viz., collection and characterization of soil samples from the acid sulphate soils of Kerala in two seasons, fractionation of phosphorus, adsorption study and an incubation study. In the first experiment, 125 representative soil samples from Kuttanad (AEU 4) (15 each from Upper Kuttanad, Lower Kuttanad, Vechur Kari, Purakkad Kari and Kayal lands) and Kole lands (25 each from Thrissur and Ponnani Kole) in pre-monsoon (April) and post-monsoon (November) were collected and characterised. The experiments on the fractionation and adsorption of phosphorus were done in thirty-five samples ie., five each from the seven selected locations with varying available P status. Phosphorus fractionation was carried out to quantify different fractions of phosphorus and their contribution to the available pool. The inorganic P fractions includes saloid bound P, Fe-P, Al-P, reductant soluble P and Ca-P. Adsorption study was carried out to work out the quantity/ intensity (Q/I) relationship of phosphorus and the pattern of adsorption in acid sulphate soils. Finally, an incubation experiment of 90 days duration was conducted to understand the effect of phosphatic fertilisers, lime and farmyard manure at different levels in low and high available P soils collected from Kuttanad and Kole lands. The treatment details of the incubation study were three levels of phosphatic fertilisers (as SSP - 0, 35 and 70 kg ha-1), two levels of lime (as CaO - without lime and lime as per POP recommendations) and two levels of farmyard manure (0 t ha-1 and 5 t ha-1). The observations were made on 30th, 60th and 90th days of incubation. Seasonal characterisation of soil samples during the two seasons revealed that among the collected samples, 50 per cent was sandy clay loam and 40 per cent was sandy loam in texture. The acidity characterisation of soil samples reaffirmed the extreme acidity condition of acid sulphate soils with 40 per cent of samples coming under extremely acidic class and 20 per cent under very strongly acidic. Among the collected soil samples, 37.60 per cent was low in available P, 23.20 per cent and 39.20 per cent under medium and high P respectively. The soil sample from Vechur Kari region showed the highest value of organic carbon (11.46 %). The available micronutrients viz., Fe and Mn showed very high concentrations. Among the acidity fractions, potential acidity was dominant followed by pH-dependent acidity in both seasons. Seasonal variation in electrochemical properties like pH and EC was noticed between two seasons. Ultra acidic soil reaction with high electrical conductivity was noticed during pre-monsoon period which reaffirm the salt water intrusion in these locations. Oxidation of pyrite mineral resulted in high amount of available sulphur as well as potential acidity during pre-monsoon. Reduced condition prevailing in the post monsoon resulted in high concentration of available iron. The fractionation study of phosphorus indicated that the per cent distribution of different phosphorus fractions followed the order, Fe- P > organic P > reductant soluble P > calcium P > aluminium P > saloid bound P. The contribution of dominant fraction (Fe-P) to the available P is mainly through saloid bound P. The phosphorus fixing capacity was significantly and positively correlated with clay, organic matter content, and negatively correlated with the available P. In the adsorption study, high buffer power indicated the ability of acid sulphate soils to replenish the depleted available P. Freundlich adsorption isotherm was found to be the best to explain P adsorption followed by Langmuir and Temkin adsorption isotherms. The Freundlich adsorption constant, KF was found to be correlated with organic matter which confirmed the fixation of phosphorus by organic matter in acid sulphate soils. In most of the soils, Langmuir adsorption constant (KL) increased with rise in temperature, indicates chemisorption behaviour of P adsorption. The incubation study affirmed that in soils with low available P, the addition of SSP at doses of 70 kg ha-1 and 35 kg ha-1 along with lime and FYM showed a significant increase in pH. In these soils, the addition of SSP (70 kg ha-1) along with lime and FYM registered the highest available P of 51.63 and 73.33 kg ha-1 respectively in Kuttanad and Kole soils at 60th day of incubation. In the same treatment, Fe bound P fraction was found to be highest with a decreasing trend towards 60th day of incubation, which increased after that. In the case of soils with high available P, the