1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Integrated weed management for rice based cropping system of Onattukara tract(Department of Agronomy, College of Agriculture, Vellayani, 2000) Rajan, S; Muraleedharan Nair, VField experiments were conducted at Rice Research Station, Kayamkulam from April 1996 to May 1998 to study the effect of integrated weed management practices for rice-rice-sesamum cropping system of Onattukara tract. The experiment was laid out in randomised block design with twelve treatments during the first crop season and in split plot randomised block design with twelve treatments and twelve residual effects during second crop season and with twenty four residual effects during the third crop season. Rice varieties Bhagya and Dhanya and sesamum variety Thilak were used for the study during the first, second and third crop seasons respectively. Results of the study revealed that grasses, broad leaved weeds and sedges competed with the crop plants in the rice-rice-sesamum cropping system. The herbicide treatments significantly reduced the monocot, dicot and total weed population in the cropping system. Pendimethalin pre-emergence application alone or integrated with hand weeding/2,4-D post emergence significantly reduced the weed growth during the first crop season whereas thiobencarb pre-emergence + hand weeding reduced the weed growth in the second crop of rice. The weed count and dry matter accumulation by weeds in the sesamum crop during the third crop season was significantly reduced by the carry over effect of herbicide 2 treatments applied both to first and second crop rice compared to the carry over effect of herbicide treatments applied to first crop rice alone. The herbicide treatments significantly influenced the growth and yield attributing characters .of the first and second crop of rice. The residual effects of previous weed control treatments on the growth and yield of sesamum was not significant. Pendimethalin pre-emergence + hand weeding or its integration with 2,4-D post emergence influenced the growth characters of first crop of rice, thiobencarb pre-emergence + hand weeding found to exert considerable influence on the growth and yield of second crop of rice. Weedy check recorded the lowest yield and under weed free situation the crop plants had registered maximum growth and yield. The yield loss due to weed indicated by the weed indices was maximum under weedy check and minimum for pendimethalin pre- emergence + hand weeding and thiobencarb pre-emergence + hand weeding applied to first and second crop of rice in rice-rice-sesamum cropping system. The weed management practices and their carry over effects had significant influence on the uptake of nutrients by the crop and weeds during the first, second and third crop seasons. Unweeded check exploited the available nutrients and water resulting in better weed growth and dry matter accumulation through out the cropping system. The soil nutrient status was also affected by the weed management practices studied. The N, P, K status of soil was high for weedy check 3 compared to herbicide treatments and weed free treatments owing to poor crop utilization of the nutrients. The herbicide treatments applied both to the first and second crop of rice and their carry over• effects on third crop of sesamum had no significant effect on the population of soil organisms. Economic analysis revealed that herbicide treatments were remunerative compared to weedy check and farmers practice in the first and second crop seasons. The residual effects of weed management practices had not influenced the economics of sesamum crop during third crop season. Bioassay studies revealed no phytotoxic concentration of herbicide residues in the soil after the rice-rice-sesamurn cropping sequence.Item Production potential of amaranthus under irrigation and nitrogen levels(Department of Agronomy, College of Agriculture, Vellayani, 1991) Rajan, S; Oomen, MAn experiment was conducted at the Instructional Farm, College of Agriculture, Vellayani, during the summer seasons of 1989 and 1990 to study the response of amaranthus to different water management practices and nitrogen doses. The trial was laid out in split-plot design with three replications. The main plot treatments consisted of a combination of two varieties (red and green ) and four irrigation treatments. (Irrigation at IW/CPE ratio of 0.75, 1.00 and 1.25 and the farmer’s practice of daily irrigation). Sub plot treatments consisted of four levels of nitrogen (50, 75,100 and 125 kg N/ha). The study revealed that amaranthus responded well to frequent irrigations and higher levels of nitrogen. Red variety of amaranthus was superior to green variety in most of the growth and yield attributing characters studied. Biometric characters