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Open Access
Comparative micromorphologial and physico- chemical study of the upland and midupland laterite soils of Kerala
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1986) Sankarankutty Nair, R; KAU; Aiyer, R S
Open Access
Exchangeable aluminium as an index of liming for the acidic upland soils of Kerala
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1987) Meena, K; KAU; Alice, Abraham
Aluminium toxicity is the major factor limiting crop production in the acidic soils and the usual practice of alleviating aluminium toxicity is liming* / The present investigation was carried out to find out the distribution of water s dluhle and exchangeable aluminium in the acidic upland soils of Kerala and to test the suitability of exchangeable aluminium as an index for liming them* It was further programmed to find out the growth, yield and nutrient uptake pattern of two acid sensitive crops namely cowpea and fodder maize in soils under different levels of exchangeable aluminium brought out by the use of different levels of lime* Chemical analysis of eighty soil samples representing the five major upland soil types of Kerala viz* laterlte, alluvial, red loam, sandy and forest a oil have indicated the highest amount of exchangeable aluminium and percentage aluminium saturation in the laterite soils* The soil with 3 high level of exchangeable aluminium and percentage aluminium saturation was selected for conducting a pot culture experiment to test the suitability of using exchangeable aluminium as an index of liming* The exchangeable aluminium content of this soil was maintained at different levels by applying different levels of lime and the performance of these crops in this soil was compared by making biometric observations and by chemically analysing plant and soil samples* From the results of the study it was seen that higher levels of exchangeable aluminium adversely affected the growth, yield and nutrient uptake In cowpea and fodder maize* Maintenance of exchangeable aluminium at 1*26 me/100 g with a corresponding percentage aluminium saturation valua of around 30, by the use of 500 kg lime/ha appeared to be the optimum for maximising the yield of cowpea* But in fodder maize this level of lime was found to be insufficient and complete elimination of aluminium toxicity appeared to be essential for maximising production* Since the critical levels of exchangeable aiuainiua appears to be different for different crop3, it is desirable that lias levels to reduce exchangeable aluminium to such a critical level alono be applied. The results of the present study thus point to the advantage in adopting the exchangeable aluminium level of soil as a better index of liming for various crops grown in the upland acidic soils of Kerala.
Open Access
Effect of submergence on the soil testing parameters of paddy soils
(Department of soil Science and Agricultural Chemistry, College of Agriculture, Vellayani., 1986) Usha, Mathew; Alice, Abraham
Open Access
Potassium utilization in cassava (Manihot utilissina pohl) as influenced by neem cake - urea blend
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1985) Manorama Thampatti, K C; KAU; Padmaja, P
Potassium utilization in cassava (manihot utilissima pohl.) as influenced by neem cake – urea blend. An investigation was carried out at the College of Horticulture, Vellanikkara, during the year 1983-84, which include a soil column study to understand the dynamics of NH4+- N and K+ ions when applied as urea or urea-neem cake blend either alone or along with muriate of potash. The columns were filled with soil collected from the field surface upto 60 cm depth. Each 15 cm was taken as a separate layer maintaining the same bulk density as observed in the field. Fertilizer treatments comprising, no fertilizer, urea or urea-neem cake blend to supply 100 ppm N and muriate of potash to supply 100 ppm K either alone or in combination were applied to the surface 15 cm soil and mixed thoroughly. The study indicated that under natural conditions NH4+ - N was concentrated more in the lower layers of soil beyond the root zone of cassava whereas potassium was concentrated more in the surface layers of 0-30 cm depth. Application of muriate of potash either alone or in combination with urea-neem cake blend increased potassium in the surface layer within eight hours after fertilizer application. When untreated urea granules were applied along with potassic fertilizer, a major part NH4+ - N was found either concentrated in lower layers, or nitrified and lost. But when urea-neem cake blend was applied along with potassic fertilizer a major part of nitrogen was retained as NH4+ - N in the surface layers upto two weeks and later it moved downwards. There was a drastic reduction of NH4+ - N status in the surface layers upto 45 cm after one week in untreated urea, whereas urea-neem cake blend maintained much of NH4+ - N in the surface 30 cm upto three weeks. Application of muriate of potash maintained highest potassium status followed by urea-neem cake blend along with muriate of potash. The maximum leaching loss of potassium was observed from untreated urea when applied along with muriate of potash. The loss was reduced considerably when potassic fertilizer was applied along with urea-neem cake blend. A field experiment was conducted as a continuation of the study carried out at the College of Agriculture, Vellayani, when urea-neem cake blend at 5:3 ratio increased nitrogen availability, nitrogen uptake and yield. But it had an adverse effect on potassium utilization of the crop resulting in poor quality tubers and the yield increase observed was not significant. The present