1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Quantification and depth distribution analysis of carbon, nitrogen, and microbiomes in soils of Miyawaki forests in Kerala(Department of Soil Science, College of Agriculture, Vellayani, 2024-12-11) Sreelekshmi, M; Naveen LenoA study entitled “Quantification and depth distribution analysis of carbon, nitrogen and microbiomes in soils of Miyawaki forests in Kerala” was undertaken with the objectives of quantifying the levels of carbon and nitrogen in Miyawaki forest soils in Kerala, analysing the effect of increasing carbon sinks in achieving carbon sequestration and to investigate abundance of microbiomes in these soils. A preliminary survey was conducted to identify the locations where Miyawaki forests were established and is existent in the entire Kerala state. Altogether 58 Miyawaki forests have been established till date in Kerala. Five well established and oldest Miyawaki forests out of these were selected for further study. A survey was conducted during December 2023 in the selected study area and 20 georeferenced soil samples were collected from surface and subsurface layers from five Miyawaki forest and nearby undisturbed plots. The selected sites were located at Puliyarakonam, Peyad, Kanakakkunnu, Vilappilsala and Chalai. The soil samples were characterized for selected physical, chemical and biological attributes, carbon pools and nitrogen fractions. Various carbon indices like carbon pool index (CPI), lability index (CLI) and management index (CMI) were worked out. The carbon sequestration potential of each Miyawaki forest was also calculated. A metagenomic analysis of one sample each from Miyawaki forest and undisturbed plot was also conducted. A minimum data set (MDS) of indicators to assess soil quality index (SQI) was set up using Principal component analysis (PCA). The spatial variation in temperature within the confines of the Miyawaki forest as well as outside were recorded for a period of three months from March 2024 to May 2024 at two locations, viz., Puliyarakonam and Vilappilsala. The soils under study belong to sandy clay loam. The bulk density was found to be the lowest in the Miyawaki forest (1.15 Mg m-3) than the control. Other physical properties like water holding capacity (60.28%), soil moisture content (34.83%) and water stable aggregates (88.48%) were found to be higher in the surface soils of Miyawaki forest than the control plots. The soil acidity (pH 5.40) and EC (0.059 dSm-1) were found to be more in the Miyawaki forest. Soil biological properties like soil enzyme dehydrogenase activity (80.20 mg TPF g-1 soil 24 h-1), bacterial density (7.573 log cfu g-1), fungal count (5.507 log cfu g-1) and actinobacterial count (4.909 log cfu g-1) were also found to be higher in Miyawaki forest and decreased with depth. A higher total organic carbon of 10.31% was recorded in Miyawaki forest, which was observed to decrease with depth. Other carbon fractions like water soluble carbon (21.21 mg kg-1), labile carbon (4.51 mg g-1), particulate organic carbon (1.03%) and microbial biomass carbon (152.69 mg kg-1) were also observed to be higher in the Miyawaki forest when compared to the control plots. Total nitrogen content (0.36%) and available nitrogen (264.26 kg ha-1) was highest in Miyawaki forest. A higher C:N ratio was observed in Miyawaki forest (28.77) and was observed to increase with depth. The soil organic carbon stock (38.08 Mg ha-1) and carbon sequestration rates 9.05 Mg ha-1yr-1 were also found higher in Miyawaki forest soils compared to the control plots. A temperature difference up to 3.93°C and 4.21°C was observed between the mean maximum temperature between the inside and outside of Miyawaki forest during the summer months in Puliyarakonam and Vilappilsala respectively. No significant difference was observed for CPI, CLI, CMI, and SQI. The study on Miyawaki forests in Kerala reveal their substantial contribution to soil carbon storage and nutrient enrichment. The findings indicate that these forests not only enhance soil quality through increased organic carbon and nitrogen levels but also support a diverse microbiome, which is vital for soil health. Miyawaki forests in Kerala exhibit lower bulk density and higher water holding capacity compared to control plots, indicating improved soil structure and moisture retention. Additionally, the significant temperature regulation observed within the forests highlights their role in moderating local microclimates. Overall, the results underscore the potential of Miyawaki forests as effective carbon sinks and valuable ecological assets, advocating for their expansion as a strategy for carbon sequestration and soil restoration in the region. Further research is recommended to explore the long-term ecological impacts and management practices that can optimize these benefits.Item Productivity enhancement of vegetables through salt stree mitigation in the sandy loam soils of Onattukara(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2025-12-14) Salma Nizar.; Mini, VThe study entitled “Productivity enhancement of vegetables through salt stress mitigation in the sandy loam soils of Onattukara” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2022-2024. The main objective of the study was to evaluate the ameliorative effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables in the salt stressed areas of Onattukara using tomato as the test crop. The three parts of the study were the development of multinutrient formulation for supplementary foliar nutrition, germination test for identifying the critical level of salinity for tomato and the evaluation of the effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables under salt stress. The salient research findings emanated from the experiments are summarized below. A multi nutrient formulation containing K, Ca, Mg, N, B and Zn was developed for supplementary foliar nutrition based on general soil status. General soil status of these nutrients was low and literature references and adhoc recommendations for secondary and micronutrient management and information on crop requirement were also used for developing the formulation. Suitable nutrient carriers were used for developing the foliar formulation. The carriers evaluated to prepare the mixture were KNO3, CaNO3, MgSO4. 7H2O, H3BO3, ZnSO4.7H2O, Na2B8O13. 