Loading...
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.
Browse
5 results
Search Results
ThesisItem Open Access Nitrogen losses from the rice soils of Kerala with special reference to ammonia volatilization(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1989) Anila Kumar, K; KAU; Rajaram, K PIn order to get a deeper insight in to the N dynamics of selected submerged rice soils, an investigation entitled “Nitrogen losses from the rice soils of Kerala with special reference to ammonia volatilization” was carried at the Regional Agricultural Research Station, Pattambi during 1985 – 87 with the following objectives. 1. To estimate the magnitude of ammonia volatilization losses from submerged rice soils, representing major rice growing tracts of Kerala. 2. To study the factors which are responsible for accelerating the rate of ammonia volatilization under flooded soil conditions. 3. To evaluate the effect of submergence, organic matter application, complementary effect of P and K on ammonia volatilization from the rice soil ecosystem. 4. To identity suitable N carriers capable of reducing the loss of N due to ammonia volatilization from submerged paddy soils. 5. To find out the effect of continuous application of organic and inorganic manures in lateritic submerged paddy soils on the quantum of N loss through ammonia volatilization. 6. To find out the transformations and extent of mineralization of applied urea. With these objectives, in view, a serious of laboratory incubation studies, followed by pot culture trials were carried out and the results were finally verified under field experiment also. Besides these, the plots of permanent manorial trial (dwarf indica) were utilized for estimating the N loss through ammonia volatilization on long term application of organic manures and inorganic fertilizers. In the incubation study for estimating the magnitude of N loss though ammonia volatilization, eight rice soils of kerala viz., sandy, karapadam, kayal, kari, pokkali, kole, poonthalpadam and laterite soils representing the major rice growing tracts of Kerala were incubated with no N and 27 g N m-2 as urea. Air train and acid trapping device was utilized to collect the volatilized ammonia. The results showed that sandy soil collected from Onattukara region registered an increased N loss through ammonia volatilization, whereas in the kole soil of kattukampal, the process was retarded to the lowest level. More than 75 per cent of the volatilization loss was observed within 9 days after urea application. Significant negative correlation was observed between ammonia volatilization and organic matter content, clay fraction and cation exchange capacity of the soil, whereas the coarse sand fraction showed significant positive correlation. Soil sterilization had little influence on ammonia volatilization in any of the soil under study. Another incubation study to assess the impact of quantity of urea applied on the quantum of N loss through ammonia volatilization was carried out using four soil types (sandy, kayal, poonthlpadam and laterite soils) with four rates of N application (9, 18, 27 and 36 g N m-2 ). The results indicated that the N loss through ammonia volatilization had a positive relationship with increased rates of urea application, though not linear. The complementary effect of phosphorus and potassium on the extended loss of N through ammonia volatilization was estimated in another incubation study utilizing the same four soil types with treatment as N alone, N and P, N and K and N, P, K @ 27:13.5:13.5 g N, P, K m-2 respectively as urea, superphosphate and muriate of potash. The results revealed that combind application of urea and muriate of potash was found to be significantly better in reducing the volatilization loss to be significantly better in reducing the volatilization loss of ammonia compared to the treatments, N alone and N and P. The incubation study to find out the influence of depth of submergence on the rate of volatilization of ammonia was conducted using the same soil types and four treatments (soil saturation, 5,10 and 20 cm submergence). The results showed that the soil samples maintained at saturation point recorded double the values for ammonia volatilization, compared to samples kept under submergence of 20 cm depth. The effect of application of organic matter on N loss through ammonia volatilization was studied in the same four soil types with the treatments as no organic matter, 0.25, 0.50, 0.75 kg organic matter m-2 as farm yard manure. The results indicated that application of organic matter was found to reduce volatilization losses considerably in all the soils studied and the lowest value recorded was for the treatment receiving farm yard manure @ 0.75 kg m-2. The relationship between N sources and the extent of volatilization of ammonia was investigated in another incubation study employing the same four soil types and ten different N carriers to supply 27 g N m-2. The relative efficiency of different N carriers in reducing the ammonia volatilization loss was in the