1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1
Browse
4 results
Search Results
Item Assessment, mapping and modelling of soil carbon pools and stock in selected agro-ecological units of south Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture ,Vellayani, 2024-04-22) Bincy, B; KAUA study entitled “Assessment, mapping and modelling of soil carbon pools and stock in selected agro-ecological units of south Kerala” was carried out to examine the impact of various agricultural land use systems on soil carbon fractions, pools and stock, soil aggregation, glomalin and polysaccharide contents, and to generate soil carbon maps using GIS and predict soil carbon changes in the future climate change scenario using modelling technique. The agro-ecological units (AEUs) of south Kerala namely, southern coastal plain (AEU 1), Onattukara sandy plain (AEU 3), southern laterites (AEU 8), south central laterites (AEU 9) and southern and central foothills (AEU 12) were selected for the study. In each AEU, different agricultural land use categories as described by IPCC for the carbon inventory such as, garden land (coconut), wet land (rice), fallow land (uncultivated) and plantation (rubber) were also selected. Soil profiles upto a depth of one meter was taken from the selected sites and samples were collected from various depth intervals of 0 to 25, 25 to 50, 50 to 75 and 75 to 100 cm. The surface soil samples (0 – 25 cm) were analyzed for soil properties such as pH, EC, CEC, texture, soil carbon fractions (organic, inorganic, water soluble, permanganate oxidizable, microbial biomass carbon and mineralizable carbon) and organic matter fractions (humic acid, fulvic acid and humin). The depth wise distribution of soil carbon pools (active, passive and slow carbon pools), bulk density and total organic carbon (TOC) were analyzed. Soil organic carbon stock, density, carbon indices (CPI, CLI, CMI, LQI, GWP) and carbon proportion/ turnover were computed. Soil aggregation was evaluated by analyzing water stable aggregates, mean weight diameter, macro-micro aggregate size distribution, aggregate associated organic carbon, glomalin and total polysaccharides in soil. GIS based thematic maps of soil organic carbon, stock, density and land quality were generated in ArcGIS 10.5.1 software. The soil organic carbon changes in the future climate change scenario were predicted using DNDC (Denitrification Decomposition) model. The results revealed that soil texture was loamy sand to sandy clay loam in AEU 1, sandy loam to sandy clay loam in AEU 3 and 9, sandy loam to sandy clay in AEU 8 and sandy clay loam to sandy clay in AEU 12. The sand fraction (45.32-80.34 %) was found to be more than silt (9.60 – 21.14%) and clay (8.87-39.15 %). The pH and EC of soils ranged 254 from 4.77 to 5.73 and 0.06 to 0.44 dS m⁻1 respectively. The CEC of soil varied between 2.60 and 6.69 c mol(p+) kg-1 with the highest value in rubber land use and the lowest in uncultivated land. Soil organic carbon (SOC) ranged from 0.34 to 0.73, 0.44 to 0.99, 0.40 to 1.09, 0.25 to 0.97 and 0.26 to 1.26 per cent in AEU 1, 3, 8, 9 and 12 respectively. Among the land uses, rubber land use recorded the highest SOC (1.03 %) followed by coconut (0.75 %) and rice (0.60 %) and the lowest SOC was observed in uncultivated land (0.34 %). The water soluble, permanganate oxidizable and the particulate organic carbon varied from 34.01 to 162.81 mg kg-1, 1.21 to 7.37 mg g-1 and 0.37 to 2.75 per cent respectively. The different AEUs and land uses followed the order AEU 12 > AEU 9 >AEU 8 > AEU 3>AEU 1 and rubber > coconut > rice >uncultivated land respectively. Similar trend was observed for microbial biomass carbon which ranged from 121.2 to 424.4 mg kg-1 with the highest value in AEU 12 and rubber land use. Percentage contribution of water soluble, particulate and permanganate oxidizable C to TOC was 0.31 to 0.43, 40.12 to 69.72 and 