PhD Thesis

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End date: 1989Subject: search.filters.subject.Agronomy

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    Production potential of two fodder grasses under different management practices
    (Department of Agronomy, College of Agriculture, Vellayani, 1986) Raghavan Pillai, G; Madhavan Nair, K P
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    Effect of NPK on seed progeny and air layers in cashew ( Anacardium occidentale L. )
    (Department of agronomy, College of Agriculture Vellayani , Trivandrum, 1985) Harishu Kumar, P; Sreedharan, C
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    Phosphorus management in a rice based cropping system
    (Department of Agronomy, College of Agriculture, Vellayani, 1989) Annamma George; Sasidhar, V K
    In order to standardize an appropriate phosphorus management practice in a rice based cropping system involving rice-rice-cowpea/sesamum, field experiments were carried out in the rice fields of the Instructional Farm, College of Agriculture, Vellayani from June 1984 to September 1986. The experiment was laid out in a randomized block design with three replications. There were eight treatments. The treatments comprised of (1) continuous phosphorus application to all the three crops in the system (2) phosphorus application to the first and second crops of rice (3) phosphorus application to the first crop of rice and third crop of cowpea/sesamum (4) phosphorus application to the first crop of rice only (5) phosphorus application to the second crop of rice and third crop of cowpea/sesamum (6) phosphorus application to the second crop of rice only (7) phosphorus application to the third crop of cowpea/sesamum only (8) control plot with no addition of phosphorus to any of the crops in the system. The salient findings of the experiment are as follows: Phosphorus application had no significant influence on grain and straw yield of first crop of rice. But available nitrogen, available and total phosphorus and available potassium of the soil were increased with phosphorus application. Direct, residual and cumulative effects of phosphorus had no significant influence on grain and straw yield of second crop of rice. Phosphorus uptake could not show any variation due to the different treatments. Available and total phosphorus content of the soil were highest under cumulative phosphorus treatment. All the growth and yield attributes of third crop of cowpea and sesamum were increased by the direct and cumulative effects of phosphorus. Grain yield of cowpea was significantly increased by the direct application of phosphorus. Eventhough not significant the highest sesamum yield was accorded by the direct and cumulative application of phosphorus. Phosphorus uptake in all the growth stages of the crop was highest in direct phosphorus plots. Available and total phosphorus content of the soil was highest in continuous phosphorus applied plots. There was no significant influence on grain and straw yield of first crop of rice after cowpea and sesamum in the direct, residual and cumulative effects of phosphorus. Residual phosphorus was sufficient to maintain the available nitrogen status of the soil. Available phosphorus of the soil was increased by the direct, cumulative and continuous application of phosphorus and total phosphorus by continuous application of phosphorus. Balance sheet of available phosphorus revealed that the soil phosphorus level almost maintained, where phosphorus was applied only to the third crop of cowpea or sesamum. The highest net return and benefit-cost ratio for the rice-rice-cowpea and rice-rice-sesamum system was obtained when phosphorus was applied only to the third crop in the rice fallow and the residual effect being utilized by the succeeding rice crops.
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    Seed production in stylosanthes gracilis under varying levels of population density, nutrition, moisturiser regimes and cuttings
    (Department of Agronomy, College of Agriculture, Vellayani, 1989) Balachandran Nair, G K; Sreedharan, C
    An investigation was carried out during the period from July 1980 to March 1982 in the Instructional Farm, College of Agriculture, Vellayani to study the agronomic techniques required for maximum seed production in Brazilian lucerne (Stylosanthes gracilis). The following three separate field experiments were conducted and data collected and analysed. The first experiment entitled ‘influence of cultivars and plant population on seed production’ was laid out as a22 Factorial Experiment in R. B. D and replicated five times with the objective to find out the best cultivar of Stylosanthes gracilis for seed production along with the seed rate. The treatments consisted of combinations of two cultivars of Stylosanthes gracilis viz. Schofield and Cook, and two seed rates viz. 2.5 and 5 kg/ha. The second experiment entitled ‘nutritional requirements of Stylosanthes for seed production’ was laid out as a32 Factorial Experiment in R. B. D and replicated thrice with the treatment combinations of three levels of phosphorus viz.80, 120 and 160 kg P2 O5/ha and three levels of lime viz. no lime, 375 and 750 kg lime/ha. The objective was to assess the phosphorus and lime requirement of the crop for maximum seed yield. The third experiment entitled ‘Effect of moisture regimes and cuttings on seed production’ was conducted as a 32 Factorial Experiment in R.B. D and replicated thrice with treatment combinations of three irrigation schedules (IW/CPE ratios) viz. 0.50, 0.75 and 1.00 and three cutting schedules viz. no cutting, one cutting and two cutting. The objective was to investigate the efficiency of irrigation schedules and cuttings on seed yield. The results from the investigation revealed that the variety cook produced significantly higher seed yield of about 64 kg/ha as against 35 kg/ha obtained from the variety schofield. The seed rate of 5 kg/ha gave the higher seed yield of about 56 kg/ha as against the seed yield of about 43 kg/ha under the seed rate of 2.5 kg/ha. The seed yield attributing characters like setting percentage of seeds and number of seeds per plant were maximum for the variety cook. All the growth characters contributed to about 66 per cent of the variation in seed yield. The highest net return per hectare was obtained when the variety schofield was grown under a seed rate of 2.5 kg/ha. Application of phosphorus at 120 kg and lime at 375 kg per hectare gave maximum seed yield of about 80 kg/ha. It was also found that higher levels of phosphorus like 120 or 160 kg/ha helped to increase the setting percentage of seeds. The biometric characters such as spread of plants, number of branches and LAI were significantly influenced by the application of 120 kg phosphorus and 375 kg lime per hectare. The nutrients uptake was also enhanced by the application of phosphorus and lime at the above levels. The growth characters influenced the seed yield by 53 per cent. The economic optimum doses of phosphorus and lime for maximum seed yield were found to be 149 kg and 593 kg per hectare respectively. The highest gross and net returns were obtained from plots treated with phosphorus and lime at 120 kg and 375 kg per hectare respectively. Irrigating the crop at IW/CPE ratio 1.00 gave the maximum seed yield of 89 kg/ha. When the crop was left without cut it produced the highest seed yield of 92 kg/ha. The maximum setting percentage of seeds and leaf production were observed when the crop was irrigated at ratio 1.00 and without cut. The no cutting treatment gave maximum number of seeds per plant. The biometric charaters like height, spread, number of branches and length of branches were all found maximum in treatments where no cutting was given. Maximum water use efficiency for seed production was recorded by the lowest irrigation ratio of 0.50 and also when the crop was left without cut. About 46 per cent of the variation in seed yield was explained by the growth characters. Maximum net return per hectare was obtained when the crop was irrigated at IW/CPE ratio 1.00 and without cut.
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    Cultural, manurial and water requirements for sweet potato (Iponoea batatas (L) Lam.)
    (Department of Agronomy, College of Agriculture, Vellayani, 1989) Oommen, M; Sadanandan, N
    Three field experiments were conducted in the wet lands and garden lands of Instructional farm of College of Agriculture, Vellayani to work out cultural, manurial and water requirements for sweet potato. The treatments in the first experiment – Nutritional requirements of sweet potato – consisted of three level of nitrogen (50, 70 and 100kg N/ha), three levels of phosphorus (25, 50 and 75kg P2O5/ha) and three levels of potassium (50, 75 and 100kg K2O/ha). The experiment was laid out in a 33 partially confounded factorial design with two replications. The second experiment – spacing cum depth of application of fertilizers – consisted of three spacing (40cm x 20cm, 60cm x 20cm and 80cm x 20cm) and three depths of application of fertilizers (10cm, 20cm and 30cm). The experiment was laid out in a 32 factorial design in RBD with four replications. The third experiment – Irrigation requirement – consisted of four levels of irrigation (IW/CPE ratios 0.25, 0.50, 0.75 and 1.00) and four levels of fertilizers (50:25:50, 75:50:75, 100:75:100 and 125:100:125 kg N,P and k/ha). The experiment was laid out in a split plot design with five replications. In the experiment to study the nutritional requirement of sweet potato growth attributes like length of vine, number of branches and leaf area index were maximum at higher levels of nitrogen and potassium. The highest values of tuber number, tuber weight, length of tuber and girth of tuber were obtained by the application of 75kg N, 50kg P2O5 and 100kg K2O/ha. Application of nitrogen, phosphorus and potassium at the rate of 75:50:100 kg/ha was found to be optimum for higher tuber yield. While nitrogen nutrition increased the protein content of tuber, potassium application enhanced the starch content. Highest levels of nitrogen, phosphorus and potassium increased the leaf, stem and tuber dry matter production and tuber bulking rate. Potassium only did influence the net assimilation rate. Crop growth rate was maximum at higher levels of nitrogen, phosphorus and potassium. The plant uptake of nitrogen, phosphorus and potassium was maximum at the highest level of these nutrients. The NPK combination of 75kg N, 50kg P2O5 and 100kg K2O/ha resulted in the maximum net return. Experiment on spacing cum depth of application of fertilizers revealed that wider spacing of 80cm x 20cm enhanced the growth