1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Productivity enhancement of vegetables through salt stree mitigation in the sandy loam soils of Onattukara(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2025-12-14) Salma Nizar.; Mini, VThe study entitled “Productivity enhancement of vegetables through salt stress mitigation in the sandy loam soils of Onattukara” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2022-2024. The main objective of the study was to evaluate the ameliorative effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables in the salt stressed areas of Onattukara using tomato as the test crop. The three parts of the study were the development of multinutrient formulation for supplementary foliar nutrition, germination test for identifying the critical level of salinity for tomato and the evaluation of the effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables under salt stress. The salient research findings emanated from the experiments are summarized below. A multi nutrient formulation containing K, Ca, Mg, N, B and Zn was developed for supplementary foliar nutrition based on general soil status. General soil status of these nutrients was low and literature references and adhoc recommendations for secondary and micronutrient management and information on crop requirement were also used for developing the formulation. Suitable nutrient carriers were used for developing the foliar formulation. The carriers evaluated to prepare the mixture were KNO3, CaNO3, MgSO4. 7H2O, H3BO3, ZnSO4.7H2O, Na2B8O13. 4H2O and Zinc acetate. Humic acid and potassium silicate were used as surfactant and binder materials. Based on the properties like pH, EC and solubility in water and trial on standing crop, the mixture containing KNO3, Ca (NO3)2, MgSO4.7H2O, Boric acid and ZnSO4.7H2O was found to be the best. This formulation had a nutrient composition of K (10%), N (4%), Ca (6%), Mg (2.5%), B (5%) and Zn (2%) and recorded a pH of 6.32 and EC of 0.6dSm-1, which was within the desirable limit for foliar formulations and was 100% soluble. The germination test for identifying the critical level of salinity for tomato was carried out in the laboratory in completely randomized design using seeds of tomato variety Vellayani vijai. Different levels of salinity (10mM, 20mM, 30mM, 40mM of NaCl) was evaluated along with control and critical level of salinity for tomato identified. Observations taken on the 14th day of experiment showed that the germination percentage of tomato seeds reduced from 96.52% to 30.87% , days needed to complete germination increased from 3.70 days to 12.15 days and root shoot dry weight ratio increased from 0.433 to 0.611 with an increase in salinity levels from 0mM NaCl (T1) to 40mM NaCl (T5). The analysis of Na and K content of tomato seedlings also revealed a significant increasing trend in Na+/ K+ ratio of shoot and root with increase in salinity levels. Na+/ K+ ratio of shoot ranged from 2.23 to 4.21 and Na+/ K+ ratio of root ranged from 1.90 to 3.36 with treatments T1 to T5. The germination study could identify the treatment T4 - Hoagland solution containing 30 mM NaCl which recorded a noticeably greater reduction in germination percentage (<80%) as the critical level of salinity for tomato. Hence 30 mM NaCl and 40 mM NaCl were selected for the pot culture experiment. The pot culture experiment was conducted from January to April 2024 at O.R.A.R.S., Kayamkulam using tomato (var. Vellayani vijai) as the test crop to evaluate the effect of various doses of calcium silicate (100 kg ha-1 to 150 kg ha-1) and supplementary foliar nutrition (0.5%) on growth and mineral nutrition of vegetables under salt stress. Biometric observations like plant height, number of branches, fruit set percentage and internodal length were significantly higher in the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress) whereas days to first fruit set, root length, root volume and root dry weight was higher in treatment T8 ( Soil test based POP + CaSiO3 @ 150 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress). Treatments containing calcium silicate and supplementary foliar nutrition showed a significant improvement in all of the biometric observations recorded. With regard to the yield attributes such as fruits per plant, fruit weight and yield per plant, the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of The study entitled “Productivity enhancement of vegetables through salt stress mitigation in the sandy loam soils of Onattukara” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2022-2024. The main objective of the study was to evaluate the ameliorative effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables in the salt stressed areas of Onattukara using tomato as the test crop. The three parts of the study were the development of multinutrient formulation for supplementary foliar nutrition, germination test for identifying the critical level of salinity for tomato and the evaluation of the effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables under salt stress. The salient research findings emanated from the experiments are summarized below. A multi nutrient formulation containing K, Ca, Mg, N, B and Zn was developed for supplementary foliar nutrition based on general soil status. General soil status of these nutrients was low and literature references and adhoc recommendations for secondary and micronutrient management and information on crop requirement were also used for developing the formulation. Suitable nutrient carriers were used for developing the foliar formulation. The carriers evaluated to prepare the mixture were KNO3, CaNO3, MgSO4. 7H2O, H3BO3, ZnSO4.7H2O, Na2B8O13. 4H2O and Zinc acetate. Humic acid and potassium silicate were used as surfactant and binder materials. Based on the properties like pH, EC and solubility in water and trial on standing crop, the mixture containing KNO3, Ca (NO3)2, MgSO4.7H2O, Boric acid and ZnSO4.7H2O was found to be the best. This formulation had a nutrient composition of K (10%), N (4%), Ca (6%), Mg (2.5%), B (5%) and Zn (2%) and recorded a pH of 6.32 and EC of 0.6dSm-1, which was within the desirable limit for foliar formulations and was 100% soluble. The germination test for identifying the critical level of salinity for tomato was carried out in the laboratory in completely randomized design using seeds of tomato variety Vellayani vijai. Different levels of salinity (10mM, 20mM, 30mM, 40mM of NaCl) was evaluated along with control and critical level of salinity for tomato identified. Observations taken on the 14th day of experiment showed that the germination percentage of tomato seeds reduced from 96.52% to 30.87% , days needed to complete germination increased from 3.70 days to 12.15 days and root shoot dry weight ratio increased from 0.433 to 0.611 with an increase in salinity levels from 0mM NaCl (T1) to 40mM NaCl (T5). The analysis of Na and K content of tomato seedlings also revealed a significant increasing trend in Na+/ K+ ratio of shoot and root with increase in salinity levels. Na+/ K+ ratio of shoot ranged from 2.23 to 4.21 and Na+/ K+ ratio of root ranged from 1.90 to 3.36 with treatments T1 to T5. The germination study could identify the treatment T4 - Hoagland solution containing 30 mM NaCl which recorded a noticeably greater reduction in germination percentage (<80%) as the critical level of salinity for tomato. Hence 30 mM NaCl and 40 mM NaCl were selected for the pot culture experiment. The pot culture experiment was conducted from January to April 2024 at O.R.A.R.S., Kayamkulam using tomato (var. Vellayani vijai) as the test crop to evaluate the effect of various doses of calcium silicate (100 kg ha-1 to 150 kg ha-1) and supplementary foliar nutrition (0.5%) on growth and mineral nutrition of vegetables under salt stress. Biometric observations like plant height, number of branches, fruit set percentage and internodal length were significantly higher in the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress) whereas days to first fruit set, root length, root volume and root dry weight was higher in treatment T8 ( Soil test based POP + CaSiO3 @ 150 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress). Treatments containing calcium silicate and supplementary foliar nutrition showed a significant improvement in all of the biometric observations recorded.Item Biostimulants for enhancing soil biological properties in wetland ecosystem(Department of Soil science and Agricultural Chemistry,, College of Agriculture, Vellayani, 2025-06-16) Kamali,B; Aparna,BThe study entitled “Biostimulants for enhancing soil biological properties in wetland ecosystem” was undertaken in Department of Soil Science and Agricultural Chemistry during the period December 2022 to October 2024. The objective of the study was to assess the effect of selected biostimulants in a wetland ecosystem on soil biological properties for crop growth and yield. The project was envisaged in four different parts, collection of geo-referenced soil samples from rice growing tracts of Southern Kerala, generation of thematic maps with highlighting Biological Fertility Index (BFI), characterization of biostimulants and evaluation of biostimulants through pot culture and field experiment. Geo-referenced soil samples (100 samples) were collected from five agroecological units (AEUs) viz. AEU 3 (Onattukara sandy soil), AEU 4 (Kuttanad soil), AEU 5 (Pokkali soil), AEU 8 (Southern laterites), and AEU 9 (South central laterites) of Southern Kerala at a depth of 0-15 cm. The collected samples were subjected to the characterization of soil biological properties. The biological properties of soil across the agroecological units (AEUs) exhibited notable variations. AEU 4 (Kuttanad soil) recorded the highest organic carbon (3.03 ± 1.19 %), microbial biomass carbon (628.57 ± 207.76 µg g-1), β-glucosidase activity (76.70 ± 14.88 µg p-nitrophenol g-1 soil h⁻¹) and acid phosphatase activity (111.60 ± 17.94 µg p- nitrophenol g-1 soil h-1). AEU 5 (Pokkali soil) noticed the highest microbial biomass nitrogen (197.30 ± 60.72 µg g-1), soil respiration (5.28 - 11.01 mg CO₂ g-1), dehydrogenase activity (682.54 ± 189.76 µg TPF g-1 soil h-1) and protease activity (111.09 ± 42.04 µg tyrosine g-1 soil h-1). In contrast, AEU 8 (Southern laterites) recorded the lowest microbial biomass nitrogen (50.17 ± 15.76 µg g-1), microbial biomass carbon (163.65 ± 84.16 µg g- 1), water soluble carbon, labile carbon, enzyme activities and microbial population. Using Principal Component Analysis (PCA), dehydrogenase was selected as PC1 (0.913), organic carbon from PC2 (0.669), microbial biomass carbon from PC3 (0.702), soil respiration from PC4 (0.847), and microbial biomass nitrogen from PC5 (0.721). The Biological Fertility Index (BFI) was computed using the procedure prescribed by Brookes et al. (1995). It was noted that AEU 5 recorded the highest biological fertility index, followed by AEU 4, AEU 9, AEU 3 and AEU 8 (AEU 5 > AEU 4 > AEU 9 > AEU 3 >AEU 8). The lowest biological fertility index (AEU 8) was selected for the pot culture experiment to evaluate the biostimulants. In Part II of the study, characterization of the biostimulants was carried out. As Part III of the study, a pot culture experiment was conducted in 2023 at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, to evaluate the effects of various biostimulants on rice (Oryza sativa L.) growth and yield. The rice variety used was Uma and the treatments consisted of RDF (100 % RDF: 90:45:45 kg N, P₂O₅, K₂O per hectare), supplemented with FYM and lime as per KAU POP. Treatments included T1 (RDF + Seaweed extract at 12.5 kg ha-1), T2 (RDF + Humic acid at 10 kg ha-1), T3 (RDF + Fulvic acid at 5 kg ha-1), T4 (RDF + Lignosulphatehumate at 10 kg ha-1), T5 (RDF + Protein hydrolysate at 2.5 kg ha-1), T6 (RDF + Panchagavya at 3 %), T7 (RDF + PGPR mix- 1 at 2 %), T8 (RDF + Pseudomonas consortium at 2 %), T9 (RDF as per KAU POP) and T10 (Absolute control). This study involved the evaluation of different treatments on soil chemical, biological and enzymatic properties across three crop stages. T2 (RDF + Humic acid) recorded the highest pH, organic carbon, available K, Mg, B and enzyme activities of β- glucosidase, amylase and the lowest EC. T7 (RDF + PGPR mix-1) exhibited the highest available N, available P, labile carbon, microbial biomass carbon, soil respiration, glomalin content and enzyme activities of dehydrogenase, acid phosphatase and protease, along with the highest microbial populations. The highest available S was noticed in T1 (RDF + Seaweed extract), whereas, water soluble carbon in T3 (RDF + Fulvic acid). In contrast, T10 (Absolute control) recorded the highest micronutrient content (Fe, Mn, Zn and Cu). The enzyme activity number was computed based on the activity of five different enzymes viz., dehydrogenase, catalase, acid phosphatase, protease and amylase proposed by Beck (1984). The highest EAN was in T7 (RDF + PGPR mix-1) at 20.28, followed by T2 (RDF + Humic acid) at 19.45, T1 (RDF + Seaweed extract) as 18.63. Growth and yield parameters, including plant height, tillers, thousand grain weight and yield were the highest in T7 (RDF + PGPR mix-1). Chlorophyll content was the highest in T7 comparable to T2 (RDF + Humic acid), while proline content was the highest in control. N and P content along with their uptake in straw and grain were the highest in T7 (RDF + PGPR mix-1) while treatment T2 recorded the highest K content and uptake. Micronutrient content (Fe, Mn, Zn and Cu) in straw and grain were the highest in controlwith significant difference compared to other treatments, but uptake was the lowest. However, the lowest micronutrient content was recorded in T2 (RDF + Humic acid). The root parameters such as active roots, root length, root dry weight, root volume were reported the highest in T7 (RDF + PGPR mix-1). SEM micrograph of rice roots revealed that PGPR mix-1 enhanced microbial colonization and root-microbe interactions, with biofilm-like structures. Treatment with Humic acid resulted in moderate microbial attachment. This was further confirmed by TEM with higher magnification, with the presence of PGPR within the epidermal layers and near the cell walls of rice roots. Bacterial colonization in the root tissues was absent in SEM and TEM images of the control samples. Root metabolites such as p-coumaric acid, vanillic acid, and syringic acid were observed and found that significant variation among the treatments with the highest concentrations found in T7 (RDF + PGPR mix-1), followed by T2 (RDF + Humic acid) and T1 (RDF + Seaweed extract). The standing water analysis showed a slight increase in pH from the 1st to 14th week and the highest pH was observed in T2 (RDF + Humic acid). Total Fe and Al were the highest in the absolute control while the CO2 evolution rate was highest in T7 (RDF + PGPR mix-1). From the interpretations of results of pot culture experiment, based on the enzymatic activities, nutrient uptake, plant growth, yield and root parameters, three best treatments were selected such T7 (RDF + PGPR mix 1), T2 (RDF + Humic acid) and T1 (RDF + Seaweed extract). In Part 1V of the study, the superior three treatments from the pot culture experiment were evaluated through a field experiment conducted at the College of Agriculture, Vellayani. The study included six treatments: T1 (Best treatment 1), T2 (Best treatment 2), T3 (Best treatment 3), T4 (KAU organic POP), T5 (RDF as per KAU POP), and T6 (Absolute control). The experiment was laid out in a Randomized Block Design (RBD) with four replications. The results revealed that T2 (RDF + Humic acid) noticed the highest pH, organic carbon, available Ca and Mg. Available N and P were the highest in T1 (RDF + PGPR mix- 1) and K in T2 while the highest available S was noticed in T3 (RDF + Seaweed extract), while micronutrients (Fe, Mn, Zn and Cu) were the highest in the control except the boron. The labile and water-soluble carbon was the highest in T1 and T3 respectively. Enzyme activities were highest in T1 (RDF + PGPR mix-1). Humic acid fractions were the highest in T2 (RDF + Humic acid) treatmentThe study also assessed the effects of various treatments on rice growth, yield, nutrient uptake, root morphology and microbial interactions. RDF + PGPR mix-1 (T1) significantly recorded the highest EAN, improving growth, yield, root parameters, nutrient uptake (N, P, Ca and Mg), and microbial interactions. RDF + Humic acid (T2) recorded the highest K content and uptake. The control (T6) recorded the lowest growth, yield and nutrient uptake, but the highest Fe, Mn, Zn and Cu content. Root metabolites, chlorophyll, sugars and amylase were also the highest in PGPR mix-1, while proline content was the highest in the control. Standing water analysis showed the highest pH in RDF + Humic acid and the highest CO2 evolution rate in PGPR mix-1, indicating enhanced microbial activity. The economic analysis of treatments T1 (RDF + PGPR mix-1) recorded the highest net return, gross return and benefit-cost (B:C) ratio. The results suggest that T1 (RDF + PGPR mix-1) is the most cost-effective treatment, providing the highest profitability among all the treatments evaluated. The study concluded that biostimulants, particularly RDF + PGPR mix-1 @ 2 %, significantly improved rice growth, yield and nutrient uptake, while also enhancing soil biological properties, microbial interactions and nutrient dynamics in rice as evaluated through both pot and field experiments.Item Geospatial variability and nutrient dynamics of soils of lateritic wetlands vis-avis coastal wetlands(Department of Soil Science & Agricultural Chemistry, College of Agriculture , Padanakkad, 2025-01-17) Anzala Shahanas.; Nideesh, PA research study entitled “Geospatial variability and nutrient dynamics of soils of lateritic wetlands vis-a-vis coastal wetlands” was done with the objective to assess the spatial and temporal variability of the wetland soils in the two AEU’s (northern laterites and northern coastal plains) of north Kerala using GIS and also to assess the soil dynamics as modified by amendments for evolving best management practices. Paddy growing wetland of RARS, Pilicode (AEU 11) and Muppathil kandam at Nileshwar (AEU 2) were selected for the spatial and temporal variability assessment of soil nutrient dynamics. Grid based soil samples were collected from 10 locations at quarterly intervals for one year from these wetlands (from February 2023 to November 2023). Additionally, a pot culture experiment was conducted at the College of Agriculture, Padannakkad, using paddy as the test crop. Experiment was conducted with 2 types of soils (coastal sandy and lateritic alluvial wetland) under 5 levels of treatments using CRD. Treatment combinations were T1 (KAU POP (2016) based fertilizers + lime), T2 (Soil test based fertilizers), T3 (Soil test based fertilisers and lime), T4 (KAU organic POP based FYM + Lime) and T5 (Soil test based fertilisers and dolomite). In the clay loam soils of lateritic wetland (AEU 11), pH was found to be in the range of 4.44 to 5.64 and were non saline. Organic C content ranged from 0.60 % to 2.85 % and available N ranged from 81.54 to 476.67 kg ha⁻¹. Available P was high (>29 kg ha⁻¹) and available K ranged from 56.22 to 263.65 kg ha⁻¹. Available Ca varied between 160.00 and 480 mg kg⁻¹ and available Mg varied between 48.00 and 156.00 mg kg⁻¹. Available S, Fe, Mn, Zn and Cu content were sufficient and available B was deficient. MBC varied between 216.97 and 1390.59 μg g⁻¹ and DHA varied between 1.28 and 13.59 μg TPF released g⁻¹ soil 24 h⁻¹. . In the coastal sandy wetland soils (AEU 2), pH ranged from 5.60 to 6.94 and were non saline. Organic C was in the range from 0.45 % to 1.20 % and available N ranged from 43.90 to 244.61 kg ha⁻¹. Available P was high (>29 kg ha⁻¹) and available K was low to medium (15.68 and 210.13 kg ha⁻¹). Available Ca varied between 160.00 and 480 mg kg⁻¹ and available Mg varied between 72 and 192 mg kg⁻¹. Available S, Fe, Mn, Zn and Cu content were sufficient and available B was deficient. MBC ranged between 54.59 and 338.66 μg g⁻¹ and DHA ranged between 0.65 and 9.66 μg TPF released g⁻¹ soil 24 h⁻¹. On assessing the temporal variability of nutrient dynamics in lateritic wetland soils, it was found that the mean organic C, available Ca and Mg content were highest in August which was on par with May. The mean available S, MBC and DHA were highest in August. The highest mean available N was observed in November, while the mean available P was maximum in August, which was on par with November and May. In coastal wetland soils, the highest mean value of organic C, available N, K, mean MBC and DHA were recorded in November. The mean available Ca, Mg and S were highest in May which was on par with August and mean available P was highest in February. In both wetland soils, the highest mean pH value was observed in May which was on par with February. Results of pot culture experiment showed that there is significant effect of treatments on soil nutrient content and plant growth. Treatments have no significant effect on plant height. In lateritic wetland soils, highest number of productive tillers was recorded in T5 which was on par with T3 and T2. Highest number of grains per panicle was recorded in T3 which was on par with T5 and T2. Highest 1000 grain weight was recorded in T3 which was on par with T5. In coastal wetland soils, number of productive tillers was maximum in T3 which was on par with T5 and T2. Number of grains per panicle was maximum in T5 which was on par with T3 and T2. Highest 1000 grain weight was recorded in T5 which was on par with T3. Available N, K, Ca, Mg and B showed similar trend in both lateritic and coastal wetland soils. Available N was maximum in T1 and available K was maximum in T3 which was on par with T2 and T5. Highest available Ca was recorded in T1 which was on par with T4 and T3. Highest available Mg was recorded in T3 which was on par with T5 and T2. Highest available B was recorded in T3 which was on par with T5 and T2. Total nutrient content in plants (N, Ca, Mg, S and B) showed similar trend in both soil types. Highest plant N content was recorded in T1 which was on par with T3 and T5. Highest plant Ca and S content were recorded in T1 which was on par with T4. Highest Mg content was recorded in T3 which was on par with T5 and T2. Plant B content was maximum in T3 which was on par with T5. Highest plant K content was recorded in T3 in lateritic wetland soils while it was maximum in T3 which was on par with T5 in coastal wetland soils.Item Spatial variability and dynamics of arsenic in selected coastal rice ecosystems of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2025-02-12) Rashbi Jahan, V; Mayadevi, M RArsenic (As) is a naturally occurring toxic metalloid, that can cause detrimental effects on plants as well as humans. Though the elevated level of As is not reported from the paddy soils of Kerala, the tropical climate and high amorphous Fe minerals in the soil may cause an excessive dissolution of arsenic in the soils of Kerala. Hence, a study entitled “Spatial variability and dynamics of As in selected coastal rice ecosystems of Kerala” was designed to understand the