Theses

Browse

Search Results

Now showing 1 - 9 of 53

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
Impact of eucalyptus and acacia plantations on soil properties in different pedogenic environments in Kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Byju, G; KAU; Thomas, Varghese
Eucalyptus tereticornis and Acacia Auriculiformis are two important exotic tree species introduced into our environment through National Social Forestry programme. These two species are said to have many qualities which qualify them for inclusion under the social forestry programme. These fast growing tree species have the unique capability of surviving and regulating their growth to prevailing growth factors. But environmentalists in India and abroad have questioned the feasibility of bringing fertile lands under these exotic species which they claim to have deleterious impact on soil properties, hydrological parameters, biotic associations and long-term socio-economic consequences. However, these arguments do not have a sound scientific basis due to lack of sufficient research data base. So a study was undertaken to find out the impact of these monoculture plantations on soil properties in different pedogenic environments in kerala. Soil profiles were taken from four locations representing different geoclimatic regions of Kerala. The locations were Wynad (Northern forested highland), Kottoor (Southern forested highland), Nileswar (Northern coastal) and Kazhakkoottam (Southern coastal). Altogether thirteen pedons were studied from different locations representing reserve forest, cultivated land, barrenland, Eucaiyptus plantation and Acacia plantation. Pedons were described systematically and subjected to physico-chemical analyses and also for assessing the extent and nature of microflora. Biomass studies and chemical analyses of plant samples have alsobeen undertaken. From the studies, it was revealed that monoculture plantations of Eucalyptus and Acacia have got deleterious impact on soil physical, chemical and biological characteristics. These deleterious effects were more in a forest environment compared to sandy tracts. Increase in gravel content, eluviation of clay, lower silt/clay ratio, increase in bulk density, lower water holding capacity, low moisture content and low water dispersible clay in soils under Eucalyptus in forest areas show that the process of ferrallitisation and soil degradation proceed faster under Eucalyptus. Chemical composition also showed decrease in soil fertility under Eucalyptus. In the sandy tracts, Eucalyptus and Acacia increased the soil organic matter, total nitrogen and available potassium, while almost all other parameters used for the study showed deleterious effects. Active iron ratio (Fe oxalate/ Fe dithionite) was calculated to assess the extent of induration and the results indicated a relative enrichment of crystalline iron oxides in monoculture plantations of Eucalyptus and Acacia which may also lead to induration. A decrease in microbial population was also observed in these plantations except the population of Rhozobium whose number increased in plantations of Acacia which is a leguminous tree. The above results indicated that planting of Eucalyptus and Acacia as monoculture has got very deleterious impact on soil characteristics and fertility . All these throw light on the imminent necessity to have a rethinking about the introduction of monoculture plantations with these exotic species especially in the reserve forest areas.
Open Access
Comparative morphology and physico-chemical properties of some forest and defrosted soils of Kerala
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1989) Sivadasan, N; KAU; Aiyer, R S
In Kerala, continuous denudation of forests along the Western Ghats region has brought about hastening of the process of laterisation which becomes one of the major constraints to agricultural development. Deforestation of different types of forests such as deciduous, semi – evergreen, evergreen and shola may bring about laterisation to different extents. Deforestation and monoculture with different economically important species and plantation crops may delay or hasten the process of laterisation. The present study is, therefore an attempt to understand more about the effect of different monoculture vegetation such as cashew, eucalyptus, tea and acacia on soil properties in comparison with soils of adjoining virgin soils in deciduous, semi- evergreen, evergreen and shola forest ecosystems respectively. The present study reveals that deforestation has harmful effect on soil irrespective of the type of forest vegetation. It causes mechanical eluviation with higher migration of finer particles from surface downwards, increases bulk density of surface soil and lowers the aggregate stability of the soil. Organic carbon is found to be partly leached off and eroded off along with mineral soil. It is also burnt faster due to denudation. The contents of nitrogen and phosphorus increase while that of calcium and manganese decrease as a result of