12.62 to 19.73 per cent respectively. The organic matter fractions viz. humic acid, fulvic acid and humin varied from 0.57 to 2.06, 0.73 to 2.33, 0.62 to 1.59 per cent respectively in different AEUs. The rubber land use showed significantly higher humic acid (1.72 %), fulvic acid (2.01 %) and humin (1.44 %) than coconut, rice and uncultivated land. Percentage contribution of humic acid, fulvic acid and humin to total organic matter ranged from 29.40 to 32.51, 32.30 to 36.42 and 26 to 29.25 per cent respectively. The active, slow and passive pools of carbon in soil ranged between 0.09 and 1.03, 0.17 and 0.78, 0.13 and 1.26 per cent respectively with the highest value in AEU 12 and the lowest in AEU 1. In different land uses it followed the order rubber >coconut> rice> uncultivated land. The soil carbon pool showed a gradual decline from 0 - 25 cm to 75 - 100 cm depth with a decrease of 0.82 to 0.14, 0.63 to 0.18 and 0.97 to 0.24 per cent for active, slow and passive carbon pools respectively. The passive pool of carbon (31.95 – 38.08 %) contributed more towards total organic carbon than active (23.64-37.66 %) and slow (22.73-32.12 %) pools. 255 With depth (0-25 cm to 75-100 cm) bulk density of soil increased from 1.38 to 1.66, 1.33 to 1.68, 1.35 to 1.64, 1.33 to 1.60 and 1.29 to 1.55 Mg m-3 in AEU 1, 3, 8, 9 and 12 respectively. Higher bulk density was observed in uncultivated land than rice, coconut and rubber land uses. The TOC in soil ranged from 0.72 to 2.80, 0.69 to 2.89, 0.79 to 3.46, 0.88 to 3.18 and 0.75 to 3.56 per cent in AEU 1, 3, 8, 9 and 12 respectively. In all the AEUs the highest TOC was registered from rubber land use followed by coconut, rice and the lowest from uncultivated land. The TOC content decreased with depth (0 - 25 cm to 75 - 100 cm) and the values were 1.99 to 0.95, 2.24 to 0.92, 2.45 to 1.05, 2.53 to 1.05 and 2.38 to 1.01 per cent for AEU 1, 3, 8, 9 and 12 respectively. Total soil organic carbon stock varied from 162.71 to 293.22, 175.80 to 275.79, 188.63 to 322.36, 199.73 to 331.48, 144.54 to 355.63 Mg ha-1 in AEU 1, 3, 8, 9 and 12 respectively with the highest stock in AEU 12. Among the land uses it followed the order rubber>coconut>rice>uncultivated land. SOC stock decreased from 0 to 25 cm to 75 to 100 cm depths and the values were 76.28 to 36.59, 79.97 to 35.88, 86.70 to 39.61, 88.10 to 39.48 and 79.90 to 35.80 Mg C ha-1 for AEU 1,3, 8, 9 and 12 respectively. The soil organic carbon density of the surface (0-25 cm) soil varied from 3.07 to 6.01, 3.68 to 5.76, 3.84 to 7.81, 4.19 to 7.19 and 3.27 to 6.96 kg m-2 in AEU 1, 3, 8, 9 and 12 respectively with the highest density observed for AEU 12. With respect to different land uses it followed the order rubber (6.96 kg m⁻2 )> coconut (5.86 kg m⁻2) > rice (5.10 kg m⁻2) > uncultivated land (3.61 kg m⁻2). The carbon indices such as lability, pool and management index ranged from 0.30 to 0.93, 0.19 to 0.51 and 5.55 to 38.42 respectively in different AEUs and were found to be the highest in AEU 12 and rubber land use. The land quality index based on SOC stock in kg m-2 was rated as medium (6 - 9 kg m-2 ) in all AEUs. The mineralizable C content in soil varied from 1.40 to 3.45, 1.18 to 3.41, 1.04 to 3.04, 1.23 to 3.35 and 1.01 to 3.02 mg g⁻¹ in AEU 1, 3, 8, 9 and 12 respectively. The highest value was observed from AEU 1 and rice land use. Similar trend was obtained for global warming potential of soils based on CO2 evolution which varied from 31.82 to 78.41, 26.89 to 79.02, 22.89 to 69.02, 28.03 to 76.06 and 22.96 to 68.64 in AEU 1, 3, 8, 9 and 12 respectively. The C proportion and turnover rates were in the range of 0.25 to 0.77 256 and 0.04 to 0.17 respectively. The C proportion was the highest in AEU 12 and rubber land use whereas the C turnover was the highest in AEU 1 and rice land use. With respect to aggregate distribution, the larger size fractions (5-8, 2-5, 1-2 & 0.5-1 