spatial distribution of As in paddy soils of coastal agroecological units (AEU), namely, Northern coastal plain (AEU 2) and Kaipad lands (AEU 7) and to study the effects of agricultural amendments such as lime and organic manure on As content in these soils. Thirty-eight and eight georeferenced, grid-based (5 x5 km2) irrigation water and soil samples each were collected from paddy fields of panchayats under the Northern coastal plain (AEU 2) and Kaipad lands (AEU 7), respectively, at a sampling intensity of one panchayat from one grid forming a total of ninety-two samples. The pH of irrigation water from AEU 2 varied between 5.94 and 8.58, and that of Kaipad lands (AEU 7) from 7.46 to 8.6. The electrical conductivity (EC) of AEU 2 varied from 0.03 to 4.59 dS m-1 and between 0.02 and 17.02 dS m-1 from AEU 7. The content of As in irrigation water ranged from 0.02 µg L-1 (Feroke, Kozhikode) to 1.56 µg L-1 (Matool, Kannur) in AEU 2. In AEU 7, the lowest and highest As reported were 0.08 µg L-1 (Cheruvathur, Kasaragode) and 4.67 µg L-1 (Ezhome, Kannur), respectively The pH of the soils of the Northern coastal plain (AEU 2) varied from 3.08 to 7.42, and EC from 0.05 dS m-1 to 4.46 dS m-1. The organic carbon varied from 0.19 per cent to 5.33 per cent. The pH of soil from Kaipad lands (AEU 7) varied from 4.2 to 7.23; EC from 0.05 dS m-1 to 12.12 dS m-1. The organic carbon varied between 0.31 per cent and 3.94 per cent. The available As in soils of AEU 2 varied from 0.65 µg kg1 (Chorodu, Kozhikode) to 832.87 µg kg-1(Vallikkunnu, Malappuram) and showed a significant negative correlation with available Iron (Fe) (r = -0.369*), Phosphorus (P) (r = - 0.351*), and a significant positive correlation with available Calcium (r = 0.384*), Magnesium (r = 0.432**). The available As in soils of Kaipad lands varied from 0.35 µg kg-1 at Pilicode to 1255.2 µg kg 1 at Pallikkara, Kasaragod. However, none of the samples reported As content more than the prescribed critical limit of 100µg L-1 set by the Food and Agricultural Organization for irrigation water and 5800 µg kg-1 set by the Geological Survey of India for agricultural soils. The total As in soils of AEU 2 varied from 1.5 mg kg-1 (Chemnad, Kasargode) to 37 mg kg-1(Vallikkunnu, Malappuram), and that of AEU 7 from 6.5 mg kg-1(Pilicode, Kasargode) to 36.5 mg kg-1(Pallikkara, Kasaragode) and was positively correlated (r = 0.639***) with available As. Results revealed that 58 % (N=38) of soil samples from AEU 2 and 25% (N=8) from AEU 7 recorded more than the critical limit of 20 mg kg-1 of total As recommended by The European Union and Agency for Toxic Substances and Disease Registry (ASTDR) for agricultural Soils. A batch incubation study was conducted to study the effects of lime (fine lime powder) and organic manure (cow dung) on available arsenic content for 30 days, and chemical analyses were done at 1,3,5,10,15 and 30th day of incubation. The composite soil samples from AEU 2 and 7 were spiked individually with As at 400 mg kg-1 of soil and were used for the study. The As spiked soils were incubated with lime at 600 kg ha-1 (T2) and 1200 kg ha-1 (T3), organic manure at 5t ha1 (T4), 10t ha-1 (T5) and a combination of lime at 600kg ha-1 and fresh cow dung at 5t ha-1 (T6) against As spiked soil as control (T1). The combined application of lime at 600 kg ha-1 and organic manure at 5t ha-1 (T6) significantly increased the soil pH of the AEU 2 from the 15th to 30th day of incubation, whereas in AEU 7, lime at 1200 kg ha-1 (T3) significantly (p=0.05) increased the pH up to 30th day of incubation. Irrespective of the AEUs, the highest reduction in available Fe was recorded in lime-amended soils at 600 kg ha-1 from the 10th to the 30th day of incubation and available As exhibited a significant negative correlation with available Fe in soils of Northern coastal plains under organic manure amendment. Irrespective of the AEUs, the organic manure at 10t ha-1 significantly increased the available P content up to 15th day of incubation. Irrespective of AEUs, the highest available As was recorded by control soil (T1) up to the 30th day of incubation. A significant reduction in available As was reported from T5 (organic manure at 10 t ha-1) up to the 10th day of incubation in AEU 2. However, irrespective of AEUs, the combined application lime and organic manure (T6) significantly reduced the available As up to 30th day of incubation. Hence, incubation study of arsenic dynamics under liming and organic manure regimes revealed that the application of soil amendments like lime and organic manure effectively reduced available As in soils of the Northern coastal plain and Kaipad lands. Also the sources and dynamics of geogenic and anthropogenic As and its contributing factors in agricultural systems need to be studied extensively.Item Soil organic carbon estimation using non imaging hyperspectral data in upland and wetland ecosystem of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2024-01-11) Nandaluru Kalpana; Divya VijayanKerala, characterized by diverse physiography, landscapes, and soil compositions, confronts challenges related to soil quality, primarily due to unpredictable shifts in weather conditions. Given the dynamic nature of the soil, which adapts to evolving environmental factors, assessing soil quality becomes crucial. Traditional soil analysis methods are both time-consuming and expensive, necessitating the exploration of innovative alternatives to expedite the analysis process. Visible-NIR (Vis-NIR) reflectance spectroscopy has emerged as a rapid, cost-effective, environmentally friendly, non-destructive, reproducible, and repeatable analytical technique. Among various soil quality parameters, Soil Organic Carbon (SOC) plays a significant role in influencing the physicochemical and biological aspects of soil, thereby positively affecting crop growth. Determining SOC is particularly crucial in tropical regions due to its dynamic nature and its contribution to climate change adaptation through carbon sequestration. Against this backdrop, a research study was conducted between 2021-2023 with the aim of estimating and quantitatively predicting soil organic carbon in upland and wetland ecosystems of Kerala using hyperspectral reflectance spectroscopy in the Department of Soil Science & Agricultural Chemistry. The study was conducted under the different land use systems of the three Agro Ecological Units (AEU) of Kerala namely Kole lands (AEU 6), North central Laterite (AEU 10) and Palakkad central plain (AEU 22). Georeferenced surface soil samples (0– 15cm) were collected from 70 locations under each AEU and anlyzed for physico- chemical properties of soil including SOC. The results of physico-chemical analysis showed that, mean bulk density was lower in AEU 6 (1.12 Mg m-3) compared to AEU 10 and 22 (1.3 Mg m-3). SOC ranged from (0.6 to 4.26 %) in AEU 6, AEU 10 (0.53 to 6.42%) and AEU 22 (0.21 to 3.74 %). Total Carbon (Tot. C) in AEU 6 varied from (0.7 to 4.46 %), AEU 10 (0.53 to 6.42) and AEU 22(0.34 to 3.83 %). Available Nitrogen (Av. N) ranged from (125.4 to 363.2 kg ha-1) in AEU 6, AEU 10 (108.9 to 439.04 kg ha-1) and AEU 22 (75.2 to 489.2 kg ha-1). Total Nitrogen (Tot. N) values ranging from AEU 6 (0.04 to 0.36 %), AEU 10 (0.07 to 0.87 %) and AEU 22 (0.05 to 0.33 %). Reflectance spectra were collected in controlled dark room condition for 210 samples in the wavelength region (350-2500 nm) using the ASD FieldSpec 4 spectroradiometer. The spectra were then pre-processed by using different techniques like First order derivative (FOD), second order derivative (SOD), log (1/R) transformation, and continuum removal (CR) for enhancing quality of the spectra for better prediction. Further, correlation analysis was carried for both raw and