treatment combination with the addition of the highest dose of SSP (70 kg ha-1) along with lime and FYM showed the highest pH with an increasing trend towards 60th day. On the contrary to low P soils, in high P soils, the addition of SSP at 35 kg ha-1 along with lime and FYM registered the highest available P of 309.44 and 126.94 kg ha-1 respectively in Kuttanad and Kole at 30th day of incubation followed by a reduction towards 60th day of incubation. Phosphorus, a widely varying nutrient in acid sulphate soils is prone to high adsorption and fixation in soil depending upon the type of clay, organic matter content and amount of oxides and hydroxides of Fe and Al. There was no significant seasonal variation of P in soil samples from AEU 4 and AEU 6. In acid sulphate soils, the most dominant fraction, Fe-P contributed to available P mainly through saloid bound P, which is the water-soluble and loosely bound P fraction. The reduction of available P with the increase in P fixing capacity necessitates its estimation at least for the grouping of soils for the efficient management of phosphorus. In soils with high available P, addition of lower dose of SSP (35 kg ha-1) along with organic manure (FYM @ 5 t ha- 1) and lime (POP recommendations) is sufficient to enhance the P availability. Where as, in soils with low available P, addition of higher dose of SSP (70 kg ha-1) along with organic manure (FYM @ 5 t ha-1) and lime (POP recommendations) enhanced the P availability than its sole application. In this regard, field experiments in acid sulphate soils have to be conducted to confirm the results of incubation study in rice under natural system and more investigation is needed to know the interaction between organic matter and organic P fraction. As the organic matter plays the dual function in the environment- as a link and as a bottleneck for phosphorus availability, detailed study should be undertaken to know the complex formed by P fixation and its degree of crystallinity for developing better P management strategies in acid sulphate soils
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    Studies on the chemo dynamics of phosphorus in the laterite soils of Kerala and utilization of fixed phosphorus for crop production
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2024-02-05) Kota Adilakshmi; Aparna, B
    A study entitled “Studies on the chemo dynamics of phosphorus in the laterite soils of Kerala and utilization of fixed phosphorus for crop production” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, during 2018-2021, with the objectives to characterize in detail the dynamics of inorganic phosphorus and phosphorus fractions in the laterite soils of Kerala, identify the dominant phytoaccumulators of phosphorus, screening of suitable extractants for available P, and evaluate various organic and inorganic solubilizers/mobilizers on the solubility and availability of fixed phosphorus. The study was carried out in four parts. The first part consisted of the collection and characterization of georeferenced soil samples and the identification of dominant phytoaccumulators of phosphorus (P). For that, by following a preliminary survey, a total of 100 georeferenced representative soil samples (0-15 cm depth), 25 from each of the four agro-ecological units (AEUs), viz., southern laterites (AEU 8) of Thiruvananthapuram district, south central laterites (AEU 9) of Kollam district, north central laterites (AEU 10) of Thrissur district, and northern laterites (AEU 11) of Kozhikode district of Kerala were collected for assessing its fertility status. From scrutiny of the data, it was observed that among the four AEUs, AEU 8 reported the highest values for electrical conductivity (EC), organic carbon (OC), available P, sulphur (S), iron (Fe), manganese (Mn), exchangeable hydrogen (H+), anion exchange capacity (AEC), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), and population of P solubilizers, AEU 9 for available boron (B), exchangeable aluminium (Al3+), hydrogen (H+), acidity, and MB C/P ratio, and AEU 11 for pH, available nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu). According to the results of frequency distribution, it was observed that, among the four AEUs (8, 9, 10, and 11), sandy clay loam was the prevalent soil textural class. Data on the mean values of pH revealed that the pH ranged between 5.42 and 6.21 among the four AEUs, and the majority of the collected soils were found to be strongly acidic (37%) and moderately acidic (40%) in nature. The EC values