PhD Thesis
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Item Irrigation and crop establishment techniques in Bajra Napier hybrid(Department of Agronomy, College of Agriculture, Vellayani, 2025-07-23) Greeshma, U; Usha C ThomasThe research entitled “Irrigation and crop establishment techniques in Bajra Napier hybrid” was conducted at Department of Agronomy, College of Agriculture, Vellayani, during 2022 to 2025. The major objectives of the study were standardization of irrigation levels for popular Bajra Napier hybrid varieties in Kerala and standardization of sett size, age and method of planting of Bajra Napier hybrid. The study was undertaken as two separate parts. Part 1 entitled “Standardization of irrigation levels for popular Bajra Napier hybrid varieties in Kerala” was conducted from March 2023 to August 2024 at Instructional Farm, College of Agriculture, Vellayani. The experiment was laid out in split plot design with 4 main plots (i1 - IW/CPE- 1.00, i2 - IW/CPE- 0.80, i3 - IW/CPE- 0.60 and i4 - Rainfed), 3 sub plots (v1 – Susthira, v2 – Suguna and v3 – CO-5) and three replications. Crop was irrigated to a depth of 2.5 cm. Initial 6 months was taken as establishment period and after that, observations were recorded for 12 months. The results revealed that irrigation scheduling at IW/CPE ratio of 1.0 significantly enhanced the growth attributes including mean plant height, number of tillers per hill, leaf stem ratio (1.85), leaf area, and leaf area index compared to lower irrigation levels. Among the varieties, CO-5 consistently recorded superior growth performance, achieving the highest mean plant height (208.07 cm), leaf stem ratio (1.69), leaf area (228.87 cm²), and leaf area index (12.13). The mean number of tillers per hill was the highest in Suguna (v2). Among the interactions, CO-5 irrigated at an IW/CPE of 1.0 (i1v3) yielded the highest growth values like mean leaf stem ratio, leaf area and leaf area index. The results on yield revealed that total green and dry fodder yield were the highest in irrigation at an IW/CPE of 1.0 (175.45 t ha-1 and 40.95 t ha-1, respectively). Variety CO-5 (v3) produced the highest total green fodder (186.74 t ha-1) and dry fodder yield (39.05 t ha-1). Among the treatment combinations, i2v3 (CO-5 at an IW/CPE of 0.8) recorded the higher total green fodder (206.06 t ha⁻¹) and dry fodder (51.26 t ha⁻¹) yield, and remained comparable with i1v3. Across all harvests, green fodder yield and dry fodder yield followed a declining trend from the first to the fifth cut, with consistently higher yields recorded under IW/CPE of 1.0 and CO-5 variety at each harvest. Root studies revealed that rainfed conditions encouraged deeper rooting (46.56 cm), whereas irrigation at IW/CPE 1.0 improved root biomass (318.83 g per plant), with CO-5 exhibiting superior root dry weight (389.08 g per plant). Among the interactions, the treatment combination of rainfed irrigation with variety CO-5 (i4v3) recorded the deepest roots (51.73 cm). Conversely, the highest root dry weight (503.83 g per plant) was recorded in the combination of IW/CPE 1.0 with CO-5 (i1v3). Biochemical analysis showed significantly higher chlorophyll content in treatments involving IW/CPE 1.0 and CO-5, although crude protein content remained unaffected by treatments. Lower crude fibre content was noticed in IW/CPE of 0.8 (29.91%) and was on on par with i1. Crude protein yield was the highest in i1v3 (IW/CPE of 1.0 in CO-5) recording the maximum crude protein yield of 4739 kg ha⁻¹, which was statistically on par with i2v3. Analysis of post-experiment soil showed no significant effect for interactions in soil pH, electrical conductivity, organic carbon and available N. However, available phosphorus was the highest under rainfed conditions (i4). Interaction between irrigation levels and varieties also influenced soil potassium status, with i1v3 (IW/CPE of 1.0 x CO-5 variety) recording the highest value. Nutrient uptake studies revealed that nitrogen, phosphorus, and potassium uptake closely followed the same trend as that of dry fodder yield, with the highest uptake under IW/CPE of 1.0 and in the variety CO-5, particularly in the treatment combination i1v3 (CO-5 at an IW/CPE of 1.0). The water use efficiency and economic water productivity was found to be higher in irrigation