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Kerala Agricultural University, Thrissur
The history of agricultural education in Kerala can be traced back to the year 1896 when a scheme was evolved in the erstwhile Travancore State to train a few young men in scientific agriculture at the Demonstration Farm, Karamana, Thiruvananthapuram, presently, the Cropping Systems Research Centre under Kerala Agricultural University. Agriculture was introduced as an optional subject in the middle school classes in the State in 1922 when an Agricultural Middle School was started at Aluva, Ernakulam District. The popularity and usefulness of this school led to the starting of similar institutions at Kottarakkara and Konni in 1928 and 1931 respectively.
Agriculture was later introduced as an optional subject for Intermediate Course in 1953. In 1955, the erstwhile Government of Travancore-Cochin started the Agricultural College and Research Institute at Vellayani, Thiruvananthapuram and the College of Veterinary and Animal Sciences at Mannuthy, Thrissur for imparting higher education in agricultural and veterinary sciences, respectively. These institutions were brought under the direct administrative control of the Department of Agriculture and the Department of Animal Husbandry, respectively. With the formation of Kerala State in 1956, these two colleges were affiliated to the University of Kerala. The post-graduate programmes leading to M.Sc. (Ag), M.V.Sc. and Ph.D. degrees were started in 1961, 1962 and 1965 respectively.
On the recommendation of the Second National Education Commission (1964-66) headed by Dr. D.S. Kothari, the then Chairman of the University Grants Commission, one Agricultural University in each State was established. The State Agricultural Universities (SAUs) were established in India as an integral part of the National Agricultural Research System to give the much needed impetus to Agriculture Education and Research in the Country. As a result the Kerala Agricultural University (KAU) was established on 24th February 1971 by virtue of the Act 33 of 1971 and started functioning on 1st February 1972. The Kerala Agricultural University is the 15th in the series of the SAUs.
In accordance with the provisions of KAU Act of 1971, the Agricultural College and Research Institute at Vellayani, and the College of Veterinary and Animal Sciences, Mannuthy, were brought under the Kerala Agricultural University. In addition, twenty one agricultural and animal husbandry research stations were also transferred to the KAU for taking up research and extension programmes on various crops, animals, birds, etc.
During 2011, Kerala Agricultural University was trifurcated into Kerala Veterinary and Animal Sciences University (KVASU), Kerala University of Fisheries and Ocean Studies (KUFOS) and Kerala Agricultural University (KAU).
Now the University has seven colleges (four Agriculture, one Agricultural Engineering, one Forestry, one Co-operation Banking & Management), six RARSs, seven KVKs, 15 Research Stations and 16 Research and Extension Units under the faculties of Agriculture, Agricultural Engineering and Forestry. In addition, one Academy on Climate Change Adaptation and one Institute of Agricultural Technology offering M.Sc. (Integrated) Climate Change Adaptation and Diploma in Agricultural Sciences respectively are also functioning in Kerala Agricultural University.
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ThesisItem Open Access Biomineral enriched composts (BOKASHI) - a tool for enhancing nutrient availability and enzyme activity in Rhizosphere(Department of soil science and agricultural chemistry, college of agriculture, Vellayani, 2023-08-05) Shilpa, S.; KAU; Aprna, BBiomineral enriched composts (Bokashi) – A tool for enhancing nutrient availability and enzyme activity in rhizosphere The study entitled “Biomineral enriched composts (Bokashi) – A tool for enhancing nutrient availability and enzyme activity in rhizosphere” was carried out during 2020-22 in the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani. The objective of the study was the production and evaluation of biomineral enriched composts for enhanced nutrient availability, yield of test crop (Bhindi) and enzyme activity in the rhizosphere. The study comprised of three parts viz., production and characterization of biomineral (Bokashi) composts from different organic sources, soil incubation study for evaluating the nutrient release pattern and field experiment for evaluating the performance of the biomineral enriched (Bokashi) compost. Bokashi composts were prepared from two substrates S1 (Aquatic weed Limnocharis flava) and S2 (Aquatic weed Limnocharis flava and banana pseudostem in 1:1 ratio). The substrates were allowed to ferment anaerobically using EM solution and the matured composts were enriched with three minerals like M1 (Calcium apatite), M2 (Epsom salt) and M3 (Sylvinite) at 2% rate in different combinations. The design followed was Completely Randomized Design with 14 treatments replicated thrice. The treatment combinations were T1 – Bokashi compost prepared from L.flava enriched with calcium apatite, T2 - Bokashi compost prepared from L.flava enriched with epsom salt, T3- Bokashi compost prepared from L.flava enriched with sylvinite, T4 –Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with calcium apatite, T5 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with epsom salt, T6 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with sylvinite, T7- Bokashi compost prepared from L.flava enriched with calcium apatite and epsom salt, T8 - Bokashi compost prepared from L.flava enriched with epsom salt and sylvinite, T9 - Bokashi compost prepared from L.flava enriched with calcium apatite and sylvinite, T10 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with calcium apatite and epsom salt, T11 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with epsom salt and sylvinite, T12 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with calcium apatite and sylvinite , T13 – Bokashi compost prepared from L.flava enriched with calcium apatite, epsom salt and sylvinite and T14 - Bokashi compost prepared from 1:1 mixture of L.flava and banana pseudostem enriched with calcium apatite, epsom salt and sylvinite. To all the treatments (T1 – T4) zeolite was added at a rate of 0.5%. The physico-chemical and biological properties of the produced composts were subjected to analysis. Based on the analysed parameters like major and minor nutrient, enzyme activity, C:N ratio, fertilizing index the best seven composts selected for incubation study and field experiment were T2, T7 , T10, T11, T12, T13 and T14. Among these T13 (Bokashi compost prepared from L.flava enriched with calcium apatite, epsom salt and sylvinite) was selected as the best compost with the highest values of nitrogen, phosphorous, micro nutrients and enzyme activity while the lowest value of C:N ratio was also reported by T13. In part 2 of the study a soil incubation was carried out to investigate the nutrient release pattern of selected composts. The design followed is CRD with 8 treatments which was replicated thrice. One kg soil was incubated at field capacity for four months. The treatments were T1 - Absolute control, T2 to T8 - selected best seven composts. The treatments were imposed at surface of the soil at 20 g kg-1 and thoroughly mixed. Soil sample was drawn at 1st, 4th, 8th, 12th and 16th week of incubation and analysed for organic carbon, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, dehydrogenase and cellulase activity. From the study, it was observed that nitrogen, phosphorous, potassium, calcium, sulphur, iron, copper, organic carbon and enzyme activity were found to be maximum at the 4th week of incubation. Zinc content was observed to be maximum during 12th week of incubation while magnesium content was highest during 16th week of incubation. Manganese availability was maximum during 8th week of incubation. In part 3 of the study a field experiment was conducted from February – May 2022 with Bhindi (var. Anjitha) as the main crop and Amaranthus (var. Arun) as the residual crop. In the field experiment 9 treatments were imposed viz. T1 - Absolute control, T2 to T8 – selected best seven composts and T9¬ - KAU POP recommendation. Analysis of postharvest soil for chemical properties revealed that the highest value of organic carbon (1.14 %) and nitrogen (319.86 kg ha-1) was recorded for T7. The highest value for available phosphorous (91.65 kg ha-1) was recorded for T8 which was on par with T6 (89.67 kg ha-1) and T7 (88.59 kg ha-1). The potassium content was found to be the highest for T6 (273.91 kg ha-1) which was on par with T8 (270.60 kg ha-1). T7 recorded the highest values of iron (48.54 mg kg-1), zinc (4.79 mg kg-1), copper (1.88 mg kg-1) and boron (0.832 mg kg-1). While manganese (25.62 mg kg-1) was reported to be the highest with regard to T8. The highest value of cellulase activity was recorded by T7 (45.53 µg glucose hydrolysed g-1 soil h-1) while T8 recorded the highest value of dehydrogenase activity (302.68 µg of TPF hydrolysed g-1 of soil 24 h-1). Analysis of rhizosphere soil showed the highest value of microbial biomass carbon (91.14 mg kg-1 