of the four AEUs were found to be within the critical limit. The mean values of OC varied from 0.63 From the present study, it can be concluded that the soils of southern laterites (AEU 8) exhibited the highest values for available P. Amaranthus viridis from AEUs 8, 9, and 10, and Synedrella nodiflora from AEU 11, were identified as dominant phytoaccumulators of P. Among the various fractions of P, with respect to the Po fractions such as the labile Po fraction, HCl extractable Po fraction, fulvic acid Po fraction, moderately labile Po fraction, humic acid Po fraction, residual Po fraction, and non-labile Po fraction, the soils collected from AEU 8 showed the highest values compared to other soils. It was also observed that the soils treated with vermicompost @ 15 t ha-1 showed the highest values for all the Po fractions when compared to soils without any manure, including total Po. Similarly, for Pi fractions, the soils collected from AEU 8 treated with vermicompost @ 15 t ha-1 showed the highest values for saloid-Pi, Al-Pi, and Fe-Pi, while the soils collected from AEU 8 without manure showed the highest values for residual/occluded Pi. Furthermore, soils treated with vermicompost @ 15 t ha-1 displayed the highest values for Ca-Pi in AEU 10 and reductant-soluble Pi in AEU 11. Notably, the soils of AEU 8 exhibited the highest capacity for P fixation among all studied soils. From the study, it was also observed that ion exchange resins were found to be the best extractants for available P determination, and biochar was the best amendment for alleviating P fixation, thus augmenting soil fertility
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    Development of multi nutrient formulation and pellets for organic farming and their evaluation in Banana (Musa AAB cv. Nendran)
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2024-11-05) Lucy Taki; Biju Joseph
    A study entitled “Development of multi nutrient formulations and pellets for organic farming and their evaluation in banana (Musa AAB cv. Nendran)” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2019-2023, with the objective to develop multi nutrient formulations and pellets using nutrient sources permitted under National Programme for Organic Production (NPOP) and to evaluate them in relation to nutrient release characteristics and productivity of nendran banana in agro-ecological unit 8 of Kerala. The study comprised of four parts viz., preparation and characterization of organic multi nutrient formulations, development of organic multi nutrient pellets and their quality evaluation, incubation study to investigate the nutrient release characteristics of organic multi nutrient formulations and pellets and a field study to evaluate the organic multi nutrient formulations and pellets in nendran banana. Organic multi nutrient formulations were prepared using organic nutrient sources like blood meal (BM), soybean meal (SM), rock phosphate (RP), steamed bone meal (SBM), potassium sulfate (SOP), langbeinite (L), epsom salt (ES) and borax (B) permitted in NPOP. Formulations were prepared by mixing nutrient sources considering the nutrient requirement of nendran banana (N:P2O5:K2O @ 300:115:450 g plant-1) and the fertility status of the experimental soil. The multi nutrient formulations prepared were F1 (BM+RP+SOP+ES+B), F2 (BM+RP+L+ES+B), F3 (BM+SBM+SOP+ES+B), F4 (BM+SBM+L+ES+B), F5 (SM+RP+SOP+ES+B), F6 (SM+RP+L+ES+B), F7 (SM+SBM+SOP+ES+B) and F8 (SM+SBM+L+ES+B). The multi nutrient formulations were characterized for their physical, chemical and biochemical properties. The results of characterization study were subjected to principal component analysis which revealed that the formulation F1 containing blood meal, rock phosphate, potassium sulfate, epsom salt and borax was superior to other formulations with index mean value of 13.07. Formulation F1 had 3.73 g cm-3 bulk 348 density, 2.67% moisture content, 6.5 pH, 3.23 dSm-1 EC, 29.43% OC, 7.21% N, 2.71% P, 10.78% K, 5.98% Ca, 0.35% Mg, 4.45% S, 1174.11 mg kg-1 Fe, 4.53 mg kg-1 Mn, 13.55 mg kg-1 Zn, 8.65 mg kg-1 Cu and 93.67 mg kg-1 B. It also contained 45.04% crude protein, 2.95% humic acid and 3.55% fulvic acid. Based on the result of the PCA, formulations F1 (BM + RP + SOP + ES + B), F2 (BM + RP + L + ES + B), F3 ((BM + SBM + SOP + ES + B) and F6 (SM + RP + L + ES + B) with index value of 13.07, 9.82, 11.93 and 7.35 were selected for further pelletization studies. Four selected organic multi nutrient formulations were mixed with 2 binding agents viz. bentonite (Bn) and