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ThesisItem Open Access Exploration on the links between soil carbon storage and root biomass and elucidation of drivers of carbon stabilization(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2022) Geethu Jacob; KAU; Manorama Thampatti, K CThe study entitled ―Exploration on the links between soil carbon storage and root biomass and elucidation of drivers of carbon stabilization‖ was conducted at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during November 2019 to September 2021 with the objective to study the links between soil carbon storage and root biomass in soils of different agro ecological units and to identify the key drivers of C stabilization and NP fluxes under different management practices. The study area comprised of three Agro ecological units (AEUs) of Southern Kerala viz. Southern and Central Foot Hills (AEU 12), Southern High Hills (AEU 14) and Kumily High Hills (AEU 16). The study was carried out in three parts namely exploration on the links between soil organic C and NP pools with root biomass in soils of different AEUs, assessment of carbon storage under different land use system and identifying the drivers of C stabilization and field experiments to study the effect of management practices on the link between root and shoot biomass C and SOC and NP pools. For the study exploration on the links between soil organic C and NP pools with root biomass in soils of different AEUs, the study area was surveyed and geocoded soil samples from 0-20 cm and 20-60 cm depth were collected using core samplers. The root biomass from the soil samples were separated out and weighed. The soil samples were analyzed for its various physical, chemical and biological properties. For assessment of carbon storage under different land use system and identifying the drivers of C stabilization, the most prominent land use system of each AEU was identified and five samples were collected from each system. The sampling size was one sq.m to a depth of 60 cm. The plants of the same area were uprooted and their shoot and root biomass were recorded. Both the soil and plant samples were collected and analysed for various parameters. The field experiment in split plot design on grain cowpea – fodder maize cropping sequence was laid out with the main plot treatments as m1: conventional tillage, m2: deep tillage (30 cm depth) and m3: no till and sub plot treatments as s1: POP recommendation, s2: soil test based POP, s3: organic nutrient management (TOF-F), s4: POP + AMF, s5: soil test based POP + AMF, s6: TOF-F + AMF and s7: absolute control. After the harvest of grain cowpea, shoot biomass were removed and roots were retained in three replications and in the other three replications total biomass of grain cowpea were added into the soil and left for decomposition. After that fodder maize was raised in the field and the crop and soil samples were collected and analysed for various parameters. The results of the Part I revealed that the physical properties like bulk density (BD) and gravel per cent of all the AEUs showed an increase towards depth while the electrochemical properties showed a decrease. Among the different AEUs, AEU 16 recorded lowest BD (1.22 Mg m-3 ) and gravel per cent (30.53 %) and had a subsoil increase of 12 per cent and 17 per cent for BD and gravel per cent respectively. The different fractions of soil C and N showed a decrease with depth for all AEUs. The soil total organic carbon (TOC-5.94 %) and recalcitrant C (RC-1.64 %) content were highest for AEU 14 with a decrease of 26 per cent and 31 per cent respectively for subsoil. The highest dissolved organic C (DOC-54.63 mg kg -1 ) and labile C (LC- 877.50 mg kg -1 ) content were for AEU 16 with a subsoil decrease of 45 per cent and 27 per cent respectively. AEU 12 recorded lower values for C fractions which may be due to decreased root biomass by 38 per cent and 25 per cent in surface soil and 55 per cent and 70 per cent in subsoil than that of AEU 14 and AEU 16 respectively. The root biomass and soil C fractions were positively and significantly correlated at both sampling depths. The highest correlation coefficients between root biomass and soil C fractions were recorded by DOC (0.976) followed by RC (0.931) and LC (0.975) followed by DOC (0.953) for surface and subsoil respectively. From the regression analysis perfect fit towards linear regression model, expressed as R2 value, was highest for DOC (0.95) and LC (0.94) at sampling depths of 0-20 cm and 20-60 cm respectively. The different fractions of N were highest for AEU 12 and surface soil showed an increase in total nitrogen (TN) by 6 per cent and NH4-N by 20 per cent, NO3 – N by 18 per cent and organic N (ON) by 5 per cent than subsoil. For soil P fractions an increase was observed with depth and AEU 12 recorded highest values for P fractions. Among soil N and P fractions, ON and labile P (LP) were found to be more correlated to root biomass and with higher R2 values at both sampling depths. The MBC (26.89 mg kg -1 ) and DHA (34.94 µg TPF g-1 24 hr-1 ) were highest for AEU 16 and surface soil showed an increase in MBC by 28 per cent and DHA by 30 per cent, than subsoil. For part II, the most prominent land use system of each AEU were identified as rubber plantations for AEU 12 and AEU 14 and cardamom plantations for AEU 16. The rubber plantations of AEU 14 recorded highest C storage (434.0 t ha-1 ) and lowest value was observed for cardamom plantations of AEU 16 (329.9 t ha-1 ). The soil physical properties and electrochemical properties behaved similar to that of Part I. Cardamom plantations of AEU 16 recorded lowest BD (0.97 Mg m-3 ) and gravel content (28 %) while AEU 12 had highest pH (5.61) and lowest EC (0.39 dS m-1 ). Among the different land use systems, rubber plantations of AEU 14 recorded highest values for soil TOC (6.72 %) and DOC (55.16 mg kg-1 ) content while cardamom plantations had highest soil LC (910.91 mg kg-1 ) and surface soil RC (1.92 %) content but subsoil RC content was more for rubber plantations of AEU 14. In rubber plantations the root biomass were correlated to all C fractions and more correlated to RC and TOC and in cardamom plantations root biomass were significantly correlated to TOC (0.98) and DOC (0.95) fractions only. A significant and positive correlation between root lignin and soil C fractions (RC and TOC) was also observed. The different fractions of N and P were highest for cardamom plantations of AEU 16 and surface soil showed an increase in TN by 5 per cent, NH4-N by 14 per cent, NO3– N by 22 per cent and ON by 4 per cent than subsoil and a subsoil increase of TP by 12 per cent, LP by 29 per cent and NLP by 11 per cent were also observed. The shoot biomass were more correlated to soil N and P fractions than root biomass and were more correlated to ON and TN and to TP and NLP among soil N and P fractions respectively. A significant positive correlation between N and P removal and soil NP pools were also obtained. The MBC and DHA were highest for cardamom plantations of AEU 16 and surface soil showed an increase in MBC by 25 per cent and DHA by 23 per cent than subsoil. In the field experiment, among the various nutrient management treatments, soil test based POP + AMF (s5) recorded the highest plant height, shoot biomass and grain yield plant-1 (107.70 g) and TOF-F + AMF (s6) showed highest values for root characteristics and quality parameters for grain cowpea. Similarly for fodder maize grown under both conditions, the treatment soil test based POP + AMF (s5) gave highest shoot biomass, fodder yield and quality parameters while highest root biomass were recorded by the treatment, TOF-F + AMF (s6). Among the tillage levels, the no till treatment (m3) performed best in connection with growth, yield and quality characteristics throughout the cropping period. Tillage and nutrient management had significantly influenced various