preprocessed spectra and correlated spectral bands were taken for developing PLSR (Partial least square Regression) model, the coefficient of determination (R2) was better for first and second order derivatives for SOC compared with raw and other preprocessed data. Hence, FOD was taken for developing PLSR model. The model was developed for the prediction of soil organic carbon (SOC), total carbon (Tot. C), available nitrogen (Av. N), and total nitrogen (Tot. N). For all the four parameters the datasets were divided in the ratio of 70:30, with 70% of the data (n=147) used for calibration and the remaining 30% used for validation (n=63). The PLSR model developed in this study underwent validation based on R2 and RMSE, demonstrating its efficacy in predicting SOC, Tot. C, Av. N and Tot. N values. The model exhibited strong predictive capabilities, achieving R2 values of 0.88 for SOC, 0.86 for Tot. C, 0.85 for Av. N, and 0.87 for Tot. N, with corresponding RMSE values of 0.66 %, 0.73 %, 66.9 kg ha-1, and 0.06%, respectively. The high variability in carbon and nitrogen content within the soil samples underscored the model's effectiveness. This study concludes that hyperspectral reflectance spectroscopy is a successful approach for predicting carbon and nitrogen levels in different ecosystems in Kerala. The research findings emphasize the significance of employing Chemometrics as an advanced tool for soil property prediction. Looking ahead, there is a pressing need to develop spectral libraries and prediction models tailored to regional and field-level variations in soil properties across diverse soil types in Kerala.Item Effect of long term fertilization on soil carbon dynamics in rice-rice cropping sequence of Onattukara(Department of Soil Science and Agricultural Chemistry , Vellayani, 2021-11-21) Kavyasree, G; Mini, VA study entitled “Effect of long term fertilization on soil carbon dynamics in rice-rice cropping sequence of Onattukara” was carried out with the objective of studying the effect of long term fertilization on soil carbon dynamics and to explain the relationship between different active pools of soil organic carbon and rice yield. The study was conducted at the permanent manurial trial (PMT) plot at Onattukara Regional Agricultural Research Station, Kayamkulam, during 2019-21. The experiment comprised of field experiment during Virippu and Mundakan season, soil analysis and computation of various indices like Carbon pool index (CPI), Carbon lability index (CLI), Carbon management index (CMI), sensitivity index (SI), critical carbon input, carbon budgeting and plant analysis. Field experiment comprised of 8 treatments viz., T 1 (80 kg N ha -1 as FYM), T 2 (80 kg N ha -1 as Ammonium Sulphate), T 3 (80 kg N ha -1 as A.S + 40 kg P 2 O 5 ha -1 as Rajphos), T 4 (80 kg N ha -1 as A.S + 40 kg K 2 O ha -1 as MOP), T 5 (40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP), T 6 (80 kg N ha -1 as A.S + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP), T 7 (80 kg N ha -1 (20 kg as FYM and 60 kg as A.S.) + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP) and T 8 (Absolute control) replicated thrice using rice variety Jaya. Treatment receiving 80 kg N ha -1 (20 kg as FYM and 60 kg as A.S.) + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP (T 7 ) recorded the highest growth and yield. Soil samples were drawn from 3 different depths at 15 cm interval viz., 0-15 cm, 15-30 cm and 30-45 cm and analysed for physical, chemical and biological properties. There was no textural variation and the texture of the soil remained as sandy loam in all the treatments during both the seasons. An improved physical condition was noticed in T 7 with low BD (1.32 Mg C ha -1 ), high WHC (33%) and hydraulic conductivity (1.25 cm h -1 ). The soil acidity varied from very strongly acidic to strongly acidic. The highest content of available N, P, K and S was recorded in T 7 during both the seasons, while T 1 (FYM) recorded the highest content of Ca and Mg. The highest content of Zn, Cu and B were recorded in T 7 whereas Fe and Mn recorded the highest values under T 2 (Ammonium sulphate). Deficiencies of Ca, Mg, S and B were recorded in all the treatments. Generally all the parameters showed a decreasing trend with increasing depth except BD and pH. The highest nutrient content in grain and straw were also recorded in T 7 . Highest BC ratio (1.61 and 1.64) was recorded in T 7 during both the seasons. 244SOC, SMBC, SMBN, SMBP, WSC, water soluble carbohydrates and dehydrogenase activity were the highest under T 7 . T 7 recorded the highest TOC, very labile, labile, less labile and non labile C fractions and in all the treatments active C pool dominated the passive C pool. The contribution of active C pool to TOC accounted for 55-66%. Computed indices viz., CPI (1.56), CLI (1.34) and CMI (209.04) were found to be the highest in T 7 . Sensitivity Index (SI) was worked out to determine the sensitivity of each fraction to management practices and observed that active pool, SOC, water soluble carbon and water soluble carbohydrates were the most sensitive fractions while TOC and passive C pool were the least sensitive to management practices. Critical carbon input to maintain the initial level of SOC stock in soil was worked out. All the treatments recorded a positive critical carbon input which indicates that additional C has to be given inorder to sustain the present level of SOC stock. Among the treatments T 7 recorded the highest critical carbon input (0.470 Mg C ha -1 ) and it was due to initial high SOC stock. Carbon budgeting was done by computing SOC stock, C build up per cent, C build up rate and C sequestered and were the highest in T 7 followed by T 1 . Significant positive correlation was observed between different C pools, C pools and nutrient availability, C pools and biological activity and C pools and yield. Present study provided an insight on how management practices affect soil C buildup and C sequestration in rice-rice cropping sequence of Onattukara. Integrated nutrient management (T 7 ) with application of 20 kg N ha -1 as FYM and 60 kg N ha -1 as Ammonium sulphate along with 40 kg P 2 O 5 ha -1 as Rajphos and 40 kg K 2 O ha -1 as MOP significantly improved TOC, C fractions, CPI, CLI, CMI, C buildup rate and yield. Application of FYM @ 8t ha -1 (T 1 ) also improved the above mentioned parameters but the BC ratio was less (1.19 and 1.21) compared to T 7 . Increased soil acidity and deficiencies of secondary and micronutrients were also observed in all the treatments under study. Hence along with integrated nutrient management practices, soil test based fertilizer and lime application including secondary and micronutrients should be given importance to sustain the soil fertility in rice-rice cropping sequence of Onattukara.Item Soil organic carbon estimation using non imaging hyperspectral data in upland and wetland ecosystem of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2024-01-11) Nandaluru Kalpana; Divya VijayanKerala, characterized by diverse physiography, landscapes, and soil compositions, confronts challenges related to soil quality, primarily due to unpredictable shifts in weather conditions. Given the dynamic nature of the soil, which adapts to evolving environmental factors, assessing soil quality becomes crucial. Traditional soil analysis methods are both time-consuming and expensive, necessitating the exploration of innovative alternatives to expedite the analysis process. Visible-NIR (Vis-NIR) reflectance spectroscopy has emerged as a rapid, cost-effective, environmentally friendly, non-destructive, reproducible, and repeatable analytical technique. Among various soil quality parameters, Soil Organic Carbon (SOC) plays a significant role in