soil), glomalin (14.27 mg g-1), humic acid (9.21 %), fulvic acid (9.98), fungi (5.52 log cfu g-1), actinomycetes (5.16 log cfu g-1) and soil respiration (4.17 mg CO2 g-1) for T7 while T8 recorded highest value for bacteria (7.90 log cfu g-1). T7 recorded the highest value for number of fruits per plant (30.67) which was on par with T5, T6, and T8. Fruit girth was found to be the highest for T7 (5.06 cm) which was on par with T6, T8 and T9. T7 also recorded the highest value for fruit length (23.81 cm), yield per plant (570.42 g) and total yield (21.05 t ha-1). The highest B: C ratio (2.26) was reported by T7. The highest yield of amaranthus (130.23 kg ha-1) was recorded for T7. From the study, T13 (Bokashi compost prepared from L.flava enriched with calcium apatite, epsom salt and sylvinite) was concluded as the best compost. T7 (Bokashi compost prepared from L. flava enriched with calcium apatite, epsom salt and sylvinite) and T8 (Bokashi compost prepared from the 1:1 mixture of L.flava and banana pseudostem enriched with calcium apatite, epsom salt and sylvinite) recorded the highest values for the available nutrient status during incubation period like nitrogen, phosphorous, magnesium, sulphur, iron, manganese, zinc, copper, organic carbon and enzyme activity. Considering both the soil parameters and yield parameters T7 (Bokashi compost prepared from L. flava enriched with calcium apatite, epsom salt and sylvinite) was recorded as the best treatment.ThesisItem Open Access Carrier based slow release fertilizer formulations for sustained nutrient release and enhanced crop production(Department of soil science and agricultural chemistry, Vellayani, 2023-08-10) Farha, M K.; KAU; Gladis, RThe study entitled “Carrier based slow release fertilizer formulations for sustained nutrient release and enhanced crop production” was conducted at the Department of Soil Science, College of Agriculture, Vellayani during the year 2022. In this study slow release fertilizer formulations were prepared, characterized and investigated for its nutrient release characteristics through leaching experiment with soil column and incubation study. Based on the stability and sustained release of nutrients throughout the leaching and incubation study, best formulations were selected and evaluated. A pot culture experiment was conducted in a completely randomized design replicated thrice using chilli variety Vellayani Athulya as test crop and evaluated the effect of slow release fertilizer formulations on nutrient availability, uptake, use efficiency, yield and quality of chilli. Carrier based slow release fertilizer formulations containing major, secondary and micro nutrients were prepared using compatible fertilizer sources (urea, rajphos, muriate of potash, phosphogypsum, magnesium sulphate, zinc sulphate and borax), carrier materials (zeolite, humic acid, charcoal, chitosan and nano zeolite) and binding/stabilizing agent carboxy methyl cellulose (CMC). The slow release fertilizer pellets prepared were, T1 - Fertilizer mix: Zeolite+ CMC (1:1), T2 - Fertilizer mix: Zeolite+ CMC (1:0.5), T3 - Fertilizer mix: humic acid+ CMC (1:1), T4 - Fertilizer mix: humic acid+ CMC (1:0.5), T5 - Fertilizer mix: charcoal+ CMC (1:1), T6 - Fertilizer mix: charcoal+ CMC (1:0.5), T7 - Fertilizer mix: chitosan+ CMC (1:1), T8 - Fertilizer mix: chitosan+ CMC (1:0.5), T9 - Fertilizer mix: nano zeolite+ CMC (1:1), T10- Fertilizer mix: nano zeolite+ CMC (1:0.5). The pellets prepared were found to be stable, disintegration time 9-13 hours, moisture 5.75- 8.68 %, pH 6.37- 6.90, EC 17.25- 23.17 dSm-1 , bulk density 0.5-0.58 Mg m-3 and weight 4.0- 4.5 g. They contained 8.21 to 9.02 % nitrogen, 5.36 to 5.76 % phosphorus, 3.0 to 3.50% potassium, 5.40 to 5.68 % calcium, 2.01 to 2.86 % magnesium, 4.10 to 5.30 % sulphur , 1.2 to 1.6 % zinc and 0.17 to 0.23 % boron. A soil column experiment was conducted for two weeks to study the nutrient leaching and to confirm the slow release tendency of formulations. The results showed a gradual increase in the release of nutrients from 2 to 14 days of leachate collected from slow release formulations while, fertilizer mix alone showed increasing trend initially and later decreased. A laboratory incubation study was carried out to investigate the nutrient release patterns of the formulations after addition to soil. The results revealed that the pH of soil remained acidic (5.30- 6.17) throughout the incubation period and the EC was found to be increasing from 0.11- 1.45 dSm-1 . The release of nutrients in soil was found to be increasing gradually from 0 to 90 days of incubation with maximum concentration