experiment was planned to tide over this difficulty either by changing the time of application or increasing the rate of potassic fertilizer. Results of the experiment clearly showed that urea-neem cake blend increased nitrogen use efficiency of cassava as evident in higher soil available nitrogen and higher nitrogen uptake by the crop. When muriate of potash was applied one month after application of urea-neem cake blend, the uptake of potassium was not reduced considerably in the initial stages and at the same time uptake was comparatively higher at the sixth month and harvest stages. Potassium at 75 kg K2O ha-1 increased uptake of all nutrients and also produced maximum tuber yield of 21.39 tonnes ha-1, whereas application of potassium one month after application of urea-neem cake blend recorded 19.76 tonnes ha-1 of tuber yield which was on par with the former treatment. Potassium uptake at all major growth stages were significantly correlated with plant dry weight and tuber yield. Maximum benefit per rupee invested was obtained when the rate of potassium was raised from 50 kg K2O ha-1 to 75 kg K2O ha-1 along with 50 kg N as urea-neem cake blend. Changing the time of application of potassic fertilizers to one month and three months after planting also increased the benefit obtained. Both three treatments were on par with each other and significantly superior to others.
Open Access
Characterization of Kerala soils into fertility classes with respect to available P and K extracted by a common extractant
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1988) Kamalam, P V; KAU; Jose, A I
A laboratory study was undertaken to evaluate the suitability of Mathew’s triacid extractant (0.06 N H2SO4 + 0.06 N HCI + 0.05 N oxalic acid) for the combined extraction of available P and available K in soil. The suitability of this triacid extractant was confirmed on a large number of soil samples. Precise relationships between triacid K and NH4OAc K were established. The ten fertility classes for available P and K currently followed in the soil testing laboratories are based on Bray-1 P and NH4OAc K. By making use of suitable regression equations the class intervals in terms of triacid P and triacid K values have to be formulated for the purpose of fertilizer recommendation. The use of this extractant can simplify the work in soil testing procedures thus enabling considerable savings of time and labour. A large number of soil samples was collected representing the entire state of Kerala. The available phosphorus of soil was extracted by Bray No.1 solution (1:10 soil solution ratio with an equilibration period of 5 min) and by Mathew’s triacid extractant (1:10 soil solution ratio with an equilibration period of 30 min). Phosphorus in the extract was then determined colorimetrically by the chlorostannous reduced molybdophosphoric blue colour method in HCI system. The available potassium of the soil was determined by neutral N NH4OAc with a soil solution ratio of 1:5 and an equilibration period of 5 min as well as by the triacid acid method. Potassium in the extract was determined flame photometrically. Soils were also analysed for organic carbon, pH and EC. Suitable correlation was worked out between Bray-1 P and triacid P. A linear regression equation was fitted to predict triacid P values from Bray-1 P values. Suitable relationship was also established between NH4OAc K and triacid K. The linear regression model worked out between NH4OAc K and triacid K was used to predict triacid K values from NH4OAc K. Most of the soils were acidic and non-saline. The pH showed a negative correlation with Ec and organic carbon content of soil. Soils varied in the content of organic carbon from 0.04 per cent to 4.41 per cent but in general was rich with a mean organic carbon content of 1.14 per cent. Electrical conductivity was positively correlated with organic carbon content of soil. A positive correlation was observed between organic carbon and available K. Mineralisation of organic matter contributed significantly to the increasing acidity of soil. The available P estimated by Bray-1 was found to range from 0.46 to 370.30 ppm whereas triacid P ranged from 1.73 to 462.50 ppm. The triacid extracted larger amounts of available P than the Bray-1. A significant correlation was observed between triacid P and Bray-1 P (r = 0.9575**). By fitting the regression equation y = 1.15x, where y represented triacid P and x represented Bray-1 P, the triacid P values of the ten fertility classes have been worked out. The available K as estimated by neutral N NH4OAc ranged from 10.0 to 425.0 ppm whereas triacid K ranged from 4.0 to 154.0 ppm. Triacid extracted lower amounts of available K (42.38 ppm) than the neutral N NH4OAc K (105.23 ppm). Although triacid showed less efficiency for releasing K from soil it was found to have high correlation with neutral N NH4OAc (r = 0.9235**). The linear regression equation of the form y = 0.44x was worked out where y represented triacid K and x represented NH4OAc K. This was employed to redefine the ten fertility classes in terms of triacid K values. The increase in precision obtained by the relationship between P estimated by Bray 1 and triacid as well as K estimated by neutral N NH4OAc and triacid by grouping the soils into separate textural classes was only marginal. The present study therefore confirmed the suitability of the triacid for estimation of both available P and K in the soil of Kerala. The revised class intervals for the ten fertility classes followed in the soil testing laboratories of Kerala have been formulated in terms of triacid P and triacid K values which will serve as a guide for giving fertilizer recommendations for various crops.
