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Kerala Agricultural University, Thrissur
The history of agricultural education in Kerala can be traced back to the year 1896 when a scheme was evolved in the erstwhile Travancore State to train a few young men in scientific agriculture at the Demonstration Farm, Karamana, Thiruvananthapuram, presently, the Cropping Systems Research Centre under Kerala Agricultural University. Agriculture was introduced as an optional subject in the middle school classes in the State in 1922 when an Agricultural Middle School was started at Aluva, Ernakulam District. The popularity and usefulness of this school led to the starting of similar institutions at Kottarakkara and Konni in 1928 and 1931 respectively.
Agriculture was later introduced as an optional subject for Intermediate Course in 1953. In 1955, the erstwhile Government of Travancore-Cochin started the Agricultural College and Research Institute at Vellayani, Thiruvananthapuram and the College of Veterinary and Animal Sciences at Mannuthy, Thrissur for imparting higher education in agricultural and veterinary sciences, respectively. These institutions were brought under the direct administrative control of the Department of Agriculture and the Department of Animal Husbandry, respectively. With the formation of Kerala State in 1956, these two colleges were affiliated to the University of Kerala. The post-graduate programmes leading to M.Sc. (Ag), M.V.Sc. and Ph.D. degrees were started in 1961, 1962 and 1965 respectively.
On the recommendation of the Second National Education Commission (1964-66) headed by Dr. D.S. Kothari, the then Chairman of the University Grants Commission, one Agricultural University in each State was established. The State Agricultural Universities (SAUs) were established in India as an integral part of the National Agricultural Research System to give the much needed impetus to Agriculture Education and Research in the Country. As a result the Kerala Agricultural University (KAU) was established on 24th February 1971 by virtue of the Act 33 of 1971 and started functioning on 1st February 1972. The Kerala Agricultural University is the 15th in the series of the SAUs.
In accordance with the provisions of KAU Act of 1971, the Agricultural College and Research Institute at Vellayani, and the College of Veterinary and Animal Sciences, Mannuthy, were brought under the Kerala Agricultural University. In addition, twenty one agricultural and animal husbandry research stations were also transferred to the KAU for taking up research and extension programmes on various crops, animals, birds, etc.
During 2011, Kerala Agricultural University was trifurcated into Kerala Veterinary and Animal Sciences University (KVASU), Kerala University of Fisheries and Ocean Studies (KUFOS) and Kerala Agricultural University (KAU).
Now the University has seven colleges (four Agriculture, one Agricultural Engineering, one Forestry, one Co-operation Banking & Management), six RARSs, seven KVKs, 15 Research Stations and 16 Research and Extension Units under the faculties of Agriculture, Agricultural Engineering and Forestry. In addition, one Academy on Climate Change Adaptation and one Institute of Agricultural Technology offering M.Sc. (Integrated) Climate Change Adaptation and Diploma in Agricultural Sciences respectively are also functioning in Kerala Agricultural University.
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ThesisItem Open Access Effect of Vermicompost on the yield and quality of tomato (lycopersicon esculentum Mill.)(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1996) Pushpa, S; KAU; Prabhakumari, PAn investigation was carried out at the Instructional Farm, attached to the College of Agriculture, Vellayani to evaluate the Effect of vermicompost on the yield and quality of tomato. The experiment was laid out in Randomised Block Design with ten treatments and three replications. Biometric observations viz. height of the plant, number of leaves and number of floweres were greately influenced by the application of vermicompost compared to farm yard manure. Yield attributes like mean fruit weight and girth of fruits were also found to be significantly influenced by the vermicompost application. Vermicompost application has got a significant influence on the yield of tomato. Plants receiving 25t vermicompost along with full dose of inorganic fertilizers produced maximum yield followed by the plants receiving 25 t farm yard manure along with full dose of inorganic fertilizers. Germination count and viability was maximum when vermicompost was used as the organic source. Maximum germination count and viability was observed when 100t ha-1 vermicompost was used. Vermicompost application has also got a significant influence on fruit qualities. Protein, and carbohydrate content were more in vermicompost treated plants compared to farm yard manure application. Chemical properties of the soil was significantly influenced by the application of vermicompost. pH, organic carbon, available N, P2O5, K2O, Ca and Mg was maximum when 25t vermicompost along with full dose of inorganic ferilizers was used. However availability of micronutrients Mn, Cu, Zn was more in 100t vermicompost applied plots. Application of vermicompost increased the uptake of nutrients by plants. Maximum uptake of all nutrients viz. N, P, K, Ca, Mg, Mn, Cu and Zn was found