4H2O and Zinc acetate. Humic acid and potassium silicate were used as surfactant and binder materials. Based on the properties like pH, EC and solubility in water and trial on standing crop, the mixture containing KNO3, Ca (NO3)2, MgSO4.7H2O, Boric acid and ZnSO4.7H2O was found to be the best. This formulation had a nutrient composition of K (10%), N (4%), Ca (6%), Mg (2.5%), B (5%) and Zn (2%) and recorded a pH of 6.32 and EC of 0.6dSm-1, which was within the desirable limit for foliar formulations and was 100% soluble. The germination test for identifying the critical level of salinity for tomato was carried out in the laboratory in completely randomized design using seeds of tomato variety Vellayani vijai. Different levels of salinity (10mM, 20mM, 30mM, 40mM of NaCl) was evaluated along with control and critical level of salinity for tomato identified. Observations taken on the 14th day of experiment showed that the germination percentage of tomato seeds reduced from 96.52% to 30.87% , days needed to complete germination increased from 3.70 days to 12.15 days and root shoot dry weight ratio increased from 0.433 to 0.611 with an increase in salinity levels from 0mM NaCl (T1) to 40mM NaCl (T5). The analysis of Na and K content of tomato seedlings also revealed a significant increasing trend in Na+/ K+ ratio of shoot and root with increase in salinity levels. Na+/ K+ ratio of shoot ranged from 2.23 to 4.21 and Na+/ K+ ratio of root ranged from 1.90 to 3.36 with treatments T1 to T5. The germination study could identify the treatment T4 - Hoagland solution containing 30 mM NaCl which recorded a noticeably greater reduction in germination percentage (<80%) as the critical level of salinity for tomato. Hence 30 mM NaCl and 40 mM NaCl were selected for the pot culture experiment. The pot culture experiment was conducted from January to April 2024 at O.R.A.R.S., Kayamkulam using tomato (var. Vellayani vijai) as the test crop to evaluate the effect of various doses of calcium silicate (100 kg ha-1 to 150 kg ha-1) and supplementary foliar nutrition (0.5%) on growth and mineral nutrition of vegetables under salt stress. Biometric observations like plant height, number of branches, fruit set percentage and internodal length were significantly higher in the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress) whereas days to first fruit set, root length, root volume and root dry weight was higher in treatment T8 ( Soil test based POP + CaSiO3 @ 150 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress). Treatments containing calcium silicate and supplementary foliar nutrition showed a significant improvement in all of the biometric observations recorded. With regard to the yield attributes such as fruits per plant, fruit weight and yield per plant, the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of The study entitled “Productivity enhancement of vegetables through salt stress mitigation in the sandy loam soils of Onattukara” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani during 2022-2024. The main objective of the study was to evaluate the ameliorative effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables in the salt stressed areas of Onattukara using tomato as the test crop. The three parts of the study were the development of multinutrient formulation for supplementary foliar nutrition, germination test for identifying the critical level of salinity for tomato and the evaluation of the effect of calcium silicate and supplementary foliar nutrition on growth and mineral nutrition of vegetables under salt stress. The salient research findings emanated from the experiments are summarized below. A multi nutrient formulation containing K, Ca, Mg, N, B and Zn was developed for supplementary foliar nutrition based on general soil status. General soil status of these nutrients was low and literature references and adhoc recommendations for secondary and micronutrient management and information on crop requirement were also used for developing the formulation. Suitable nutrient carriers were used for developing the foliar formulation. The carriers evaluated to prepare the mixture were KNO3, CaNO3, MgSO4. 7H2O, H3BO3, ZnSO4.7H2O, Na2B8O13. 4H2O and Zinc acetate. Humic acid and potassium silicate were used as surfactant and binder materials. Based on the properties like pH, EC and solubility in water and trial on standing crop, the mixture containing KNO3, Ca (NO3)2, MgSO4.7H2O, Boric acid and ZnSO4.7H2O was found to be the best. This formulation had a nutrient composition of K (10%), N (4%), Ca (6%), Mg (2.5%), B (5%) and Zn (2%) and recorded a pH of 6.32 and EC of 0.6dSm-1, which was within the desirable limit for foliar formulations and was 100% soluble. The germination test for identifying the critical level of salinity for tomato was carried out in the laboratory in completely randomized design using seeds of tomato variety Vellayani vijai. Different levels of salinity (10mM, 20mM, 30mM, 40mM of NaCl) was evaluated along with control and critical level of salinity for tomato identified. Observations taken on the 14th day of experiment showed that the germination percentage of tomato seeds reduced from 96.52% to 30.87% , days needed to complete germination increased from 3.70 days to 12.15 days and root shoot dry weight ratio increased from 0.433 to 0.611 with an increase in salinity levels from 0mM NaCl (T1) to 40mM NaCl (T5). The analysis of Na and K content of tomato seedlings also revealed a significant increasing trend in Na+/ K+ ratio of shoot and root with increase in salinity levels. Na+/ K+ ratio of shoot ranged from 2.23 to 4.21 and Na+/ K+ ratio of root ranged from 1.90 to 3.36 with treatments T1 to T5. The germination study could identify the treatment T4 - Hoagland solution containing 30 mM NaCl which recorded a noticeably greater reduction in germination percentage (<80%) as the critical level of salinity for tomato. Hence 30 mM NaCl and 40 mM NaCl were selected for the pot culture experiment. The pot culture experiment was conducted from January to April 2024 at O.R.A.R.S., Kayamkulam using tomato (var. Vellayani vijai) as the test crop to evaluate the effect of various doses of calcium silicate (100 kg ha-1 to 150 kg ha-1) and supplementary foliar nutrition (0.5%) on growth and mineral nutrition of vegetables under salt stress. Biometric observations like plant height, number of branches, fruit set percentage and internodal length were significantly higher in the treatment T7 ( Soil test based POP + CaSiO3 @ 125 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress) whereas days to first fruit set, root length, root volume and root dry weight was higher in treatment T8 ( Soil test based POP + CaSiO3 @ 150 kg ha-1 + 0.5 % spray of multi nutrient mixture @ 30 mM salt stress). Treatments containing calcium silicate and supplementary foliar nutrition showed a significant improvement in all of the biometric observations recorded.Item Geospatial variability and nutrient dynamics of soils of lateritic wetlands