characters such as length of vine, number of branches and LAI. Depth of application was not influential on this aspect. Yield attributes like tuber number, tuber weight and girth of tuber were higher at the spacing of 40cm x 20cm but length of tuber was maximum under wider spacing. Application of fertilizers at 20cm depth recorded maximum values for the aforesaid characters. Closer spacing of 40cm x 20cm and 20cm deep placement of fertilizers recorded higher tuber yield. Among the quality attributes protein content alone was influenced by wiser spacing, but protein and starch contents were increased when fertilizers were applied at 20cm depth. Wider spacing increased leaf and stem dry matter and CGR while closer spacing recorded higher tuber dry matter, tuber bulking rate and net assimilation rate. Depth of application of fertilizers did not influence the dry matter production. Plant uptake of nitrogen, phosphorus and potassium was increased by wider spacing and by the application of fertilizers at a depth of 20cm. A combination of 40cm x 20cm spacing and 20cm deep fertilizer placement resulted in maximum net return. Experiment on irrigation requirements divulged that highest IW/CPE ratio and higher fertilizer combinations recorded maximum length of vine and LAI, but number of branches was not influenced by them. Number of tubers, weight of tubers, length of tubers and girth of tubers were not influenced by irrigation, while levels of fertilizers increased the length of tubers. Tuber yield was higher at IW/CPE ratio of 0.75. Fertilizer combination of 100:75:100 kg of N, P and k/ha produced the maximum yield. Starch and protein contents were increased at higher levels of irrigation and fertilizer application. Total dry matter production and bulking rate increased upto an IW/CPE ratio of 0.75 and upto a fertilizer lever of 100:75:100 kg N, P and k/ha. Plant uptake of nitrogen, phosphorus and potassium at harvest was maximum at higher levels of irrigation and fertilizer application. Irrigating the field when the IW/CPE ratio becomes 0.75 and application of fertilizers at a ratio of 100:75:100 kg N, P and k/ha recorded maximum net returns.
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    Evaluation of lowcost agronomic techniques for sustained rice production
    (Department of Agronomy, College of Horticulture, Vellenikkara, 1985) Sreedevi, P; Sreedharan, C
    Three field experiments were conducted at the Regional Agricultural Research Station, Pattambi, Kerala to evaluate some of the low cost agronomic techniques for sustained rice production during the period from 1982 to 1985. In the first experiment the performance of IR 42, a rice variety suited to low fertility conditions was assessed under varying levels of nutrition and spacing. Fertilizer, age of seedlings and planting density, for IR 42 were the experimental variables for the second experiment. In the third trial, azolla was evaluated as a low cost biofertilizer for IR 42. The first and third trials were laid out in split plot design while the second trial in factorial RBD. The rice cultivar IR 42 proved its mettle under the low fertility conditions. In fact, it gave an average yield of 2.78 t ha-1 in virippu and 2.32 t ha-1 in mundakan without any fertilizer application. A plant population of 33 hills m-2 (spacing 20 x 15 cm) in conjunction with full dose of fertilizer of 90 : 45 :45 kg NPK ha-1 recorded substantially more grain yield of 4.24 and 3.20 t ha-1 in virippu and mundakan seasons, respectively. Relatively lower grain and straw yields were registered by the treatment 100 hills m-2 (spacing 20 x 5 cm) at all levels of fertilizer application. The net return and benefit cost ratio were more in the former combination. Increasing the seedling number hill-1 from two to four or six was also found to be beneficial for this variety. At lower levels of fertilizer six seedlings hill-1 recorded higher grain yields. However, at higher levels four seedlings hill-1 was found to be superior. During virippu season planting of 35 days old seedlings was found to perform better compared to 30 and 25 days old seedlings whereas in mundakan season, 30 days old seedlings were found preferable in terms of grain yield. Recommended dose of fertilizers (90 : 45 : 45 kg NPK ha-1) with azolla @ 10 t ha-1 and 75 per cent of the same with azolla @ 15 t ha-1 recorded similar grain yields indicating that an extra dose of 5 t of azolla ha-1 could substantially reduce the chemical fertilizer requirement and save as much as 25 per cent of the fertilizer. The benefit cost ratios were almost equal in both the combinations while the return per rupee invested was more in the latter combination. The finding appears to caution against excessive use of azolla expecting better exploitation of all the benefits attributed to it. Nevertheless, data on the residual fertility of the soil after each crop indicate that residual fertility was higher in the plots receiving full dose of fertilizer along with the highest level of azolla, 20 t ha-1
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    Production potential of cassava-based cropping systems
    (Department of Agronomy, College of Horticulture, Vellanikkara, 1986) Ashokan, P K; Sreedharan, C