scheduling at IW/CPE ratio of 0.8 (45.67 kg ha-1 mm-1 and 161.55 ₹ ha-1 mm-1) and it was on par with IW/CPE ratio 1.0. Among varieties, CO-5 recorded higher WUE and economic water productivity. CO-5 irrigated at an IW/CPE of 0.8 recorded higher WUE and the highest economic water productivity. Economic analysis showed that CO-5 irrigated at an IW/CPE of 0.8 (i2v3) achieved the highest net returns (348655 ₹ ha-1) and B: C ratio (1.94). The part II of the study for “standardization of crop establishment methods in Bajra Napier hybrid” was conducted from June to October 2023 and the confirmatory trial was conducted from June – October 2024 at Instructional Farm, College of Agriculture, Vellayani. The experiment was laid out in randomized block design with 3 factors and at three levels each, replicated thrice. The treatments comprised three levels of nodes per cutting (n1 – Single noded cutting, n2 – Two noded cutting, n3 – Three noded cutting), three planting method (p1 – Horizontal planting, p2 - Vertical planting, p3 – Planting at 45 degree) and three stages of maturity (s1 – 3 months, s2 – 4 months, s3 – 5 months). The observations were recorded to two harvests and the variety used for the study was Susthira. The results revealed that growth, yield, establishment, and economics were significantly influenced by nodes per cutting, planting methods, stage of maturity and their interactions. Among the nodes per cutting, three noded cutting (n3) recorded tallest plants (170.93 and 227.72 cm respectively), mean number of tillers per hill (8.92 and 8.32 respectively), leaf stem ratio, leaf area, LAI (8.07 and 8.54 respectively), total green fodder yield (88.49 and 85.27 t ha-1 respectively) and total dry fodder yield (22.12 and 21.32 t ha-1 respectively) in first and second year. But the specific leaf area was the highest in single noded cutting (n1). Among the planting methods, horizontal planting (p1) recorded the highest mean number of tillers per hill, leaf stem ratio, LAI, mean specific leaf area, total green fodder yield (92.78 and 90.84 t ha-1 respectively), total dry fodder yield (23.19 and 22.71 t ha-1 respectively) and crude protein yield (2032 and 2131 kg ha-1 respectively) in first and second year. Among the stages of maturity, cuttings from 4 month old plants (s2) recorded the highest number of tillers per hill, leaf stem ratio, LAI, total green (85.91 and 86.30 t ha-1 respectively) and dry fodder yield (21.48 and 21.57 t ha-1 respectively) and crude protein yield (1892 and 2034 t ha-1 respectively) in first and second year. The lowest number of days for first harvest (75 days in both years) was observed in 4 month old cutting (s2). Horizontal planting of three noded cutting taken from 4 month old plants (n3p1s2) recorded the highest mean number of tillers per hill, mean leaf stem ratio, mean LAI, total green (156.46 and 155.80 t ha-1 respectively) and dry fodder yield (39.12 and 38.95 t ha-1 respectively) and crude protein yield in both years. Among the establishment characters, 4 month old cutting (s2) established earlier (10.33 and 10.52 respectively) in both years. The treatment combination n3p1s2 (horizontal planting of three noded cutting taken from 4 month old plants) recorded higher establishment percentage in first and second year. The economic analysis revealed that, horizontal planting of three noded cutting taken from 4 month old plants (n3p1s2) recorded the highest B: C ratio in first (3.91) and second (3.89) year. It could be concluded that, among the Bajra Napier hybrid screened, the variety CO-5 irrigated at an IW/CPE of 0.8 could be recommended for realizing higher green fodder yield, dry fodder yield, WUE, economic water productivity, net returns and B:C ratio. In Bajra Napier hybrid variety Susthira, horizontal planting of three noded cutting taken from 4 month old plants could be adjudged as the best establishment method for higher growth, yield, establishment and B:C ratio.Item Modelling groundwater pollution using visual modflow in Eloor industrial belt(Department of Soil and Water Conservation Engineering, Kelappaji College of Agricultural Engineering and Technology ,Thavanur, 2023) Anjaly C Sunny.; Sathian, K KGroundwater of shallow aquifer is a good source of fresh water for drinking and irrigation for the state of Kerala. However, in some