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ThesisItem Open Access Floristic diversity, autecology and competitive behaviour of weed flora in wetland rice ecosystem(Department of Agronomy, College of Agriculture, Vellayani, 2010) Sajith Babu, D; KAU; Sansamma GeorgeFloristic diversity, autecology and competitive behaviour of weed flora in the wetland rice ecosystem were studied by conducting a field survey and two field experiments. The field survey was conducted during the first and second crop seasons of 2003 in the rice fields of 30 panchayaths in Thiruvananthapuram district having more than 50 hectares of net sown area, covering all the four thaluks of the district. Weed flora was surveyed from both cultivated and fallow fields. The design adopted for conducting the floristic survey was Stratified Multistage Random Sampling and the methodology was Census Quadrate Method. The field experiments were conducted during the first crop seasons of 2003 and 2004 at College of Agriculture, Vellayani. The design adopted was Strip plot. The treatments included four levels of nutrient management and three levels of crop spacing and the number of replications was five. Part III of the investigation was an autecological study wherein the growth and development pattern of two of the major weed flora observed in the experimental area was studied by keeping an area of 1.2 X 4.2 m2 on the same side of all the plots in Part II. Perusal of the results of the field survey indicated that substantial diversity of weed flora existed in the wetland rice ecosystem in Thiruvananthapuram district of Kerala. In the cultivated rice fields, there were 46 weed specii during the first crop season and 49 species during the second crop season. In the rice fallows during the first crop season there were 43 specii while during the second crop season there were 54 specii. In the cultivated fields during both seasons, the most prominent species among the different classes of weeds (grasses, sedges and broad leaved weeds) were Isachne miliacea Roth ex Roem et Schult, Cyperus iria L. and Monochoria vaginalis (Burm.f.) Presl. Ex Kunth respectively. Isachne miliacea Roth ex Roem et Schult was the dominant grass weed in the fallows as well. However the dominant sedge weed in the fallows was Cyperus distans L.f. during the first crop season while it was Fimbristylis miliacea. during the second crop season. Monochoria vaginalis (Burm.f.) Presl. Ex Kunth and Ludwigia perennis topped the list of broad leaved weeds in the rice fallows during first and second crop seasons respectively. Results of the field experiment showed that weed growth in the rice field was influenced significantly by the sources and levels of nutrients as well as by crop spacing. During both the years at 20 and 40 DAT the weed density and dry weight were the lowest when the rice crop was treated with NPK @ 90:45:45 kg ha-1 applied with 25 per cent N as organic (N2) while at 60 DAT enhanced nutrient level (NPK @ 112.5:56:25:56.25 kg ha-1) applied with 25 per cent N as organic (N4) recorded the lowest value. During both the years, at all growth stages the weed density and dry weight were the lowest under the closer spacing of 15 X 15 cm (P1) The grain and straw yield were maximum under NPK @ 112.5:56:25:56.25 kg ha-1 applied with 25 per cent N as organic in combination with widest spacing (n4p3). Dead heart occurrence was minimum under the widest crop spacing The net income and Benefit : Cost ratio were the highest when rice crop was treated with 125 per cent of the recommended NPK with 25 per cent organic substitution in combination with widest spacing (n4p3) Autecological studies showed that the growth and development of Isachne miliacea Roth ex Roem et Schult. was significantly influenced by the management practices for the associated rice crop. The higher dose of NPK applied as chemical fertilizers only (N3) along with widest spacing (P3) stimulated all the vegetative parameters (shoot / root length and plant spread) of the weed. During both the years plants growing in rice fields treated with recommended dose of NPK with 25 per cent organic substitution (N2) and rice crop planted at wider spacing (P3) recorded delayed flowering but produced more seeds per panicle The root and shoot length of Cyperus iria L growing in rice fields treated with 100 per cent recommended NPK as chemical fertilizers (N1) with minimum spacing (P1) recorded the maximum value during the both years. Delayed flowering of the sedge was noticed under N2. The number of seeds produced per plant was significantly high under N4 and P3. The general trend was that addition of organic manures in rice delayed flowering but increased seed production in the associated sedge weed From the studies it may be concluded that by altering nutrient management and adjusting the plant population, the competitive ability and productivity of rice crop can be