was observed on 90th day for all the nutrients. Based on the stability of pellets and the release of nutrients throughout the leaching and incubation experiment three promising formulations were selected for the pot culture experiment. They were, T2 (FM: Z+CMC 1:0.5), T4 (FM:HA+CMC 1:0.5) and T5 (FM: CC+CMC 1:1) . The treatments of pot culture experiment were T1 -100% RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied as basal,T2 -100% RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied in two splits (basal & 1 MAP), T3 -75% RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied as basal, T4 -75% RDF as SRF 1 (FM: Z+ CMC -1:0.5) applied in two splits (basal & 1 MAP), T5 -100% RDF as SRF 2 (FM: HA+ CMC -1:0.5) appliedas basal, T6 -100% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits (basal & 1 MAP), T7-75% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied as basal, T8 -75% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits (basal & 1 MAP), T9-100% RDF as SRF 3 (FM: CHAR+ CMC -1:1) applied as basal, T10-100% RDF as SRF 3 (FM: CHAR+ CMC -1:1) applied in two splits (basal & 1 MAP), T11-75% RDF as SRF 3 (FM: CHAR+ CMC -1:1) applied as basal, T12-75% RDF as SRF 3 (FM: CHAR+ CMC -1:1) applied in two splits (basal & 1 MAP), T13-Soil test based POP recommendation, T14- Control (No fertilizers). The analysis of post harvest soil showed the highest content of available N (320.8 kgha-1 ), P (87.15 kgha-1 ), K (214.3 kgha-1 ), Ca (351.1 mg kg-1 ), Mg (106.5 mg kg-1 ), S (9.32 mg kg-1 ), Zn (4.25 mg kg-1 ) and B (0.46 mg kg-1 ) in T8 receiving 75% RDF as SRF 2 (FM: HA+ CMC -1:0.5) applied in two splits (basal & 1 MAP). With regard to nutrient content and uptake, the treatment T8 registered the highest value. The growth and yield parameters like plant height (56.52 cm), number of branches per plant (9.5), number of fruits per plant (56.70), fruit length (13.44 cm), fruit girth (6.89 cm), fruit weight (11.03), fruit yield (581.2g plant -1 ) and total dry matter production (89.07 g) were found to be the highest in T8. Quality parameters of chilli such as ascorbic acid and capsaicin content were also found to be the highest in T8.The fertilizer use efficiency, agronomic efficiency, apparent recovery of major nutrients and partial factor productivity were found to be the highest recorded in treatment T8.The highest B:C ratio of 2.41 was recorded by treatment T8. Slow release fertilizer formulations containing macro and micro nutrients can be prepared using compatible fertilizer materials (urea, rajphos, MOP, phosphogypsum, magnesium sulphate, zinc sulphate and borax), carrier agents(zeolite, humic acid, charcoal, chitosan and nanozeolite) and binding agent (CMC). The slow release fertilizer pellets were found to be superior with respect to stability, disintegration time, nutrient content and release of nutrients. From the results it can be concluded that the slow release fertilizer formulations containing fertilizer mix: humic acid+ CMC in the ratio of 1:0.5 applied at 75% RDF in two splits as basal & 1 MAP was able to significantly increase the yield, uptake of nutrients, NUE, B:C ratio and quality of chilliThesisItem Open Access Management of calcium, magnesium and boron deficiency for enhancing yield and quality in chilli (Capsicum annuum L.)(Department of Soil Science and Agricultural Chemistry, College of Agriculture ,Padanakkad, 2022-04-28) Anjitha K.; KAU; Sailaja kumari M SThe investigation entitled ‘Management of calcium, magnesium and boron deficiency for enhancing yield and quality in chilli’ was carried out at Instructional farm, Nileshwar, College of Agriculture Padannakkad, with an objective to develop nutrient management practices for mitigating calcium, magnesium and boron deficiency and to evaluate its effect on growth, yield and quality parameters. The field experiment was carried out during December 2020 to May 2021. The experiment was carried out with chilli variety Anugraha, in randomized block design with ten treatments and three replications. Treatment combinations were T1(KAU POP + lime (based on soil test)), T2 (T1 + 125 kg gypsum per hectare), T3 (T1 + 80 kg magnesium sulphate per hectare), T4 (T1 + 125 kg gypsum per hectare + 80 kg magnesium sulphate per hectare), T5 (T1 + foliar application of borax (0.2%)), T6 (T2 + foliar application of borax (0.2%)), T7 (T3 + foliar application of borax (0.2%)), T8 (T4 + foliar application of borax (0.2%)), T9 (KAU POP + dolomite (based on soil test)) and T10 (T9 + foliar application of borax (0.2%)). Soil application of amendments were done as a single dose and foliar nutrition was given