in plants treated with 25t vermicompost along with full dose of inorganic fertilizers. Correlation studies showed that nutrient uptake was significantly and positively correlated with availability of nutrients. Yield and nutrient uptake of plants were significantly and positively correlated with availability of nutrients and so vermicompost can be effectively used for increasing the fruit yield and quality of fruits in tomato.ThesisItem Open Access Characterisation of the gravels in the major soil series of Trivandrum district(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1996) Suraj, John; KAU; Subramonia Iyer, SSoil gravels are different in their morphological, physical, chemical and mineralogical features; as well as in their origin. In the major soil series of Trivandrum district, soil gravel inclusions make up a considerable part of the soil mass. Presence of soil gravels interferes with the cultivation operations, reduce soil volume and quantity of available water. In soil textural determinations and the soil fertility evaluation, presence of soil component greater than 2mm is usually disregarded and ignored. In order to gather information on the nature and properties of soil gravels, their genesis and distribution and their specific contribution to soil fertility; an integrated and systematic morphological, physical, chemical, mineralogical and micromorphological characterisation and interpretation of soil gravels of the representative profiles of the major soil serious of Trivandrum district namely Palode, Nedumangad, Varkala, Thonnackal and Trivandrum series were attempted. All the series except Thonnackal were gravelly throughout; Palode, Varkala, and Trivandrum series showed an increase in gravel content with depth but no specific profile pattern was observed at Nedumangad and Thonnackal. Palode series is unique with all the different gravel fractions (2mm to 2.5 cm, 2.5 to 7.5 cm and 7.5 to 25 cm). Another uniqueness of the Palode series is the presence of gneissic cobbles. Cobbles were absent in all the other series. Combination of grayels different in morphology and genesis are present at Palode and Trivandrum series. Gravel consolidation and soil hardening were observed maximum at Varkala series and least at Thonnackal series. Higher total phosphorus and potassium content of gravels indicate that gravels are the potential source of phosphorus and potassium for crop production. Acid insoluble content of gravels are in the increasing order Varkala< Trivandrum Quartz content of the finer gravels are in the increasing order at Varkala Palode and Nedumangad series contain multiglaebular microgravels and multimicrogravelly coarse gravels and cobbles. The gravels of Varkala are dominantly nodular than concretionary. The uniqueness of the Thonnackal series is the presence of rubefied less hard kaolinitic gravels. The gravels of the Trivandrum series are nodular, plinthic to petroplinthic with bigger angular skeletons. The preponderance of gravels with geodic internal morphology in the lower horizons and pseudomorphic in the surface horizons are direct expressions of geogenic and pedogenic origin of gravels. The observation of nucleic type of gravels in the last horizon of Thonnackal series is indicative of its detrital origin from microgravels of nearby landscapes. The preponderance of quartz both in the soil and gravels is obviously due to the acid igneous and metamorphic parent material. The hardened plinthite gravel ie., the petroplinthite gravel is proposed in the soil taxonomy to differentiate Entisols and Inceptisols from Oxisols and Ultisols. The comparative gravel contribution to available nitrogen content of the soil is in the increasing order Palode A multilocational field experiment based on the information gathered in the present study is desired to be taken up to reveal the effect of gravels on the performance of crops in the actual field situation.ThesisItem Open Access Effect of vermicompost/ vermiculture on physico-chemical properties of soil(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1996) Rajalalekshmi, K; KAU; Pushkala, SA study was undertaken to assess the effect of application of vermin compost / vermin culture on physic – chemical properties of soil and yield of chilli making use of the soil and plant samples taken from the trial conducted at College of Agriculture, Vellayani. The experiment was conducted during the period from December 1994 to April 1995. The soil of the experimental site was sandy loam. (fine loamy kaolinitic isohypothermic Typic Kandiustults). The experiment was laid out in randomized block design with four replications and six treatments. The treatments consisted of FYM + NPK fertilizers, vermin compost + NPK fertilizers, vermin culture with local worms and with Eudrillussps, vermin culture with above sps. Of worms + basal dose of NPK fertilizers. Soil samples were collected from all the replications of the various treatment before planting, at maximum flowering stage and at harvest. Plant samples were also collected at the above growth stages. Soil and plant samples were analysed in the laboratory to find out the effect of application of vermi compost / vermin culture on physic – chemical properties of soil and content of nutrients in plant parts viz. leaf, shoot and root. Results of preliminary analysis of soil samples collected before the experiment revealed the beneficial