soil properties. The lowest soil BD and higher WSA per cent and soil pH were reported by the treatment TOF-F + AMF (s6) throughout the cropping sequence. Among tillage levels, deep tillage (m2) remained superior for soil BD and pH and no till treatment (m3) for WSA per cent respectively. The treatment, TOF-F + AMF (s6) remained superior for soil C fractions viz., TOC, LC and RC content, mineralizable N fractions (NH4-N and NO3-N), labile P and MBC content and dehydrogenase activity throughout the cropping sequence. The treatment, soil test based POP +AMF (s5) recorded higher values for NP fractions like TN, ON, TP and non labile P (NLP). Among the tillage levels, the no till treatment (m3) remained superior in connection with soil chemical and biological properties especially towards the end of cropping period. As the cropping sequence advances an improvement in soil physical, chemical and biological properties were observed and this is mainly attributed to the crop residue addition of grain cowpea and more improvement was observed for total residue incorporation than root residue alone addition. The soil C pools were highly linked to root biomass and NP pools to shoot biomass. The root biomass and root lignin were the main drivers of C stabilization. The treatments with AMF remained superior in various soil properties and yield and growth attributes emphasizing the favourable role of AMF in C storage and nutrient cycling in soils. With regard to nutrient management, soil test based POP + AMF recorded the highest yield in cropping sequence while organic nutrition (TOF-F) + AMF contributed more to soil properties indicating the need for further research on nutrient translocation and assimilation under organic nutrition. The no tilled condition with total residue incorporation responded better than root residue alone incorporation, hinting to the fact that more organic matter contributing practices improved the physicochemical and biological conditions of soils favourably.ThesisItem Open Access Dissipation and distribution of fipronil, carbosulfan and their metabolites in banana var. Nendran (AAB) and soil(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2021) Visveswaran, S; KAU; Thomas, GeorgeThe study entitled “Dissipation and distribution of fipronil and carbosulfan and their metabolites in banana (Musa spp) and soil” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during the period from August 2016 to April 2017. The objective was to assess the dissipation, metabolism and persistence of fipronil and carbosulfan in banana, cv. Nendran (AAB), grown under red loam soils (AEU 8-southern laterites) of College of Agriculture, Vellayani, and its impact on soil organisms. Banana variety Nendran, grown as per package of practices recommendations, KAU in randomized block design at the Instructional Farm, Vellayani, with five treatments viz., T1- absolute control (No application of carbosulfan and or fipronil), T2- recommended practice of 30 mg ai of fipronil per plant per application, applied 3 times on 0, 60 and 150 days of planting, T3 – double dose of T2, T4- recommended practice of 400 mg ai of carbosulfan per plant per application, applied 3 times on 0, 60 and 150 days of planting and T5- double the dose of T4. Samples viz, soil, leaves, fingers bunches and flower bud, central core of pseudo-stem and corm were collected and analyzed for residue at definite time intervals. The residue estimation of the target pesticide molecules and their toxic metabolites were performed by adopting standard extraction and clean up procedure viz., conventional acetone extraction followed by hexane partitioning as well as by QuEChERS method. Method validation was conducted by spiking with analytical standards from which recovery, (accuracy 70-120% of spiked values), standard deviation of recoveries, RSD value (below 20%), linearity (calibration curve), for the adopted method were worked out and compared for compliance. Acetonitrile extracted samples were analyzed using “Waters Acuity UPLC 137 system” with suitable column and then subjecting the effluent to triple quadrupole API 3200 MS/MS system equipped with electrospray ionization interface (ESI) operating in required mode as per the molecule. Extraction using QuEChERS method gave satisfactory values for validation parameters and hence adopted for the studies. The presence of carbosulfan in the 1st to 4th leaves till day 20th and subsequent dissipation pattern prediction for BDL in 22.5 day indicated that, at recommended dose of application, it is not safe to use the leaves within 23 days of application for serving or food packing (as commonly practiced in many households of Kerala). Sample matrices revealed the presence of metabolites each for fipronil and carbosulfan with variation from below detectable limit (BDL) to a highest content of 3.804 μg/g carbosulfan at 2 hours of application in the soil. Blossom bud, flower bract alone, bunch on 15th day of emergence, bunch on 30th day of emergence, peel, bunch on harvest, pseudo stem and corm did not register any detectable level of fipronil or carbosulfan and their metabolites and even with an additional application of treatment on the day of bunching also did not register any detectable level of fipronil or carbosulfan and their metabolites. Residue of fipronil and their toxic metabolites in the first, second and third leaves of banana on penultimate day of completion of pre-bunching application was found to be below the detectable levels throughout the period of sampling and this may be attributed to low absorption, fast metabolism and mobility. However, on 40th day the fipronil was detected in the 4th leaf to the extent of 0.034 μg g-1 and was not detectable on 50th day. Metabolites of Carbosulfan residue existed in the first, second and third leaves between 5th and 20th day and it dissipated to below detectable limit on 40th day of application. The content of residue under treatment T5 was distinctly higher than T4 during these periods and dissipated to BDL on 25th day. 138 In soil, the fipronil though dissipated to BDL before 50th day, persisted from 2 hours of application till 40th day. However, carbosulfan and its metabolites were early to dissipate to BDL on 7th day of completion of application. Sample in experiment with 5 times the recommended dose of application as injection into pseudostem at the time of bunch emergence also did not record any residue above detectable level in the flower bud, flower bract alone, bunch on 15th day of emergence, bunch on 30th day of emergence, peel, bunch on harvest and pseudostem. Soil urease activity on 10th day was significantly influenced by the treatment where T1, T3 and T5 are significantly lower than T2 and T4. However, dehydrogenase activity and acid phosphatase activity were not significantly influenced by the treatment. Bacterial population was higher in T1. Treatments were found to significantly influence the weight of blossom bud on dehorning, pseudostem, bunches and corm. Other biometric parameters were not influenced by the treatment. The above results show complete dissipation of fipronil and carbosulfan to safe limits in soil and banana leaf, when applied as per package of practices recommendation for banana cultivation (fipronil 30 mg a.i. and carbosulfan 400 mg a.i. per plant applied thrice viz., on 0, 60 and 150 days of planting), within 50 and 23 days of application. Also, the application of fipronil and carbosulfan as per the above dose in no way results in the accumulation of residue on any of the edible plant parts of banana and hence it is safe for human consumption.ThesisItem Open Access Sulphur dynamics in major rice-growing soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2022) Unnikrishnan, R; KAU; Jayasree Sankar, SSulphur has been recognized as an essential nutrient to plants and it is ranked as fourth among major plant nutrients after nitrogen, phosphorus, and potassium. Most