four times in a 20 days interval. Analysis of experimental results showed that various treatments showed significant effect on growth characters, fruit quality parameters as well as nutrient content in both soil and plant, over KAU POP recommendation. Significant positive effect of treatments on plant root characters and total dry matter production was observed whereas plant height and days to 50% flowering were found to be non significant. Among the treatments, maximum tap root length (13.50 cm), root volume (23.23 cm3 ), root shoot ratio (0.16) and total dry matter production (2694.65 kg ha-1 ) were recorded in T8 (KAU POP + lime application based on soil test) +125 kg gypsum per hectare + 80 kg magnesium sulphate per hectare + foliar application of borax (0.2%). Various treatments showed significant influence on yield and yield attributes. Maximum fruit weight (37.16 g) and total fruit yield (4456.79 kg ha-1 ) was also observed in T8 and in case of fruit yield, it was significantly superior to all other treatments. Combined application of gypsum, magnesium sulphate and borax were effective and maximized fruit yield. 94 Soil analysis was carried out at flowering and harvest wherein, the treatments showed significant effect on soil pH, EC, available potassium, calcium, magnesium, sulphur, iron, manganese and zinc content whereas available nitrogen, phosphorus, copper and boron were not influenced by treatments. Addition of calcium and magnesium sources significantly increased available calcium and magnesium content in soil. Among the various treatments, the highest available calcium was recorded in T8 and was on par with T2, T6 and T4 at flowering. Highest available magnesium content was recorded in T9 and T10 at flowering and harvest respectively. Analysis of Index leaves at flowering and total plant analysis at harvest were carried out and it was found that plant nutrient content was significantly influenced by treatments. Significant effect of various treatments on plant nutrients except nitrogen and phosphorus was observed. Foliar application of borax significantly improved boron content in plants. Fruit quality parameters such as capsaicin, oleoresin, ascorbic acid and shelf life and total nutrient content were analysed and results showed significant positive response to treatments. Analysis of nutrient content in fruits showed that primary nutrients mainly, nitrogen and potassium, secondary nutrients and micronutrients in fruits were significantly influenced by various treatments. The treatment, T8 (KAU POP + lime based on soil test) +125 kg gypsum per hectare + 80 kg magnesium sulphate per hectare + foliar application of borax (0.2%)) recorded highest capsaicin (0.352 %), oleoresin (11.00 %), ascorbic acid (96.83 mg 100 g-1 ) and maximum shelf life (13.66 days) in chilli. The results obtained from the experiment revealed the significant influence of soil amendments over KAU POP recommendation and it can be concluded that combined application of gypsum, magnesium sulphate and borax was effective for increasing fruit yield and quality in chilliThesisItem Open Access Soil quality index and nutrient balance in rice-rice cropping system under long-term fertilizer experiment(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Drishya, D S; KAU; Thulasi, VLong-term experiments provide the best possible platform for studying the changes in soil properties and processes, identifying emerging trends in nutrient imbalances and deficiencies and help to formulate future strategies for maintaining soil health and quality. The present study entitled “Soil quality index and nutrient balance in rice-rice cropping system under Long Term Fertilizer Experiment” was undertaken at RARS, Pattambi and College of Agriculture, Vellanikkara. The objectives were set out to estimate soil quality index and NPK balance in rice-rice cropping system as affected by nutrient management practices under Long Term Fertilizer Experiment. The Long Term Fertilizer Experiment (LTFE) in rice-rice cropping system maintained (since 1997) at RARS Pattambi has been laid out in RBD consists of 12 treatments viz.,T1 : 50 per cent NPK, T2 : 100 per cent NPK, T3 : 150 per cent NPK, T4 : 100 per cent NPK + 600 kg ha -1 CaCO3 , T5 : 100 per cent NPK, T6 : 100 per cent NP, T7 : 100 per cent N, T8 : 100 per cent NPK + Farm Yard Manure (FYM) @ 5 t ha -1 , T9 : 50 per cent NPK + FYM @ 5 t ha -1 , T10 : 100 per cent NPK + in situ growing of Sesbania aculeata, T11 : 50 per cent NPK + in situ growing of Sesbania aculeata and T12 : Absolute control (No fertilizer or manures). The soil samples from 0-15 cm depth were