PG Thesis
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Item Biomass production, root distribution and yield responses of green leaf manure trees on wetland paddy bunds(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2024-02-28) Aravind, R.; Asha K RajIndia's agriculture sector, which accounts for 18.2 per cent of the GDP and employs nearly half of the workforce, is heavily dependent on imported fertilizers, placing a significant fiscal burden on the economy. To mitigate this dependency and enhance soil fertility, the practice of green leaf manuring offers a sustainable solution. Traditionally, green leaf manuring in paddy fields was a popular practise among Kerala paddy farmers by gathering green leaves from nearby trees, but changes in cropping systems, reduced tree availability, land constraints, and labour shortages hindered this practice. Planting green leaf manure trees directly on bunds can address these issues. This study assesses the growth and green biomass production of selected green leaf manure tree species on wetland paddy bunds, as well as root distribution patterns and interactions with adjacent paddy crops. This study was conducted at paddy fields of State Seed Farm, Mannuthy, Kerala, on existing bund-grown trees comprising of nine different species such as Sesbania grandiflora, Terminalia arjuna, Gliricidia sepium, Cassia siamea, Gmelina arborea, Calliandra calothyrsus, Morus indica, Neolamarckia cadamba, and Cajanus cajan. The study was designed using a Randomized Block Design (RBD) with three replications. Trees were planted at 1-meter spacing and maintained as hedgerows. Growth, yield and root distribution parameters were measured during the second year after establishment. The results revealed significant variation in growth and green biomass production among the bund-grown tree species. N. cadamba excelled in collar diameter, while Morus indica underperformed. C. cajan exhibited complete mortality after one-and-half years, resulting in a survival percentage of zero by the end of the study. N. cadamba and T. arjuna showed notably high annual green biomass yields, at 7.03 kg and 4.54 kg per tree, with survival rates of 96 and 90 per cent, respectively. Other species produced moderate levels of green biomass, with the exception of G. arborea and M. indica, which yielded minimal to no biomass. Root distribution analysis revealed that T. arjuna demonstrated a pronounced rooting depth of 106 cm and a taproot length of 75.67 cm. The maximum lateral root spread was observed in N. cadamba (1.96 m) and G. arborea (1.94 m), both exhibiting a high number of roots with substantial diameter, enhancing bund stability and resource utilization. Root angle analysis showed a preference for lateral spread in G. sepium (82.62°) and C. siamea (80.57°). Conversely, M. indica and C. cajan underperformed across most of the root parameters. 124 Paddy beneath S. grandiflora showed highest grain yield of 5.31 Mg ha-1 within 1m distance from the tree and 5.22 Mg ha-1 at 1-2 m, which indicates the complementary interactions. Moreover, paddy yield under all other tree species were comparable to the control plot except M. indica, T. arjuna and C. calothyrsus, which exhibited competitive interactions with paddy up to a distance of 2 m from the tree base. Paddy nutrient content analysis revealed that paddy fields adjacent to C. cajan exhibited higher concentrations of nitrogen, phosphorus, and potassium compared to other treatments. Soil pH significantly influenced nutrient availability, with C. cajan showing the highest pH (6.06) and C. siamea the lowest (4.31). Electrical conductivity (EC) was highest in treeless bunds (0.17 dS m-¹) and T. arjuna (0.13 dS m-¹), while C. cajan and N. cadamba exhibited lower EC (0.06 dS m-¹). Soil organic carbon (SOC) was highest in open fields (1.21%). Soil beneath T. arjuna had the highest nitrogen (172.20 kg ha-¹) and potassium (41.44 kg ha-¹), while C. cajan had the highest phosphorus (62.09 kg ha-¹). In conclusion, the study highlights N. cadamba and T. arjuna as the most productive and adaptable species, demonstrating superior growth and green biomass production on wetland paddy bunds. S. grandiflora and C. siamea also produced considerable green biomass with minimal interactions with paddy crops. T. arjuna and M. indica were associated with reduced paddy yields, likely due to competition and pest pressures. G. sepium is also a potential species, however, it may perform optimally under conditions that include seedling planting and specific management practices. However, long-term studies are required to get more concluding results on crop interactions and soil fertility changesItem Long term effect of thinning on productivity and wood properties for twenty year old Acacia mangium wild stands(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Suresh Ramanan, S; Kunhamu, T KItem Biomass production and nutrient accumulation in an age series of caesalpinia sappan Linn. plantations(Department of Forest Management and Utilisation, College of Forestry, Vellanikkara, 2006) Imrose Elias Navas, E; Vidyasagaran, KThe present study was conducted at College of Forestry, Kerala Agricultural University, Vellanikkara on biomass production