of the soils in Kerala are rich in total S and the maximum amount of sulphates has been reported in Kari and Pokkali soils. Representative soil samples were collected from seven different rice growing tracts falling under different agro-ecological units (AEU) of Kerala for the study entitled Sulphur dynamics in major rice-growing soils of Kerala. Five samples each were collected from various locations pertaining to a particular soil type for initial characterisation. In addition three soil and plant samples were also collected from each soil type at active tillering and harvest stage of rice crop. The study aims at understanding sulphur dynamics in major rice soils of Kerala and its relationship with that of carbon, nitrogen and phosphorus. It also envisages at unfolding the antagonism/ synergism between sulphur and other nutrients, if any. Sixteen out of 35 samples belonged to the category of strongly acidic to moderately acidic. It can be concluded from characterisation study that the sandy soils of Onattukara was low in terms of fertility wherein Pokkali soils, Kole land and Kari soils of Kuttanad were high with respect to soil fertility. None of the soils were found deficient in available sulphur with Pokkali soils being the remarkably highest. The low land brown hydromorphic laterite and Onattukara sandy soils had relatively lower sulphur content. The Kari soils accounted for highest microbial biomass carbon and aryl sulphatase activity. The estimated soil pH was slightly elevated at active tillering and harvest stage. The sulphur exhibited an antagonistic relationship with phosphorous, potassium as well as manganese Fractionation of S was conducted at three stages to find out the dominant different forms of sulphur. The Pokkali soils and Onattukara sandy soils had the highest as well as lowest value for all the sulphur fractions before cropping. The Kari soil concluded the highest total organic sulphur at active tillering and harvest stage. All the sulphur fractions were positively influenced by microbial biomass carbon and aryl sulphatase activity. An identifiable positive relation existed between available nitrogen and total organic sulphur as well. The C:S ratio was high in Laterite soil and lowest in Pokkali soil at all the three stages. The Onattukara sandy soil and Laterite soil accounted for the highest N:S ratio wherein Kari soil and Pokkali soil had the lowest ratio. The decreased C:S and N:S ratio contributed to the raised plant available sulphur in soil. Sulphur adsorption experiment was conducted at 25 ℃ as well as 40℃ and quantity-intensity relations were carried out based on data. While The samples from Pokkali and Kari soil exhibited desorption of sulphur at both the temperatures (25 ℃ and 40 ℃) studied, it was found to get adsorbed in the case of Laterite soil and Onattukara sandy soils at both 25 ℃ and 40 ℃.ThesisItem Open Access Spatial and temporal variations in nutrient dynamics in Pokkali soils of Kerala(Department of Soil Science and Agricultural Chemistry, Vellanikkara, 2022) Silpa, P; KAU; Jayasree Sankar, SThe Pokkali soils (Typic Sulfaquents) are low land soils situated below the mean sea level, located along the coastal tracts of Alappuzha, Ernamkulam and Thrissur districts. These soils are acid saline in nature where shrimp/prawn farming is practiced during high saline phase (December to April) coinciding with sea water entry followed by cultivating the salt tolerant Pokkali rice during low saline phase (June to October) when the dilution of salts occurs after South West monsoon. Only very few studies have been undertaken so far on nutrient status in Pokkali soils. Wide variations in nutrient content ranging from deficient to toxic level were reported in these studies. A comprehensive study is very much essential to unravel the seasonal and temporal variations of nutrient dynamics in Pokkali soils. The soil samples (lowland soils and neighbouring upland soils) from different land use systems and the water samples (both standing water and nearby brackish water inundating the Pokkali tract) were collected at bimonthly intervals starting from June 2017 to April 2018 to understand the nutrient dynamics in these soils with respect to spatial and temporal variation and to find out the influence of source water on them. Physico-chemical properties and biological properties of the collected soils were analysed. Salt water intrusion during high saline phase into Pokkali fields caused drastic increase in electrical conductivity, decrease in soil pH and associated changes in available plant nutrients. A gradual decrease in redox potential from June to October and increase from December to April were also observed as an influence of sea water intrusion. The south west monsoon received during the low saline phase played a significant role in diluting soil salinity and loss of H + ions from top soil, thus affecting the soil nutrient dynamics in total. High content of available plant nutrients and the change in nutrient content with respect to spatial and temporal variations were observed in low land soils compared to the nearby upland soils. Spatial variation of all available nutrients except phosphorus was highly influenced by the nearness of brackish water rather than the type of land use system. Highest available phosphorus recorded in paddy alone land use might be due to the phosphorus mineralisation from left out crop stubbles in paddy field. Some land uses in uplands showed deficiency of available Ca, Mg and B also. In terms of temporal variation, all nutrients except available phosphorus remained very high during high saline phase as influenced by marine water whereas availability of phosphorus was highly influenced by soil pH. High acidity and salinity during high saline phase adversely affected the soil biological properties. Fractionation of phosphorus and copper was carried out to study their major fractions and to ascertain their contribution to the available pool. All the P fractions were high in Pokkali soil. Temporal variation of all the P fractions was also prominent in Pokkali soil. Ws-P, Ca-P and residual-P were very high in October (low saline phase) whereas other fractions were high in April (high saline phase). Effect of land uses on P fractions was absent except for Org-P and Ca-P. Temporal variation of all the Cu fractions was clearly evident in Pokkali soil. Ws-Cu, Ex-Cu and residual Cu were high in April (high saline phase). All other fractions were high in October (low saline phase). Land uses did not show any direct effect on distribution of copper fractions. All the land uses showed same trend in copper fractions across the seasons. Phosphorus adsorption was high in April (high saline phase) whereas Cu adsorption was high in October (low saline phase). L and S-shaped curves were obtained for P and Cu adsorption respectively. Adsorption of P and Cu increased with increase in soil temperature. Adsorption of P and Cu among various soil textural classes followed the order clay>clay loam>sandy clay loam>loam>silt loam. Adsorption of P was mainly in inorganic forms ie. oxide and oxy hydroxides of Fe and Al surface whereas that of Cu was mainly in organic form. Freundlich adsorption isotherm was found as the best to explain the adsorption of P and Cu in Pokkali soils. Adsorption of both P and Cu was spontaneous and endothermic in nature. Low and high saline phases attributed to variations in physico-chemical and biological properties of Pokkali soils. South West monsoon caused leaching losses of nutrients particularly potassium, sulphur, magnesium and boron during low saline phase. The presence of brackish water source nearer to field had more effect on nutrient dynamics in Pokkali soils, rather the type of land use system. The influence of temperature on nutrient was visible in the quantity –intensity relations of P and Cu. The present study has clearly shown that the nutrient dynamics in