1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Utilization of biochar from different bioresources for soil health and crop production(Vellayani Department of Soil Science and Agricultural Chemistry, College of Agriculture,Vellayani, 2024-01-20) Diya Rajendran; Meera, A VThe study entitled “Utilization of biochar from different bioresources for soil health and crop production” was carried out during 2021-2023 in the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani and Integrated Farming System Research Station, Karamana. The objectives of the study were characterization of biochar produced by pyrolytic conversion of bioresources generated in farming systems and assessing their influence on soil health and crop production. The study comprised of four parts viz., production and characterization of biochar from different bioresources, bioassay study for selection of best four biochar, incubation experiment to study the nutrient release pattern and field evaluation of the effect of biochar on crop performance and soil health. Biochar was produced from seven different organic residues viz., teak leaf, coconut leaf, banana pseudostem, crop residue of vegetables, Eichhornia crassipes, Limnocharis flava and Colocasia esculenta, by the process of pyrolysis and the synthesized biochar were analysed for physical and chemical properties using standard procedures. Temperature of pyrolysis and residence time for various organic residues ranged between 250-5000C and 30-120 minutes, respectively. Highest recovery percentage of 46.53 % was recorded for coconut leaf biochar and lowest, 24.93 % for E. crassipes. Teak leaf biochar recorded the highest bulk density (0.48 Mg m-3) and EC (4.70 dS m-1), while banana pseudostem biochar had a higher water holding capacity (327.74 %). The produced biochar has an alkaline characteristic, with pH values ranging from 8.19 (C. esculenta biochar) to 10.40 (Banana pseudostem biochar). CEC (14.10 cmol kg-1), total carbon (67.52 %), N (1.34 %), K (2.24 %), S (0.33 %) and Zn (69.37 mg kg-1) content were highest for banana pseudostem biochar while P (0.77 %), Mn (173.76 mg kg-1), Cu (37.12 mg kg-1) and B (47.40 mg kg-1) were highest for L. flava biochar. Calcium (0.57 %) and magnesium (0.43 %) content were highest for crop residues of vegetable biochar while iron (2314.15 mg kg-1) content was highest in biochar produced from C. esculenta. C: N ratio was highest in C. esculenta biochar (128.35) and lowest in banana pseudostem biochar (50.38). 159 Bioassay study was carried out for 28 days using okra seedlings to select best four biochar for field study. The biochar produced from seven different bioresources were mixed with 2 kg soil @ 0.5 and 1 % w/w basis and FYM @ 1 % w/w basis and 10 okra seeds were placed in each pot. Coconut leaf, banana pseudostem and L. flava biochar recorded the highest germination percentage (96.67 %) and it was on par with biochar derived from crop residues. Banana pseudostem biochar recorded the highest values for shoot length (33.04 cm) and shoot biomass (2.23 g plant-1) and it was on par with L. flava biochar and FYM treated soil. Root length (23.97 cm), root biomass (0.60 g plant-1) and root volume (4.90 cm3) of the okra seedlings were highest in L. flava biochar treated soil and it was found to be on par with crop residue of vegetables biochar and FYM supplied treatments. Teak leaf biochar applied @ 1 % recorded the lowest values for germination percentage, shoot length, shoot biomass, root length, root biomass and root volume. Based on the results obtained from bioassay study, four biochar viz., coconut leaf, banana pseudostem, crop residue of vegetables and L. flava were selected for the incubation and field experiments. The nutrient release pattern from the selected four biochar was monitored after incorporation to soil based on a 90 day incubation study. Biochar and FYM were added @10 g kg-1 of soil. Periodic sampling and analysis of samples were done at 0, 30, 60 and 90 days of incubation. The incubation study revealed a slow and sustained release of nutrients from biochar. Biochar treated soils showed significantly higher value for pH and EC compared to FYM treated soil till the end of the incubation period. The pH was significantly higher for banana pseudostem biochar treated soil while EC was higher in soil applied with crop residue of vegetables biochar. During initial period of incubation, the mean values for available N, K, S and Zn content were highest for FYM treated soil but as incubation period progressed, banana pseudostem biochar treated soil recorded the highest values. The mean value for P, Fe, Cu and B were significantly higher for FYM treated soil during initial period and later stages, it was for L. flava biochar applied soil. Similarly, exchangeable Ca and Mg content were highest in FYM treated soil during initial period and as incubation period progressed, the crop residue of vegetables biochar treated soil recorded the highest values. A field experiment was conducted during 2023 to compare the effect of biochar from different bioresidues and FYM application on soil health and crop production using okra as the test crop. The treatments consisted application of selected four biochar viz., coconut leaf, banana pseudostem, crop residue of vegetables and L. flava biochar @ 25 t ha-1 along with 100 and 75 % of recommended dose of fertilizers (RDF) and FYM @ 25 t ha-1 along with 100 % RDF and soil with 100 % RDF only. The physical, chemical and biological properties of soil were markedly improved by the application of biochar. Reduction in bulk density, increase in water holding capacity, pH, EC, CEC, organic carbon and nutrient availability were observed with biochar application compared to FYM incorporation. Banana pseudostem biochar application recorded the highest values for organic carbon (1.92 %), available N (334.56 kg ha-1), K (258.45 kg ha-1), S (23.27 mg kg-1), Zn (3.73 mg kg-1) and dehydrogenase (192.78 µg of TPF g-1 