vis-avis coastal wetlands(Department of Soil Science & Agricultural Chemistry, College of Agriculture , Padanakkad, 2025-01-17) Anzala Shahanas.; Nideesh, PA research study entitled “Geospatial variability and nutrient dynamics of soils of lateritic wetlands vis-a-vis coastal wetlands” was done with the objective to assess the spatial and temporal variability of the wetland soils in the two AEU’s (northern laterites and northern coastal plains) of north Kerala using GIS and also to assess the soil dynamics as modified by amendments for evolving best management practices. Paddy growing wetland of RARS, Pilicode (AEU 11) and Muppathil kandam at Nileshwar (AEU 2) were selected for the spatial and temporal variability assessment of soil nutrient dynamics. Grid based soil samples were collected from 10 locations at quarterly intervals for one year from these wetlands (from February 2023 to November 2023). Additionally, a pot culture experiment was conducted at the College of Agriculture, Padannakkad, using paddy as the test crop. Experiment was conducted with 2 types of soils (coastal sandy and lateritic alluvial wetland) under 5 levels of treatments using CRD. Treatment combinations were T1 (KAU POP (2016) based fertilizers + lime), T2 (Soil test based fertilizers), T3 (Soil test based fertilisers and lime), T4 (KAU organic POP based FYM + Lime) and T5 (Soil test based fertilisers and dolomite). In the clay loam soils of lateritic wetland (AEU 11), pH was found to be in the range of 4.44 to 5.64 and were non saline. Organic C content ranged from 0.60 % to 2.85 % and available N ranged from 81.54 to 476.67 kg ha⁻¹. Available P was high (>29 kg ha⁻¹) and available K ranged from 56.22 to 263.65 kg ha⁻¹. Available Ca varied between 160.00 and 480 mg kg⁻¹ and available Mg varied between 48.00 and 156.00 mg kg⁻¹. Available S, Fe, Mn, Zn and Cu content were sufficient and available B was deficient. MBC varied between 216.97 and 1390.59 μg g⁻¹ and DHA varied between 1.28 and 13.59 μg TPF released g⁻¹ soil 24 h⁻¹. . In the coastal sandy wetland soils (AEU 2), pH ranged from 5.60 to 6.94 and were non saline. Organic C was in the range from 0.45 % to 1.20 % and available N ranged from 43.90 to 244.61 kg ha⁻¹. Available P was high (>29 kg ha⁻¹) and available K was low to medium (15.68 and 210.13 kg ha⁻¹). Available Ca varied between 160.00 and 480 mg kg⁻¹ and available Mg varied between 72 and 192 mg kg⁻¹. Available S, Fe, Mn, Zn and Cu content were sufficient and available B was deficient. MBC ranged between 54.59 and 338.66 μg g⁻¹ and DHA ranged between 0.65 and 9.66 μg TPF released g⁻¹ soil 24 h⁻¹. On assessing the temporal variability of nutrient dynamics in lateritic wetland soils, it was found that the mean organic C, available Ca and Mg content were highest in August which was on par with May. The mean available S, MBC and DHA were highest in August. The highest mean available N was observed in November, while the mean available P was maximum in August, which was on par with November and May. In coastal wetland soils, the highest mean value of organic C, available N, K, mean MBC and DHA were recorded in November. The mean available Ca, Mg and S were highest in May which was on par with August and mean available P was highest in February. In both wetland soils, the highest mean pH value was observed in May which was on par with February. Results of pot culture experiment showed that there is significant effect of treatments on soil nutrient content and plant growth. Treatments have no significant effect on plant height. In lateritic wetland soils, highest number of productive tillers was recorded in T5 which was on par with T3 and T2. Highest number of grains per panicle was recorded in T3 which was on par with T5 and T2. Highest 1000 grain weight was recorded in T3 which was on par with T5. In coastal wetland soils, number of productive tillers was maximum in T3 which was on par with T5 and T2. Number of grains per panicle was maximum in T5 which was on par with T3 and T2. Highest 1000 grain weight was recorded in T5 which was on par with T3. Available N, K, Ca, Mg and B showed similar trend in both lateritic and coastal wetland soils. Available N was maximum in T1 and available K was maximum in T3 which was on par with T2 and T5. Highest available Ca was recorded in T1 which was on par with T4 and T3. Highest available Mg was recorded in T3 which was on par with T5 and T2. Highest available B was recorded in T3 which was on par with T5 and T2. Total nutrient content in plants (N, Ca, Mg, S and B) showed similar trend in both soil types. Highest plant N content was recorded in T1 which was on par with T3 and T5. Highest plant Ca and S content were recorded in T1 which was on par with T4. Highest Mg content was recorded in T3 which was on par with T5 and T2. Plant B content was maximum in T3 which was on par with T5. Highest plant K content was recorded in T3 in lateritic wetland soils while it was maximum in T3 which was on par with T5 in coastal wetland soils.Item Soil quality and biological resilience of AEU 17 (Marayur hills) of Kerala(Department of Soil Science, College of Agriculture , Vellayani, 2023-01-20) Muthyala Abhiram.The study entitled “Soil quality and biological resilience of AEU 17 (Marayur Hills) of Kerala” was carried out with the objective of characterization and assessment of soil quality, development of thematic maps and to explore the soil biological resilience of AEU 17 (Marayur Hills) of Kerala to transient (heat) and persistent (Cu induced) stress. Sixty geo referenced surface (0-15 cm) and subsurface (15-30 cm) soil samples were collected and analyzed for physical (bulk density, particle density, texture porosity, water holding capacity, soil moisture content and aggregate analysis), chemical (pH, EC, exchangeable acidity, organic carbon, available macronutrients, available Fe, Mn, Zn, Cu and B) and biological (acid phosphatase and dehydrogenase activity) attributes. Ten surface samples from each of four major land use systems (forest, sugarcane, cool season vegetables and fruits) were bulked together to make single representative sample to explore biological resilience. A weighted soil quality index was formulated based on minimum data set (MDS) of soil physical, chemical and biological parameters derived through principal component analysis (PCA). The PCA gave six principal components for surface soils (0-15 cm) with eigen value greater than 1, which yielded nine parameters viz., organic carbon, available copper, per cent sand, available sulphur, electrical conductivity, available magnesium, boron, calcium and per cent silt. For subsurface soils (15 – 30 cm), PCA gave seven principal components