Pokkali soils is influenced more by temporal variations than the spatial variations.ThesisItem Open Access Exploration on the links between soil carbon storage and root biomass and elucidation of drivers of carbon stabilization(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2022) Geethu Jacob; KAU; Manorama Thampatti, K CThe study entitled ―Exploration on the links between soil carbon storage and root biomass and elucidation of drivers of carbon stabilization‖ was conducted at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during November 2019 to September 2021 with the objective to study the links between soil carbon storage and root biomass in soils of different agro ecological units and to identify the key drivers of C stabilization and NP fluxes under different management practices. The study area comprised of three Agro ecological units (AEUs) of Southern Kerala viz. Southern and Central Foot Hills (AEU 12), Southern High Hills (AEU 14) and Kumily High Hills (AEU 16). The study was carried out in three parts namely exploration on the links between soil organic C and NP pools with root biomass in soils of different AEUs, assessment of carbon storage under different land use system and identifying the drivers of C stabilization and field experiments to study the effect of management practices on the link between root and shoot biomass C and SOC and NP pools. For the study exploration on the links between soil organic C and NP pools with root biomass in soils of different AEUs, the study area was surveyed and geocoded soil samples from 0-20 cm and 20-60 cm depth were collected using core samplers. The root biomass from the soil samples were separated out and weighed. The soil samples were analyzed for its various physical, chemical and biological properties. For assessment of carbon storage under different land use system and identifying the drivers of C stabilization, the most prominent land use system of each AEU was identified and five samples were collected from each system. The sampling size was one sq.m to a depth of 60 cm. The plants of the same area were uprooted and their shoot and root biomass were recorded. Both the soil and plant samples were collected and analysed for various parameters. The field experiment in split plot design on grain cowpea – fodder maize cropping sequence was laid out with the main plot treatments as m1: conventional tillage, m2: deep tillage (30 cm depth) and m3: no till and sub plot treatments as s1: POP recommendation, s2: soil test based POP, s3: organic nutrient management (TOF-F), s4: POP + AMF, s5: soil test based POP + AMF, s6: TOF-F + AMF and s7: absolute control. After the harvest of grain cowpea, shoot biomass were removed and roots were retained in three replications and in the other three replications total biomass of grain cowpea were added into the soil and left for decomposition. After that fodder maize was raised in the field and the crop and soil samples were collected and analysed for various parameters. The results of the Part I revealed that the physical properties like bulk density (BD) and gravel per cent of all the AEUs showed an increase towards depth while the electrochemical properties showed a decrease. Among the different AEUs, AEU 16 recorded lowest BD (1.22 Mg m-3 ) and gravel per cent (30.53 %) and had a subsoil increase of 12 per cent and 17 per cent for BD and gravel per cent respectively. The different fractions of soil C and N showed a decrease with depth for all AEUs. The soil total organic carbon (TOC-5.94 %) and recalcitrant C (RC-1.64 %) content were highest for AEU 14 with a decrease of 26 per cent and 31 per cent respectively for subsoil. The highest dissolved organic C (DOC-54.63 mg kg -1 ) and labile C (LC- 877.50 mg kg -1 ) content were for AEU 16 with a subsoil decrease of 45 per cent and 27 per cent respectively. AEU 12 recorded lower values for C fractions which may be due to decreased root biomass by 38 per cent and 25 per cent in surface soil and 55 per cent and 70 per cent in subsoil than that of AEU 14 and AEU 16 respectively. The root biomass and soil C fractions were positively and significantly correlated at both sampling depths. The highest correlation coefficients between root biomass and soil C fractions were recorded by DOC (0.976) followed by RC (0.931) and LC (0.975) followed by DOC (0.953) for surface and subsoil respectively. From the regression analysis perfect fit towards linear regression model, expressed as R2 value, was highest for DOC (0.95) and LC (0.94) at sampling depths of 0-20 cm and 20-60 cm respectively. The different fractions of N were highest for AEU 12 and surface soil showed an increase in total nitrogen (TN) by 6 per cent and NH4-N by 20 per cent, NO3 – N by 18 per cent and organic N (ON) by 5 per cent than subsoil. For soil P fractions an increase was observed with depth and AEU 12 recorded highest values for P fractions. Among soil N and P fractions, ON and labile P (LP) were found to be more correlated to root biomass and with higher R2 values at both sampling depths. The MBC (26.89 mg kg -1 ) and DHA (34.94 µg TPF g-1 24 hr-1 ) were highest for AEU 16 and surface soil showed an increase in MBC by 28 per cent and DHA by 30 per cent, than subsoil. For part II, the most prominent land use system of each AEU were identified as rubber plantations for AEU 12 and AEU 14 and cardamom plantations for AEU 16. The rubber plantations of AEU 14 recorded highest C storage (434.0 t ha-1 ) and lowest value was observed for cardamom plantations of AEU 16 (329.9 t ha-1 ). The soil physical properties and electrochemical properties behaved similar to that of Part I. Cardamom plantations of AEU 16 recorded lowest BD (0.97 Mg m-3 ) and gravel content (28 %) while AEU 12 had highest pH (5.61) and lowest EC (0.39 dS m-1 ). Among the different land use systems, rubber plantations of AEU 14 recorded highest values for soil TOC (6.72 %) and DOC (55.16 mg kg-1 ) content while cardamom plantations had highest soil LC (910.91 mg kg-1 ) and surface soil RC (1.92 %) content but subsoil RC content was more for rubber plantations of AEU 14. In rubber plantations the root biomass were correlated to all C fractions and more correlated to RC and TOC and in cardamom plantations root biomass were significantly correlated to TOC (0.98) and DOC (0.95) fractions only. A significant and positive correlation between root lignin and soil C fractions (RC and TOC) was also observed. The different fractions of N and P were highest for cardamom plantations of AEU 16 and surface soil showed an increase in TN by 5 per cent, NH4-N by 14 per cent, NO3– N by 22 per cent and ON by 4 per cent than subsoil and a subsoil increase of TP by 12 per cent, LP by 29 per cent and NLP by 11 per cent were also observed. The shoot biomass were more correlated to soil N and P fractions than root biomass and were more correlated to ON and TN and to TP and NLP among soil N and P fractions respectively. A significant positive correlation between N and P removal and soil NP pools were also obtained. The MBC and DHA were highest for cardamom plantations of AEU 16 and surface soil showed an increase in MBC by 25 per cent and DHA by 23 per cent than subsoil. In the field experiment, among the various nutrient management treatments, soil test based POP + AMF (s5) recorded the highest plant height, shoot biomass and grain yield plant-1 (107.70 g) and TOF-F + AMF (s6) showed highest values for root characteristics and quality parameters for grain cowpea. Similarly for fodder maize grown under both conditions, the treatment soil test based POP + AMF (s5) gave highest shoot biomass, fodder yield and quality parameters while highest root biomass were recorded by the treatment, TOF-F + AMF (s6). Among the tillage levels, the no till treatment (m3) performed best in connection with growth, yield and quality characteristics throughout the cropping period. Tillage and nutrient management had