improved substantially. Though, closer spacing of 15 X 15 cm significantly reduced the density and dry weight of weeds, the wider spacing of 20 X 20 cm in conjunction with enhanced fertilizer dose of 112.5:56:25:56.25 kg NPK ha-1 applied with 25 per cent N as organic manures significantly enhanced the rice grain and straw yield. The treatment also resulted in significant enhancement in net income and B:C ratio in medium duration variety Aiswarya in first crop season.ThesisItem Open Access Productivity of rice in laterite soil in relation to nitrogen-sulphur interaction(Department of Agronomy, College of Horticulture, Vellanikkara, 2010) Rathish, S T; KAU; John, P SThe research programme entitled “Productivity of rice in laterite soil in relation to nitrogen - sulphur interaction” was conducted mainly to study the nitrogen and sulphur availability and their interaction as influenced by organic manure sources, particularly straw incorporation in rice cultivation. The “Mineralization pattern of nitrogen and sulphur” was studied in pot culture experiment at College of Horticulture, Vellanikkara during the rabi season (Mundakan) Sep 2007 – Feb 08. “Response of rice to nitrogen and sulphur mineralization from organic matter with varying C:N ratios” was studied in farmers field, Pudhunagaram, Palakkad during the rabi seasons (Mundakan) Sep 2006 – Feb 07 and Sep 2007 – Feb 08. The mineralization of nitrogen and sulphur from the organic materials was influenced by time after application. The straw incorporated treatment released noticeably lower amount of nitrogen and sulphur in the initial stages than no manure application. The early growth characters of rice such as plant height, tiller production and dry matter production were significantly lower in straw incorporated treatments. Straw incorporation followed by application of nitrogen and sulphur or both, did not make any significant change in growth pattern probably due to inadequacy or improper timing. Increasing levels of nitrogen and sulphur positively influenced the vegetative growth and yield. The interactive effects of manures × N/S were significant for several characters. Beneficial effects of higher nitrogen and sulphur with straw incorporation were less evident in the early stages and was pronounced in the later stages. Nitrogen application with cow dung showed better performance during vegetative stage, but declined towards harvest. The tiller decline was lower in the straw incorporated treatments than either cow dung applied or unmanured treatments. Yield attributing characters were significantly influenced by incorporation of straw and cow dung along with nitrogen and sulphur. Grain yield increased from 3432 kg ha-1 in the absolute control to 7085 kg in the straw + N90 + S30 treatment in first year and from 3657 kg to 7116 kg in the cow dung + N90 + S30 treatment in second year. The interaction effects of manures × N/S were more pronounced than N × S. Combined application of organic manures and nitrogen noticeably increased protein nitrogen and protein sulphur content. Most of the plant nutrients were positively correlated with each other and positively correlated with grain yield. N × Fe and S × Fe have showed significant negative correlation. Agronomic efficiency of nitrogen or sulphur (kg grain/kg nutrient applied) was not influenced by organic manure application. Apparent recovery of nitrogen as well as physiological efficiency of nitrogen was the highest in combination of organic manures with 45 kg nitrogen and 30 kg sulphur. The utilization or physiological efficiency was also highest (kg grain/kg nutrient taken up) for the above combination. Straw incorporation resulted in long term maintenance of soil fertility as evidenced by higher mineral nitrogen and sulphur in soil upto a period of 110 days. In sulphur deficient soil, sulphur fertilizers could increase the rice yield and the use efficiency of nitrogen. The finding of the study points to beneficial effects of rice straw left in the field after harvesting using combine harvesters. However 37 to 52 kg ha-1 less mineral N was observed in the straw incorporated soil during the 30 days after incorporation and 20 days after rice planting compared to cow dung, both incorporated at 10 t ha-1. If this deficit could be compensated by N added at appropriate time, the straw will be a better and cheaper source of organic matter than cow dung.ThesisItem Open Access Response of medicinal rice (Oryza Sativa L.) cv njavara to SRI and other management systems(College of Agriculture, Vellayani, 2010) Rani, S; KAU; Sukumari, PField experiments were conducted at Cropping Systems Research Center, Karamana, Thiruvananthapuram, Kerala, during the summer seasons of 2007 and 2008 (January to April) to study the response of medicinal rice (Oryza sativa L.) cv Njavara to nutrient sources under different management systems like SRI, ICM, PoP of KAU and