effect of application of vermin compost/vermin culture on physic – chemical properties of soil. Physical properties of soil such as bulk density and particle density were found to be much reduced in plots treated with earthworms while porosity was increased in them. Percent of water stable aggregates in plots with insitu application of worms was found to be more than 50 percent but an optimum mean weight diameter of above 0.50 mm was recorded by all treatments. Water stable aggregates with greater than 0.25 mm size had helped to retain more moisture due to the increased intraggregate spaces. The moisture content in soil was found to be more due to the coverage of organic wastes on soil surface. Water holding capacity and hydraulic conductivity were also much influenced by the presence of earthworms. The increased infiltration rate with insitu application of worms to soil indicated the improvement in water permeability of the soil as compared to plots without worms. But surface compaction of soil was found to be not much affected by the application of vermin compost / vermin culture and it showed negative correlation. Application of organic manures either as farmyard manure or vermin compost with inorganic fertilizers had significant influence on soil reaction and organic carbon content of the soil. Organic carbon content was found to be increased with increasing nitrogen rates at both depths of 0 – 15 cm and 15 - 30 cm. Available nutrient contents of the soil viz. available nitrogen, phosphorus and potassium and exchangeable calcium and magnesium were influenced significantly due to different treatments at maximum flowering stage and at harvest. Application of vermin compost + NPK increased the availability of nutrients in soil while application of vermin culture alone with local worms or Eudrillussps. Had resulted in a lower value. Regarding the nutrient content in plant parts such as leaf, shoot and root, all the nutrient contents were highest in the plot treated with vermin compost + NPK fertilizers followed by farmyard manure + NPK. Significant correlation existed between available nutrient in soil and plant nutrient content. Maximum yield and growth parameters were also recorded by the treatment receiving application of vermin compost + NPK fertilizers and the results thus clearly indicate that application of vermin compost along with NPK is essential to maintain high yields. Application of vermin culture alone with local worms or Eudrillussps. Or together with basal dose of fertilizers also failed to give higher yields. Thus by adopting vermin culture technique only the physical properties of soil can be improved while its effect on chemical properties is negligible. So combined application of vermin compost/vermi culture with inorganic fertilizers is found to be better for improving the soil productivity and fertility.ThesisItem Open Access Interrelations of humans with the fertility components of wetland soils(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1996) Sreedevi, K; KAU; Alice, AbrahamSurface soil samples from the major wetland soil types of Kerala were studied to establish the relationship between soil organic matter and its fractions with the total and available nutrients and other physicochemical characters. Destruction of organic matter has resulted in a substantial drop in the status of almost all nutrients and an appreciable change in soil properties. The SOM separated from the soils were fractionated and the correlation between soil characters and the SOM and its fractions were determined. Regression equations relating soil properties which were significantly correlated with SOM and its fractions were also derived in each soil type. The study has revealed that CEC,WHC,SOM, lime requirement, buffering capacity as well as total and available nutrients in all the four soil types showed considerable degree of variability between samples in each soil type. The content of SOM was highest in Kayal soils (8.03%) and lowest in lateritic alluvial (2.24%) soils with Kari and Karappadam soils with intermediate values of 7.58 and 6.81% respectively. Fractionation of organic matter has shown that humification of SOM was maximum in Karappadam soils, followed by Kayal, Kari and lateritic alluvial soils. The degree of degradation of humified organic matter was high in all the soil types except Kari soils, as evidenced from the HA/FA ratios. The SOM in Kayal soils may probably exist as a stable clay humus complex which has resulted in its lower contribution to CEC, lime requirement and nutrient status. All the four soil types were acidic and the contribution of SOM to free acidity was maximum in Karappadam soils (18.4%) followed by Kayal (17.2%) and lateritic alluvial soils (4.2%). Inspite of the high content of SOM, its contribution to free acidity in Kari soils was only 7.1%, probably due to the low deprotonation of SOM at low pH values. pH in all soil types is negatively correlated to SOM and its fractions. The Kari, Karappadam and Kayal soils are highly buffered when compared to lateritic alluvial soils and the slope of the buffer curves for these soils showed a drastic drop due to the destruction of organic matter. The contribution of SOM to lime requirement ranged from 13.9 to 25.5% which is evident from the drastic drop in lime requirement values consequent to the destruction of organic matter. Maximum contribution of