starch (St) at 2 levels (2% and 4%). The formulations were mixed with binding agents as per the treatments and moistened with deionized water and compressed into pellet form. The 16 multi nutrient pellets prepared were P1 (BM+RP+SOP+ES+B+2%St), P2 (BM+RP+SOP+ES+B+4%St), P3 (BM+RP+SOP+ES+B+2%Bn), P4 (BM+RP+SOP+ES+B+4%Bn), P5 (BM+RP+L+ES+B+2%St), P6 (BM+RP+L+ES+B+4%St), P7 (BM+RP+L+ES+B+2%Bn), P8 (BM+RP+L+ES+ B+4%Bn), P9 (BM+SBM+SOP+ES+B+2%St), P10 (BM+SBM+SOP+ES+B+4%St), P11 (BM+SBM+SOP+ES+B+2%Bn), P12 (BM+SBM+SOP+ES+B+4%Bn), P13 (SM+RP+L+ES+B+2%St), P14 (SM+RP+L+ES+B+4%St), P15 (SM+RP+L+ES+B+2%Bn) and P16 (SM+RP+L+ES+B+4%Bn). The results of laboratory analysis of multi nutrient pellets were also subjected to PCA. Four different groups were made out of the 16 multi nutrient pellets with group 1 consisting of P1 to P4; group 2 consisting of P5 to P8; group 3 consisting of P9 to P12 and group 4 consisting of P13 to P16. PCA was performed separately on different groups to select one best multi nutrient pellet from each group. After one-way ANOVA of index values, the mean values of pellets P3 (11.23), P5 (8.21), P11 (11.36) and P15 (6.17) were greater found in their respective groups. However, the pellets P4 (BM+RP+SOP+ES+B+4%Bn), P6 (BM+RP+L+ES+B+4%St), P12 (BM+SBM+SOP+ES+B+4%Bn) and P16 (SM+RP+L+ES+B+4%Bn) with next higher 349 mean values of 11.03, 8.02, 11.16 and 6.05 were selected for further studies because of their superior physical qualities and stability. In the third part of the study a laboratory incubation experiment was carried out for 300 days to evaluate the nutrient release pattern of the 4 selected formulations (F1, F2, F3 and F6) and pellets (P4, P6, P12 and P16) upon addition to soil. Soil samples were drawn at 60 days interval (60th, 120th, 180th, 240th and 300th day of incubation) and nutrient release characteristics were studied. The result revealed that the soil organic carbon, water soluble carbon, labile carbon and particulate carbon increased till 60th day in all treatments then decreased till the end of incubation period. Significantly higher water soluble carbon (49.07 mg kg-1), labile carbon (1084.33 mg kg-1) and particulate carbon (3950.00 mg kg-1) was observed throughout the incubation period in T4 containing soyabean meal, rock phosphate, langbeinite, epsom salt and borax which was on par with T8 containing same formulation with 4% bentonite. The available N, NH4 +-N and NO3 --N content increased till 120th day irrespective of treatments and thereafter it decreased. Treatment T1 having blood meal + rock phosphate + potassium sulphate + epsom salt + borax recorded highest available N (246.46 kg ha-1), NH4 +-N (84.00 mg kg-1) and NO3 --N (46.67 mg kg-1) content throughout the incubation period followed by its corresponding pellet T5 having blood meal + rock phosphate + potassium sulphate + epsom salt + borax + 4% bentonite. The available P, labile P and non labile P increased upto 240th day for all the treatments. T1 showed significantly higher level of available P (111.41 kg ha-1), labile P (22.27 mg kg-1) and non labile P (42.89 mg kg-1), throughout the incubation period which was on par with T5. It was observed that available K, water soluble K, exchangeable K and non exchangeable K increased till 240th days of incubation and then declined in all treatments. Formulation T3 having blood meal + steamed bone meal + potassium sulphate + epsom salt + borax had significantly higher available K (972.93 kg ha-1), water soluble K (81.67 mg kg-1) and exchangeable K (352.68 mg kg-1) throughout the incubation period. However, the highest non exchangeable K varied during different 350 incubation period. Secondary nutrients Ca, Mg and S showed maximum release in all treatments till 240th day and thereafter declined with T2 formulation containing BM+RP+L+ES+B showing significantly higher content throughout the incubation period. The highest available micronutrient (Fe, Mn, Zn, Cu) was in treatment T5 which was on par with T1. A field experiment was conducted during 2021-2022 to evaluate the effect of organic multi nutrient formulations and pellets on soil fertility and crop productivity using nendran banana as test crop. The results of soil analysis revealed that application of multi nutrient formulations and pellets did not have much influence on physical properties of soil in both basin and 1m away from the plant. However, the chemical and biological attributes were significantly improved in both the soil. Application of T2 containing formulation BM+RP+SOP+ES+B