order sulphur coated urea > urea mudball > gypsum coated urea > rock phosphate coated urea = neem cake coated urea = ammonium sulphate = ammonium chloride > urea : coconut pith: soil = urea. The pot culture study to trace the pathway of transformation and extent of mineralisation of urea under flooded soil condition consisted of three soil types (laterite, kari and poonthalpadam soil) and two levels of N (no N and 90 kg N ha-1 as urea). The rate of mineralisation of applied urea followed the soil reaction and the mineralisation stopped at the stage of NH+4 formation and hence chances of N loss through denitrification is meagre, unless the soil is aerobic. The second pot culture experiment was conducted with a view to identify the different ways that result in minimum loss of N through ammonia volatilization in sandy and laterite soils. The study showed that the decreasing order of N loss through ammonia volatalization from different N carriers followed the order, urea basal = urea; coconut pith: soil = coaltar coated urea = gypsum coated urea = rock phosphate > coated urea > urea split > urea super granule > urea mudball > sulphur coated urea. The five treatments selected from this experiments viz., urea split, urea mudball, urea super granule, gypsum coated urea and rock phosphate coated urea on reduced ammonia volatilization and high grain yield were compared in another pot culture trial and finally it was verified under field experiments in trial and finally it was verified under field experiments in laterite soil. The results revealed that urea mudball placement in the anaerobic layer of soil was found to reduce the n loss through ammonia volatilization to negligible level. Treatments with surface application of rock phosphate coated urea and urea in split dose ranked second and third position respectively in reducing the volatilization losses. Treatment receiving split application (top dressing of urea at 20 and 40 DAT) reduced ammonia volatilization considerably. Significant positive correlation was found between the cumulative N loss through ammonia volatilization and flood water pH measured at 0800 hrs and 1400 hrs, flood water NH4 – N content and flood water bicarbonate content. The pH of flood water measured at 1400 hrs were significantly higher than the value recorded at 0800 hrs and highest diurnal variation was observed for treatment with urea super granule deep placement. The urea super granule deep placement treatment resulted in increased grain yield in both the pot culture trials and field experiment. However, in field experiment the effect of different N carriers on grain yield was found to be uniform. The periodical N uptake by plants as well as N accumulation in grain and straw at harvest were found to be higher in the case of treatments receiving USG deep placement and urea split application. The effect of long term application of organic and inorganic nitrogen sources in soil on the rate of n lose through ammonia volatilization was studied utilizing the permanent manorial experiments. Plots receiving combined application of cattle manure + green leaves + NPK @ 45:45:45 kg N, P2 o5, K2 o as ammonium sulphate, super phosphate and muriate of potash were recorded the lowest value of n loss via ammonia volatilization when compared to other treatment plots.ThesisItem Open Access Nutrient dynamics in the rice based cropping systems(Division of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Sundaresan Nair, C; KAU; Subramonia Aiyer, RThe experiment consisting of five cropping sequences viz. rice - rice – rice (A1), sweet potato – rice – rice (A2) cowpea – rice – rice (A3) daincha – rice – rice (A4) and fallow – rice – rice (A5) and six treatments with varying doses of N P and K were conducted to study the performance of the sequences in relation to the nutrients required for optimising the out put from the sequences. The field experiment was laid out at R.R.S., Pattambi in 1980 – 81 and the experiment was conducted for two consecutive years ie. For six seasons. The experiment was started with the summer crop of 1981, namely summer rice (Triveni), sweet potato, cowpea, daincha and a summer fallow wherein the land was ploughed twice and left as such without any crops. The component crops were raised with five treatment variations modified from the recommended doses for each crop. The biometric observations for the summer crops, virippu and mundakan crops were recorded. The indications were that treatments have a significant effect on summer crops virippu and mundakan rice crops of 1981 and 1982. The yield shows that both treatments and sequences have a significant effect. The sequence daincha – rice – rice and the cowpea – rice – rice sequence gave the highest yield. The chemical analyses of plant parts of the summer crops, virippu and mundakan rice crops of both 1981 and 1982 show that the treatments have no effect on the NPK content. The soil study shows that the cropping sequences have a significant effect on soil pH. A pH decrease was noticed in all the sequences, the highest decrease being in