with eigen value greater than 1, which yielded ten parameters viz., organic carbon, per cent clay, available manganese, pH, available sulphur, boron, iron, magnesium, per cent silt and available calcium. Parameters in MDS were classified, scored and weights assigned based on current soil characteristics, agricultural systems, and agro climatic variables. The relative soil quality indices were computed. Nutrient indices of organic carbon and available primary nutrients were calculated. GIS maps were generated to depict the spatial variability in soil properties, quality and nutrient indices. Correlations between the analyzed parameters were worked out in both surface and subsurface layers. Sandy clay loam was the predominant (40 %) soil textural class observed in the study area, followed by clay (33.3 %), sandy loam (16.7 %) and clay loam (10 %). Soil pH was slightly acidic in the surface (54 %) and subsurface (50 %) soils with a slight 176 depth wise decrease. No such depth wise variation was observed for electrical conductivity which indicated their non-saline nature (< 1dS m-1 ). Exchangeable acidity of 90 per cent surface soils was less than 0.5 cmol (+) kg-1 whereas majority of subsurface samples (83.3 %) ranged between 0.5 and 1.0 cmol (+) kg-1 . Available N was low (< 280 kg ha-1 ) in majority of samples in both surface (53 %) and subsurface (63 %) soils. Available P (>24 kg ha-1 ) and K (>275 kg ha-1 ) status were high for majority of both surface and subsurface soils. Surface (83 %) and subsurface (67 %) soils were sufficient in available Ca. Majority of surface (67 %) soils showed sufficiency in available Mg while it was deficient in 63 per cent of subsurface soil samples. Available sulphur status was sufficient for all the samples in both surface and subsurface layers. All micro nutrients except B indicated sufficiency. Relative soil quality index was high for all the surface soil samples while 76 per cent of sub surface soil samples showed good relative soil quality index and 23.3 per cent samples showed medium relative soil quality index. Nutrient indices were high for OC, available P and low for available N in both surface and subsurface soils in all the panchayaths. Nutrient index for K was high for surface soil in all panchayaths. Though it was high in subsurface soil of Vattavada panchayath, it was medium in both Marayur and Kanthalloor panchayaths. Majority of the soils in surface (67 %) and subsurface (63 %) layers showed very low land quality index. Biological resilience assay for transient heat stress and persistent copper stress in different land use systems revealed that forest soils showed high stability index and resilience index for both heat and copper induced stress. This was followed by sugarcane and cool season vegetable land use systems which also exhibited an increase in respiration expressed in terms of carbon mineralization potential after 21 days of incubation. Fruits land use system showed low value for both soil stability index and resilience index for applied heat stress. Fruits land use system exhibited a progressive decline in both stability index and resilience index over a period of 21 days of incubation. Maintenance of a high soil quality index is a pre-requisite for soil health. Assessment of soil quality index on a regular basis would facilitate adoption of effective alternate site-specific management of crops. Liming of acid soils, regular application of recommended doses of nitrogenous fertilizers, application of phosphorous and potassic 177 fertilizers in P and K deficient areas, applications of borax at regular intervals are the suggested interventions in AEU 17 (Marayur Hills). Integrated application of organic manures along with inorganic fertilizers is to be encouraged in the fruits land use system for enhancing the soil biological resilience to transient and persistent abiotic stress as is evident in the forest land use system.Item Performance of Ayar nutrient mix on rice grown in coarse sandy soil of Kasaragod(Department of Soil Science and Agricultural Chemistry, Colleg e of Agriculture, Padannakkad, 2024-12-27) Swetha, J; Binitha, N KThe study entitled “performance of ayar nutrient mix on rice grown in coarse sandy soil of Kasaragod” was carried out with the objective of characterization of rice growing soils of AEU 2 and modification and standardization of ayar nutrient mix for the rice grown in the coarse sandy soil. A comprehensive soil characterization study was conducted in AEU 2 by collecting 25 geo-referenced soil and plant samples. Bulk density of the collected samples ranges from 1.02-1.81 Mg m-³, particle density in this region had an average of 2.8 Mg m-³and moisture content ranges from 18.85-38.15%. The predominant soil texture recorded in this region was sandy. Soil reaction was acidic and non saline. Organic carbon content ranged from 0.30-1.68%. Soil was deficient in essential nutrients such as available nitrogen, potassium, calcium, magnesium, zinc and boron, while available phosphorus, sulphur and iron levels were sufficient. Silicon content of the soil was from 55.35 to 130.38 mg kg-1 and aluminum content ranges 198.8-289.5 mg kg-1. On analysis it was found that microbial biomass carbon value ranges 149.88-342.81 µg g-1, dehydrogenase ranges from 1.742-3.82 µmol min-1, phosphatase ranges 3.083-8.921 µmol min-1 and urease ranges from 0.729 1.569 µmol min-1 indicating the low biological activity of the soil. Plant analysis of the study area revealed widespread deficiencies in total nitrogen, manganese and boron, while phosphorus, potassium, calcium, magnesium, sulphur, iron, zinc and copper levels were generally sufficient. Biochemical analysis of grain samples showed total sugar values ranging from 434.2 to 693.76 µg mL-1, vitamin B1 ranging from 2.191 to 5.59 µg mL-1, vitamin B3 from 2.82 to 19.352 µg mL-1and vitamin B5 from 39.564 to 70.146 µg mL-1. The analysis of amino acids such as lysine and glycine were also done and their mean values are 0.057 µg mL-1 and 0.015 µg mL-1respectively. The ayar nutrient mix which had been previously formulated for banana was modified based on the data of nutrient availability in coastal sandy soils and formulated a mixture containing 15% calcium, 7.6% magnesium, 2% sulphur, 1.75% zinc and 1% boron. After one year of airtight storage, the mix showed no change in color or odour changes and remained lump-free. The results of the incubation study proved that treatment T4 (ayar at 30 kg/ha) resulted the highest available calcium, sulphur and boron levels across the four-month study period compared to the control (T1). The value of available magnesium was maximum for treatment T4 during the second and fourth