Open Access
Foliar diagnosis, yield and quality of pepper (Piper nigrum L.) in relation to nitrogen, phosphorus and potassium
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1982) Sushama, P K; KAU; Jose, A I
Pepper vines of variety, Panniyoor-1, of the NPK fertilizer trial maintained at the Pepper Research Station, Panniyoor, Canncanore District were selected for the collection of tissue samples under the present study during 1979-81. The experiment was laid out in a 33 factorial design in a randomized block design, confounding the effect of NP2K2 totally. In order to standardize the best leaf position for foliar diagnosis, the mature leaves of fruit bearing laterals were numbered from the youngest to the oldest, taking the youngest fully matured leaf as the first and they were collected separately. The most suitable season for the collection of leaf intended for foliar diagnosis was also standardized by drawing samples of first mature leaf at different stages of growth of the vine. The suitability of different types of stem of the plant such a runner shoot, top shoot, fruit bearing lateral and hanging shoot for tissue analysis was also examined. For studying the variations in the oleoresin content of berry as influenced by fertilizer nutrients, the berries were sampled at different stages of maturity. The first mature leaf better reflected variation in the levels of application of nitrogen to the vine. As the phosphorus and potassium contents of the first mature leaf established significant positive correlation with yield of pepper, it is recommended as an index for foliar diagnosis in pepper in relation to nitrogen, phosphorus and potassium status of the vine. The period just prior to flushing is the most suitable season for the collection of leaf samples intended for foliar diagnosis. During this period, the first mature leaf is sensitive to application for different levels of nitrogen and its potassium content established significant positive correlation with yield. For assessing the phosphorus status of the vine, the runner shoot appeared to be a better tissue as its phosphorus content established a high degree of correlation with yield. As compared to other types of stem, the highest content of potassium was found in the fruit bearing laterals. The periods of maturity significantly influenced the phosphorus, potassium and oleoresin contents of the berry. Their contents increased from four to six months after flowering and then decreased. The graded doses of nitrogen, phosphorus and potassium and their interaction failed to influence the percentage of oleoresin content of pepper.
