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ThesisItem Open Access Influence of Water and Specific Anions and Cations on Physico-Chemical and Biological Properties of Soil(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Jaya, V; KAU; Pushkala, SThe availability of nutrients either present in the soil or applied as fertilizer is governed by various factors like the physical, chemical and biological reactions in the soil. The present investigation is undertaken to study the direct and interaction effects of different levels of phosphorus, sodium and water on the physic-chemical and biological properties of soil. An experiment is laid out in the farm area of College of Agriculture, Vellayani. The lay out is in randomised block design with 18 treatments and three replications. Banana var. Nendran is used as the test crop. The treatment combinations include, three levels of phosphorus (control, 90 and 115 g P2o5/plant/annum), three levels of sodium (control, 68 and 136 g Na/plant/annum) and two levels of water (20 and 40 per cent depletion from field capacity moisture condition). Soil and plant analysis are done for the elements, nitrogen, phosphorus, potassium, calcium, magnesium and sodium. Initial soil samples and samples collected at 90, 180 and 270 days after planting are used for different physic-chemical analysis. Physical properties such as moisture parameter, bulk density, particle density, porosity, water holding capacity, volume of expansion and aggregation are done for all the soil samples. Total nutrient contents and hydraulic conductivity for the soil samples collected at the final stage are also done. Plant samples collected at the harvest are analysed for total nitrogen, phosphorus, potassium, calcium, magnesium and sodium. Biometric parameters such as plant height, number of leaves, girth of pseudostem and leaf area index are observed and recorded during three stages. Mycorrhizal counting is carried out, during all the stages, considering as three seasons. All the data are statistically analysed and interpreted. Phosphorus at the highest dose is beneficial for all the biometric parameters studied. In the case of sodium, it has an adverse effect on the girth of the pseudostem, even at the highest level of phosphorus. Leaf area index is very high in the presence of sodium and phosphorus even at 40 per cent depletion from field capacity. Soil phosphorous and soil moisture are negatively correlated with mycorrhizal percentage during second and third stage. Plant phosphorous and sodium positively correlated with the mycorrhizal percentage. Even with moisture at 40 per cent deplection from field capacity and lower amounts of phosphorous applied, the uptake of phosphorous by the plant is increased by mycorrhizal association. Higher levels of phosphorous and sodium increase the waterholding capacity and volume of expansion. Bulk density and particle density give optimum values with medium levels of phosphorous and sodium. Moisture percentage increased in plots with optimum sodium than with plots receiving higher dose of water with no sodium. Lower water level reduces bulk density and particle density. The mean weight diameter which is a measure of soil aggregation is positively correlated with soil phosphorous and negatively correlated with soil moisture. Optimum dose of phosphorous and sodium favour hydraulic conductivity of soil. Medium dose of sodium and phosphorous increase organic carbon and soil available nitrogen. Lower level of water is sufficient for increasing soil available nitrogen, soil available phosphorous and organic carbon, in the presence of sodium. Positive correlation exists between soil available phosphorous and mycorrhizal percentage in the first stage. Maximum phosphorous is available during the second stage with a negative correlation with mycorrhiza. Optimum dose of sodium and high level of phosphorous, increase the availability of available potassium, exchangeable calcium, and exchangeable magnesium. There is a positive correlation exist between soil moisture and soil sodium. As the plant grows the soil available potassium decrease. Higher levels of water, increase, exchangeable calcium and magnesium also. Total nutrient content of nitrogen, phosphorous and potassium are decreased with increasing phosphorous, sodium and water, which is, because of their increased availability. Plant phosphorous is related with soil available phosphorous. For optimum dose of phosphorous, lower level of water and higher level of sodium, the availability and uptake of potassium is at the optimum. Positive correlation obtained for plant phosphorous with mycorrhiza, soil sodium, soil available phosphorous, and mean weight diameter. Plant sodium is also positively correlated with soil available phosphorous, mycorrhizal population, plant phosphorous and hydraulic conductivity. Highest level of phosphorous and water and medium level of sodium favour the uptake of calcium and magnesium. For increasing sodium availability, only optimum dose of phosphorous is required. Sodium at the optimum dose improve soil hydraulic properties. Optimum dose of phosphorous