mm) were found to be higher in rubber land use and the smaller size fractions (0.25-0.5 & 0.1-0.25 mm) were higher in rice land use. The macro aggregate fraction (> 250 μm) ranged from 22.60 to 75.70 per cent with the highest value in rubber land use while the micro aggregate fraction (53 – 250 μm) ranged from 10.78 to 56.46 per cent with the highest value in rice land use. The water stable aggregates and mean weight diameter were ranged from 22.60 to 34.31 per cent and 0.56 to 2.90 mm respectively and were the highest in rubber land use. The aggregate associated organic carbon was the highest in the size fraction of 1 to 2 and 0.5 to 1 mm (1.03-1.27 g kg-1) compared to other fractions. The organic carbon associated with macro (> 250 μm) and micro (53-250 μm) aggregates are in the range of 2.16 to 5.70 and 0.30 to 0.95 g kg-1 respectively with the highest value in rubber land use. The glomalin related soil protein ranged from 1.22 to 6.35 mg g-1 and polysaccharides from 2.12 to 9.24 mg g-1 . Irrespective of the AEUs the highest glomalin and polysaccharides were observed in rubber land use. The DNDC model predicted organic carbon changes in coconut land use systems in Thuravoor (AEU 1), Bharanikkavu (AEU 3), Ookkod (AEU 8), Karavaram (AEU 9) and Vellarada (AEU 12) under RCP 4.5 and RCP 8.5 future climate change scenario. The DNDC model predicted an increase in soil organic carbon status from 2020 to 2050 under RCP 4.5 and RCP 8.5 scenario but the rate of increase in soil carbon were more pronounced under 4.5 scenario where relatively lower CO2 emission was observed. The predicted SOC for 2050 under RCP 4.5 scenario were 1.26, 1.04, 1.44, 1.23 and 1.27 for Thuravoor (AEU 1), Bharanikkavu (AEU 3), Ookkod (AEU 8), Karavaram (AEU 9) and Vellarada (AEU 12) respectively. The organic carbon fractions, pools and stock were the highest in agro-ecological unit 12. Among the land uses, rubber contributed more to the SOC stock and pools indicating the prevalence of conducive environment for the buildup of carbon. The macro 257 and micro aggregates, aggregate associated carbon, glomalin, polysaccharides and C proportion were also higher in rubber land use indicating it as a potential carbon sink. Among the carbon fractions particulate organic carbon contributed more to total organic carbon. Among the carbon pools passive pool contributed more towards the total organic carbon. The carbon associated with larger fractions (1-2 mm and 0.5-1 mm) and macro aggregates (> 250 μm) were high in rubber land use indicating physical protection and sequestration in soil. The DNDC model predicted an increase in the SOC status from 2020 to 2050 under RCP 4.5 and RCP 8.5 scenario of future climate change.Item Soil Carbon Storage and Nitrogen Dynamics In Certified Organic Farms of Kerala(Department Of Soil Science and Agricultural Chemistry College Of Agriculture, Vellayani, 2021-11-22) Nayana, M V; Gladis, RThe study entitled “Soil carbon storage and nitrogen dynamics in certified organic farms of Kerala” was carried out to assess the influence of organic farming on the various physical, chemical and biological properties and also the carbon and nitrogen pools of the soil. A field survey was conducted and ten certified organic (certified for more than 10 years) and nearby conventional farms representing Northern zone (Kannur), hill zone (Wayanad), central zone (Palakkad) and Southern zone (Thiruvananthapuram) were selected for the study. Two composite samples each from two depths (0-15 cm and 15-30 cm) were collected and analyzed for soil properties, organic carbon pools and fractions, organic matter fractions and nitrogen fractions. Various carbon indices like carbon pool index, lability index and management index were worked out. For studying the temporal variation of nitrogen, samples were collected from two certified organic farms and nearby conventional farms of College of Agriculture, Vellayani