Open Access
Evaluation of available phosphorus and potassium in soil using a common extractant
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1986) Durga Devi, K M; KAU; Jose, A I
A laboratory evaluation and an uptake study using Neubauer seedling technique was carried out for evolving a single extractment suitable for extracting both available P and available K, so as to simplify the process of extracting these available plant nutrients in soil testing works. Eighty seven soil samples from different parts of the State were used to evaluate the performance of the selected number of extractants based on a 3 step evaluation i.e., (i) an initial study consisting one soil, 18 extractants at a single soil solution ratio (1:10) and two equilibration periods (30 and 60 min); (ii) a preliminary screening consisting of 9 soils, 15 extractants at a single soil solution ratio (1:10) and 5 equilibration periods (5, 10, 15, 30 and 60 min). An uptake study was also conducted using Neubauer seedling technique and correlation coefficients were worked out between the amount of P extracted by the various extractants and the P and K uptake by rice; (iii) a final selection of the common extractant consisting of 10 extractants with suitable equilibration periods, at 1:10 soil solution ratio and 87 soils. In combination of NH4 F and DTPA, increasing concentration of NH4 F retarded the extraction of both P and K and they extracted much smaller quantities of P and K as compared to that of Bray No.1 and neutral normal NH4 OAC. Use of ammonium acetate along with Bray No.1 inhibited the release of P drastically. Mathew’s triacid extractant viz., 0.06 N H2 SO4 + 0.06 N HCL + 0.05 N oxalic acid extracted relatively large amounts of P and K. The pattern of P and K release when examined together as a function of period of equilibration found that the equilibration period for different extractants was varying. The suitable equilibration period for 0.1 M NH4F + 0.001 M DTPA, 0.1 M NH4F + 0.003 M DTPA, 0.5 M NH4F + 0.005 M DTPA, 0.05 M NH4F + 0.05 M acetic acid, and Dray No. 1 is 5 min. for 0.3 M NH4F + 0.001 M DTPA combination and Bray No.1 + 0.005 M DTPA an equilibration period of 10 min is found to be the optimum. An equilibration period of 30 min is suitable for Mathew’s triaced extractant, Olsen’s extractant and neutral normal ammonium acetate. Since the initial and preliminary studies established the suitability of Bray No.1 for available P and the neutral normal ammonium acetate for available K and because the coefficient of correlation between the amount of K extracted by the extractants and the K uptake by rice were highly significant at all the equilibration periods the final selection of the common extractant was based on the correlation of the P and K values of the selected extractants with that of Bray No. 1 P and neutral normal ammonium acetate extractable K. The correlation coefficients with Bray No.1 P established by the various extractants have shown the following decreasing order of efficiency. 0.5 M NH4F + 0.005 M DTPA > 0.05 M NH4F + 0.05 M acetic acid > NH4OAC > Olsen > Mathew’s triacid > Bry No.1 + 0.005 M DTPA > 0.3 M NH4F + 0.001 M DTPA > 0.1 M NH4F + 0.001 M DTPA > 0.1 M nH4F + 0.003 M DTPA. All the extractants were not significantly and positively correlated with NH4 OAC (std) K. The three extractants viz., Mathew’s triacid, 0.1 M NH4F + 0.001 M DTPA and Olsen’s extractant have given significant positive relationship with NH4 OAC (std) K. Highest correlation was obtained with Mathew’s triacid followed by 0.1 M NH4F + 0.001 M DTPA and Olsen’s extractant. Thus it is confirmed that Mathew’s triacid extractant is the best common extractant for available P and available K. No analytical difficulty in the determination both P and K was observed while using this extractant. Inter-correlations worked out between the various soil properties have cleared the following facts. Mathew’s triacid P and Bray No.1 P were significantly and positively correlated with total P and negatively correlated with P fixing capacity. NH4 OAC (std) K and Mathew’s triacid K gave significant positive correlation with total K as well as CEC. Mathew’s triacid extractant viz., 0.06 N H2SO4 + 0.06 N HCL + 0.05 N oxalic acid with a soil solution ratio of 1:10 and an equilibration period of 30 min is recommended as a commom extractant for available P and available K by the present study, since it saves considerable time and materials in soil testing.