collected from the different treatments of LTFE after the harvest of Virippu crop, 2020 and were analysed for various physical, chemical and biological properties. Principal Component Analysis (PCA) was performed to arrive at the Minimum Data Set (MDS) and Soil Quality Index (SQI) was formulated for different nutrient management practices. Integrated nutrient management with FYM and in situ green manuring with daincha recorded higher grain and straw yields of rice. The increase in fertilizer load into the soil resulted in increase in yields while the omission of primary nutrients resulted as decline in yields. Integrated Nutrient Management practice (INM) of application of FYM along with 100 percent NPK had lower bulk density (1.17 Mg m-3 ) and higher water holding capacity (43.65 %), higher levels of available nutrients and enzyme activities in the soil. However, dehydrogenase activity did not follow the same trend as that of microbial biomass carbon in treatments wherein fertilizers alone were applied indicating the chances of shift in the microbial populations as a result of the long term application of nutrient management practices. Principal Component Analysis (PCA) was performed for 28 soil attributes to develop the MDS and SQI was formulated using non linear scoring method. The MDS included bulk density, porosity, soil pH, permanganate oxidizable carbon, available N, total N, available sulphur, microbial biomass carbon, acid phosphatase and aryl sulfatase activities. The SQI ranged from 1.82 to 3.01. The SQI declined in the order of: T8> T10 >T9> T11> T4> T3> T2= T1> T5> T6 >T7> T12. The highest SQI was observed in T8 where 100 per cent NPK and FYM were applied. When the dosage of fertilizers was increased from 50% to 100% NPK on integration with FYM, the SQI increased. The soil quality index of the INM treatments (55.50 to 62.11%) and lime incorporation (52.98%) were categorized under medium category as per the computed Relative SQI (RSQI) values. The virippu crop (2020) under LTFE maintained at RARS Pattambi was monitored and various inputs and outputs regarding primary nutrients were assessed for balance predictions using NUTMON toolbox. The NUTMON toolbox includes five inflows, viz., mineral fertilizers (IN1), manure (IN2), atmospheric deposition (IN3), biological N fixation (IN4), and sedimentation (IN5), and five outflows, viz., harvested product (OUT1), crop residues (OUT2), leaching (OUT3), gaseous losses (OUT4), and erosion (OUT5). Nutrient flows like fertilizers, manures, crop residues and harvested outputs were monitored and measured during the experiment. Other flows like nitrogen fixation, leaching, and erosion were estimated by means of regression models from the data related to climate and crop parameters. Available NPK content of soils, rice grain, straw, stubbles, weeds and all inputs were analysed and stored in background database. The data were fed into the data processing module of the NUTMON toolbox to arrive at the partial and total balance of N, P and K in the experimental soil. The total balance of N, P and K were found to decline in order of: T3>T7>T8>T6>T5>T2>T4>T10>T9>T1>T11>T12 for N, T3>T8>T6>T10>T2>T5>T4>T9>T1>T11>T12>T7 for P and T3>T2>T5>T8>T9>T10>T4>T11>T1>T12>T7>T6 for K Summarizing the results, integrated nutrient management with FYM and in situ green manuring with daincha recorded higher yield and available nutrients in the soil. The incorporation inorganic fertilizers with FYM, daincha and lime maintain the soil quality index in the long run while, SQI was poor in control, imbalanced nutrition as well as in treatments where only fertilizers were incorporated. The balance sheet of P establishes the need for maintenance dose of P fertilizers in rice-rice cropping system. The negative balance of N and K indicate the need for supplementing the nitrogen pool and the possibility of mining of K on long term intensive cropping, respectively. Further study should be focused on monitoring the soil quality index at regular intervals and analyzing the effect of nutrient management practices on microbial diversity in rhizosphere and phyllosphere.ThesisItem Open Access Evaluation of water hyacinth co- composts for nutrient retention in lateritic soil(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2021) Anisha, V A; KAU; Durga Devi, K MWater hyacinth is a serious menace in low land ecosystems and it’s spread has threatened water quality and aquatic life. Various biological, chemical and physical methods that have been employed to control the weed has yielded minimal results. Hence management through utilization is a viable strategy. It can