and T6 containing pellet BM+RP+SOP+ES+B+4%Bn improved the availability of N, P, K, Fe, Mn and Zn content in both the soils. Dehydrogenase activity and microbial population was enhanced by application of KAU organic POP (T1), formulation SM+RP+L+ES+B (T5) and pellet SM+RP+L+ES+B+4%Bn (T9) in basin soil. Crop growth parameters like plant height, girth of pseudostem and no of functional leaves per plant were significantly higher in T2 which was on par with T6. Yield parameters like length, girth and weight of index finger, bunch weight, no. of hands per bunch, no. of fingers per bunch and no. of fingers in D-hand was also significantly higher in T2 and T6 compared to other treatments. T2 recorded the highest yield of 34.17 t/ha which was on par with T6 (31.25 t/ha). The crop receiving T9 (SM+RP+L+ES+B+4%Bn) had the longest crop duration and the shortest was observed in T2. The fruit quality parameters like TSS, TSS/acidity ratio, total sugar, reducing sugar, non reducing sugar, total sugar/ acidity ratio, carbohydrate, pulp to peel ratio was significantly higher in treatments T2 and T6. The foliar N, P, K, Ca, Fe content at harvest was highest in T2 containing formulation BM+RP+L+ES+B, foliar Mg, S content was highest in T3 containing formulation BM+RP+L+ES+B and foliar 351 Mn, Zn, Cu, B content was highest in T4 containing formulation BM+SBM+SOP+ES+B. Total uptake of N, Zn and B was highest in T2 while the total uptake of P, K, Ca, Mg, Fe, Mn, Cu was highest in T6. Fruit quality parameters like TSS, total sugar, reducing sugar, non reducing sugar and pulp/peel ratio was significantly higher in T2 which was on par with T6. Shelf-life of nendran fruit increased significantly in T4 receiving the formulation BM+SBM+SOP+ES+B and T8 receiving the same formulation with 4% bentonite. Nutrient use efficiency was higher in T2 and T6. The highest B:C ratio of 2.21 was recorded in T2. From the results of the study, it can be concluded that multi nutrient formulation prepared using blood meal, rock phosphate, potassium sulphate, epsom salt and borax (T2) and multi nutrient pellet prepared using blood meal, rock phosphate, potassium sulphate, epsom salt, borax and 4% bentonite (T6) was superior to other formulations and pellets. The nutrient release from above formulation and pellet were maximum at incubation period of 120th day for N and 240th day for P, K, secondary and micronutrients. The treatment T2 applied @ 4.2 kg plant-1 was found to be superior to other treatments with respect to available nutrient status of soil, nutrient uptake, growth parameter, yield and quality of nendran banana, which was found to be on par in the case of the most of the parameters with the treatment T6 applied @ 4.5 kg plant-1. T2 was also the most economical treatment. Hence, the application of organic multi nutrient formulation prepared using blood meal, rock phosphate, potassium sulphate, epsom salt and borax at the rate of 4.2 kg plant-1 as 3 equal split doses at 2MAP, 4MAP and 6MAP can be recommended for nutrient management in organically grown nendran banana.
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    Assessment of ion interactions in the acid saline soils (Orumundakan) to evolve a customized rice nutrition strategy
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2023-07-21) Anjali Bhadra, Vijay
    A study on 'ʽʽAssessment of ion interactions in the acid saline soils (Orumundakan) to evolve a customized rice nutrition strategy ˮ was undertaken with an objective to identify the major nutritional constraints for rice production and to evolve a customized nutrient management strategy by integrating varietal tolerance and nutrition. From the investigation it can be concluded that there is soil fertility constraints in the Orumundakan tract of AEU 3. The soil was very strongly acidic with low nutrient status except for P, Fe, Mn and S. From the different indices computed it was found that K and Mg are the limiting ion in this soil. Management of nutritional constraints in this tract should be based give more emphasis on K and Mg fertilizers. Soil test based NPK + lime along with foliar application of customised fertilizer (T7) was found to be effective in management of the fertility constraints of Orumundakan tract which resulted in the highest yield and B: C ratio. Profitable rice cultivation in this tract is possible through the integration of acid-saline tolerant rice variety and soil test based NPK+ lime with foliar application of customised fertilizer at critical growth stages of the crop.