Open Access
Suitability of rockphosphate for direct application in acid rice soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1985) Regi, P Mathews; KAU; Jose, A I
An incubation study and a potculture experiment were conducted to assess the suitability of Rajastan rockphosphate (RRP) supplied from Rajastan State Mineral Development Corporation, in comparison with that of Mussooria rockphosphate (MRP) supplied from pyrites phosphate and chemicals Ltd. (U. P) and superphosphate (SP) in two acid rice soils of Kerala namely laterite (Kodakara, Trichur district) and kari (karumadi, Alleppey district) soils. Transformations of P fertilizers applied at the rate of 45 and 90 kg P2O5/ha in these soils under continuous submergence were studied in the incubation experiment. Soil samples were drawn at 15 days interval for the determination of various inorganic P fractions and available P. The direct and residual effects of the two rockphosphates in comparison with the water soluble SP were studied in the potculture experiment using rice (Jaya) as the test crop. The soils and levels of P applications were the same as in the incubation study. Application of N and K was done uniformly in all the treatments. Soil and plant samples were drawn at 15 days interval for the determination of available P and the uptake of major nutrients. The residual effect of phosphatic fertilizers was assed by continuing the experiment for the second season with out the addition of P fertilizers. However, for the second season a treatment receiving P at the rate of 45 kg P2O5/ha as SP in both the season was incorporated for comparison in both the soils. Application of phosphatic fertilizers irrespective of their water solubility increased the various inorganic fractions and available P content of the soil. The total native inorganic P increased in the presence of added P due to the enhanced mineralization of organic P. Among the various inorganic fractions, Fe-P was the dominant form accounting for 41 to 44 per cent of the total inorganic P. Second most abundant fraction was A1-P. The contents of reductant soluble-P, occluded-P and Ca-P were relatively less and that of saloid-P was negligible. The three sources of P did not differ significantly in increasing the various inorganic fractions of the soil except that of saloid-P. The contents of A1-P, Fe-P, reductant soluble-P and occluded-P were more in laterite soil compared to kari soil, while saloid-P and Ca-P were high in kari soil. Prediction equations were worked out to establish various inorganic P fractions and available-P at different periods of incubation. The peak values of saloid-P were observed during the seventh fortnight. Saloid-P was found to be positively correlated with Fe-P (r = 0.77*2*), AI-P (r = 0.73*1*) and Ca-P (r = 0.27*8*) and negatively correlated with reductant soluble-P (r = -0.249*) and occluded-P (r = -0.31*9*). Concentrations of AI-P and Fe-P were maximum during the twelfth period of sampling and they were negatively correlated with reductant soluble-P occluded-P. Highest values of reductant soluble-P and occluded-P were observed during the first period of incubation and the concentration of Ca-P was minimum in the twelfth fortnight. Forms and levels of applied P had little effect on increasing the available P content of the soil. The contribution of various inorganic fractions to available P was different. Direct and indirect effects of various inorganic P fractions on available P from RRP, MRP and SP were brought out by the path analysis. Saloid-P, Fe-P, AI-P and Ca-P were positively correlated with available P (Bray 1 and 2) and reductant soluble-P and occluded-P were negatively correlated. The extent of contribution of various inorganic fractions to available P was the same in all the three sources of P added to the soil. Application of SP at the rate of 90 kg P2O5/ha twice in two equal doses during the first and ninety-first day of incubation did not increase conspicuously the inorganic fractions and available P content of the soil compared to the initial application of the same quantity of P as SP and rockphosphate. In the potculture experiment in general, application of P fertilizers had resulted in a better utilization of major nutrients by the rice plant and this effect was more pronounced in kari soil during the first crop season. However, in the second crop season, the effect of P fertilizers on uptake of nutrients was pronounced in both the soils. During the first crop season, in the absence of added P, the uptake of nutrients and yield of straw and grain were more in laterite soil compared to kari soil while in the presence of added P, uptake of nutrients and yield were higher in kari soil. However, in the second crop season, both in the presence and absence of added P, the uptake of nutrients and yield were more in laterite soil. Uptake of N and K by the straw during the first crop season was significantly higher in treatments receiving SP compared to other treatments receiving rockphosphates though the uptake of P by the straw did not vary significantly with the variations in the source of P. However, in the second crop season, uptake of N, P and K by the straw was significantly higher in treatments receiving SP. Increasing the level of application of P from 45 to 90 kg P2O5/ha increased the uptake of N and K significantly while uptake of P by the straw and straw yield did not increase significantly with increasing the level of application. But in the second crop season, the uptake of N, P and K by the straw and straw yield increased markedly with increasing the level of application. Uptake of N and P by the grain of the first crop did not increase significantly over control in laterite soil, while that of K showed significant increase over control in both the soils. However, in the second crop, uptake of N, P and K by the grain increased conspicuously in both these soils. In the first crop season, total uptake of K was significantly higher over control in both the soils, while that of N and P was higher only in kari soil. But the total uptake of N, P and K increased over control in both the soils in the second crop season. In general, application of SP was found to be superior to the application of rockphosphates with respect of the uptake of N, P and K grain and their total uptake by rice plant in both the seasons of crop growth. The yield of grain by the application of phosphatic fertilizers showed significant increase over control only in kari soil during the first crop season. In the second crop season, both the soils were found to be responsive to the application of P fertilizers with respect to the increase in the yield of grain. In the treatments receiving rockphosphates as a source of P, the yield of grain was 93.18 and 92.67 per cent of that obtained in treatments receiving SP during the first crop and second crop seasons respectively. In both the seasons of crop growth, available P in the soil was significantly higher in treatments receiving SP than that in treatments receiving rockphosphates. Increasing the level of application of P from 45 to 90 kg P2O5/ha increased the available P content of the soil to the extent of 11.97 and 17.43 per cent over the lower level during the first and second crop seasons respectively. Application of SP at the rate of 90 kg P2O5/ha applied twice in two equal doses separately for the first crop and second crop seasons increased the uptake of nutrients, yield of grain and straw and available P content of the soil compared to the application of the same total quantity of P initially for the first crop only as SP and rockphosphate.