influencing the physicochemical and biological aspects of soil, thereby positively affecting crop growth. Determining SOC is particularly crucial in tropical regions due to its dynamic nature and its contribution to climate change adaptation through carbon sequestration. Against this backdrop, a research study was conducted between 2021-2023 with the aim of estimating and quantitatively predicting soil organic carbon in upland and wetland ecosystems of Kerala using hyperspectral reflectance spectroscopy in the Department of Soil Science & Agricultural Chemistry. The study was conducted under the different land use systems of the three Agro Ecological Units (AEU) of Kerala namely Kole lands (AEU 6), North central Laterite (AEU 10) and Palakkad central plain (AEU 22). Georeferenced surface soil samples (0– 15cm) were collected from 70 locations under each AEU and anlyzed for physico- chemical properties of soil including SOC. The results of physico-chemical analysis showed that, mean bulk density was lower in AEU 6 (1.12 Mg m-3) compared to AEU 10 and 22 (1.3 Mg m-3). SOC ranged from (0.6 to 4.26 %) in AEU 6, AEU 10 (0.53 to 6.42%) and AEU 22 (0.21 to 3.74 %). Total Carbon (Tot. C) in AEU 6 varied from (0.7 to 4.46 %), AEU 10 (0.53 to 6.42) and AEU 22(0.34 to 3.83 %). Available Nitrogen (Av. N) ranged from (125.4 to 363.2 kg ha-1) in AEU 6, AEU 10 (108.9 to 439.04 kg ha-1) and AEU 22 (75.2 to 489.2 kg ha-1). Total Nitrogen (Tot. N) values ranging from AEU 6 (0.04 to 0.36 %), AEU 10 (0.07 to 0.87 %) and AEU 22 (0.05 to 0.33 %). Reflectance spectra were collected in controlled dark room condition for 210 samples in the wavelength region (350-2500 nm) using the ASD FieldSpec 4 spectroradiometer. The spectra were then pre-processed by using different techniques like First order derivative (FOD), second order derivative (SOD), log (1/R) transformation, and continuum removal (CR) for enhancing quality of the spectra for better prediction. Further, correlation analysis was carried for both raw and preprocessed spectra and correlated spectral bands were taken for developing PLSR (Partial least square Regression) model, the coefficient of determination (R2) was better for first and second order derivatives for SOC compared with raw and other preprocessed data. Hence, FOD was taken for developing PLSR model. The model was developed for the prediction of soil organic carbon (SOC), total carbon (Tot. C), available nitrogen (Av. N), and total nitrogen (Tot. N). For all the four parameters the datasets were divided in the ratio of 70:30, with 70% of the data (n=147) used for calibration and the remaining 30% used for validation (n=63). The PLSR model developed in this study underwent validation based on R2 and RMSE, demonstrating its efficacy in predicting SOC, Tot. C, Av. N and Tot. N values. The model exhibited strong predictive capabilities, achieving R2 values of 0.88 for SOC, 0.86 for Tot. C, 0.85 for Av. N, and 0.87 for Tot. N, with corresponding RMSE values of 0.66 %, 0.73 %, 66.9 kg ha-1, and 0.06%, respectively. The high variability in carbon and nitrogen content within the soil samples underscored the model's effectiveness. This study concludes that hyperspectral reflectance spectroscopy is a successful approach for predicting carbon and nitrogen levels in different ecosystems in Kerala. The research findings emphasize the significance of employing Chemometrics as an advanced tool for soil property prediction. Looking ahead, there is a pressing need to develop spectral libraries and prediction models tailored to regional and field-level variations in soil properties across diverse soil types in Kerala.Item Sorption and movement of cyantraniliprole in sandy loam soils with and without organic amendments(Department of Soil Science and Agricultural Chemistry , Vellayani, 2021-10-08) Al Noufiya, S; Thomas GeorgeThe study entitled “Sorption and movement of cyantraniliprole in sandy loam soils with and without organic amendments” was conducted in 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 2019-21. The main objectives of the experiment were to study the adsorption, desorption, persistence and leaching of cyantraniliprole in sandy loam soils with and without addition of organic amendment at the rate of 0.5 per cent Farm Yard Manure (FYM). The soil was collected from the sandy belts of Kazhakkoottam, Thiruvananthapuram. The physical and chemical analysis of the soil revealed that the soil was moderately acidic, with 0.84 per cent organic matter, 11.80 per cent clay, 22.30 per cent silt and 65.90 per cent sand. Among the major nutrients, phosphorus content was found to be high; potassium was medium while the other nutrients were low. The method for estimation of cyantraniliprole residues in soil were validated by modified QuEChERS method and was found ideal. Liquid- liquid partitioning using dichloromethane was found suitable for cyantraniliprole residue estimation in water. The adsorption-desorption studies were carried out at 5 different concentrations of 20, 40, 60, 80 and 100 μg levels each both in normal soil and 0.5 per cent FYM amended soil in Completely Randomized Design (CRD) with ten treatments and three replications and was repeated by direct spiking also. The adsorption- desorption data fitted well in Freundlich adsorption isotherm. The distribution coefficient, K d (mean value) was found high in amended soil (2.55) than normal soil (2.40) which indicated increased sorption in relation to organic matter content. The K f values (adsorption coefficient) were 2.60 and 2.45 for amended and normal soil respectively, indicating a high sorption capacity for the amended soil. The desorption was carried out in three cycles, the percentage desorption was decreasing in each consecutive cycle. In all levels of concentration, desorption was slower than adsorption indicating a hysteresis effect. In the soil samples directly spikedwith cyantraniliprole also, the desorption percentages were found lower and formed a still higher hysteresis. Mobility of cyantraniliprole was assessed in CRD with eighteen treatments and three replications i.e., by loading 3 levels viz., 25, 50 and 75 μg concentrations of cyantraniliprole, separately on top of 200 g soil columns loaded in PVC pipes and followed by eluting with 40, 80 and 160 mL of water @ 0.4 ml min -1 . In all the treatments residues were obtained in 0-25 cm packed columns and also in the leachate. In the normal soil, cyantraniliprole moved down the soil column which resulted in residue levels ranging from 7.48-3.98, 19.27- 9.57 and 27.67- 13.41 μg at 25, 50 and 75 μg levels, respectively when eluted with different volumes of water. In the soil amended with 0.5 per cent FYM, the corresponding residues ranged from 10.41- 4.48, 21.08- 9.89 and 29.98- 14.19 μg at 25, 50 and 75 μg levels indicating a higher retention in soil. The persistence of cyantraniliprole in normal soil and amended soil under three soil moisture conditions (air dry, field capacity and saturated) were studied using the formulation of cyantraniliprole added at the rate of 1, 2 and 4 mg kg -1 in CRD with eighteen treatments and three replications. The half- life of cyantraniliprole was found highest in amended soil spiked with 4 mg kg -1 cyantraniliprole under air dry soil condition i.e., 32.44 days followed by the same under normal soil condition i.e., 30.45 days. In the persistence study, no metabolites of cyantraniliprole were detected. The study concluded that the adsorption coefficient was higher in FYM amended soil indicating stronger adsorption than normal soil and the desorption percentages were reduced in the same. Hysteresis effect was noticed in all the treatments indicating slower desorption than adsorption. The mobility of cyantraniliprole was found