soil 24 h-1) and microbial biomass carbon (81.97 mg kg-1) content of post harvest soil. Available P (91.78 kg ha-1), Fe (132.08 mg kg-1), Mn (34.89 mg kg-1) Cu (2.77 mg kg-1) and B (0.667 mg kg-1) content were higher in soil applied with L. flava biochar. Biochar application had significantly influenced the biometric and yield parameters of okra. Plant height, biomass yield and fruit yield were highest in treatments supplied with banana pseudostem biochar and it was on par with the treatments received L. flava biochar. Nutrient content of index leaf at harvest also indicated the beneficial effect of biochar in comparison to FYM and conventional fertilizers. Plant biometric attributes, fruit yield and soil health parameters for biochar application @ 25 t ha-1 and RDF at 100 and 75 % were on par. The highest B: C ratio (1.70) was recorded in treatment supplied with banana pseudostem biochar @25 t ha-1 along with 75 % RDF, which indicated that 25 % reduction in fertilizer application is possible through biochar application. There was 21 % increase in yield by banana pseudostem biochar application compared to FYM. It may be inferred that physico-chemical properties of biochar varies with the source material and their assessment for phytotoxicity is essential for ensuring the safety for agricultural use. Coconut leaf biochar, banana pseudostem biochar, crop residues of vegetable biochar and L. flava biochar had ideal physical and chemical 161 properties that qualify them to be used as good soil amendments which improve the soil physical, chemical and biological properties. FYM and biochar application had a positive effect on soil properties during incubation and field study. However biochar application exhibited sustainable effects than FYM. From the study, it can be concluded that banana pseudostem biochar @ 25 t ha-1 along with 75 % RDF is the economically viable and best treatment.Item Studies on the chemo dynamics of phosphorus in the laterite soils of Kerala and utilization of fixed phosphorus for crop production(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2024-02-05) Kota Adilakshmi; Aparna, BA study entitled “Studies on the chemo dynamics of phosphorus in the laterite soils of Kerala and utilization of fixed phosphorus for crop production” was carried out at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, during 2018-2021, with the objectives to characterize in detail the dynamics of inorganic phosphorus and phosphorus fractions in the laterite soils of Kerala, identify the dominant phytoaccumulators of phosphorus, screening of suitable extractants for available P, and evaluate various organic and inorganic solubilizers/mobilizers on the solubility and availability of fixed phosphorus. The study was carried out in four parts. The first part consisted of the collection and characterization of georeferenced soil samples and the identification of dominant phytoaccumulators of phosphorus (P). For that, by following a preliminary survey, a total of 100 georeferenced representative soil samples (0-15 cm depth), 25 from each of the four agro-ecological units (AEUs), viz., southern laterites (AEU 8) of Thiruvananthapuram district, south central laterites (AEU 9) of Kollam district, north central laterites (AEU 10) of Thrissur district, and northern laterites (AEU 11) of Kozhikode district of Kerala were collected for assessing its fertility status. From scrutiny of the data, it was observed that among the four AEUs, AEU 8 reported the highest values for electrical conductivity (EC), organic carbon (OC), available P, sulphur (S), iron (Fe), manganese (Mn), exchangeable hydrogen (H+), anion exchange capacity (AEC), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), and population of P solubilizers, AEU 9 for available boron (B), exchangeable aluminium (Al3+), hydrogen (H+), acidity, and MB C/P ratio, and AEU 11 for pH, available nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), zinc (Zn), and copper (Cu). According to the results of frequency distribution, it was observed that, among the four AEUs (8, 9, 10, and 11), sandy clay loam was the prevalent soil textural class. Data on the mean values of pH revealed that the pH ranged between 5.42 and 6.21 among the four AEUs, and the majority of the collected soils were found to be strongly acidic (37%) and moderately acidic (40%) in nature. The EC values of the four AEUs were found to be within the critical limit. The mean values of OC varied from 0.63 From the present study, it can be concluded that the soils of southern laterites (AEU 8) exhibited the highest values for available P. Amaranthus viridis from AEUs 8, 9, and 10, and Synedrella nodiflora from AEU 11, were identified as dominant phytoaccumulators of P. Among the various fractions of P, with respect to the Po fractions such as the labile Po fraction, HCl extractable Po fraction, fulvic acid Po fraction, moderately labile Po fraction, humic acid Po fraction, residual Po fraction, and non-labile Po fraction, the soils collected from AEU 8 showed the highest values compared to other soils. It was also observed that the soils treated with vermicompost @ 15 t ha-1 showed the highest values for all the Po fractions when compared to soils without any manure, including total Po. Similarly, for Pi fractions, the soils collected from AEU 8 treated with vermicompost @ 15 t ha-1 showed the highest values for saloid-Pi, Al-Pi, and Fe-Pi, while the soils collected from AEU 8 without manure showed the highest values for residual/occluded Pi. Furthermore, soils treated with vermicompost @ 15 t ha-1 displayed the highest values for Ca-Pi in AEU 10 and reductant-soluble Pi in AEU 11. Notably, the soils of AEU 8 exhibited the highest capacity for P fixation among all studied soils. From the study, it was also observed that ion exchange resins were found to be the best extractants for available P determination, and biochar was the best amendment for alleviating P fixation, thus augmenting soil fertility