month whereas it was maximum for treatment T3 in the first month. There was no significant change in the available zinc content for the first two months and in the next two months available zinc content was maximum for treatment T4. In the pot culture experiment, there were no significant changes among the various treatment means for the pH and EC of the soil. The organic carbon analysis showed that treatments T2 (KAU POP, 2016) and T6 (T2 + ayar at 25 kg/ha in two equal splits at active tillering and panicle initiation) recorded the highest values. Application of KAU POP and Ayar at 25 kg/ha during active tillering stage led to high levels of available nitrogen, potassium, zinc and aluminum. Treatment T6 was the best treatment with respect to available phosphorus, calcium, boron and silicon, while treatments T7 (T2 + ayar at 30 kg/ha during active tillering stage) and T8 (T2 + ayar at 30 kg/ha in two equal splits during active tillering and panicle initiation stage) were superior with respect to magnesium and sulphur, respectively. The results of the plant analysis during the harvest stage revealed that treatment T7 was superior with respect to total nitrogen, T3 for phosphorus and sulphur, T6 for total potassium and boron and T5 proved to be the best treatment for total calcium, iron and zinc. There was no significant difference among the various treatment means for total magnesium, copper and manganese content in the plant. Treatment T5 exhibited superior performance with respect to growth and yield parameters, including grains per panicle, grain yield, test weight and straw yield. Whereas plant height and leaf length were maximum in treatments T7 and T4, respectively. For the biochemical analysis of the grain treatment T4 had recorded the highest levels of glycine, vitamins B1, B3 and B5. T8 recorded maximum total sugar. Lysine levels showed no significant difference. The salient findings of the study suggest that the application of ayar at 25 kg/ha during the active tillering stage along with KAU POP recommendations (T5) as the best treatment as it improves the nutrient and economical status of the plant. The Ayar nutrient mix proved effective in ameliorating soil fertility constraints, enhancing rice growth and nutritional quality, making it a valuable resource for farmers cultivating rice in challenging coastal sandy soils.Item Spatial variability and dynamics of arsenic in selected coastal rice ecosystems of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2025-02-12) Rashbi Jahan, V; Mayadevi, M RArsenic (As) is a naturally occurring toxic metalloid, that can cause detrimental effects on plants as well as humans. Though the elevated level of As is not reported from the paddy soils of Kerala, the tropical climate and high amorphous Fe minerals in the soil may cause an excessive dissolution of arsenic in the soils of Kerala. Hence, a study entitled “Spatial variability and dynamics of As in selected coastal rice ecosystems of Kerala” was designed to understand the spatial distribution of As in paddy soils of coastal agroecological units (AEU), namely, Northern coastal plain (AEU 2) and Kaipad lands (AEU 7) and to study the effects of agricultural amendments such as lime and organic manure on As content in these soils. Thirty-eight and eight georeferenced, grid-based (5 x5 km2) irrigation water and soil samples each were collected from paddy fields of panchayats under the Northern coastal plain (AEU 2) and Kaipad lands (AEU 7), respectively, at a sampling intensity of one panchayat from one grid forming a total of ninety-two samples. The pH of irrigation water from AEU 2 varied between 5.94 and 8.58, and that of Kaipad lands (AEU 7) from 7.46 to 8.6. The electrical conductivity (EC) of AEU 2 varied from 0.03 to 4.59 dS m-1 and between 0.02 and 17.02 dS m-1 from AEU 7. The content of As in irrigation water ranged from 0.02 µg L-1 (Feroke, Kozhikode) to 1.56 µg L-1 (Matool, Kannur) in AEU 2. In AEU 7, the lowest and highest As reported were 0.08 µg L-1 (Cheruvathur, Kasaragode) and 4.67 µg L-1 (Ezhome, Kannur), respectively The pH of the soils of the Northern coastal plain (AEU 2) varied from 3.08 to 7.42, and EC from 0.05 dS m-1 to 4.46 dS m-1. The organic carbon varied from 0.19 per cent to 5.33 per cent. The pH of soil from Kaipad lands (AEU 7) varied from 4.2 to 7.23; EC from 0.05 dS m-1 to 12.12 dS m-1. The organic carbon varied between 0.31 per cent and 3.94 per cent. The available As in soils of AEU 2 varied from 0.65 µg kg1 (Chorodu, Kozhikode) to 832.87 µg kg-1(Vallikkunnu, Malappuram) and showed a significant negative correlation with available Iron (Fe) (r = -0.369*), Phosphorus (P) (r = - 0.351*), and a significant positive correlation with available Calcium (r = 0.384*), Magnesium (r = 0.432**). The available As in soils of Kaipad lands varied from 0.35 µg kg-1 at Pilicode to 1255.2 µg kg 1 at Pallikkara, Kasaragod. However, none of the samples reported As content more than the prescribed critical limit of 100µg L-1 set by the Food and Agricultural Organization for irrigation water and 5800 µg kg-1 set by the Geological Survey of India for agricultural soils. The total As in soils of AEU 2 varied from 1.5 mg kg-1 (Chemnad, Kasargode) to 37 mg kg-1(Vallikkunnu, Malappuram), and that of AEU 7 from 6.5 mg kg-1(Pilicode, Kasargode) to 36.5 mg kg-1(Pallikkara, Kasaragode) and was positively correlated (r = 0.639***) with available As. Results revealed that 58 % (N=38) of soil samples from AEU 2 and 25% (N=8) from AEU 7 recorded more than the critical limit of 20 mg kg-1 of total As recommended by The European Union and Agency for Toxic Substances and Disease Registry (ASTDR) for agricultural Soils. A batch incubation study was conducted to study the effects of lime (fine lime powder) and organic manure (cow dung) on available arsenic content for 30 days, and chemical analyses were done at 1,3,5,10,15 and 30th day of incubation. The composite soil samples from AEU 2 and 7 were spiked individually with As at 400 mg kg-1 of soil and were used for the study. The As spiked soils were incubated with lime at 600 kg ha-1 (T2) and 1200 kg ha-1 (T3), organic manure at 5t ha1 (T4), 10t ha-1 (T5) and a combination of lime at 600kg ha-1 and fresh cow dung at 5t ha-1 (T6) against As spiked soil as control (T1). The combined application of lime at 600 kg ha-1 and organic manure at 5t ha-1 (T6) significantly increased the soil pH of the AEU 2 from the 15th to 30th day of incubation, whereas in AEU 7, lime at 1200 kg ha-1 (T3) significantly (p=0.05) increased the pH up to 30th day of incubation. Irrespective of the AEUs, the highest reduction in available Fe was recorded in lime-amended soils at 600 kg ha-1 from