SOM to WHC was shown by lateritic alluvial soils (49.8%). In Kari, Karappadam and kayal soils, the contribution was 24.7, 29.4 and 25.3% respectively.WHC is positively related to SOM and its fractions in all the soils. CEC was highest in Kari soils and lowest lateritic alluvial soils. The contribution of SOM to CEC was maximum in Kari soils (27.2%) and least in Kayal soils (9.7%). CEC of all soils except Kayal soil showed significant positive and linear relationship with SOM as well as with its components. The lack of such a relationship in Kayal soil is attributed to the existence of stable clay-humus complexes. Karappadam soils showed the highest content of total nitrogen and lateritic alluvial soils the lowest. Available nitrogen was highest in Kari soils and lowest in Karappadam soils. In all the four soil types, SOM contributed to more than 90% of total and available nitrogen and it is positively correlated to total and available nitrogen. Total phosphorous was highest in Kayal soils and lowest in Kari soils. Inspite of the lowest content of SOM in Kari soils, it made the maximum contribution to total phosphorous (35.2%). In the Kayal soils the contribution of SOM to total phosphorus was minimum and representing only 5.4%. The available phosphorous in all the soil types showed maximum degree of variability (85.1 to 160.8%) between samples and the contribution of SOM to available phosphorus was also very low. It showed a negative correlation with SOM and its fractions in Kari, Karappadam and Kayal soils probably due to the strong linkage of phosphorus to humus via iron and aluminium bridges. In lateritic alluvial soils, the relationship between SOM and available phosphorus was positive. The total and exchangeable potassium, calcium and magnesium are positively correlated to SOM and its fractions. However these are influenced only to a very low degree by the SOM content. The pattern of relationship of each soil property with SOM is the same as that with its fractions and hence, in studies on soil organic matter, the derivation of relationship between soil properties and soil organic matter alone is sufficient to bring out the interaction between soil organic matter and components of soil fertility.ThesisItem Open Access Seasonal variations in the nutrient transformation in the lateritic alluvial rice soils of permanent manuurial trials(Department of Soil science and Agricultural chemistry, College of Horticulture, Vellanikkara, 1996) Dineskumar, K K; KAU; Chinnamma, N PA study was conducted during the first and second crop season of 1992 to find out the seasonal variations in nutrient transformations in the existing two permanent manorial trials (one with tall indica varieties and the other with dwarf indica varieties) at the Regional Agricultural Research Station, Pattambi. The experiment with tall indica variety was started in 1961 and the experiment with dwarf indica variety was started in 1973. The experiments were laid out in randomised block design with four replications and eight treatments. The treatments consisted of application of entire quantity of N as organic manure (cattle manure alone, green leaves alone and cattle manure + green leaves), inorganic fertilizers alone (ammonium sulphate alone and NPK fertilizers) and a combination of organics with inorganics (cattle manure + NPK fertilizers, green manure + NPK fertilizers and cattle manure + green leaves + NPK fertilizers). In both the experiments, the treatments are the same, but the dose of manures and fertilizers varied based on the nutrient requirements of all indica and dwarf indica varieties. For all indica the dose of NPK applied is 40:20:20 kg/ha whereas in the dwarf indica varieties the dose applied is 90:45:45 kg/ha. Soil samples were collected from all the replications of the various treatments at 11 stages from harvesting of second crop of 1991 to harvest of second crop of 1992. Plant samples were also collected at different stages of crop growth viz., tillering, 50 per cent flowering and harvest. Data on yield of grain and straw were collected from the Regional Agricultural Research Station, Pattambi. Soil and plant samples were analysed in the laboratory to find out the seasonal variations in the availability of nutrients in the soil and in the content and uptake of nutrients by the crop. Results of analysis of soil samples showed that significantly higher values of organic carbon, available N,P,K and Ca were recorded in the initial stages of crop growth namely transplanting, tillering and 50 per cent flowering in the first crop season but at harvest the trend reversed in both the experiments. In the case of magnesium significant difference between the seasons was noticed only at 50 per cent flowering and at this stage higher values were recorded in the first crop season in both the experiments. At the initial stages of crop growth, namely at tillering and 50 per cent flowering higher content of available nutrients namely N, P, K and Ca were recorded in the soil in the first crop season but higher contents of N, P and K in the plant were recorded in the second crop season for both tall and dwarf indica varieties. For magnesium content in plant comparatively higher values were recorded in the first crop season compared to second crop season for both tall and dwarf indica varieties at tillering and 50 per cent flowering. With regard to calcium higher contents were