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    Carbon dynamics in midland laterite rice soils under long term application of manures and fertilizers
    (Department of Soil Science and Agricultural Chemistry, College of Agricultural, Vellanikkara, 2024-02-07) Roshni John; Thulasi, V
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    Nutrient release pattern and performance of biochar blended N and K fertilizers in laterite and sandy soils
    (Nutrient release pattern and performance of biochar blended N and K fertilizers in laterite and sandy soils,Vellayani, 2024-01-24) Kavya, S R; Rani, B
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    Assessment, mapping and modelling of soil carbon pools and stock in selected agro-ecological units of south Kerala
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture ,Vellayani, 2024-04-22) Bincy, B; KAU
    A study entitled “Assessment, mapping and modelling of soil carbon pools and stock in selected agro-ecological units of south Kerala” was carried out to examine the impact of various agricultural land use systems on soil carbon fractions, pools and stock, soil aggregation, glomalin and polysaccharide contents, and to generate soil carbon maps using GIS and predict soil carbon changes in the future climate change scenario using modelling technique. The agro-ecological units (AEUs) of south Kerala namely, southern coastal plain (AEU 1), Onattukara sandy plain (AEU 3), southern laterites (AEU 8), south central laterites (AEU 9) and southern and central foothills (AEU 12) were selected for the study. In each AEU, different agricultural land use categories as described by IPCC for the carbon inventory such as, garden land (coconut), wet land (rice), fallow land (uncultivated) and plantation (rubber) were also selected. Soil profiles upto a depth of one meter was taken from the selected sites and samples were collected from various depth intervals of 0 to 25, 25 to 50, 50 to 75 and 75 to 100 cm. The surface soil samples (0 – 25 cm) were analyzed for soil properties such as pH, EC, CEC, texture, soil carbon fractions (organic, inorganic, water soluble, permanganate oxidizable, microbial biomass carbon and mineralizable carbon) and organic matter fractions (humic acid, fulvic acid and humin). The depth wise distribution of soil carbon pools (active, passive and slow carbon pools), bulk density and total organic carbon (TOC) were analyzed. Soil organic carbon stock, density, carbon indices (CPI, CLI, CMI, LQI, GWP) and carbon proportion/ turnover were computed. Soil aggregation was evaluated by analyzing water stable aggregates, mean weight diameter, macro-micro aggregate size distribution, aggregate associated organic carbon, glomalin and total polysaccharides in soil. GIS based thematic maps of soil organic carbon, stock, density and land quality were generated in ArcGIS 10.5.1 software. The soil organic carbon changes in the future climate change scenario were predicted using DNDC (Denitrification Decomposition) model. The results revealed that soil texture was loamy sand to sandy clay loam in AEU 1, sandy loam to sandy clay loam in AEU 3 and 9, sandy loam to sandy clay in AEU 8 and sandy clay loam to sandy clay in AEU 12. The sand fraction (45.32-80.34 %) was found to be more than silt (9.60 – 21.14%) and clay (8.87-39.15 %). The pH and EC of soils ranged 254 from 4.77 to 5.73 and 0.06 to 0.44 dS m⁻1 respectively. The CEC of soil varied between 2.60 and 6.69 c mol(p+) kg-1 with the highest value in rubber land use and the lowest in uncultivated land. Soil organic carbon (SOC) ranged from 0.34 to 0.73, 0.44 to 0.99, 0.40 to 1.09, 0.25 to 0.97 and 0.26 to 1.26 per cent in AEU 1, 3, 8, 9 and 12 