the 10th to the 30th day of incubation and available As exhibited a significant negative correlation with available Fe in soils of Northern coastal plains under organic manure amendment. Irrespective of the AEUs, the organic manure at 10t ha-1 significantly increased the available P content up to 15th day of incubation. Irrespective of AEUs, the highest available As was recorded by control soil (T1) up to the 30th day of incubation. A significant reduction in available As was reported from T5 (organic manure at 10 t ha-1) up to the 10th day of incubation in AEU 2. However, irrespective of AEUs, the combined application lime and organic manure (T6) significantly reduced the available As up to 30th day of incubation. Hence, incubation study of arsenic dynamics under liming and organic manure regimes revealed that the application of soil amendments like lime and organic manure effectively reduced available As in soils of the Northern coastal plain and Kaipad lands. Also the sources and dynamics of geogenic and anthropogenic As and its contributing factors in agricultural systems need to be studied extensively.Item Soil organic carbon estimation using non imaging hyperspectral data in upland and wetland ecosystem of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2024-01-11) Nandaluru Kalpana; Divya VijayanKerala, characterized by diverse physiography, landscapes, and soil compositions, confronts challenges related to soil quality, primarily due to unpredictable shifts in weather conditions. Given the dynamic nature of the soil, which adapts to evolving environmental factors, assessing soil quality becomes crucial. Traditional soil analysis methods are both time-consuming and expensive, necessitating the exploration of innovative alternatives to expedite the analysis process. Visible-NIR (Vis-NIR) reflectance spectroscopy has emerged as a rapid, cost-effective, environmentally friendly, non-destructive, reproducible, and repeatable analytical technique. Among various soil quality parameters, Soil Organic Carbon (SOC) plays a significant role in influencing the physicochemical and biological aspects of soil, thereby positively affecting crop growth. Determining SOC is particularly crucial in tropical regions due to its dynamic nature and its contribution to climate change adaptation through carbon sequestration. Against this backdrop, a research study was conducted between 2021-2023 with the aim of estimating and quantitatively predicting soil organic carbon in upland and wetland ecosystems of Kerala using hyperspectral reflectance spectroscopy in the Department of Soil Science & Agricultural Chemistry. The study was conducted under the different land use systems of the three Agro Ecological Units (AEU) of Kerala namely Kole lands (AEU 6), North central Laterite (AEU 10) and Palakkad central plain (AEU 22). Georeferenced surface soil samples (0– 15cm) were collected from 70 locations under each AEU and anlyzed for physico- chemical properties of soil including SOC. The results of physico-chemical analysis showed that, mean bulk density was lower in AEU 6 (1.12 Mg m-3) compared to AEU 10 and 22 (1.3 Mg m-3). SOC ranged from (0.6 to 4.26 %) in AEU 6, AEU 10 (0.53 to 6.42%) and AEU 22 (0.21 to 3.74 %). Total Carbon (Tot. C) in AEU 6 varied from (0.7 to 4.46 %), AEU 10 (0.53 to 6.42) and AEU 22(0.34 to 3.83 %). Available Nitrogen (Av. N) ranged from (125.4 to 363.2 kg ha-1) in AEU 6, AEU 10 (108.9 to 439.04 kg ha-1) and AEU 22 (75.2 to 489.2 kg ha-1). Total Nitrogen (Tot. N) values ranging from AEU 6 (0.04 to 0.36 %), AEU 10 (0.07 to 0.87 %) and AEU 22 (0.05 to 0.33 %). Reflectance spectra were collected in controlled dark room condition for 210 samples in the wavelength region (350-2500 nm) using the ASD FieldSpec 4 spectroradiometer. The spectra were then pre-processed by using different techniques like First order derivative (FOD), second order derivative (SOD), log (1/R) transformation, and continuum removal (CR) for enhancing quality of the spectra for better prediction. Further, correlation analysis was carried for both raw and preprocessed spectra and correlated spectral bands were taken for developing PLSR (Partial least square Regression) model, the coefficient of determination (R2) was better for first and second order derivatives for SOC compared with raw and other preprocessed data. Hence, FOD was taken for developing PLSR model. The model was developed for the prediction of soil organic carbon (SOC), total carbon (Tot. C), available nitrogen (Av. N), and total nitrogen (Tot. N). For all the four parameters the datasets were divided in the ratio of 70:30, with 70% of the data (n=147) used for calibration and the remaining 30% used for validation (n=63). The PLSR model developed in this study underwent validation based on R2 and RMSE, demonstrating its efficacy in predicting SOC, Tot. C, Av. N and Tot. N values. The model exhibited strong predictive capabilities, achieving R2 values of 0.88 for SOC, 0.86 for Tot. C, 0.85 for Av. N, and 0.87 for Tot. N, with corresponding RMSE values of 0.66 %, 0.73 %, 66.9 kg ha-1, and 0.06%, respectively. The high variability in carbon and nitrogen content within the soil samples underscored the model's effectiveness. This study concludes that hyperspectral reflectance spectroscopy is a successful approach for predicting carbon and nitrogen levels in different ecosystems in Kerala. The research findings emphasize the significance of employing Chemometrics as an advanced tool for soil property prediction. Looking ahead, there is a pressing need to develop spectral libraries and prediction models tailored to regional and field-level variations in soil properties across diverse soil types in Kerala.Item Effect of long term fertilization on soil carbon dynamics in rice-rice cropping sequence of Onattukara(Department of Soil Science and Agricultural Chemistry , Vellayani, 2021-11-21) Kavyasree, G; Mini, VA study entitled “Effect of long term fertilization on soil carbon dynamics in rice-rice cropping sequence of Onattukara” was carried out with the objective of studying the effect of long term fertilization on soil carbon dynamics and to explain the relationship between different active pools of soil organic carbon and rice yield. The study was conducted at the permanent manurial trial (PMT) plot at Onattukara Regional Agricultural Research Station, Kayamkulam, during 2019-21. The experiment comprised of field experiment during Virippu and Mundakan season, soil analysis and computation of various indices like Carbon pool index (CPI), Carbon lability index (CLI), Carbon management index (CMI), sensitivity index (SI), critical carbon input, carbon budgeting and plant analysis. Field