the rice – rice – rice sequence. The organic carbon level of the soil is also affected due to the cropping sequence. The rice – rice – rice sequence shows a maximum decrease in organic carbon level and the daincha – rice – rice – rice shows a gain in organic carbon level of the soil. The total nitrogen of the soil shows a decrease in all the sequences and maximum decrease was noticed in sweet potato – rice – rice sequence. The available nitrogen level also was influence both by the sequences and treatments. A decrease in available nitrogen was noted to be a maximum in the rice – rice – rice sequence. The total P and available P levels show an increase in all the sequences and were high in daincha – rice – rice and cowpea – rice – rice sequences. The treatments also have a significant effect in maintain the P level in soils. The total K status of the soil as well as the exchangeable status of K shows a decrease after two year of cropping. The nutrient uptake studies reveal that the maximum NPK uptake takes place in the sequences sweet potato – rice – rice followed by rice – rice – rice and cowpea- rice – rice – rice followed by rice – rice – rice and cowpea - rice – rice. The balance sheet of nutrients reveals that nitrogen and available phosphorus in all sequences show a decrease and increases with decrease in fertilizer levels. The balance sheet of K shows that the soil maintains K levels. The sequence daincha – rice – rice is the best in maintaining a high K status in the soil. An analysis of the economics of cropping sequences reveal that the sequence sweet potato – rice – rice with full recommended dose of fertilizers gave the highest net return, which was followed by Cowpea in – rice – rice and rice – rice – rice. From nutrient balance studies, yield and economic analysis it is clear that any attempt in reducing the quantity of fertilizer for the component crops of the sequences affects the yield, besides deleteriously affecting the fertility of the soils. Any decrease in the fertilizer doses in the sequences will not be economical. With a long range view of enhancing crop output from cropping sequences and maintaining soil fertility, it becomes necessary to enhance and maintain higher fertility levels.ThesisItem Open Access Potassium supplying capacity of Neyattinkara- Vellayani soil association and its relationship with potash nutrition of major crops on them(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1989) Valsaji, K; KAU; Subramonia Aiyer, RDetailed study on the potassium supplying capacity of Neyattinkara-Vellayani soil association and its relationship to potash nutrition of major crops on them namely coconut and cassava has been made. This soil association represents the red loam soil type and consists of Neyattinkara series tentatively classified under Typic Eutropepts and Vellayani series under Typic Tropudalfs. Soil samples were collected from selected fields under coconut and cassava for the dominant soil types namely sandy clay loam and sandy loam soils under Neyattinkara and Vellayani series. To find the most suitable depth and location of soil sampling for coconut samples were also drawn at two different depths of 0-30 and 30-60 cm from basins and interrows. Empirical methods, quantity intensity studies, electro ultrafiltration studies and foliar diagnostic techniques were employed to decide on the most suitable method for plant available K. The various intensity, quantity and capacity factors which relate the readily available, difficultly available and storage or buffer capacity were assessed for a proper appraisal of the K status and supplying capacity. The various soil K parameters such as total K, water soluble K, exchangeable K, available K, nonexchangeable K, HNO3 extractable K, H2SO4 extractable K, sodium tetraphenylboron extractable K and percentage K saturation were found to be low. The water soluable K formed higher proportion of available K than exchangeable K. Interrelations showed that water soluble K, exchangeable K and available K are in dynamic equilibrium. Nonexchangeable K did not show any relationship with available K indicating that it is a poor source of available K. Quantity-intensity studies showed that the shape of the Q/I curve was similar in all types of soil since they belong to a group of related soils. The Q/I parameters like Are.K, Ko, Kx. KL and potential buffering capacity values were low. The KL values were higher than NH4OAc.K. The free energy values were found to be high indicating easy release rates of K. For both coconut and cassava, the leaf K did not show any consistent relationship with the soil K parameters. Among the Q/I parameters, KL had significant relation with leaf K of coconut. EUF 10 and EUF 35 showed significant relationship with leaf K of both coconut and cassava. Electro-ultrafiltration studies showed that the easily desorbed K was more than the strongly desorbed K indicating easy supply rate. The EUF 30-35 values were related to HNO3.K showing that this fraction included some initially nonexchangeable K. EUF 10 had significant