respectively. Among the land uses, rubber land use recorded the highest SOC (1.03 %) followed by coconut (0.75 %) and rice (0.60 %) and the lowest SOC was observed in uncultivated land (0.34 %). The water soluble, permanganate oxidizable and the particulate organic carbon varied from 34.01 to 162.81 mg kg-1, 1.21 to 7.37 mg g-1 and 0.37 to 2.75 per cent respectively. The different AEUs and land uses followed the order AEU 12 > AEU 9 >AEU 8 > AEU 3>AEU 1 and rubber > coconut > rice >uncultivated land respectively. Similar trend was observed for microbial biomass carbon which ranged from 121.2 to 424.4 mg kg-1 with the highest value in AEU 12 and rubber land use. Percentage contribution of water soluble, particulate and permanganate oxidizable C to TOC was 0.31 to 0.43, 40.12 to 69.72 and 12.62 to 19.73 per cent respectively. The organic matter fractions viz. humic acid, fulvic acid and humin varied from 0.57 to 2.06, 0.73 to 2.33, 0.62 to 1.59 per cent respectively in different AEUs. The rubber land use showed significantly higher humic acid (1.72 %), fulvic acid (2.01 %) and humin (1.44 %) than coconut, rice and uncultivated land. Percentage contribution of humic acid, fulvic acid and humin to total organic matter ranged from 29.40 to 32.51, 32.30 to 36.42 and 26 to 29.25 per cent respectively. The active, slow and passive pools of carbon in soil ranged between 0.09 and 1.03, 0.17 and 0.78, 0.13 and 1.26 per cent respectively with the highest value in AEU 12 and the lowest in AEU 1. In different land uses it followed the order rubber >coconut> rice> uncultivated land. The soil carbon pool showed a gradual decline from 0 - 25 cm to 75 - 100 cm depth with a decrease of 0.82 to 0.14, 0.63 to 0.18 and 0.97 to 0.24 per cent for active, slow and passive carbon pools respectively. The passive pool of carbon (31.95 – 38.08 %) contributed more towards total organic carbon than active (23.64-37.66 %) and slow (22.73-32.12 %) pools. 255 With depth (0-25 cm to 75-100 cm) bulk density of soil increased from 1.38 to 1.66, 1.33 to 1.68, 1.35 to 1.64, 1.33 to 1.60 and 1.29 to 1.55 Mg m-3 in AEU 1, 3, 8, 9 and 12 respectively. Higher bulk density was observed in uncultivated land than rice, coconut and rubber land uses. The TOC in soil ranged from 0.72 to 2.80, 0.69 to 2.89, 0.79 to 3.46, 0.88 to 3.18 and 0.75 to 3.56 per cent in AEU 1, 3, 8, 9 and 12 respectively. In all the AEUs the highest TOC was registered from rubber land use followed by coconut, rice and the lowest from uncultivated land. The TOC content decreased with depth (0 - 25 cm to 75 - 100 cm) and the values were 1.99 to 0.95, 2.24 to 0.92, 2.45 to 1.05, 2.53 to 1.05 and 2.38 to 1.01 per cent for AEU 1, 3, 8, 9 and 12 respectively. Total soil organic carbon stock varied from 162.71 to 293.22, 175.80 to 275.79, 188.63 to 322.36, 199.73 to 331.48, 144.54 to 355.63 Mg ha-1 in AEU 1, 3, 8, 9 and 12 respectively with the highest stock in AEU 12. Among the land uses it followed the order rubber>coconut>rice>uncultivated land. SOC stock decreased from 0 to 25 cm to 75 to 100 cm depths and the values were 76.28 to 36.59, 79.97 to 35.88, 86.70 to 39.61, 88.10 to 39.48 and 79.90 to 35.80 Mg C ha-1 for AEU 1,3, 8, 9 and 12 respectively. The soil organic carbon density of the surface (0-25 cm) soil varied from 3.07 to 6.01, 3.68 to 5.76, 3.84 to 7.81, 4.19 to 7.19 and 3.27 to 6.96 kg m-2 in AEU 1, 3, 8, 9 and 12 respectively with the highest density observed for AEU 12. With respect to different land uses it followed the order rubber (6.96 kg m⁻2 )> coconut (5.86 kg m⁻2) > rice (5.10 kg m⁻2) > uncultivated land (3.61 kg m⁻2). The carbon indices such as lability, pool and management index ranged from 0.30 to 0.93, 0.19 