recorded in the first crop season at tillering but at 50 per cent flowering the trend reversed in the case of tall indica varieties. At both the stage higher contents were recorded in the first crop season in the dwarf indica varieties. In the grain significantly higher content of N, K and Mg were recorded in the second season. There was not much difference in the P content between the seasons. Similar trend was noticed in the nutrient content for both tall and dwarf indica varieties except for Ca. In the case of calcium no uniform trend was shown in both the experiments. Higher contents of P, K and Ca were noticed in the second crop season in the straw. Significantly higher values were recorded in the first crop season for nitrogen. No significant difference in magnesium content was noticed between the seasons. Similar trend was noticed in both the experiments for all the elements. Significantly higher uptake of N, P and K was noticed at all the growth stages in the second crop season in both the experiments. In the case of Ca and Mg though higher uptake was recorded in the initial growth periods, at the time of harvest the trend reversed and for these elements also higher values were recorded in the second crop season.ThesisItem Open Access Standardisation of rooting media for selected tree crop seedlings with special reference to plant nutrients(Department of Soil science and Agricultural chemistry, College of Horticulture, Vellanikkara, 1996) Sudheesan, V P; KAU; Hassan, M AA randomized block design (split plot) experiment involving twelve important tree crop seedlings (Ailanthus triphysa, Albiziafalcataria, Albizialebbeck. Casuarinaequisetifolia, Ceiba pentandra, Dalbergia latifolia, Gmelina alborea, Hopea parviflora, Santalum album, Swietenea macrophylla, Tectona grandis and Vateria indica) was conducted in the Instructional Farm, College of Horticulture, Vellanikkara, Kerala Agricultural University, with an objective of standardising the most suitable rooting media for the best growth of above tree seedlings in the nursery for agroforestry planting. In this study altogether twelve different media were tried, considering their relative cheapness, easy availabily and more or less satisfying the desired qualities of an ideal rooting medium. The results showed that the rooting medium containing soil, sand and FYM in the ratio of 1:1:1 was ideal for all the species except for Dalbergia and Vateria. For Dalbergia, the best medium found was soil ½, sand 1/3 and neem cake 1/6 and for Vateria it was soil 1/3, sand 1/3 and saw dust 1/3.ThesisItem Open Access Micromorphology and mineralogy of the soils of major land resource areas of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1996) Anup, V M; KAU; Subramonia Iyer, MAn integrated study was conducted on the macromorphology, granulometric composition, primary mineral assemblage, micromorphology and clay mineralogy of the diagnostic horizons from the representative profiles of the major land resource areas of the state for their refined description and classification. The investigated MLRAS of the state are the southern dissected terriplain, southern low land laterites, southern coastal plain, southern dissected midland laterites, southern foot hills, Kuttanad coastal basin, central backwater basin, central dissected midland laterites, Palakkad gap, northern dissected midland laterites and the Wayanad plateau. All the MLRAs are classified within isohyperthermic temperature regime but with aquic, udic and ustic moisture regimes. The universal observation of ochric horizon and its transition to argillic horizon, ill – developed to well developedargillic horizon, presence of sulphuric horizon or sulphidic materials and vertic features could be safely arrived at with the comparative macro and micromorphology of the soils, supported with clay mineralogy. Wide differences in gravel and clay distribution is another unique observation between the MLRAs. Primary mineral assemblage indicate granite, qneiss, quartzite, mica schist and gabbro parentage of the soils of the various major land resource areas. Irrespective of the MLRAS kaolinite is the dominantclay mineral followed by smectite, mica and illite. In the Palakkad gap smectite minerals dominate over kaolinite while in the Kuttanad coastal basin kaolinite and smectite are in almost equal amounts. The non – clay clay minerals mica quartz, feldspars, goethite and gibbsite are also present. Haematite was not seen present in the clay fraction. Smectite and mica are also present even in weathered laterite MLRAs. Diagenesis is observed in the Kuttanad coastal basin and in the Palakkad gap whereas the other MLRAs are with polygenetic or paleoclimatic influenced soils. The study could help in arriving at the safe and refined soil description and classification upto family level on the basis of the results of the investigation. A critical analysis of detailed survey of MLRAs and detailed sampling may be attempted as future line of work with the present investigation as baseline to submit suitable proposals in Soil Taxonomy incorporating detailed soil microfabric criteria as a safe and specific information.ThesisItem Open Access Dynamics of potassium in the soil of kole land(Department of Soil science and Agricultural chemistry, College of Horticulture, Vellanikkara, 1996) Jyothikumari, K N; KAU; Mariam, K AIn the present investigation, attempt has