Farmers’ practice. The experiment was laid out in split plot design with four replications. The treatments consisted of four management systems viz., SRI (M1), ICM (M2), PoP (M3) of KAU and Farmers’ practice (M4) in main plots. Nutrient sources viz., organic sources (S1), integrated sources (S2) and inorganic sources (S3) were the sub plot treatments. Growth components viz., plant height, number of leaves hill-1, leaf area index (LAI), leaf area duration (LAD), culm strength, number of tillers m-2, root dry matter production hill-1 and flag leaf area were recorded. The data on yield attributes like number of productive tillers m-2, panicle length, number of grains panicle-1, number of filled grains panicle-1, 1000 grain weight, harvest index, sterility percentage, dry matter partitioning, paddy grain ratio, grain husk ratio were also worked out. Yield and uptake of nutrients (N, P, K,S Fe, Mn and Zn by grain, straw and crop (grain + straw) were also recorded. Biochemical components such as total free amino acids, phenols, starch, amylose, amylopectin and crude protein content of grain were estimated. Data on weed dry matter production and weed flora and crop duration in the treatments were also recorded. Soil enzymes (urease, phosphatase and dehydrogenase) and soil fertility status were assessed after the harvest of the crop. D. Effect of management systems Growth parameters like height of plants, number of leaves hill-1, leaf area index (LAI), culm strength, root biomass and number of tillers m-2 were significantly influenced by management systems. Leaf area duration and flag leaf area showed significant variation only in 2008. Plant height and leaf area index (at physiological maturity) were in the order Farmer’s practice > PoP > SRI > ICM and they differed significantly from one another. Number of leaves hill-1, leaf area index at panicle initiation, flag leaf area and number of tillers m-2 (from 4 WAS/WAT till physiological maturity) were in the order Farmer’s practice > PoP > ICM >SRI . Number of tillers m-2 in the four management systems differed significantly from one another. Culm strength (physiological maturity) and root biomass production all the management systems differed significantly from one another. Culm strength and root biomass production (7 WAS/WAT to physiological maturity) were in the order SRI > ICM > PoP > Farmer’s practice. All the yield attributes except 1000 grain weight were significantly influenced by management systems resulting in significant variation in the crop yield (grain and straw). Number of productive tillers m-2, sterility percentage and dry matter accumulation in panicle were in the order Farmer’s practice > PoP > ICM > SRI and they all differed significantly from one another. Grain and straw yield in the management systems differed significantly from one another and their order was Farmer’s practice > PoP > SRI > ICM. Number of grains panicle-1, number of filled grains panicle-1 and dry matter partitioning in root and straw were in the order SRI > ICM > PoP > Farmer’s practice. All the characters except dry matter partitioning in straw differed significantly from one another. Among the biochemical properties of grain total free amino acid content and amylopectin content (2007) were significantly influenced by management systems. Free amino acid content of grain was in the order SRI > ICM > PoP > Farmer’s practice. Amylopectin (2007) was in the order ICM > Farmer’s practice > PoP > SRI . Weed biomass at 15 and 35 DAS/DAT in the management systems differed significantly from one another. Weed biomass recorded at 15 DAS/DAT were in the order Farmer’s practice > PoP > SRI > ICM and that at 35 DAS/DAT Farmer’s practice > ICM > PoP > SRI. Management systems showed significant influence on nutrient uptake by grain (N, P, K, Fe and Mn), by straw (N, K, Fe, Mn and Zn) and total uptake by the crop (N, P, K, Fe, Mn and Zn). Uptake of all the nutrients in Farmer’s practice was significantly higher than that in the other three management systems. Management systems did not show significant influence on the available nutrient status of soil after the experiments. Among the soil enzymes phosphatase activity was influenced significantly by the management systems and it was in the order SRI > ICM > PoP > Farmer’s practice. Crop raised under PoP had the longest duration (108 days) followed by ICM with 98 days, SRI with 94/95 days (2007/2008) and Farmer’s practice with 87 days. Farmer’s practice which realized highest crop yield was significantly higher than PoP, SRI and ICM with respect to many growth characters (plant height, number of leaves hill-1, leaf area index, leaf area duration, flag leaf area and tiller production) and yield characters (number of productive tillers, percentage of dry matter accumulation in panicle). Duration of the crop was lowest in Farmer’s practice and it was significantly lower than that in