cases it is polluted by salt water intrusion and industrial pollution; Eloor municipality in the central part of Kerala is a typical example for the latter situation due to the presence of several hazardous industries. The place has been considered as one of the hot spots of the world, however, not much studies have been reported on the quantitative analysis of the area extent of the pollution and plausible remedial measures. Hence, this study has been conducted at Eloor to assess the aquifer characteristics, water quality, develop groundwater and contaminant transport models and thereby to suggest remedial measures to mitigate pollution issues of an industrial area. Resistivity survey has been conducted at five different locations and the water quality parameters of ten observation wells were tested in the laboratory. Irrigation water quality parameters viz. EC, SAR (Sodium Adsorption Ratio), RSC (Residual Sodium Carbonate, KI (Kelly Ratio) and Na% (Sodium Percentage) were computed. In addition, Irrigation Water Quality Index (IWQI) and Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) were used to assess irrigation water and drinking water quality respectively. The study also utilized Visual MODFLOW and it’s MT3DMS add on module to simulate the groundwater movement and contaminant transport. The models were calibrated for the period 2008 to 2013 and validated for 2014 to 2015. Simulation studies were made with different scenarios to get insight into the arresting of groundwater contamination. Geophysical survey showed that, the site which was at close proximity to the contaminant disposal site gave a very low resistivity value for all depth ranges, indicating highe moisture content and concentration of ions in the subsoil possibly due to the leaching of the effluents. IWQI and CCME values indicated that the water of the wells viz. W1, W2, W3, W4, W5, W6 in the neighbourhood of the contaminant disposal sites have poor standards both from the perspectives of irrigation and drinking water qualities, plausibly due to the influence of leachates from the effluent’s disposal site. At the same time, water qualities of the other wells were within the acceptable limits. It was found that IWQI index was more reliable to classify the irrigation water quality as it includes multiple parameters in its computation. Calibration and validation of Visual MODFLOW Flex 8.0 resulted in a correlation coefficient of 0.89 and 0.87 for the calibration and validation periods respectively. The corresponding values for the MT3DMS model were respectively 0.86 and 0.85. Prediction of contaminant transport for the year 2025 by MT3DMS model showed that the presence of contaminants may spread to an area extent of 4.46 km2 lying in the wards of 1, 2, 3, 4, 5, 6, 29, 30 and 31 of Eloor municipality. Simulation of the effect of a C- shaped impermeable barrier to control this contaminant transport showed that radial movement of pollutants can be reduced to 1.46 km from the 2.43 km corresponding to no control measures. Though barrier appeared effective to check the spread of pollution to the habituation, it would turn out to be a costly measure and in addition, it might enhance the movement of pollutants into the river Periyar. Hence, as an alternative to physical barriers, the study recommends bio remedial measures in two different radial zones; one in the immediate neighbourhood of the point source with a radial distance of 0.4 km and other at 4 km as an economic and sustainable measure.Item Nutrient- moisture interaction under phasic stress irrigation of sweet potato in summer rice fallows(Department of Agronomy, College of Agriculture,Vellayani, 1994) Muraleedharan Nair, G; Muraleedharan Nair,VA field experiment on sweet potato was laid out in the rice field fallowed during summer season at the Instructional Farm, College of Agriculture, Vellayani. The study was intended to work out of the irrigation schedule and fertilizer practice for sweet potato grown as a catch crop during the summer season of 1990 and 1991. The experiment was designed to economise the use of irrigation water as well as fertilizers by inducing phasic stress at certain phases of plant growth which are considered critical for sweet potato. The field experiment was laid out in a strip plot design replicated thrice with irrigation