relation with exchangeable K and EUF 35 had significant relation with exchangeable and available K. The buffer parameters BK (EUF 10/EUF 30) and EUF.Q (EUF 30-35/EUF 30) values were low indicating low buffer capacity. The EUF desorption pattern showed that the first peak was within 10-20 minutes and prominent than the second peak. This indicated low reserve K but easy supply rates. The EUF desorption curve of soils with high NH4OAc.K was above that of soils with low NH4OAc.K. This indicated that with increase in NH4OAc.K the easily desorbed K also increased. The yield of coconut and cassava were related to the various K parameters to evaluate the suitability of different methods for available K. In most of the cases NH4OAc method was found to be suitable for both coconut and cassava. Leaf analysis was also found to be suitable. For cassava the result obtained after 41/2 months is meaningless for the current crop. For coconut collection of index leaf is laborious. It was also found that the Q/I and EUF were suitable for coconut. But these methods cannot be followed in routine soil testing because of the high input of laboratory work involved. Considering these aspects it was found that NH4OAc method is the most suitable one because it is simple, cheap and easy to adopt. Based on the NH4Ac.k content the fertility status was found to be low to medium. The various intensity, quantity and capacity factors of soil K, Q/I and EUF parameters revealed that this soil association has low K supplying capacity. Hence heavy dose of K fertilizers is required. Split application is preferable especially in sandy loam soils to reduce leaching losses. NH4OAc.K which was found as a suitable indicator of plant available K varied significantly in basin and inter-row samples of sandy clay loam soils. This K fraction did not vary with depth in both sites. In general, the K nutrient index indicated that the basin samples had a higher level than inter-row and surface samples. Thus basin sampling at 0-30 cm depth was found to be the ideal site of soil sampling for coconut tree.ThesisItem Open Access Studies on the Solubilisation of iron in submerged soils and methods to minimise its solubility and toxic concentration to paddy(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1989) Ramasubramonian, P R; KAU; Koshy, M MA study has been made of the extent of solubilisation of iron in the submerged acid rice soils of Kerala State where iron toxicity is likely to be a serious field problem during rice cultivation. The kayal, kari and karapadom soils of Kuttanad, brown hydromorphic soils of the midland lateric zone and the sandy soils of Onattukara were included in the study. Chemical characterisation of the soils and soil profiles in relation to forms of iron were investigated with a view to obtain a better understanding of the dynamic aspects of iron in these soils. The nature, and extent of periodical variations in soluble iron as influenced by levels of sea water, organic matter (farm yard manure) and ammonium sulphate added to kayal, kari, karapadom and brown hydromorphic soils under submerged conditions were also studied along with the influence of levels of applied lime on the amelioration of iron toxicity. Among the Kuttanad soils, kari soil was most acidic with a mean pH of 3.77, high organic carbon content and CEC compared to others. The water soluble iron ranged from 79 – 165 ppm in the Kuttanad soils. This form of iron and pH were negatively correlated. Electrical conductivity and water soluble iron were significantly and positively correlated. The exchangeable iron varied between 144 – 310 ppm and was positively correlated with CEC. Active iron ranged between 1460 and 5200 ppm. Active iron had a significant positive correlation with organic carbon and electrical conductivity. Kuttanad soils contained high contents of water soluble and exchangeable iron, together known to contribute towards the development of iron toxicity to transplanted rice in these soils. High contents of water soluble, exchangeable and active iron were noticed in the profiles of Kuttanad soils as well. Compared to these, the brown hydromorphic and sandy (Onattukara) soils had much lower contents of soluble iron. Total iron content decreased with depth in most of the profiles while water soluble, exchangeable and active iron, increased with depth studied upto 100cm. In brown hydromorphic soil the water soluble and exchangeable iron were found to decrease with depth. Incubation studies under laboratory conditions indicated that submergence of soils resulted in an increase in the soluble iron with time, reached a peak value on the 10th day in kari soil and 25th day in the other soils, after which the soluble Fe2+ decreased to lower values. Sea water submergence resulted in enhanced releases of Fe2+ with time to reach peak value around the 25th day followed by decrease. Kayal soil alone, however, needed 40 days for peak release of Fe2+. The release of Fe2+ was influenced by the dilution of sea water used. Kayal, kari and karapadom soils released significantly higher