all other management systems. Effect of nutrient sources Sources of nutrients did not influence growth characters in Njavara. Yield attributing characters like number of grains panicle-1, number of filled grains panicle-1 and harvest index as well as crop yield (grain and straw) were significantly influenced by nutrient sources. Highest number of grains panicle-1, filled grains panicle-1 and crop yield (grain and straw) were realized in integrated nutrient source and they were significantly higher than organic and inorganic sources. Effect of nutrient sources on yield attributing parameters and crop yield (individual years and pooled analysis) were in the order integrated nutrient source > organic source > inorganic source and the order was just the reverse with respect to harvest index (inorganic source > organic source > integrated nutrient source). Duration of the crop also showed significant variation due to variation in sources of nutrients and it was in the order inorganic source (98 days) > integrated nutrient source (97 days) > organic source (95 days). Among the biochemical properties starch (2008), crude protein and amylopectin were significantly influenced by nutrient sources whereas total free amino acids, phenols and amylose content of grain remained unaffected. Starch and amylopectin content of grain were in the order organic nutrient source > integrated nutrient source > inorganic nutrient source. Crude protein content of grain was in the order organic nutrient source > inorganic nutrient source > integrated nutrient source. Available N status and organic content of soil were in the order organic sources > integrated sources > inorganic sources. Available N status of soil supplied with different nutrient sources differed significantly from one another. Organic carbon content in soils receiving organic and integrated nutrient sources were on par and significantly higher than that in soil receiving only inorganic source of nutrients. Soil enzyme activity (urease, phosphatase and dehydrogenase) was influenced significantly by nutrient sources and it differed significantly from one another. Effect of nutrient sources on urease activity was in the order organic source > inorganic source > integrated source and on phosphatase and dehydrogenase activity were in the order organic source > integrated source > inorganic source. Highest total nutrient (P, K, Fe and Zn) uptake by crop (grain + straw) occurred in integrated nutrient source. Crop uptake of K and Zn in integrated source was significantly higher than that in other nutrient sources and organic and inorganic sources were on par. Interaction effect Effect of interactions did not influence growth characters in Njavara. Yield attributing characters like number of grains panicle-1, number of filled grains panicle-1, crop yield (grain + straw) and harvest index were significantly influenced by interaction effect. SRI with organic source and Farmer’s practice with inorganic source recorded highest and lowest value of number of grains panicle-1 and number of filled grains panicle-1. Farmer’s practice with integrated nutrient source recorded highest (1198.00/2251.57 kg ha-1 grain/straw yield) and ICM with inorganic source recorded lowest grain and straw yields (788.08/1167.52 kg ha-1 grain/straw yield). Interaction effect showed significant influence on nutrient uptake by grain (N and Mn), straw (K and Zn) and total uptake by the crop (K and Zn). Nutrient uptake by crop (K and Zn) was highest in Farmer’s practice with integrated nutrient source. Phenological study The developmental phenology of Njavara rice under different management systems was studied. Panicle initiation occurred at 32 DAS in Farmers’ practice, 40 DAT in PoP, 42 DAT in ICM and 45 DAT in SRI. Maximum tillering stage occurred at 36 DAS in Farmers’ practice, 45 DAT in PoP, 46 DAT in ICM and 49 DAT in SRI. Booting stage occurred at 46 DAS in Farmers’ practice, 51 DAT in PoP, 53 DAT in ICM and 57 DAT in SRI. Flowering stage occurred at 53 DAS in Farmers’ practice, 59 DAT in PoP, 60 DAT in ICM and 64 DAT in SRI. Maturity stage occurred at 86 DAS in Farmers’ practice, 88 DAT in PoP, 86 DAT in ICM and 88 DAT in SRI. Economics of crop production Cost of cultivation, gross income, net income and BCR among the management systems, nutrient sources and interactions differed significantly. Cost of cultivation was highest in SRI, organic nutrient source and SRI with organic nutrient source. Gross income, net income and BCR were highest in Farmer’s practice, integrated nutrient source and Farmer’s practice with integrated nutrient source. Farmer’s management practices coupled with integrated nutrient source can be considered as the ideal crop production package for Njavara rice in lowlands. This production package realised the highest crop yield (grain and straw), gross income ha-1(Rs 52,423), net income ha-1 (Rs 28,027) and BCR (2.15).