deforestation. Higher amounts of iron and aluminium are noticed in deforested soil than in virgin soils of the natural forests. The heavy mineral fraction constitutes from 2.5 to 27.6 per cent of the fine sand fraction. The dominant heavy minerals are the black opaques viz., ilmenite, red opaques such as hematite, limonite and goethite, sillimanite and zircon. The lighter fraction of the minerals is constituted mainly of quartz (22.6 to 97.5 per cent) with smaller amounts of feldspars and micas. The heavier fractionof the minerals are found to increase in soil due to deforestation brought about by residual accumulation. The influence of different monoculture / plantations on deforested soil varies with the type of vegetation. Increased root activity exhibited by tea and acacia at lower layers have strengthened the structural stability and improved the single value constants such as low bulk density, higher porosity and water holding capacity of the subsurface soil under these two plantations compared to soils under other plantations and virgin forests. The degree of weathering of soil varies with the type of vegetation. Based on the silt/clay ratio the soils studied can be arranged in the following order according to the observable factors on the degree of weathering : eucalyptus > tea > deciduous > semi – evergreen > cashew > shola > evergreen > acacia. Deforestation and monoculture with cashew, tea and acacia enhance the soil pH while monoculture with eucalyptus lowers the pH of the soil. Acacia is found to enrich the nitrogen status of the soil at a faster rate by its ability to fix atmospheric nitrogen. The study also reveals that ferrallitization advances in shola forest even if the level of organic matter in the surface soil is 5.19 per cent while no significant ferrallitization has been observed in acacia plantation having only 4.07 per cent organic matter in the surface soil though, both the soils fall under the same ecosystem. The critical role played by different type of vegetation in the manifestation of laterisation is yet to be studied. The micropedogenesis of kaoloinite from givvsite and silica in solution is clearly noticeable in laterised layers of the profile. Conversion of ferrouse to ferric iron the also observable in the thin section study of the soils. All soils are laterised with developing argillic horizonds and clay skins. The studies on soils of monoculture plantation crops such as cashew, eucalyptus, tea and acacia in comparison to virgin forest soils offers enough evidences from the present work to show that planted forests / plantation crops favour laterisation in general in comparison to virgin forests. Among the various types of monoculture, eucalyptus appears to enhance laterisation to the greatest extent while cashew and acacia favour laterisation to the least.
Open Access
Studies on the dynamics of forms of soil iron in the acid soils of Kerala during submergence
(Department of Soil Science & Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Harikumar, K P; KAU; Ramasubramonian, P R
The main objective of the study were to understand the pattern of distribution of water soluble, exchangeable, active free oxide, total amorphous, amorphous organic, amorphous inorganic and crystalline forms of iron and their variation under the influence of submergence, the effect of management practices on the variations in the available forms of iron under submergence and the relationship between soil reaction and the forms of iron in the major acid rice soils of Kerala. Viz., lateritic alluvium. Kari, kayal, karappadom, kole and pokkali. The pattern of distribution of different forms of iron studied, varied significantly among the six soils. The water soluble, exchangeable, active, free oxide, total amorphous and amorphous organic forms of iron were maximum in the kari soil, while crystalline iron was maximum in the lateritic alluvium. Kari and kole soils had the highest content of amorphous inorganic form of iron. The minimum content of water soluble iron was recorded in the kole and the lateritic alluvium, exchangeable and crystalline iron in karappadom soil, active, free oxide, total amorphous and amorphous inorganic forms of iron in pokkali soil and the amorphous organic iron in the lateritic alluvium. The total iron was highest in the kole and the lowest in the karappadom soils. Correlation studies indicated that pH had a significant negative correlation with water soluble and exchangeable forms of iron, while electrical conductivity, CEC, organic matter and clay content had positive correlation. Electrical conductivity and organic matter were positively correlated with active iron. Submergence significantly increased the pH and the contents of some of the forms of soil iron. Crystalline iron however, decreased with submergence. Active and free oxide forms of iron had no significant effect. The pH attained peak values on the 20th day of submergence in the lateritic alluvium, 30th day in the karappadom soil and 60th day in kayal, kole and pokkali soils. However, kari soil showed