amounts of Fe2+ compared to brown hydromorphic soils. However, at the lowest level of 25 per cent sea water all soils behaved similarly. Presence of organic matter under the submerged conditions enhanced the Fe2+ release considerably depending on the content of organic matter in the soil. Kari soil on the 25th day and kayal soil on the 40th day of submergence released significantly higher amounts of Fe2+. Addition of ammonium sulphate to soils under submerged conditions resulted in increased releases of Fe2+ in the soil solution with time. Peak releases of Fe2+ were noticed on the 25th day in all the soils. Maximum release by kari soil was influenced by ammonium sulphate applied at 100 kg N/ha, in the karapadom and brown hydromorphic soils by 200 kg N/ha. The beneficial effect of lime on the suppression of iron release was clearly evident in the soils though to varying extents. In kayal soil 600 kg lime/ha suppressed iron release upto 10 days and 1000 kg/ha could suppress more soluble iron for 25 days. However, after the 40th day, soluble iron exceeded that of the control. In kari soil the iron suppressing effect of both the levels of lime was evident only up to the 10th day after which the release of soluble iron exceeded that of the control. In karapadom and brown hydromorphic soils, lime at 600 kg/ha was helpful in suppressing the release of Fe2+ till the 40th day. Lime at 1000 kg/ha, however, could suppress more of the soluble Fe2+ throughout the period of submergence. In kayal and kari soils, levels of lime upto 1000 kg/ha appear to be inadequate in controlling iron toxicity. Flooding the field for 25 days and leaching out the released Fe2+ just before planting of rice is suggested as an alternate solution to minimise iron toxicity to rice in Kuttanad soils.ThesisItem Open Access Studies on macro meso and micromorphology and clay mineralogy of the acid sulphate soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Subramonia Iyer, M; KAU; Subramonia Aiyer, RThe acid sulphate soils of kerala cover an area of approximately 0.2 million hectares on the West coast of Kerala. A well integrated study on the genesis, morphology, mineralogy and certain physic – chemical properties of these soils was conducted. Aspects of its genesis, position in the global system of classification, macro, meso and micro morphology, mineralogy, both macro and micro as well as primary and secondary, physical and physic-chemical properties relevant to classification and management have received attention. The salient points of the study are highlighted emphasising conclusions pertinent to the expanding frontiers of our knowledge on these soils. The acid sulphate soils occurring along the West coast of Kerala based on morphological observations as well as stage by stage microscopical study are indicated to have been formed by sedimentation of finer material overlying and often impregnating wood fossils, faunal and floral relics in the recent geological past. The extent of alluviation, stage of degradation of the fossilised wood and incorporation of sediments and formation of secondary products vary from location to location as indicated in the study. In almost all the acid sulphate soils around the globe, pyrite is the major mineral component contributing to acidity. They have framboidal micro structure with size ranging from 15 – 50 u, However, in the acid sulphate soils of Kerala pyrrohtite (Fes) is the predominant sulphate mineral with a size range <2 µ along with small amounts of pyrite (Fes2) which also are < 2µ. These minerals have been formed in the recent geological past, under the anaerobic environment releasing ferrous iron from the alleviated soil materials especially laterite falls and the sulphur from the sulphates added by the ingress of sea water, fossilised wood and decaying organic matter. The pyrite (FeS2) and pyrrohtite (Fes) undergo oxidation especially when the aeration is encouraged by tidal influences, and acidity conditions. As has been demonstrated in the present study they are oxidised initially to ferric hydroxides and then to jarosites. The end product of oxidation of pyrite, however, varies from situation to situation in Kerala. Thus it may be jarosites as encountered in the surface soils of all the locations while the oxidation may be only to the stage of ferric hydroxide as observed in the fourth horizon of Mathikayal and Kattampally where the pyrite occurs overlying a bed of lime shells. The ripeness of the acid sulphate soils generally are decided by the extent of acidity generated on oxidation with H2O2and also the ‘n’ value of the soil which is related to the pH as well as the organic matter and clay content. On this basis all the acid sulphate soils of Kerala vary from half ripe to fully ripe. The ripe soils have been encountered only at Kattukambal in the kole area. Another factor, is the depth of occurrence of the jarosite mottle laden layer. In the acid sulphate soils of the present study, the jarosites have been located, within 50 cm. Below 50 cm pyrite and pyrrohtite are the dominant sulphur