experiment comprised of 8 treatments viz., T 1 (80 kg N ha -1 as FYM), T 2 (80 kg N ha -1 as Ammonium Sulphate), T 3 (80 kg N ha -1 as A.S + 40 kg P 2 O 5 ha -1 as Rajphos), T 4 (80 kg N ha -1 as A.S + 40 kg K 2 O ha -1 as MOP), T 5 (40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP), T 6 (80 kg N ha -1 as A.S + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP), T 7 (80 kg N ha -1 (20 kg as FYM and 60 kg as A.S.) + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP) and T 8 (Absolute control) replicated thrice using rice variety Jaya. Treatment receiving 80 kg N ha -1 (20 kg as FYM and 60 kg as A.S.) + 40 kg P 2 O 5 ha -1 as Rajphos + 40 kg K 2 O ha -1 as MOP (T 7 ) recorded the highest growth and yield. Soil samples were drawn from 3 different depths at 15 cm interval viz., 0-15 cm, 15-30 cm and 30-45 cm and analysed for physical, chemical and biological properties. There was no textural variation and the texture of the soil remained as sandy loam in all the treatments during both the seasons. An improved physical condition was noticed in T 7 with low BD (1.32 Mg C ha -1 ), high WHC (33%) and hydraulic conductivity (1.25 cm h -1 ). The soil acidity varied from very strongly acidic to strongly acidic. The highest content of available N, P, K and S was recorded in T 7 during both the seasons, while T 1 (FYM) recorded the highest content of Ca and Mg. The highest content of Zn, Cu and B were recorded in T 7 whereas Fe and Mn recorded the highest values under T 2 (Ammonium sulphate). Deficiencies of Ca, Mg, S and B were recorded in all the treatments. Generally all the parameters showed a decreasing trend with increasing depth except BD and pH. The highest nutrient content in grain and straw were also recorded in T 7 . Highest BC ratio (1.61 and 1.64) was recorded in T 7 during both the seasons. 244SOC, SMBC, SMBN, SMBP, WSC, water soluble carbohydrates and dehydrogenase activity were the highest under T 7 . T 7 recorded the highest TOC, very labile, labile, less labile and non labile C fractions and in all the treatments active C pool dominated the passive C pool. The contribution of active C pool to TOC accounted for 55-66%. Computed indices viz., CPI (1.56), CLI (1.34) and CMI (209.04) were found to be the highest in T 7 . Sensitivity Index (SI) was worked out to determine the sensitivity of each fraction to management practices and observed that active pool, SOC, water soluble carbon and water soluble carbohydrates were the most sensitive fractions while TOC and passive C pool were the least sensitive to management practices. Critical carbon input to maintain the initial level of SOC stock in soil was worked out. All the treatments recorded a positive critical carbon input which indicates that additional C has to be given inorder to sustain the present level of SOC stock. Among the treatments T 7 recorded the highest critical carbon input (0.470 Mg C ha -1 ) and it was due to initial high SOC stock. Carbon budgeting was done by computing SOC stock, C build up per cent, C build up rate and C sequestered and were the highest in T 7 followed by T 1 . Significant positive correlation was observed between different C pools, C pools and nutrient availability, C pools and biological activity and C pools and yield. Present study provided an insight on how management practices affect soil C buildup and C sequestration in rice-rice cropping sequence of Onattukara. Integrated nutrient management (T 7 ) with application of 20 kg N ha -1 as FYM and 60 kg N ha -1 as Ammonium sulphate along with 40 kg P 2 O 5 ha -1 as Rajphos and 40 kg K 2 O ha -1 as MOP significantly improved TOC, C fractions, CPI, CLI, CMI, C buildup rate and yield. Application of FYM @ 8t ha -1 (T 1 ) also improved the above mentioned parameters but the BC ratio was less (1.19 and 1.21) compared to T 7 . Increased soil acidity and deficiencies of secondary and micronutrients were also observed in all the treatments under study. Hence along with integrated nutrient management practices, soil test based fertilizer and lime application including secondary and micronutrients should be given importance to sustain the soil fertility in rice-rice cropping sequence of Onattukara.Item Soil organic carbon estimation using non imaging hyperspectral data in upland and wetland ecosystem of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellanikkara, 2024-01-11) Nandaluru Kalpana; Divya VijayanKerala, characterized by diverse physiography, landscapes, and soil compositions, confronts challenges related to soil quality, primarily due to unpredictable shifts in weather conditions. Given the dynamic nature of the soil, which adapts to evolving environmental factors, assessing soil quality becomes crucial. Traditional soil analysis methods are both time-consuming and expensive, necessitating the exploration of innovative alternatives to expedite the analysis process. Visible-NIR (Vis-NIR) reflectance spectroscopy has emerged as a rapid, cost-effective, environmentally friendly, non-destructive, reproducible, and repeatable analytical technique. Among various soil quality parameters, Soil Organic Carbon (SOC) plays a significant role in influencing the physicochemical and biological aspects of soil, thereby positively affecting crop growth. Determining SOC is particularly crucial in tropical regions due to its dynamic nature and its contribution to climate change adaptation through carbon sequestration. Against this backdrop, a research study was conducted between 2021-2023 with the aim of estimating and quantitatively predicting soil organic carbon in upland and wetland ecosystems of Kerala using hyperspectral reflectance spectroscopy in the Department of Soil Science & Agricultural Chemistry. The study was conducted under the different land use systems of the three Agro Ecological Units (AEU) of Kerala namely Kole lands (AEU 6), North central Laterite (AEU 10) and Palakkad central plain (AEU 22). Georeferenced surface soil samples (0– 15cm) were collected from 70 locations under each AEU and anlyzed for physico- chemical properties of soil including SOC. The results of physico-chemical analysis showed that, mean bulk density was lower in AEU 6 (1.12 Mg m-3) compared to AEU 10 and 22 (1.3 Mg m-3). SOC ranged from (0.6 to 4.26 %) in AEU 6, AEU 10 (0.53 to 6.42%) and AEU 22 (0.21 to 3.74 %). Total Carbon (Tot. C) in AEU 6 varied from (0.7 to 4.46 %), AEU 10 (0.53 to 6.42) and AEU 22(0.34 to 3.83 %). Available Nitrogen (Av. N) ranged from (125.4 to 363.2 kg ha-1) in AEU 6, AEU 10 (108.9 to 439.04 kg ha-1) and AEU 22 (75.2 to 489.2 kg ha-1). Total Nitrogen (Tot. N) values ranging from AEU 6 (0.04 to 0.36 %), AEU 10 (0.07 to 0.87 %) and AEU 22 (0.05 to 