steady slow increases throughout the period of submergence. The addition of organic matter @ 5 t/ha and 2.5 t/ha decreased the pH slightly up to 5th day and then increased and equalled that of the control on the 90th day in all the soils. The decrease in pH was significantly more in the higher level of treatment then in the lower level. Water soluble iron increased significantly due to the treatments in all the soils. The maximum increase was observed in kari soil and the minimum in kayal and karappadom soils. However, the release of water soluble iron due to the higher level treatment was more than that of the lower level. The exchangeable iron also increased due to the organic matter treatment. The maximum increase was observed in the lateritic alluvium and the minimum in karappadom soils. The increase in the content of exchangeable iron due to higher level of organic matter was significantly higher than that due to the lower level. The lime application at full LR and half LR levels substantially increased the pH upto the 5th day in all the soils except in the kari soil, after which it decreased with further periods of submergence. However, in the kari soil, a peak value could be noticed on the 20th day. Water soluble and exchangeable iron decreased significantly due to the lime treatment. The decrease due to full LR treatment was significantly more than that due to the lower level. The active iron neither increased nor decreased significantly due to the organic matter and the lime treatments.
Open Access
Microbial mobilization and immobilisation of nutrients in red loam soils
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1989) Susan John, K; KAU; Alice, Abraham
A field incubation study with four treatments and five replications in RED was carried out in the typical red loam soils (Alfisol) of Vellayani, Kerala to determine the extent of nutrient immobilization and mineralization by soil microorganisms under the influence of various treatments like glucose, paddy straw and inorganic fertilizers during the rainy, winter and summer seasons in 1988-1989. Representative soil samples were collected from the experimental plots before and immediately after the application of treatments and after 21 days of incubation under field conditions. These soil samples were analysed for the status of organic carbon, available N and P and exchangeable K, Ca and Mg. A portion of the soil samples collected after 21 days of incubation under field condition was subjected to chloroform fumigation for 72 hours and after reinoculation with fresh garden soil was incubated for another 21 days. After the specified period, the soil samples were analysed for the status of nutrients mentioned earlier. From the analytical data the amount of nutrients assimilated or immobilized and subsequently released through mineralization was derived and the data subjected to statistical analysis. The study has shown that there is considerable variation between treatments in the extent of immobilization and mineralization of nutrients during the three seasons. Appreciable difference between the treatments was obtained for the contents of organic carbon and available nitrogen during the rainy season, available phosphorus during winter and organic carbon and exchangeable K, Ca and Mg during the summer season. The influence of treatments on the transformation of other nutrients during the different seasons was not appreciable eventhough a variation during the three seasons was noticed between treatments. The extent of organic carbon immobilization and mineralization was maximum during rainy season in the glucose amended plots registering a net assimilation of 18.0 – 23.9% and net mineralization of 14.1 – 17.3% respectively of the total organic carbon content of the soil. Amendment of the soil with glucose, paddy straw and fertilizers did not cause any appreciable difference in the mineralization of organic carbon. The fertilizer treated plots registered the highest rate of nitrogen mineralization equivalent to 26.2 – 34.0 kg N ha-1 during the rainy season. The immobilization and mineralization of available phosphorus was highest during summer with a net immobilization of 4.0 – 16.5 kg P ha-1 and mineralization of 3.0 – 12.5 kg P ha-1. In the case of exchangeable potassium, the net immobilization and mineralization was maximum during rainy season in the fertilizer treated plots. The rates of immobilization and mineralization of calcium and magnesium showed a random trend. The influence of different treatments on the microbial population of the soil has resulted in the highest population of bacteria, fungi and actinomycete during the rainy season in the straw amended plots. The favourable effect of a suitable temperature and moisture during the rainy season has presumably lead to a greater microbial activity and a correspondingly higher rate of immobilization and mineralization of the various nutrient elements.
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.

Theses

Browse

Thesis Type

Type

Author

Date

Subject

Search Results