significantly influenced various soil properties. The lowest soil BD and higher WSA per cent and soil pH were reported by the treatment TOF-F + AMF (s6) throughout the cropping sequence. Among tillage levels, deep tillage (m2) remained superior for soil BD and pH and no till treatment (m3) for WSA per cent respectively. The treatment, TOF-F + AMF (s6) remained superior for soil C fractions viz., TOC, LC and RC content, mineralizable N fractions (NH4-N and NO3-N), labile P and MBC content and dehydrogenase activity throughout the cropping sequence. The treatment, soil test based POP +AMF (s5) recorded higher values for NP fractions like TN, ON, TP and non labile P (NLP). Among the tillage levels, the no till treatment (m3) remained superior in connection with soil chemical and biological properties especially towards the end of cropping period. As the cropping sequence advances an improvement in soil physical, chemical and biological properties were observed and this is mainly attributed to the crop residue addition of grain cowpea and more improvement was observed for total residue incorporation than root residue alone addition. The soil C pools were highly linked to root biomass and NP pools to shoot biomass. The root biomass and root lignin were the main drivers of C stabilization. The treatments with AMF remained superior in various soil properties and yield and growth attributes emphasizing the favourable role of AMF in C storage and nutrient cycling in soils. With regard to nutrient management, soil test based POP + AMF recorded the highest yield in cropping sequence while organic nutrition (TOF-F) + AMF contributed more to soil properties indicating the need for further research on nutrient translocation and assimilation under organic nutrition. The no tilled condition with total residue incorporation responded better than root residue alone incorporation, hinting to the fact that more organic matter contributing practices improved the physicochemical and biological conditions of soils favourably.ThesisItem Open Access Spatial and temporal variations in nutrient dynamics in Pokkali soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2022) Silpa, P; KAU; Jayasree Sankar, SThe Pokkali soils (Typic Sulfaquents) are low land soils situated below the mean sea level, located along the coastal tracts of Alappuzha, Ernamkulam and Thrissur districts. These soils are acid saline in nature where shrimp/prawn farming is practiced during high saline phase (December to April) coinciding with sea water entry followed by cultivating the salt tolerant Pokkali rice during low saline phase (June to October) when the dilution of salts occurs after South West monsoon. Only very few studies have been undertaken so far on nutrient status in Pokkali soils. Wide variations in nutrient content ranging from deficient to toxic level were reported in these studies. A comprehensive study is very much essential to unravel the seasonal and temporal variations of nutrient dynamics in Pokkali soils. The soil samples (lowland soils and neighbouring upland soils) from different land use systems and the water samples (both standing water and nearby brackish water inundating the Pokkali tract) were collected at bimonthly intervals starting from June 2017 to April 2018 to understand the nutrient dynamics in these soils with respect to spatial and temporal variation and to find out the influence of source water on them. Physico-chemical properties and biological properties of the collected soils were analysed. Salt water intrusion during high saline phase into Pokkali fields caused drastic increase in electrical conductivity, decrease in soil pH and associated changes in available plant nutrients. A gradual decrease in redox potential from June to October and increase from December to April were also observed as an influence of sea water intrusion. The south west monsoon received during the low saline phase played a significant role in diluting soil salinity and loss of H + ions from top soil, thus affecting the soil nutrient dynamics in total. High content of available plant nutrients and the change in nutrient content with respect to spatial and temporal variations were observed in low land soils compared to the nearby upland soils. Spatial variation of all available nutrients except phosphorus was highly influenced by the nearness of brackish water rather than the type of land use system. Highest available phosphorus recorded in paddy alone land use might be due to the phosphorus mineralisation from left out crop stubbles in paddy field. Some land uses in uplands showed deficiency of available Ca, Mg and B also. In terms of temporal variation, all nutrients except available phosphorus remained very high during high saline phase as influenced by marine water whereas availability of phosphorus was highly influenced by soil pH. High acidity and salinity during high saline phase adversely affected the soil biological properties. Fractionation of phosphorus and copper was carried out to study their major fractions and to ascertain their contribution to the available pool. All the P fractions were high in Pokkali soil. Temporal variation of all the P fractions was also prominent in Pokkali soil. Ws-P, Ca-P and residual-P were very high in October (low saline phase) whereas other fractions were high in April (high saline phase). Effect of land uses on P fractions was absent except for Org-P and Ca-P. Temporal variation of all the Cu fractions was clearly evident in Pokkali soil. Ws-Cu, Ex-Cu and residual Cu were high in April (high saline phase). All other fractions were high in October (low saline phase). Land uses did not show any direct effect on distribution of copper fractions. All the land uses showed same trend in copper fractions across the seasons. Phosphorus adsorption was high in April (high saline phase) whereas Cu adsorption was high in October (low saline phase). L and S-shaped curves were obtained for P and Cu adsorption respectively. Adsorption of P and Cu increased with increase in soil temperature. Adsorption of P and Cu among various soil textural classes followed the order clay>clay loam>sandy clay loam>loam>silt loam. Adsorption of P was mainly in inorganic forms ie. oxide and oxy hydroxides of Fe and Al surface whereas that of Cu was mainly in organic form. Freundlich adsorption isotherm was found as the best to explain the adsorption of P and Cu in Pokkali soils. Adsorption of both P and Cu was spontaneous and endothermic in nature. Low and high saline phases attributed to variations in physico-chemical and biological properties of Pokkali soils. South West monsoon caused leaching losses of nutrients particularly potassium, sulphur, magnesium and boron during low saline phase. The presence of brackish water source nearer to field had more effect on nutrient dynamics in Pokkali soils, rather the type of land use system. The influence of temperature on nutrient was visible in the quantity –intensity relations of P and Cu. The present study has clearly shown that the nutrient dynamics in Pokkali soils is influenced more by temporal variations than the spatial variations.ThesisItem Open Access Nutrient dynamics and crop productivity in lowland lateritic soil (aeu 10) under rice residue management practices(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Amritha, K; KAU; Jayasree Sankar, SThe present investigation was undertaken at College of Agriculture Vellanikkara, Kerala Forest Research Institute Peechi, and Agricultural Research Station Mannuthy during 2017-2020. The experiment comprised of characterization of rice residues and their products for physical and chemical properties, an incubation experiment to study the kinetics of carbon mineralization, and a field experiment to evaluate the efficacy of rice residues and their products on lowland rice. Straw and husk, the important residues produced during the cultivation and processing of rice, respectively