to be slightly higher in normal soil compared to the 0.5 per cent FYM amended soil and also indicates its moderate mobility behaviour. The dissipation was found to be the fastest under submerged condition followed by field capacity and air dry conditions.Item Utilization of biochar from different bioresources for soil health and crop production(Vellayani Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2024-01-20) Diya Rajendran; Meera, A VThe study entitled “Utilization of biochar from different bioresources for soil health and crop production” was carried out during 2021-2023 in the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani and Integrated Farming System Research Station, Karamana. The objectives of the study were characterization of biochar produced by pyrolytic conversion of bioresources generated in farming systems and assessing their influence on soil health and crop production. The study comprised of four parts viz., production and characterization of biochar from different bioresources, bioassay study for selection of best four biochar, incubation experiment to study the nutrient release pattern and field evaluation of the effect of biochar on crop performance and soil health. Biochar was produced from seven different organic residues viz., teak leaf, coconut leaf, banana pseudostem, crop residue of vegetables, Eichhornia crassipes, Limnocharis flava and Colocasia esculenta, by the process of pyrolysis and the synthesized biochar were analysed for physical and chemical properties using standard procedures. Temperature of pyrolysis and residence time for various organic residues ranged between 250-5000C and 30-120 minutes, respectively. Highest recovery percentage of 46.53 % was recorded for coconut leaf biochar and lowest, 24.93 % for E. crassipes. Teak leaf biochar recorded the highest bulk density (0.48 Mg m-3) and EC (4.70 dS m-1), while banana pseudostem biochar had a higher water holding capacity (327.74 %). The produced biochar has an alkaline characteristic, with pH values ranging from 8.19 (C. esculenta biochar) to 10.40 (Banana pseudostem biochar). CEC (14.10 cmol kg-1), total carbon (67.52 %), N (1.34 %), K (2.24 %), S (0.33 %) and Zn (69.37 mg kg-1) content were highest for banana pseudostem biochar while P (0.77 %), Mn (173.76 mg kg-1), Cu (37.12 mg kg-1) and B (47.40 mg kg-1) were highest for L. flava biochar. Calcium (0.57 %) and magnesium (0.43 %) content were highest for crop residues of vegetable biochar while iron (2314.15 mg kg-1) content was highest in biochar produced from C. esculenta. C: N ratio was highest in C. esculenta biochar (128.35) and lowest in banana pseudostem biochar (50.38). 159 Bioassay study was carried out for 28 days using okra seedlings to select best four biochar for field study. The biochar produced from seven different bioresources were mixed with 2 kg soil @ 0.5 and 1 % w/w basis and FYM @ 1 % w/w basis and 10 okra seeds were placed in each pot. Coconut leaf, banana pseudostem and L. flava biochar recorded the highest germination percentage (96.67 %) and it was on par with biochar derived from crop residues. Banana pseudostem biochar recorded the highest values for shoot length (33.04 cm) and shoot biomass (2.23 g plant-1) and it was on par with L. flava biochar and FYM treated soil. Root length (23.97 cm), root biomass (0.60 g plant-1) and root volume (4.90 cm3) of the okra seedlings were highest in L. flava biochar treated soil and it was found to be on par with crop residue of vegetables biochar and FYM supplied treatments. Teak leaf biochar applied @ 1 % recorded the lowest values for germination percentage, shoot length, shoot biomass, root length, root biomass and root volume. Based on the results obtained from bioassay study, four biochar viz., coconut leaf, banana pseudostem, crop residue of vegetables and L. flava were selected for the incubation and field experiments. The nutrient release pattern from the selected four biochar was monitored after incorporation to soil based on a 90 day incubation study. Biochar and FYM were added @10 g kg-1 of soil. Periodic sampling and analysis of samples were done at 0, 30, 60 and 90 days of incubation. The incubation study revealed a slow and sustained release of nutrients from biochar. Biochar treated soils showed significantly higher value for pH and EC compared to FYM treated soil till the end of the incubation period. The pH was significantly higher for banana pseudostem biochar treated soil while EC was higher in soil applied with crop residue of vegetables biochar. During initial period of incubation, the mean values for available N, K, S and Zn content were highest for FYM treated soil but as incubation period progressed, banana pseudostem biochar treated soil recorded the highest values. The mean value for P, Fe, Cu and B were significantly higher for FYM treated soil during initial period and later stages, it was for L. flava biochar applied soil. Similarly, exchangeable Ca and Mg content were highest in FYM treated soil during initial period and as incubation period progressed, the crop residue of vegetables biochar treated soil recorded the highest values. A field experiment was conducted during 2023 to compare the effect of biochar from different bioresidues and FYM application on soil health and crop production using okra as the test crop. The treatments consisted application of selected four biochar viz., coconut leaf, banana pseudostem, crop residue of vegetables and L. flava biochar @ 25 t ha-1 along with 100 and 75 % of recommended dose of fertilizers (RDF) and FYM @ 25 t ha-1 along with 100 % RDF and soil with 100 % RDF only. The physical, chemical and biological properties of soil were markedly improved by the application of biochar. Reduction in bulk density, increase in water holding capacity, pH, EC, CEC, organic carbon and nutrient availability were observed with biochar application compared to FYM incorporation. Banana pseudostem biochar application recorded the highest values for organic carbon (1.92 %), available N (334.56 kg ha-1), K (258.45 kg ha-1), S (23.27 mg kg-1), Zn (3.73 mg kg-1) and dehydrogenase (192.78 µg of TPF g-1 soil 24 h-1) and microbial biomass carbon (81.97 mg kg-1) content of post harvest soil. Available P (91.78 kg ha-1), Fe (132.08 mg kg-1), Mn (34.89 mg kg-1) Cu (2.77 mg kg-1) and B (0.667 mg kg-1) content were higher in soil applied with L. flava biochar. Biochar application had significantly influenced the biometric and yield parameters of okra. Plant height, biomass yield and fruit yield were highest in treatments supplied with banana pseudostem biochar and it was on par with the treatments received L. flava biochar. Nutrient content of index leaf at harvest also indicated the beneficial effect of biochar in comparison to FYM and conventional fertilizers. Plant biometric attributes, fruit yield and soil health parameters for biochar application @ 25 t ha-1 and RDF at 100 and 75 % were on par. The highest B: C ratio (1.70) was recorded in treatment supplied with banana pseudostem biochar @25 t ha-1 along with 75 % RDF, which indicated that 25 % reduction in fertilizer application is possible through biochar application. There was 21 % increase in yield by banana pseudostem biochar application compared to FYM. It may be inferred that physico-chemical properties of biochar varies with the source material and their assessment for phytotoxicity is essential for ensuring the safety for agricultural use. Coconut leaf biochar, banana pseudostem biochar, crop residues of vegetable biochar and L. flava biochar had ideal physical and chemical 161 properties that qualify them to be used as good soil amendments which improve the soil physical, chemical and biological properties. FYM and biochar application had a