in horizontal strips and fertility levels in vertical strips. Irrigation water at full CPE was given during tuber initiation phase (10-30 DAP), full CPE at tuber maturity phase (80-100 DAP) and full CPE at tuber initiation and tuber maturity phases. The crop received irrigation at ½ CPE during the rest of the period of plant growth. Nitrogen and potassium were applied @ 25, 50 and 75 kg ha-1 and a uniform dose of P2 O5 @ 50 kg ha-1 and lime @ 500 kg ha-1 were applied. A control plot that received NPK @ 75:50:75 kg ha-1 and FYM @ 10 t ha-1 was maintained for treatment comparison. Growth characters were recorded at an interval of 21 days from planting and it was observed that providing irrigation at full CPE during tuber initiation phase resulted in significant increase in vine length and number of leaves plant-1. Enhanced rate of application of Nitrogen promoted the growth of vines, number of branches plant-1 and number of leaves produced plant-1. Potassium did not exert any influence on these growth characters. Growth analysis studies showed that the LAI was maximum in plots that received irrigation at full CPE during tuber initiation phase. Nitrogen substantially influenced the LAI, higher levels being significantly superior to the lower levels. Higher levels of potassium also influenced the LAI. The NAR and specific leaf weight were the highest in plots that received irrigation at ½ CPE during tuber initiation phase. Both NAR and CGR were high in the early stage of plant growth and decreased towards harvest. Increased rates of nitrogen supply decreased the NAR and specific leaf weight whereas no definite trend could be observed on CGR> Higher levels of potassium had a favourable influence on NAR and CGR. The dry matter of leaves, shoots, fibrous roots and tubers were significantly enhances by providing full CPE during tuber initiation phase. Increasing the level of nitrogen, influenced the dry matter in the aerial parts. The influence of K on dry matter production was not consistent. Tuber bulking rate showed a positive trend under irrigation at full CPE during tuber initiation phase. Nitrogen levels at 50 and 75 kg ha-1 had an overlapping influence on tuber bulking rate and both remained superior to 25 kg ha-1. Scheduling of irrigation did not exert any influence on the length and girth of tuber. However, an increase in the length and a corresponding decrease in the girth were noticed at enhanced rates of nitrogen supply. The number of tubers plant-1 showed a significant improvement by providing irrigation at full CPE during tuber initiation phase. The total number of tubers plant-1 was increased by high rates of N, but did not influence the number of marketable tubers. Application of K at 50 kg ha-1 promoted the production of more tubers. Tuber yield was significantly influenced by irrigation wherein providing full CPE during tuber initiation phase resulted in superior yield of both total and marketable tubers. Tuber yield was maximum at 50 kg ha-1 each of nitrogen and potash. Vine yield was significantly enhanced by higher rates of applied nitrogen. The harvest index and utilization index were enhanced by the application of irrigation water at full CPE during tuber initiation phase. Application of N at 25 kg ha-1 resulted in the production of high starch content whereas the sugar content was increased upto the highest level of 75 kg ha-1. The uptake of nitrogen by vines and tubers showed a progressive increase by applying full CPE during tuber initiation phase. Application of higher levels of nitrogen invariably promoted the uptake of N, P and K by the plant. Application of potash at 50 or 75 kg ha-1 also resulted in higher uptake of potassium. The fertility status of the soil did not show a positive trend by scheduling of irrigation. The plots that received the lowest dose of nitrogen, invariably recorded the highest level of available phosphorus. Available potassium content was also high in plots that received higher rates of potash. Irrigation at full CPE during tuber initiation and/or tuber maturity phase recorded significantly higher water use efficiency and net returns as compared to including stress during tuber initiation phase. Nitrogen and potash both at 50 kg ha-1 recorded the maximum water use efficiency and net returns from sweet potato cultivation.