was procured from farmer’s field and further materials required for the research work viz., vermicomposted rice straw (VRS), vermicomposted rice husk (VRH), rice straw biochar (RSB), and rice husk biochar (RHB) were produced from the straw (RS) and husk (RH) using vermitechnology and pyrolysis. Recovery from vermicomposting was more (74.38 % for VRS and 70.03 % for VRH) than when the residues were converted into biochar through pyrolysis (19.86 % for RSB and 38.00 % for RHB). Vermicomposting and pyrolysis reduced the bulk density of raw materials. Rice residues and their products were alkaline, with biochar exhibiting the highest level of alkalinity (9.24 for RSB and 9.20 for RHB). The electrical conductivity increased both by vermicomposting and pyrolysis. Straw was comparatively superior to the husk in respect of C, N, K, Ca, Mg, Fe, Mn, Cu, and Zn. However, husk was superior in P, S, B, Si, cellulose, and lignin. Vermicomposting helped to concentrate the nutrients viz., N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, and Si while reducing that of carbon, cellulose and lignin thereby narrowing down the C: N ratio. However, C: N ratio increased upon pyrolysis. Surface morphology of rice residues and their products were studied using scanning electron microscope (SEM). The SEM micrographs of straw and husk exhibited a complex morphology with cell wall composition. SEM micrograph of VRS showed highly fragmented, disaggregated and porous structure which could not be visualised in VRH, may be because the technology of composting using earthworms was more suited to decomposing rice straw than its husk. The SEM analysis showed that the structure of biochar was porous, fragmented and particles gave a broken or distorted appearance thus resembling the plant structure. The structural chemistry of rice residues and their products were analysed using fourier transform infra red spectrometer (FT-IR). Each peak is characteristic of correspondingfunctional group and it clearly explained the presence of C, H, O, N, and Si in the residues and products. Silicon, a major component in the chemical structure of rice material was illustrated by Si-O-Si and Si-H bond in FT-IR spectra. Vermicompost had significant level of nitrogen rich compounds and low level of aliphatic or aromatic carbon compounds compared to biochar, as confirmed by the FT-IR analysis. The FT-IR spectra of RSB and RHB revealed its aromatic and recalcitrant nature. The incubation experiment was conducted for 110 days at 15, 25, 35 and 45 oC to study the kinetics of carbon mineralization in lateritic soil over time, wherein the CO 2 evolution was determined at frequent intervals and the data were used for determination of carbon mineralization and mineralization kinetics. Lateritic soils (100g) collected from Agricultural Research Station Mannuthy, were treated with rice residues and their products (5t ha -1 ), FYM (5 t ha -1 ), and soil test based nutrient recommendation. An absolute control without the addition of organic/inorganic materials was also maintained. Dehydrogenase enzyme assay, enumeration of microbial population, and fractions of carbon were also undertaken at the end of incubation. Results of incubation experiment revealed that the amount of CO 2 –C mineralized during incubation increased with rise in temperature in all the treatments. The VRS treated soils registered higher mineralizable carbon at 15, 25, 35 and 45 oC. The rate of decomposition reaction was highest in soils that are treated with VRS and FYM. The highest activation energy was found in RHB amended soil (12.79 kJ mol -1 ) followed by RSB treated soil (12.71 kJ mol -1 ). Q 10 values represent the temperature dependency of the reaction. The results showed that all treatments had Q 10 values less than one. After incubation experiment, dehydrogenase activity as well as microbial population was found to decrease at 45 oC compared to the values at lower temperature. Comparatively, higher dehydrogenase activity and microbial population was registered in soils treated with VRS. The soils treated with VRS exhibited highest water soluble carbon (WSC), hot water extractable carbon (HWEC), microbial biomass carbon (MBC), and permanganate oxidizable carbon (POXC). However, biochar amended soils (RHB and RSB) registered higher value of total carbon. A field experiment was carried out to evaluate the efficacy of rice residues and their products in lowland with rice variety Uma as the test crop. The experiment consisted of ninetreatments with three replications viz., absolute control (T 1 ), Adhoc KAU organic POP (T 2 ), and treatments T 3 to T 9 comprised of soil test based nutrient recommendation along with FYM (T 3 ), VRH (T 4 ), VRS (T 5 ), RHB (T 6 ), RSB (T 7 ), RH (T 8 ), and RS (T 9 ) at 5t ha -1 . At weekly intervals Eh and pH were monitored. The soil and plant samples were collected at different stages of rice to analyse the effect of treatments on soil physical and chemical properties, fractions of nutrients in soil, nutrient content in plant, soil enzyme activity, and growth, yield and yield attributes of rice. Results of field experiment revealed that the application of residues and its products had a profound influence in lowering redox potential. The alkaline nature of rice residues and their products resulted in higher pH of experimental soil. Physical properties of post-harvest soil was improved by the application of T 6 and T 7 (soil test based nutrient recommendation + RHB and RSB). The application of T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ) was superior in increasing the nutrient status of post-harvest soil viz., C, N, P, Ca, Mg, S, Fe, Mn, Zn, and Si. While, K content was superior in T 7 (soil test based nutrient recommendation + RSB at 5 t ha -1 ). Soils receiving combined application of soil test based nutrient recommendation and VRS at 5 t ha -1 (T 5 ) recorded the highest WSC, HWEC, MBC, POXC, inorganic-N and P fractions, fractions of Ca and Mg at all the stages of crop. However, total- C, total hydrolysable-N, organic-P, and Si fractions were higher in biochar amended plots. Soil receiving joint application of soil test based nutrient recommendation +RSB at 5 t ha -1 (T 7 ) was statistically superior in fractions of K at all stages. Enzyme activity (dehydrogenase, urease, and acid phosphatase) was found to be highest in T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ), and it followed an increasing trend upto panicle initiation and thereafter it decreased in all treatments. The uptake of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B and Si were also highest in T 5 . With respect to the growth, yield and yield attributes of rice, application of soil test based nutrient recommendation + VRS at 5 t ha -1 (T 5 ) had superior effect. To conclude, the study has brought out the tremendous potential of rice straw and husk based biochar in improving soil physical properties and in elevating the total carbon content. However, the integration of soil test based nutrient recommendation with vermicompostedrice straw at 5t ha -1 (T 5 ) proved outstanding in augmenting soil fertility and crop productivity in the highly weathered, nutrient poor acidic lateritic soils.ThesisItem Open Access Nutrient dynamics and crop productivity in lowland lateritic soil (aeu 10) under rice residue management practices(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Amritha, K; KAU; Jayasree Sankar, SThe present investigation was undertaken at College of Agriculture Vellanikkara, Kerala Forest Research Institute Peechi, and Agricultural Research Station Mannuthy during 2017-2020. The experiment comprised of characterization of rice residues and their products for physical and chemical properties, an incubation experiment to study the kinetics of carbon mineralization, and a field experiment to evaluate the efficacy of rice residues and their products on lowland rice. Straw and husk, the