been made to evaluate the chemical nature, distribution, fixation and availability of potassium in the soils of kole lands. Soil samples were collected from 15 locations in Chathankole – Puppilakkadkole area, seven from Chittilappilly village and four each from Adat and Chalakkal villages. In each location, from two nearby plots both surface (0 - 20 cm) and subsurface (20 – 40 cm) soil samples were collected and were analysed for the physic – chemical characteristics related to potassium availability. A retention study and a laboratory incubation experiment of three month duration was carried out in order to find out the level of retention and transformation of applied potassium. In order to find out the most suitable extractant for assessing the available potassium in these soils, different chemical extractants were tried and its correlation with K uptake by rice in Neubauer experiment was carried out. The soils collected from the three villages showed wide variation in the particle size distribution and majority of them were grouped under the textural class clay and sandy clay loam. The single value constants were showing variations depending on the clay content and organic carbon. Soils were generally acidic in reaction. Organic carbon content varied among the samples and for certain sites subsurface accounts higher value. The total reserves of nitrogen, phosphorus and potassium were relatively low. Total potassium showed significant positive correlation with clay content, organic carbon and cation exchange capacity. Water soluble, exchangeable and HNO3 solubleforms of potassium were low in these soils. These forms of potassium showed significant positive correlation with each other also with total K except for water soluble fraction. From the retention study it was found that in soils with high saturation capacity the retention capacity is low and hence longer duration of time is essential for maximum retention. From incubation experiment it was found that on application of potassium fertilizer, the different fractions viz., water soluble, ammonium acetate extractable and nitric acid soluble potassium got increased at the end of the incubation period although fluctuations were noticed in all the fractions during this period. In NH4 OAC extracted higher amount of potassium compared to Mathew’s extractant and 0.01 M CaCl2. The potassium extracted by these extractants and IN HNO3 – K were positively and significantly correlated with K uptake by rice in Neubauer experiment. Among all the four extractants maximum correlation was obtained for In NH4 OAC.ThesisItem Open Access Differential response of rice cultivators to potash application in the rice soil of Onattukara(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1996) Shaji, K V; KAU; Rajendran, PIt is known that there exists varietal differences in tolerance to nutrient deficiency conditions among rice cultivars. The sandy soils of Onattukara region is inherently deficient in K which resulted in a higher POP recommendation for rice in terms of K application. So to exploit the varietal differences of rice in deficiency tolerance of K, a field experiment was undertaken to screen 48 rice cultivars belonging to tall indicas and dwarf high yielding groups of varying growth durations. The experiment was laid in 384 microplots in "Group Balanced. Block in Split Plot Design" with four K levels and two replications. The various growth and yield attributes and yield were studied with a view to locate varieties which could produce similar yields even at lower levels of K. The results indicated that in general the varietal influences on most of the growth characters in all the four groups were profound. Moreover positive and significant effect of K doses were observed. However LAI showed no variation with differing levels of K. Differential response of varieties to varying K doses as manifested by root spread was considerable only in medium duration varieties while an appreciable difference was noticed in the root spread in all the groups. Root length, thin root-thick root ratio and root CEC appeared to be varietal characters which increased with increasing levels of K. The plant nitrogen content at varying levels of K was more of a varietal character. On the contrary, long duration varieties exhibited significant variation in P content with differing K levels at all critical stages of crop growth. Both K levels and genetic variability of the varieties were equally important in deciding the K content in plants and the response to added K was of a higher magnitude. All but long duration varieties responded positively and significantly to K in terms of productive tiller formation and generally tall indicas produced relatively longer panicles than dwarf varieties. Higher levels of K also led to the production of heavier grains. Yield increases over control was comparatively higher in tall short duration varieties than. any other varieties for higher levels of K. Differential response of K was highly pronounced in tall short duration varieties with Ptb23, Ptb29, Cul 7005-6-1, Cul 7004-3-1, and Cul 7006-2-1 giving comparable yields at 22.5 kg K20 ha-1 as that of the POP recommendation. However as this experiment was done in microplots the final recommendation of varieties tolerant to K deficiency could be done only after extensive studies in large plots and in farmers' fields during various seasons.