be effectively utilized in many ways to support crop production. Co-composting has been proved as a promising technique for safe and quick disposal of the weed by utilizing the co-substrates viz., poultry manure, sawdust, biochar, glyricidia, paddy straw, dried leaves and cattle manure. As the weed accumulates N, P, K and other essential nutrients, compost made from water hyacinth can be utilized for improving soil fertility and crop production. Hence, the present investigation entitled “Evaluation of water hyacinth co-composts for nutrient retention in lateritic soil” was under taken in the Department of Soil Science and Agricultural Chemistry at College of Agriculture, Vellanikkara during 2020-2021. The objectives were; (i) To find out the suitable combination of water hyacinth and co-substrates for enhancing the quality of water hyacinth composts (ii) To assess the nutrient retention capacity of different co-composts in lateritic soil. Different co-substrates were collected from nearby areas and water hyacinth was collected from Kole lands of Thrissur. Water hyacinth and co-substrates were characterized prior to composting. Water hyacinth co-composts (vermi compost) were prepared using the aforesaid substrates in concrete tanks. The physical and chemical properties of the composting mixtures were recorded at 40 days interval starting from 20 days of composting until 100 days. The yield of water hyacinth co-composts was estimated and the various co-composts were characterized for their physical and chemical properties. Incubation study was conducted to evaluate the nutrient retention capacity of different water hyacinth co-composts in lateritic soil during December 2020 with eight treatments and three replications (soil+ 7 co-composts and soil alone as absolute control). The lateritic soil for study was collected from Instructional Farm, Vellanikkara and analysed for chemical properties. Compost amended soils were incubated for a period of 28 days and nutrient retention capacity (N, P, K, Ca, Mg, S, B, Zn) was estimated at 4 different time periods after incubation (7, 14, 21, 28 days). Data on characterization of co-substrates revealed that substrates vary in their chemical properties and nutrient content. Among the co-substrates, poultry manure possessed many favourable characteristics. Changes in physical and chemical properties of composting mixtures at different intervals indicated the progress of composting process and stage of compost maturity. All the co-substrates gave reasonably good yield of water hyacinth co-composts. A notable increase in compost yield to an extent of 159.7 per cent was realized in the biochar treatment. Addition of co-substrates improved the bulk density and porosity of water hyacinth co-composts. Application of co-substrates improved the pH of final compost. Highest increase was noticed in the treatment with paddy straw. Addition of paddy straw had significant adverse effect on the electrical conductivity of final co-compost (170.6 % increase in EC over water hyacinth sole treatment) and all the other treatments showed EC below maximum permissible limit for plant growth. The total carbon content of all the co-composts was higher than water hyacinth sole compost. Nitrogen content of the co-compost was improved to a greater extent by the application of paddy straw and poultry manure. Co-composts with sawdust, biochar and dried leaves had significantly lower quantity of nitrogen compared to water hyacinth sole compost. Glyricidia and poultry manure were highly effective in improving total phosphorus content of the co-compost. Total potassium content of water hyacinth compost was significantly improved with the addition of co-substrates like paddy straw and biochar, the extent of increase being 192 and 170 per cent, respectively. Carbon to nitrogen ratio of water hyacinth co-compost was significantly lowered by using poultry manure as a co-substrate. Addition of poultry manure improved all the three secondary nutrients viz., Ca, Mg and sulphur to a higher magnitude. No favourable effect was noticed on the boron content of co-compost by the addition of different co-substrates. However, Fe and Mn levels of final co-composts were considerably lower than the water hyacinth sole compost. This could be considered as a favourable effect of co-composting of water hyacinth with different substrates. Zinc content of the co-compost was significantly improved by the inclusion of co-substrate particularly with the use of poultry manure and dried leaves. Copper content of the co-compost was significantly higher with the addition of poultry manure as