    A series of field experiments were conducted during the years 1983-84 and 1984-85 at College of Horticulture, Kerala Agricultural University, Trichur, to evaluate some of the cassava based intercropping systems and to investigate the interspecific interactions. There were three field trials and two micro plot trials. In the first field trial, the treatments were factorial combinations of two planing geometries of cassava viz., paired row and square cluster planting geometries of cassava viz., paired row and square cluster planting and four intercropping practices viz., intercropping with colocasia, elephant foot yam, banana and no intercropping. In the second field trial, there wer 12 treatments derived from the factorial combinations of three geometries of planting (paired row, square cluster and triangular cluster) and four intercropping practices (growing a floor crop of cowpea, groundnut, elephant foot yam and not growing any floor crop) in a cassava + banana intercropping system. In the third field trial, the possibility of growing two crops of groundnut in sequence ( Kharif and cowpea and/or Rabi) and the fertilizer requirements of intercrops were studied. All the three field trials were laid out in randomised Block Design and replicated thrice. In one of the micro-plot trials, 32P absorption by the component species in a cassava + banana + elephant foot yam cassava planted in square cluster was studied. polyculture with In the other micro plot trial 32P absorption by cassava and groundnut under the situations of cassava planted in paired row-ridge, mound and flat bed methods were studied. These two microplot trials were laid out in Completely Randomized Design with three replications. Paired row and square clustered planting of cassava gave similar yields as that of normal method when the plant population was the same. Intercropping cassava in square cluster with elephant foot yam resulted in maximum yield of cassava (20.1 t/ha) and elephant foot yam (10.6 t/ha). Banana and colocasia were also found to be successful as intercrops in cassava planted in paired row or square cluster. Intercropping with elephant foot yam and banana resulted in higher yield of cassava. The intercrops colocasia and elephant foot yam recorded lesser yields than the sole crops whereas in intercrop banana such difference was not observed. The maximum LER of 1.81 was obtained in cassava + banana cropping system. The cassava + elephant foot yam intercropping removed 133, 11, 107, 46, 12 and 18 kg/ha of N, P, K, Ca, Mg and S respectively wheras in the cassava + banana combination the corresponding figures were 227, 14, 236, 70, 16 and 11 kg/ha. From the two year trials, the cassava + banana + elephant foot yam cropping system with cassava planted in square cluster (9070 plants/ha) / triangular cluster (6800 plants/ha) was found to be the most productive and economical cropping system. Elephant foot yam was found to be shade tolerant and the yield reduction in intercropped situation was only marginal. The floor crops of cowpea and groundnut were successful in the first year. The land equivalent ratio in cassava + banana + elephant foot yam intercropping was 1.7 and this cropping system gave a net profit of Rs. 13300 per hectare. The N, P, K, Ca, Mg and S removal in a cassava + banana + elephant foot yam cropping system was found to be 198, 24, 200, 166, 34 and 19 kg/ha respectively. Sequential intercropping in paired row planted cassava was not successful, but growing groundnut and red gram simultaneously in the interspace was found to be successful; groundnut was harvested after four months, red gram after eight months and cassava after nine months. The fertilizer requirements of intercrop cowpea and groundnut were found to be only about 60-90 per cent of the sole crop recommendation and the optimum doses of N, P and K worked out were 6, 18 and 18 kg/ha for cowpea and 4, 30 and 30 kg/ha for groundnut. The main crop of cassava also was benefited by the application of fertilizers to the intercrops. The organic carbon and total nitrogen content of soil were reduced in two or three component intercropping systems by the two year cropping practices. The exchangeable P, K, Ca, Mg and SO 4 increased in situations where legmues alone were intercopped and decreased when banana and a floor crop of cowpea, groundnut or elephant foot yam were intercropped. The micronutrient status of the soil was not remarkably changed by the two season cropping. The intercrop and sole crop systems were not different in their influence on the post crop nutrient status of the soil. The radiophosphorus applied to the root zone of any of the components in the mixed cropping system cassava + banana + elephant foot yam with cassava in square cluster planting was absorbed not only by the treated plants but also by the surrounding species. Banana was the most dominant component in this polyculture. In the cassava + groundnut cropping system, cassava was the most dominant component, accumulating about 90 to 98 per cent of the 32P applied to cassava on mounds/ridges and about 50 percent of that applied to the groundnut root zone in the interspaces. Groundnut root system was small and less active and was able to derive only about 2 to 5 per cent of the 32P applied to cassava mounds. It was also deduced that the root interactions were stronger when all the components of the intercropping systems were a longer duration and it would be mild with legume intercrops of short duration.