0.33 %). Reflectance spectra were collected in controlled dark room condition for 210 samples in the wavelength region (350-2500 nm) using the ASD FieldSpec 4 spectroradiometer. The spectra were then pre-processed by using different techniques like First order derivative (FOD), second order derivative (SOD), log (1/R) transformation, and continuum removal (CR) for enhancing quality of the spectra for better prediction. Further, correlation analysis was carried for both raw and preprocessed spectra and correlated spectral bands were taken for developing PLSR (Partial least square Regression) model, the coefficient of determination (R2) was better for first and second order derivatives for SOC compared with raw and other preprocessed data. Hence, FOD was taken for developing PLSR model. The model was developed for the prediction of soil organic carbon (SOC), total carbon (Tot. C), available nitrogen (Av. N), and total nitrogen (Tot. N). For all the four parameters the datasets were divided in the ratio of 70:30, with 70% of the data (n=147) used for calibration and the remaining 30% used for validation (n=63). The PLSR model developed in this study underwent validation based on R2 and RMSE, demonstrating its efficacy in predicting SOC, Tot. C, Av. N and Tot. N values. The model exhibited strong predictive capabilities, achieving R2 values of 0.88 for SOC, 0.86 for Tot. C, 0.85 for Av. N, and 0.87 for Tot. N, with corresponding RMSE values of 0.66 %, 0.73 %, 66.9 kg ha-1, and 0.06%, respectively. The high variability in carbon and nitrogen content within the soil samples underscored the model's effectiveness. This study concludes that hyperspectral reflectance spectroscopy is a successful approach for predicting carbon and nitrogen levels in different ecosystems in Kerala. The research findings emphasize the significance of employing Chemometrics as an advanced tool for soil property prediction. Looking ahead, there is a pressing need to develop spectral libraries and prediction models tailored to regional and field-level variations in soil properties across diverse soil types in Kerala.Item Sorption and movement of cyantraniliprole in sandy loam soils with and without organic amendments(Department of Soil Science and Agricultural Chemistry , Vellayani, 2021-10-08) Al Noufiya, S; Thomas GeorgeThe study entitled “Sorption and movement of cyantraniliprole in sandy loam soils with and without organic amendments” was conducted in the Department of Soil Science and Agricultural Chemistry and the laboratory attached to the All India Network Project (AINP) on Pesticide Residues, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala during 2019-21. The main objectives of the experiment were to study the adsorption, desorption, persistence and leaching of cyantraniliprole in sandy loam soils with and without addition of organic amendment at the rate of 0.5 per cent Farm Yard Manure (FYM). The soil was collected from the sandy belts of Kazhakkoottam, Thiruvananthapuram. The physical and chemical analysis of the soil revealed that the soil was moderately acidic, with 0.84 per cent organic matter, 11.80 per cent clay, 22.30 per cent silt and 65.90 per cent sand. Among the major nutrients, phosphorus content was found to be high; potassium was medium while the other nutrients were low. The method for estimation of cyantraniliprole residues in soil were validated by modified QuEChERS method and was found ideal. Liquid- liquid partitioning using dichloromethane was found suitable for cyantraniliprole residue estimation in water. The adsorption-desorption studies were carried out at 5 different concentrations of 20, 40, 60, 80 and 100 μg levels each both in normal soil and 0.5 per cent FYM amended soil in Completely Randomized Design (CRD) with ten treatments and three replications and was repeated by direct spiking also. The adsorption- desorption data fitted well in Freundlich adsorption isotherm. The distribution coefficient, K d (mean value) was found high in amended soil (2.55) than normal soil (2.40) which indicated increased sorption in relation to organic matter content. The K f values (adsorption coefficient) were 2.60 and 2.45 for amended and normal soil respectively, indicating a high sorption capacity for the amended soil. The desorption was carried out in three cycles, the percentage desorption was decreasing in each consecutive cycle. In all levels of concentration, desorption was slower than adsorption indicating a hysteresis effect. In the soil samples directly spikedwith cyantraniliprole also, the desorption percentages were found lower and formed a still higher hysteresis. Mobility of cyantraniliprole was assessed in CRD with eighteen treatments and three replications i.e., by loading 3 levels viz., 25, 50 and 75 μg concentrations of cyantraniliprole, separately on top of 200 g soil columns loaded in PVC pipes and followed by eluting with 40, 80 and 160 mL of water @ 0.4 ml min -1 . In all the treatments residues were obtained in 0-25 cm packed columns and also in the leachate. In the normal soil, cyantraniliprole moved down the soil column which resulted in residue levels ranging from 7.48-3.98, 19.27- 9.57 and 27.67- 13.41 μg at 25, 50 and 75 μg levels, respectively when eluted with different volumes of water. In the soil amended with 0.5 per cent FYM, the corresponding residues ranged from 10.41- 4.48, 21.08- 9.89 and 29.98- 14.19 μg at 25, 50 and 75 μg levels indicating a higher retention in soil. The persistence of cyantraniliprole in normal soil and amended soil under three soil moisture conditions (air dry, field capacity and saturated) were studied using the formulation of cyantraniliprole added at the rate of 1, 2 and 4 mg kg -1 in CRD with eighteen treatments and three replications. The half- life of cyantraniliprole was found highest in amended soil spiked with 4 mg kg -1 cyantraniliprole under air dry soil condition i.e., 32.44 days followed by the same under normal soil condition i.e., 30.45 days. In the persistence study, no metabolites of cyantraniliprole were detected. The study concluded that the adsorption coefficient was higher in FYM amended soil indicating stronger adsorption than normal soil and the desorption percentages were reduced in the same. Hysteresis effect was noticed in all the treatments indicating slower desorption than adsorption. The mobility of cyantraniliprole was found to be slightly higher in normal soil compared to the 0.5 per cent FYM amended soil and also indicates its moderate mobility behaviour. The dissipation was found to be the fastest under submerged condition followed by field capacity and air dry conditions.
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