to 0.51 and 5.55 to 38.42 respectively in different AEUs and were found to be the highest in AEU 12 and rubber land use. The land quality index based on SOC stock in kg m-2 was rated as medium (6 - 9 kg m-2 ) in all AEUs. The mineralizable C content in soil varied from 1.40 to 3.45, 1.18 to 3.41, 1.04 to 3.04, 1.23 to 3.35 and 1.01 to 3.02 mg g⁻¹ in AEU 1, 3, 8, 9 and 12 respectively. The highest value was observed from AEU 1 and rice land use. Similar trend was obtained for global warming potential of soils based on CO2 evolution which varied from 31.82 to 78.41, 26.89 to 79.02, 22.89 to 69.02, 28.03 to 76.06 and 22.96 to 68.64 in AEU 1, 3, 8, 9 and 12 respectively. The C proportion and turnover rates were in the range of 0.25 to 0.77 256 and 0.04 to 0.17 respectively. The C proportion was the highest in AEU 12 and rubber land use whereas the C turnover was the highest in AEU 1 and rice land use. With respect to aggregate distribution, the larger size fractions (5-8, 2-5, 1-2 & 0.5-1 mm) were found to be higher in rubber land use and the smaller size fractions (0.25-0.5 & 0.1-0.25 mm) were higher in rice land use. The macro aggregate fraction (> 250 μm) ranged from 22.60 to 75.70 per cent with the highest value in rubber land use while the micro aggregate fraction (53 – 250 μm) ranged from 10.78 to 56.46 per cent with the highest value in rice land use. The water stable aggregates and mean weight diameter were ranged from 22.60 to 34.31 per cent and 0.56 to 2.90 mm respectively and were the highest in rubber land use. The aggregate associated organic carbon was the highest in the size fraction of 1 to 2 and 0.5 to 1 mm (1.03-1.27 g kg-1) compared to other fractions. The organic carbon associated with macro (> 250 μm) and micro (53-250 μm) aggregates are in the range of 2.16 to 5.70 and 0.30 to 0.95 g kg-1 respectively with the highest value in rubber land use. The glomalin related soil protein ranged from 1.22 to 6.35 mg g-1 and polysaccharides from 2.12 to 9.24 mg g-1 . Irrespective of the AEUs the highest glomalin and polysaccharides were observed in rubber land use. The DNDC model predicted organic carbon changes in coconut land use systems in Thuravoor (AEU 1), Bharanikkavu (AEU 3), Ookkod (AEU 8), Karavaram (AEU 9) and Vellarada (AEU 12) under RCP 4.5 and RCP 8.5 future climate change scenario. The DNDC model predicted an increase in soil organic carbon status from 2020 to 2050 under RCP 4.5 and RCP 8.5 scenario but the rate of increase in soil carbon were more pronounced under 4.5 scenario where relatively lower CO2 emission was observed. The predicted SOC for 2050 under RCP 4.5 scenario were 1.26, 1.04, 1.44, 1.23 and 1.27 for Thuravoor (AEU 1), Bharanikkavu (AEU 3), Ookkod (AEU 8), Karavaram (AEU 9) and Vellarada (AEU 12) respectively. The organic carbon fractions, pools and stock were the highest in agro-ecological unit 12. Among the land uses, rubber contributed more to the SOC stock and pools indicating the prevalence of conducive environment for the buildup of carbon. The macro 257 and micro aggregates, aggregate associated carbon, glomalin, polysaccharides and C proportion were also higher in rubber land use indicating it as a potential carbon sink. Among the carbon fractions particulate organic carbon contributed more to total organic carbon. Among the carbon pools passive pool contributed more towards the total organic carbon. The carbon associated with larger fractions (1-2 mm and 0.5-1 mm) and macro aggregates (> 250 μm) were high in rubber land use indicating physical protection and sequestration in soil. The DNDC model predicted an increase in the SOC status from 2020 to 2050 under RCP 4.5 and RCP 8.5 scenario of future climate change.