important residues produced during the cultivation and processing of rice, respectively was procured from farmer’s field and further materials required for the research work viz., vermicomposted rice straw (VRS), vermicomposted rice husk (VRH), rice straw biochar (RSB), and rice husk biochar (RHB) were produced from the straw (RS) and husk (RH) using vermitechnology and pyrolysis. Recovery from vermicomposting was more (74.38 % for VRS and 70.03 % for VRH) than when the residues were converted into biochar through pyrolysis (19.86 % for RSB and 38.00 % for RHB). Vermicomposting and pyrolysis reduced the bulk density of raw materials. Rice residues and their products were alkaline, with biochar exhibiting the highest level of alkalinity (9.24 for RSB and 9.20 for RHB). The electrical conductivity increased both by vermicomposting and pyrolysis. Straw was comparatively superior to the husk in respect of C, N, K, Ca, Mg, Fe, Mn, Cu, and Zn. However, husk was superior in P, S, B, Si, cellulose, and lignin. Vermicomposting helped to concentrate the nutrients viz., N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, and Si while reducing that of carbon, cellulose and lignin thereby narrowing down the C: N ratio. However, C: N ratio increased upon pyrolysis. Surface morphology of rice residues and their products were studied using scanning electron microscope (SEM). The SEM micrographs of straw and husk exhibited a complex morphology with cell wall composition. SEM micrograph of VRS showed highly fragmented, disaggregated and porous structure which could not be visualised in VRH, may be because the technology of composting using earthworms was more suited to decomposing rice straw than its husk. The SEM analysis showed that the structure of biochar was porous, fragmented and particles gave a broken or distorted appearance thus resembling the plant structure. The structural chemistry of rice residues and their products were analysed using fourier transform infra red spectrometer (FT-IR). Each peak is characteristic of correspondingfunctional group and it clearly explained the presence of C, H, O, N, and Si in the residues and products. Silicon, a major component in the chemical structure of rice material was illustrated by Si-O-Si and Si-H bond in FT-IR spectra. Vermicompost had significant level of nitrogen rich compounds and low level of aliphatic or aromatic carbon compounds compared to biochar, as confirmed by the FT-IR analysis. The FT-IR spectra of RSB and RHB revealed its aromatic and recalcitrant nature. The incubation experiment was conducted for 110 days at 15, 25, 35 and 45 oC to study the kinetics of carbon mineralization in lateritic soil over time, wherein the CO 2 evolution was determined at frequent intervals and the data were used for determination of carbon mineralization and mineralization kinetics. Lateritic soils (100g) collected from Agricultural Research Station Mannuthy, were treated with rice residues and their products (5t ha -1 ), FYM (5 t ha -1 ), and soil test based nutrient recommendation. An absolute control without the addition of organic/inorganic materials was also maintained. Dehydrogenase enzyme assay, enumeration of microbial population, and fractions of carbon were also undertaken at the end of incubation. Results of incubation experiment revealed that the amount of CO 2 –C mineralized during incubation increased with rise in temperature in all the treatments. The VRS treated soils registered higher mineralizable carbon at 15, 25, 35 and 45 oC. The rate of decomposition reaction was highest in soils that are treated with VRS and FYM. The highest activation energy was found in RHB amended soil (12.79 kJ mol -1 ) followed by RSB treated soil (12.71 kJ mol -1 ). Q 10 values represent the temperature dependency of the reaction. The results showed that all treatments had Q 10 values less than one. After incubation experiment, dehydrogenase activity as well as microbial population was found to decrease at 45 oC compared to the values at lower temperature. Comparatively, higher dehydrogenase activity and microbial population was registered in soils treated with VRS. The soils treated with VRS exhibited highest water soluble carbon (WSC), hot water extractable carbon (HWEC), microbial biomass carbon (MBC), and permanganate oxidizable carbon (POXC). However, biochar amended soils (RHB and RSB) registered higher value of total carbon. A field experiment was carried out to evaluate the efficacy of rice residues and their products in lowland with rice variety Uma as the test crop. The experiment consisted of ninetreatments with three replications viz., absolute control (T 1 ), Adhoc KAU organic POP (T 2 ), and treatments T 3 to T 9 comprised of soil test based nutrient recommendation along with FYM (T 3 ), VRH (T 4 ), VRS (T 5 ), RHB (T 6 ), RSB (T 7 ), RH (T 8 ), and RS (T 9 ) at 5t ha -1 . At weekly intervals Eh and pH were monitored. The soil and plant samples were collected at different stages of rice to analyse the effect of treatments on soil physical and chemical properties, fractions of nutrients in soil, nutrient content in plant, soil enzyme activity, and growth, yield and yield attributes of rice. Results of field experiment revealed that the application of residues and its products had a profound influence in lowering redox potential. The alkaline nature of rice residues and their products resulted in higher pH of experimental soil. Physical properties of post-harvest soil was improved by the application of T 6 and T 7 (soil test based nutrient recommendation + RHB and RSB). The application of T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ) was superior in increasing the nutrient status of post-harvest soil viz., C, N, P, Ca, Mg, S, Fe, Mn, Zn, and Si. While, K content was superior in T 7 (soil test based nutrient recommendation + RSB at 5 t ha -1 ). Soils receiving combined application of soil test based nutrient recommendation and VRS at 5 t ha -1 (T 5 ) recorded the highest WSC, HWEC, MBC, POXC, inorganic-N and P fractions, fractions of Ca and Mg at all the stages of crop. However, total- C, total hydrolysable-N, organic-P, and Si fractions were higher in biochar amended plots. Soil receiving joint application of soil test based nutrient recommendation +RSB at 5 t ha -1 (T 7 ) was statistically superior in fractions of K at all stages. Enzyme activity (dehydrogenase, urease, and acid phosphatase) was found to be highest in T 5 (soil test based nutrient recommendation + VRS at 5 t ha -1 ), and it followed an increasing trend upto panicle initiation and thereafter it decreased in all treatments. The uptake of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B and Si were also highest in T 5 . With respect to the growth, yield and yield attributes of rice, application of soil test based nutrient recommendation + VRS at 5 t ha -1 (T 5 ) had superior effect. To conclude, the study has brought out the tremendous potential of rice straw and husk based biochar in improving soil physical properties and in elevating the total carbon content. However, the integration of soil test based nutrient recommendation with vermicompostedrice straw at 5t ha -1 (T 5 ) proved outstanding in augmenting soil fertility and crop productivity in the highly weathered, nutrient poor acidic lateritic soils.ThesisItem Open Access Effect of thermochemical organic fertilizer on soil carbon pools, nutrient dynamics and crop productivity in ultisols(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2021) Amrutha, S Ajayan; KAU; Manorama Thampatti, K CA study entitled “Effect of thermochemical organic fertilizer on soil carbon pools, nutrient dynamics and crop productivity in Ultisols” was conducted from 2018 to 2020 at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani with the objective to study the effect of thermochemical organic fertilizer on soil carbon pools, nutrient dynamics, their retention and leaching, and