containing minerals. Among the oxidation products, the mineral lepidocrocite (Fe – O – OH) a variant of goethite has been found to be associated with pyrrohtite espeacially at the Karumadi location. The occurrence of lepidocrocite in acid sulphate soils has not been reported earlier. It is possible that it is the intermediate stage in the oxidation of pyrrohtite to jarosite. The lower layers of the acid sulphate soils have lime shells in some locations such as Mathikayal, other Kayal areas of Kuttanad and some of the pokkali and kaippad soils. The pyrites are found to be closely overlying the lime shells without suffering major alterations to either of them. Thus the pyrite frambodies have been transformed partly in a few of its microcrystals to the oxidised form of ferric hydroxides, but the acidity of the embedding soils has neither dissolved nor reacted with the lime shells. X – ray diffraction, thermogravimetric as well as chemical studies conducted with the clay indicate kaolinite as the dominant minerals in these soils. Minor quantities of mineral viz., smectite, chlorite and illite have been detected. Mica and quartz have been found in quantities equal to that of Kaolinite. It is possible that like laterite falls, fine quartz also is alleviated into these soils from the midland regions of Kerala. Soils which attain pH of 2.5 by oxidation with 100 per cent H2O2 have been considered to be dangerously acid sulphate soils. The soils in the present study attain pH values less than 2.5 even with 30 per cent H2O2. Though the upper layers are half to fully ripe. They are still found to be dangerously acid. The lower layers with more of reserve pyrites are much more dangerously acid. These observations on the acid sulphate soils are a pointer to the cropping patterns and water management to be pursued in these areas in the foreseeable future. Thus the rice crop in a waterlogged situation is possibly the only crop that may throw up lesser problems in soil management. The dangerous nature of the potential acidity especially in the lower layers have to be considered in ruling out all propositions of tree crop alternatives such as rubber and oil palm. From the present studies it has been found that these soils have only a sulphidic enrichment within 50 cm from the surface, instead of a sulphuric horizon. Further the sulphur content is also not significient enough to include them in the category of soils with sulphuric horizon. Soils with sulphuric horizon only are considered to attain a pH of 4 by airdrying and 2.5 by H2O2 treatment. The soils in the present study despite an enrichment, only with sulphidic materials attain a pH of 2.5 to 3.0 by mere airdrying and pH was low as 2.0 by H2O2 oxidation. Thus the lack of a sulphuric horizon but in its place a mere sulphidic enrichment makes them almost dangerously acid. Evidently this has to be attributed to the pyrrohtitic (Fes) nature And the smaller size (< 2µ) of the framboid conferring it to be placed as a class separate from typical acid sulphate soils reported from the rest of the world. Thus these soils from the present study are found to be more dangerously acid sulphate than others though they do not satisfy the requirement of either the total sulphur content or the presence of a typical sulphuric horizon. Further the pyrite framboids have a size range of only 1/25th of that of the framboids reported elsewhere from the globe. This has made them more dangerously acid. All the same, they require to be placed as soils with sulphidic materials rather than the soils with sulphuric horizon as per soil Taxonomy. (USDA, 1975). Nevertheless, the fact remains that these soils are highly acidic with considerable amounts of reserve pyrites and hance reserve acidity. These soils call for utmost care in their management. The acid sulphate soils of Kerala are thus to be continuously managed under a waterlogged milieu to enable optimum productivity with minimum problems due to acidity and related aspects. The possibility of growing perennial crops such as rubber and oil palm require partial to fully aerobic situations. These conditions are likely to result in oxidation of the pyrite laden layer noticed up to 90 cm in the present study. This can generate an enormous quantity of free sulphuric acid. The pyrite laden layer extends up to 90 cm in the present study. The acid sulphate soils of kerala are definitely different from Malaysian acid sulphate soils in that the surface layer is not completely free of pyrites. In view of the fact that the surface soil contains only jarosite and no pyrites, the Malayasian peats and acid sulphate soils have been subjected to cultivation with oil palm and rubber. However the Malaysian experience cannot be transplanted as such to Kerala inview of the very serious initial problems likely to be thrown off by the generation of acidity by the oxidation of pyrites under aerobic situations. Being half to full ripe, acid sulphate soils of Kerala are still dangerously acid to warrant the continuation of the existing management practices and cropping systems.