positive effect on soil properties during incubation and field study. However biochar application exhibited sustainable effects than FYM. From the study, it can be concluded that banana pseudostem biochar @ 25 t ha-1 along with 75 % RDF is the economically viable and best treatment.Item Soil biodiversity under organic and integrated nutrient management system and impact on soil quality(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2024-01-11) Divya S NairA study entitled “Soil biodiversity under organic and integrated nutrient management systems and impact on soil quality” was carried out with an objective to characterize soil biodiversity in coconut based cropping systems of southern laterites (AEU-8) of Kerala under organic and integrated soil management and to correlate soil biodiversity with soil quality and plant nutrient availability. The study involved soil sample collection and characterization of soil samples for soil biodiversity and soil properties. Soil samples were collected from coconut-based cropping systems under organic soil management in the Model Organic Farm, Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani (Site 1) and also from coconut-based cropping systems under integrated nutrient management in the Instructional Farm, College of Agriculture, Vellayani (Site 2). From each site, 10 composite soil samples each were collected from 0-15cm, 15-30cm and 30-60 cm depth. Soil samples were characterised for soil macro, meso and micro fauna, microflora and beneficial microorganisms. Soil biodiversity was estimated from a single, pooled sample of each site. The soil samples were analysed for their physical (soil texture, bulk density, particle density, porosity, soil moisture content and water stable aggregates), electrochemical properties (pH and EC), chemical (cation exchange capacity, anion exchange capacity, Total N, P, K, S, available N, P, K, Ca, Mg, S, B, Fe, Mn, Cu, Zn and organic carbon) and biological properties (microbial biomass carbon, dehydrogenase activity and amylase activity). Among the soil macrofauna, annelids, hymenopterans, isopods, dermapterans, myriapods and carabids were observed. Annelid population was highest in the surface soil of site 1 (40 no.m-2 ) and these varied significantly among the managements across all depths. Hymenopterans were observed only in surface soil and were found to be significantly higher in site 1 (6 no. m-2 ). Isopods were found only in surface soil of site 1 (1.33 no. m-2 ) and were not observed in site 2. The count of dermapterans were found to be higher in site 1 but there was no significant difference observed among the managements. Myriapod population (millipedes and centipedes) were observed only in the surface and subsurface soil of site 1. Carabids (ground beetle) were observed only in the surface soil of site 1. Among mesofauna, both acari and collembola were higher in the surface soil of site 1 (3983.33 no. m-2 and 4939.33 no. m-2 respectively). Acari population varied significantly among the managements at 0-15 and 15-30 cm soil depth while collembolans varied significantly across all depths. Soil microfauna (nematodes) was higher in the surface soil of site 1 (231830 no. m-2 ) and their population varied significantly among the managements across all depths. Soil microflora including bacteria, fungi, and actinomycetes were found to be higher in the surface soil under organic management (42.6 x 105 cfu g-1 , 18 x 103 cfu g-1 , 36 x 103 cfu g-1 respectively). Significant difference among both managements were found in abundance of all organisms at each depth except for fungi at 30-60 cm. Beneficial microorganisms including Azospirillum, Phosphate Solubilizing Bacteria (PSB) and K solubilizers were cultured and enumerated from both soil managements. The population of Azospirllum was higher in the surface soil of site 1 (7 x 103 cfu g-1 ) and these varied significantly among the managements at 0-15 cm and 15-30 cm soil depth. The count of PSB and K- solubilizers obtained in the culture media was too low to be recorded. The soil texture was found to be sandy clay loam for soil samples collected from both sites. The sand fraction was observed to be decreasing with depth, while silt and clay fractions increased with increase in depth. Significantly lower bulk density was observed in organic field (1.31 Mg/m3 in surface soil) at all depths and it increased with increase in depth. Higher particle density was observed in the surface soil of site 1 (2.34 Mg/m3 ) and no significant difference among the samples was observed at any depth. Higher porosity was observed in surface soil of site 1 (46 %) and it varied significantly among the managements across all depths. The mean soil moisture content was observed to be slightly higher in soil under INM at all depths, but no significant difference between the managements were observed. Water stable aggregates were higher in surface soil of site 1 (69.34 %) and it varied significantly among the managements across all depths. All the chemical properties except pH was found to decrease with increase in depth. The surface soil of site 1 recorded the significantly higher mean values for EC (0.21 dS m-1 ), CEC (6.97 C mol (p+ ) kg-1 ), total N (1986.88 kg ha-1 ), total P (969.92 kg ha-1 ), total K (1512 kg ha-1 ), total S (947.52 kg ha-1 ), available P (88.03 kg ha-1 ), available K (361.20 kg ha-1 ), available Zn (2.83 mg kg-1 ) and OC (0.96 %). All these properties showed significantly higher mean values in site 1 across all depths. The surface soil of site 2 recorded significantly higher mean values for pH (5.57), available N (222.5 kg ha-1 ), B (0.436 mg kg-1 ), Fe (16.79 mg kg-1 ) and Cu (0.99 mg kg-1 ). These properties varied significantly among the managements across all depths, except available B at 15-30 cm and 30-60 cm, and available Cu at 30-60 cm. While AEC, available Ca, Mg, S and Mn did not show significant difference among the management at any depth. The surface soil of site 1 recorded higher microbial biomass carbon (22.96 μg g -1 ), dehydrogenase (31.02 μg TPF hydrolysed g-1 soil 24 hr-1 ) and amylase (1.24 mU g-1 of soil) activity. All these biological properties decreased with increase in depth and were observed to be significantly higher in soil under organic management at all depths. Organisms observed a positive correlation with most of the physical, chemical and biological properties of soil. Negative correlation was observed between soil organisms and bulk density and also between hymenoptera and dermaptera with soil pH. From the Bray Curtis dissimilarity index, it is observed that the average dissimilarity of biodiversity was 0.262 between the surface soil of organic management and INM. This suggests that there are differences in species composition, although there are also shared species or similarities to some extent. Average dissimilarity among the managements decreased with depth. The PERMANOVA analysis showed that "depth" had a substantial and statistically significant effect, while the "management" factor did not significantly contribute to community dissimilarity. The interaction term "management × depth" also proved to be non-significant in explaining community dissimilarity. From the Bray Curtis dissimilarity index SIMPER analysis was performed and it showed that nematode is the species that contributes the largest amount of the difference between 0-15 cm and 15-30 cm soil depths and also between 15-30 cm and 30-60 cm soil depths. From this study, it was concluded that soil biodiversity was positively correlated to most of the soil properties and no significant effect was observed in the community dissimilarity for management but, depth had a substantial and statistically significant effect on community dissimilarity.