and nutrient accumulation in an age series (5, 6 and 7) of Caesalpinia sappan plantations in three districts of Kerala. The study reveals that diameter, height, biomass, productivity and volume increased with increasing age. The above ground biomass and biomass components also increased with increasing ages. The above ground biomass produced was 23.81 t ha-1 at 5 year, 37.80 t ha-1 at 6 year and 44.36 t ha-1 at 7 year. The productivity at age 5 year was 4.77 t ha-1yr-1, at age 6 year 6.30 t ha-1 yr-1 and at age 7 year was 6.34 t ha-1 yr-1. The increase of the productivity between 6 and 7 years were very low (0.04 t ha-1yr-1), which indicated that no further increase in the productivity of the trees. It highlights that a levelling off the productivity beyond 6 year. This consideration suggests 6 year as the optimum harvesting period of C. sappan. The percentage contribution of various components to above ground biomass was in the order: bole > branch > twig > fruit > leaves> bark. The biomass components were also showed an increasing trend. The prediction equations were prepared for above ground biomass as well as biomass components with respect to dbh and height. Even though some equations were proved more fit with combination of dbh and height, R2 value and Furnival index were relatively similar to equations with dbh alone could not be selected, it is difficult to measure height of the standing trees with definite accuracy. Hence, equations with dbh alone were selected for predicting the biomass. With respect to the dbh alone as independent variable, the total above ground biomass, the best fit equation was W = b0 +b1 D+ b2 D2. In leaves also this model proves as best fit. The components like bole, bark, branch and fruit, the best fitted equation was ln W =b0 + b1 ln D. But in twig, it was W=b0 + b1 D2. Weight table prepared for bole (UB) and total above ground biomass based on the best fit equation using diameter at breast height The nutrient concentration was increased with increasing age except in bole and branches. Concentration in bole and branches increased from 5 to 6 year and decreased from 6 to 7 year. Leaves had the maximum concentration of the nutrients and bole the lowest. The nutrient accumulation of the above ground biomass as well as biomass components increased with the increasing age of plantation. The maximum nutrients accumulated in bole and minimum in bark. Among the nutrients, N accumulated maximum followed by K and P. Nutrient use efficiency increased with increasing ages. The maximum nutrient use efficiency observed for P followed by K and N. It was found to be maximum in bole and minimum in leaf.Item Influence of host, light and mineral nutrition on the growth of sandal seedlings ( santalum album L)(Department Of Tree physiology & Breeding,Co Forestry, Vellanikkara, 2008) Samom Khelen Singh; Santhosh Kumar, A VStudies on the effects of light quality, quantity and nutrient deficiency on the growth of sandal seedlings were conducted in College of Forestry, Kerala Agricultural University, Vellanikkara, Thrissur during the year 2006-2008. Radioisotopic study to understand the transfer of photosynthates from the host plants to sandal seedlings and anatomical studies of sandal haustoria were also taken up during the investigation. Sandal seedlings had better shoot growth parameters (viz. shoot length, collar diameter and leaf number), root growth parameters (viz. root length and number of secondary roots), biomass production and chlorophyll content under shaded condition and green light quality when different light qualities and quantities are taken into consideration individually. Sandal seedlings also had better rate of photosynthesis under shaded condition. As far as different light qualities are concerned, rate of photosynthesis was better under red and green light qualities. Generally, the combination of 50 per cent shade and green light quality was found to give the maximum values of different growth parameters and chlorophyll content in leaves of sandal seedlings. The combinations of 50 per cent shade and red light quality and 25 per cent shade and blue light quality were found to be the best with regard to rate of photosynthesis in sandal seedlings at the end of the study period Characteristic deficiency symptoms produced by seedlings due to deficiency of N, P and K include yellowing of older leaf tips, formation of brown spots in leaves and change in leaf colouration, curling of leaves and stunting of growth. The seedlings that received complete nutrient solution were healthy with dark green foliage. Vegetative growth of the seedlings was also found to be affected due to the nutrient stress. Nitrogen deficient seedlings showed a decline in all the fractions of chlorophyll during the study period. Visual deficiency symptoms of the nutrient elements also coincided with a corresponding reduction in foliar levels of the concerned element. Radioisotopic study showed that transfer of photosynthates takes place from the host plants to sandal seedlings and the amount of transfer varies from one host species to another host species. Anatomical studies showed that sandal roots can establish close vascular connections with host roots through haustoria.