during February, May, August and November and analyzed for various nitrogen fractions. The soils under study belong to sandy loam, loamy sand, sandy clay and loam textural classes. The bulk density was found to be the lowest in the organic soils (1.15 Mg m-3) than the conventional. Other physical properties like porosity (41.32%), water holding capacity (52.68%), water stable aggregates (73.59%) were found to be higher in the surface soils of organic farms than the conventional farms. Macro aggregates constituted greater proportion than micro aggregates. The soil acidity (pH 5.71), EC (0.09 dSm-1) and CEC (5.98 C mol (p+) kg-1) were found to be more in the organic farms. Soil biological properties like soil enzyme dehydrogenase (25.21 g TPF g-1 soil 24 h-1) and soil protein glomalin (12.31 mg g-1) were also found to be higher in organic farms and decreased with depth. The different pools of organic carbon like active (0.60%), slow (0.29%) and recalcitrant (0.51%)) pools were found to be higher in organic farms at both depths. A higher total organic carbon of 7.59% was registered in organic farm and it decreased with depth. Other carbon fractions like water soluble carbon (157.79 mg kg-1), labile carbon (2.57 mg g-1), particulate organic carbon (0.76%) and microbial biomass carbon (187.80 mg kg-1) were also found to be higher in the organic soil when compared to the conventional. Aggregate associated carbon was also found to be higher in organic soil and more carbon was associated with macro aggregates than micro aggregates. The organic matter fractions like fulvic acid (5.45%), humic acid (3.56%) and humin (0.47%) were dominated in organic soils. Total nitrogen content (0.46%) was the highest in organic soils. Other nitrogen fractions like total soluble nitrogen (257.60 mg kg-1), soluble organic nitrogen (159.3 mg kg-1), particulate organic nitrogen (0.51 g kg-1), ammoniacal (121.20 mg kg-1) and nitrate (51.80 mg kg-1) nitrogen and microbial biomass nitrogen (88.76 mg kg-1) were found to be higher in organic farm than the conventional. Total free amino acids (5.28 mg N kg-1) and soluble protein (52.48 mg N kg-1) were also found to be the highest in organic soils. C:N ratio of the organic soil was found to be 16:1. Various carbon indices like carbon pool index (0.82), lability index (0.64), management index (0.53) and soil organic carbon stock (130.93 Mg ha-1) were higher in organic soils than conventional. The seasonal/temporal dynamics of nitrogen studied revealed that the highest concentration of all the N fractions was observed during May and the least during November at both the depths. Also a higher concentration was noticed in the organic soils than the conventional. From the study it is concluded that the organic farming significantly contributed to soil carbon storage as different pools distributed in different sized aggregates of soil due to increased organic carbon addition and aggregate dynamics. The organic matter fractions, nitrogen fractions, carbon and nitrogen mineralization were also positively and significantly influenced by organic management system. The soil organic carbon stock and indices were increased by organic management system indicating the improvement in the quality and sustainability of the system. The seasonal dynamics of various nitrogen forms and fractions were also significantly influenced by organic farming demonstrating the interactive effect of management system and climate change which increased nitrogen availability from organic nitrogen sources.Item Nutritional and phytochemical quality asessment of coconut hybrids from Ayiramkachi (Cocos nucifera. L)(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Padannakkad, 2023-02-06) Ramya, M; Binitha, N KItem Biochar for carbon sequestration, soil health and crop productivity(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2022-11-21) Nhala Jabin P P.; Rani, B