Open Access
Characterisation of laterite soils from different parent materials in Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1987) Stella Jacob; KAU; Venugopal, V K
In the present investigation, an attempt has been made to evaluate the morphological, physical, chemical and mineralogical characteristics of laterite soils occurring in different regions of Kerala in relation to the parent rock. Six soil series representing laterite soils identified by the Soil Survey Unit of Department of Agriculture, Kerala State were selected for the investigation. The soil series identified were Thonnackal, Kootala, Anjur, Kanjikulam, Mannur and Nenmanda located in Trivandrum, Trichur, Palghat and Calicut districts. Soil samples representing the different horizons were collected for laboratory studies. The physico-chemical characteristics of the soils, behaviour of iron and phosphorus fractions of samples were investigated with a view to study the interrelationship between various properties and to relate these characteristics to the genesis of the soils. Mineralogy of the fine sand fraction was also carried out. Placement of these soils under soil taxonomy was also attempted based on the available data. The salient findings are summarized below. The soils from different locations had striking similarity in colour with reed hues predominating. Coarse fragments formed a predominant portion of the soil and was mainly concentrated in the subsurface horizons. Most of the elements were found to be concentrated to the gravel as compared to the soil. Sand formed the predominant size fraction but the textual class of the soils was mostly clay. Increasing clay content with depth was a characteristic feature. The slit/clay ratios were very low indicating the highly weathered nature of the soils. The available water capacity was poor and the variations observed closely followed the distribution of clay. Kootala series had the highest available water capacity while Thonnackal recorded the lowest. The soils were in general acidic with very low electrical conductivity. The content of C, N and C/N ratios were very low. Silica formed the predominant fraction followed by Fe2O3 and AI2O3. The total reserves of CaO, MgO, K2O, P2O5 were very low and is a reflection of the mineralogy of the fine sand fraction which was dominated by quartz. The cation exchange capacities of the soils were very low. The CEC5 recorded still lower values as compared to NH4OAc method. The exchangeable bases were in the order Ca> Mg>K>Na in the case of Anjur, Mannur and Nenmanda series while in Thonnackal, Kootala and Kanjikulam series. Exchangeable Na was slightly higher than K. Among the acid generating ions extractable aluminium was very low. The percentage base saturation was low and did not show appreciable variation between soil series. The Fed formed the predominant iron fraction and based on the degree of freeness of iron in soils, Kanjikulam series was the oldest followed by Anjur, Kootala, Mannur, Nenmanda and Thonnackal. The active iron ratio (Feo/ Fed) recorded very low values for all the soils. Among the inorganic P fraction Fe-P was dominant in all the soils except Thonnackal series. Nenmanda series had the lowest content of Ca-P. All the soils were highly weathered based on the behaviour of P fraction. Silica was the dominant fraction of clay. Based on Sio2/Ai2o3 ratio, Thonnackal and Nenmanda were designated as ferralitic or true laterites. The Sio2/R2o3 ratio was the lowest among the molar ratios. The rocks were siliceous in nature with poor content of bases. The fine sand fraction of the soil also revealed a predominance of quartz and very little weatherable minerals. The heavy graction consisted of mainly opaques, zircon, sillimanite, mica, rutile and sphene. The soils did not reveal contrasting characteristics in their composition that can be attributed to the parent material. Under the influence of the high temperature and heavy rainfall conditions existing in the state, the effect of parent material has been obliterated and properties of the soils appear to be mainly governed by the dominating climatic factor conditioned by the relief of the area. Based on the available data Thonnackal series was classified under fine loamy kaolinitic isohyperthermic family of Typic Haplorthox while others belong to the clayey, kaolinitic isohyperthermic family of Typic Haplorthox.

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