like height, girth of stem, number of branches, number of leaves, LAI, and dry weights of leaves, stem and roots were favourably influenced by frequent irrigations and higher nitrogen levels. Total yields were also higher in more frequently irrigated treatments and at higher nitrogen levels. The moisture content of leaves was not influenced by irrigation and nitrogen treatments. However nitrogen exerted, significant influence on the moisture content of stem. Protein content of red variety was maximum and as the frequency of irrigation and levels of nitrogen were increased, protein content of plant increased and the maximum was recorded at daily irrigation treatment and at 125 kg N/ha. A relatively higher fibre content was noted in red variety. The effect of irrigation treatments on the fibre content of plants were not conclusive but the nitrogen fertilization tended to decrease the fibre content of plants. The red variety recorded a comparatively higher uptake of nutrients. The uptake of N, P and K were enhanced by frequent irrigations and nitrogen application upto 125 kg/ha. Available N, P, K status of the soil after the experiment was reduced by red variety. Higher irrigation treatments reduced the N and k content of soil after the experiment. But the nitrogen fertilization increased the nitrogen content and reduce the potassium content of the soil after completing the experiment. However the effects of different irrigation and nitrogen treatments on available phosphorus content of the soil after the experiments were found to be inconsistent during the two seasons. The red variety showed maximum water use efficiency then the green variety. Field water use efficiency was higher in the less frequently irrigated treatments (IW/CPE) of 0.75 and 1.00) and at higher nitrogen fertilizations (125 and 100kg N/ha). The results of economic analysis revealed that net income and benefit cost ratio were maximum for red variety and these were increased by more frequent irrigations and Nitrogen fertilizations up to 125 kg N/ha.Item Selection efficiency and genetic and biochemical bases of resistance to bacterial wilt in tomato(Department of Olericulture, College of Horticulture, Vellanikkara, 1985) Rajan, S; Peter, K VItem Leaf litter addition and nutrient recycling in two clones of rubber (Hevea brasiliensis Muell. Arg.) at Vellanikkara estate of Kerala Agricultural University(Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 1994) Rajan, S; Nazeem, P AThe present study deals with the quantification of leaf litter addition and nutrient recycling in two clones of rubber in the Vellanikkara Estate of kerala Agricultural University , Trichur . Two different methods of collection were adopted for litter collection in both the clones RRII 105 and RRII 118. Wintering was found to start on 23rd November, 1993 for clone RRII 105 and continued till 12th February , 1994 whereas in RRII 118 wintering strated by 25th November, 1993 and continued till 17th February , 1994. Peak leaf fall was noticed in the month of January for RRII 105 whereas it was in the month of February in the case of RRII 118. Thus clonal variation do exist for the wintering pattern. The total leaf litter production was estimated to the 4954.297 kg for RRII105 and 4584.558 kg for RRII 118. The nutrients contributed through leaf litter during wintering in the clone RRII 105 were 72 kg N, 2 kg p, 57 kg K, 59 kg ca and 12kg mg whereas for the clone RRII 118 it was 61kg N, 2kg p, 43kg k , 79 kg ca and 9kg mg . The clone RRII 105 contributed more litter as well as nutrients than the clone RRII 118. Contrary to the previous years the nutrient levels in the leaf litter did not follow a regular pattern during the wintering period . The presence of green leaves shed due to high wind velocity resulted in an increased level of nutrients in some collection s. It was also observed that the contribution of N, K and Ca were more during the wintering period whereas p was more prior to peak wintering and Mg was more after peak wintering. Comparison of nutrient status in soil samples collected from the area enclosed by net and outside sites showed that removal of leaf litter resulted in relatively lower levels of soil nutrients in the top soil . The leaf area worked out during the study was 6.44 for the clone RRII 105 and 5.53 for clone RRII118. The study also revealed that enclosing the trees with net is the best method to quantify the leaf litter addition . The expensive and cumbersome procedure of providing nets cannot be replaced by collecting the leaf litter from a marked area provided with 15 cm high fencing . The leaf litter accumulated in the fenced area was always less and varied from 27 to 71 per cent of the quantity of litter collected by providing net to cover the canopy all around the trees.