co-substate. The addition of co-compost to lateritic soil, improved retention of nutrients particularly nitrogen. The only exception was co-compost with paddy straw (0.9 per cent decrease in the nitrogen retention capacity). Irrespective of the treatments, cocompost retained all the phosphorus and boron present in the co-compost amended soil. The soil’s potassium, magnesium, sulphur and zinc retention capacity could be improved when amended with water hyacinth co-compost. In general, soil with biochar co-compost showed significantly high retention capacity with respect to plant nutrients particularly nitrogen. Further study should be focused on field experiments to test the agronomic efficiency of different water hyacinth co-composts, testing suitability of various crop residues and organic wastes as co-substrates and to derive suitable substrate combinations and ratios to eliminate the adverse effects of co-substrate on compost quality.ThesisItem Open Access Soil test crop response studies in cluster bean (Cyamopsis tetragonoloba L.) in lateritic soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellanikkara, 2022) Ayisha, V V; KAU; Rajalekshmi, KCluster bean, commonly known as guar, is a legume crop cultivated as a vegetable, green manure and forage crop. India is the leading producer of cluster bean in the world and accounts for around 80 per cent of global production. The generalised application of fertilizers by farmers result in under or over fertilization, lowering production and profitability while also polluting the environment. So the emphasis on soil test based balanced fertilizer recommendation has become more pertinent in the current scenario of high fertilizer costs and yield maximisation programmes. Hence, the investigation entitled “Soil test crop response studies in cluster bean (Cyamopsis tetragonoloba L.) in lateritic soils of Kerala” was undertaken. The study was conducted at College of Agriculture, Vellanikkara in lateritic soils (Ultisol) in the STCR field during 2020-2021 with the objective of developing soil test based fertilizer prescription equation for cluster bean using inorganic fertilizers alone and with the combined use of organic manures. A fertility gradient experiment was conducted to create soil fertility gradient in the field by applying graded doses of N, P and K fertilizers and raising fodder maize var. CO1. After the development of fertility gradient, the main STCR experiment was conducted in the same field with the test crop, cluster bean var. Pusa naubahar. The treatment structure consisted of four levels of nitrogen (0, 10, 20 and 40 kg ha-1 ), four levels of phosphorous (0, 30, 60 and 120 kg ha-1 ) and four levels of potassium (0, 40, 80 and 120 kg ha-1 ) along with three levels of FYM (0, 15 and 25 t ha-1 ). The basic parameters such as nutrient requirement (NR) and contributions of nutrients from soil (CS), fertilizer (CF) and FYM (COM) were computed from the field experimental data. The nutrient requirements (NR) for cluster bean were worked out as 0.68, 0.05 and 0.22 kg N, P2O5 and K2O to produce one quintal yield. The contributions from soil (CS) were estimated as 9.84, 2.29 and 1.99 per cent of N, P2O5 and K2O respectively. The contributions from fertilizer (CF) were calculated as 90.90, 3.29 and 10.82 per cent and that from FYM (COM) were 7.17, 1.92 and 2.96 per cent for N, P2O5 and K2O respectively. From the above basic data, fertilizer prescription equation for specific yield targets of cluster bean in the lateritic soils were derived as follows, NPK alone: FN = 0.74*T - 0.11*SN FP2O5 = 1.47*T – 1.59*SP FK2O = 2.05*T- 0.22*SK NPK + FYM (IPNS) FN = 0.74*T - 0.11*SN – 0.08*ON FP2O5 = 1.47*T – 1.59*SP – 1.34*OP FK2O = 2.05*T - 0.22*SK – 0.33*OK Where, FN, FP2O5 and FK2O = Fertilizer N, P2O5 and K2O in kg ha-1 T = Yield target in q ha-1 SN, SP and SK = STV for available N, P and K in kg ha-1 . ON, OP and OK = Amount of N, P and K supplied through FYM in kg ha-1 . The multiple regression model calibrated with yield as dependent variable and soil test results and inorganic fertilizer doses as independent variables had 62.5 per cent predictability. The yield of cluster bean increased with the application of NPK alone and IPNS viz. NPK plus FYM treatment and the magnitude of increase was higher under IPNS over NPK alone. The study is useful to adjust fertilizer doses based on yield target and available resources of organic manure with the farmers. The equations developed for cluster bean should be tested in places with similar agro climate and soil situations for validation.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 ℃.