crop productivity in comparison with conventional organic fertilizers in Ultisols using tomato - amaranthus cropping sequence. The study includes production and characterization of organic fertilizers, leaching study using soil columns, an incubation experiment and field experiments using tomato - amaranthus cropping sequence. For the leaching study and incubation, the treatments were addition of FYM, ordinary compost (OC), vermicompost (VC), microbial compost (MC), unfortified (TOF) and fortified thermochemical organic fertilizer (F-TOF) @ 50 g per soil column/ pot and an absolute control. For the field experiment on tomato-amaranthus cropping sequence, the treatments were T 1 – FYM + POP recommendation of NPK, T 2 - FYM + soil test based recommendation of NPK (STBR), T 3 - OC + STBR, T 4 - VC + STBR, T 5 - MC + STBR, T 6 - TOF + STBR, T 7 - F-TOF + STBR, T 8 - F-TOF alone and T 9 - absolute control. The organic fertilizers required for the study viz., OC, VC, MC, TOF and F- TOF were produced from bio-waste from vegetable markets and food waste from college hostels and FYM was purchased. The physical and chemical properties of organic fertilizers were in accordance with the standards of FCO. VC, OC, MC and FYM were neutral to slightly alkaline in reaction while TOF and F-TOF were slightly acidic. The lignin content (27.9 %) and the carbon pools viz., TOC (43.90 %), WSOC (1642 mg kg -1 ), labile carbon (1776 mg kg -1 ) and recalcitrant organic carbon (32.45 mg kg -1 ) were highest for TOF followed by F-TOF. The N content was 391highest for MC (2.61 %), P for VC (1.36 %) and K (2.56 %), Ca (1.12 %), Mg (0.78 %), Zn (254 mg kg -1 ) and B (4.64 mg kg -1 ) for F-TOF while S (550 mg kg -1 ), Fe (9580 mg kg -1 ) and Pb (4.16 mg kg -1 ) for FYM. All the organic fertilizers contained Pb, but within permissible limit, while, Cd was not detected in any of them. The soil column study was conducted to assess the extent of leaching loss of nutrients from F-TOF amended soil in comparison with other organic fertilizers and their nutrient retention ability in soil. Soil columns amended with organic fertilizers in the surface layer were subjected to leaching on 1 st , 4 th , 8 th , 12 th , 16 th , 20 th and 24 th weeks with double the pore volume of water. During the leaching, the mineralized nutrients moved downwards and deposited at different depths in the soil column in accordance with their mobility and the rest was lost in leaching water. Leachates from organic fertilizer amended soils showed slightly acidic pH, which decreased up to 8 th week followed by an increase towards 12 th week. EC was highest at first week followed by a decrease towards 24 th week. The highest cumulative loss of N (172.34 mg L -1 ), Ca (273.86 mg L -1 ) and Mn (3.97 mg L -1 ) was from VC while that of P (7.22 mg L -1 ), K (333.36 mg L -1 ), Mg (144.41 mg L -1 ), Cu (0.080 mg L -1 ) and B (0.166 mg L -1 ) was from F-TOF. For S the loss (4.19 mg L -1 ) was highest from FYM, and Fe (4.71 mg L -1 ) and Zn (4.58 mg L -1 ) from OC. The leachate did not contain Pb and Cd. The leached soil in the soil columns maintained a higher level of nutrients compared to the level prior to the addition of organic fertilzers even after leaching for 24 weeks. In the surface soil, highest quantity of total N was retained by MC; P, Mn and Cu by VC and K, Ca, Mg, Zn and B by F-TOF while FYM retained highest quantity of S and Fe. Evaluating the available nutrient status of the leached soil, it was found that F-TOF had highest availability for K, Mg, S, Fe, Zn, Cu and B. Availability of P and Mn was highest in VC amended soil and Ca from MC. Availability of Pb and Cd were not detected in the leached soil. 392The incubation study for a period of 24 weeks revealed the nutrient release pattern of organic fertilizers. The peak release of most of the nutrients from organic fertilizers was from 8 th to 16 th week and for S it extended up to 20 th week. The availability of K, Ca, Mg, Fe, Zn and B was highest from F-TOF amended soil while VC maintained the highest values for P, Mn and Cu and FYM for S. The different fractions of B were highest for F-TOF amended soil and the peak was during 12 th week of incubation. Available Pb and Cd were not detected in the incubated soil. Organic fertilizers amended soil maintained a higher microbial count and exhibited a higher dehydrogenase activity compared to the control and the highest value was observed with F-TOF amended soil. During the field experiments, in the first cropping sequence, VC amended treatment T 4 (VC + STBR) recorded significantly highest fruit yield (40.97 t ha -1 ) for tomato followed by T 7 (F-TOF + STBR) while in the second cropping sequence F- TOF gave the highest yield which was statistically on par with VC. While for amaranthus, F-TOF recorded the highest yield during both the cropping sequences (24.62 t ha -1 and 26.89 t ha -1 , respectively) followed by VC and both the treatments were statistically on par in the second cropping sequence. The quality parameters of tomato and amaranthus were highest for the treatment T 7 (F-TOF + STBR) but was statistically on par with other treatments which received organic fertilizers along with POP or soil test based NPK fertilizers. Evaluating the economic benefits, the performance of VC was the best for the first tomato followed by F-TOF while for second tomato F-TOF was the best. For amaranthus, F-TOF performed best during both the sequences. When the overall B:C ratio for the whole cropping sequence was taken F-TOF was the best followed by VC. Uptake of N, P, K, Ca, Mg, S, Zn and B in tomato was highest for F-TOF while that of Fe, Mn, and Cu was for VC. For amaranthus, the uptake of N, P, K, Mg, Fe, Zn, Cu and B was highest for F-TOF for both the cropping sequences. Among the 393heavy metals tested only Pb was detected in plant parts and that too in roots only. For tomato, it was detected only in FYM treated plants while in amaranthus, all the treatments receiving organic fertilizers showed the presence of Pb. But the Pb content in the root was within the safe limit. The availability of Pb in the post-harvest soil was trace and there was no significant difference between the treatments. Cd was not detected in soil as well as plant samples. The continuous application of organic fertilizers had improved the physical, chemical and biological properties of the soil. At the end of the second cropping sequence, the lowest bulk density and highest water holding capacity was recorded by the treatment receiving F-TOF + STBR. The highest value for TOC, labile carbon, microbial biomass carbon and recalcitrant organic carbon in the post-harvest soil during the cropping sequence was maintained by F-TOF. The N pools, NH 4 -N, NO 3 - N, organic N and total N at the end of second cropping sequence was also highest for F-TOF. In the case of availability of P, S, Fe, Mn and Cu in the post-harvest soil, better performance was showed by VC while F-TOF showed higher availability for K, Ca, Mg, Zn and B. Biological properties are a better indication of soil health and application of VC, MC and F-TOF maintained a higher microbial load in soil. The highest dehydrogenase activity was maintained by F-TOF. Continuous application of F-TOF and TOF increased the carbon stock of surface and sub-surface soil than other organic fertilizers. F-TOF is superior to VC, OC, MC and FYM in terms of increasing carbon pools and carbon stock of the soil. The nutrient release was highest from F-TOF for most of the nutrients compared to other organic fertilizers, which might have resulted more leaching losses. However, the nutrient retention was also highest for F-TOF, even after the leaching for 24 weeks, suggesting a revisit on the rate and mode of fortification for F-TOF, popularly marketed in the trade name “Suchitha”. For crop production, the performance of F-TOF found equally good as that of vermicompost and was superior to FYM, OC and MC.