and sodium improves many of the physic-chemical properties of the soil. In the presence of mycorrhiza, even lower levels of phosphorous is sufficient to meet the plant requirement. With more levels of phosphorous, sodium and water, the study can extended in relation to plant growth. Yield factor is not considered in the present study.ThesisItem Open Access Investigations on the salinity problems of pokkali and kaipad areas of Kerala state(Department of Soil Science & Agricultural Chemistry, College of Agriculture, Vellayani, 1977) Samikutty, V; KAU; Aiyer, R SThe saline soils of the State viz., Pokkali, Kaipad and Orumundakan are coastal saline soils, which cover an area of about 30,000 hectares, cropped to a single crop of paddy. The profile characteristics of the soil reveal that they are Entisols. They contain varying levels of soluble salts depending upon their nearness to sea, backwater, or their situation on the flood plains of rivers and their nearness to the river mouths. The electrical conductivity of the saturation extract (ECe) of these soils range between 7.6 to 226.3 mmhos/cm showing differences in the magnitude of salinity encountered, prior to the soils being leached in summer months. Though the soils are exhibiting extremely high levels of salinity in the summer months, they get decreased rapidly below critical levels for growing a successful saline resistant paddy crop by July-August. The observed SAR and ESP values ranging to the maximum values of 25.0 and 26.3 in the months of February-March rapidly get decreased to 1 to 3 by between August and November. These low levels of salinity are maintained till December-January with an occasional spurt in salinity levels dependent on the opposing hydrological situation caused by the flood and rain waters on the one hand from east to west and the tidal waters from the west to the east on the other. The long period of nearly six months, when salinity in the soils are below critical levels, indicate the possibility of introducing a two crop system instead of one, provided nurseries are raised in non – saline uplands and transplanting resorted to in the raised mounds: previously leached free of soluble salts during the monsoon. The cationic-anionic composition of the soils reveal that they are Na-Mg-Cl-SO4 type of coastal saline soils. About 50 per cent of the soils studied have a pH below 5.5 and 15 to 20 per cent of the soils have lime requirement of more than 5 tons per hectare. In general the soils are extremely poor in phosphates and rich in potash. Application of non-magnesium containing lime materials at the time of mounding and subsequent leaching together with basal application of phosphate prior to planting are likely to enhance the yields of paddy in these areas. In short, the methods of management are highly location-specific calling for intensified research. The occurrence of saline water in the pits between the mounds even during the cropping period indicates the possibility of mixed rice culture with piscicultureThesisItem Open Access Studies on exchange equilibria and its prediction on some acid soils of Kerala(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellayani, 1988) Swarnavi, S; KAU; Pushakala, SMore than 70 per cent of the upland soils of Kerala are acidic. The acidity of the soil is primarily associated with the presence of hydrogen and aluminium in exchangeable form. The soil solution aluminium in acid soil infertility clearly establishes the agronomic significance of aluminium ion equilibria in soils. The present study, entitled “Studies on exchange equilibria and its prediction on some acid soils of Kerala” was conducted to find out(1) the effect of different concentrations of aluminium in the electrolyte solution on exchange equilibria in soils (2) the influence of different cations on the free energy and various selectivity coefficients (3) the dependence of different selectivity coefficients on potassium, calcium and magnesium saturation of soils (4) the role of organic matter on cation exchange equilibria with special reference to potassium, calcium, magnesium and aluminium. Cation exchange equilibria involving aluminium- potassium, aluminium – calcium and aluminium- magnesium were studied in three soil types, viz., Kari, laterite and redloam soils, differencing in their texture and organic matter content. The normalized exchange isotherms for different soils and cationic systems were drawn and the results were interpreted in terms of different selectivity coefficients and approximate free energy change of the exchange reactions. From the study on the effect of different electrolyte concentration of aluminium on aluminium – potassium, aluminium- calcium and aluminium – magnesium exchange, an increasing aluminium adsorption was observed with an increase in electrolyte concentration of aluminium. The adsorption of aluminium was maximum in soils with high organic matter content. The normalized exchange isotherms of aluminium for different cationic systems and soils lay above the diagonal, suggested the preferential adsorption of aluminium over other cations. Except the Gapon selectivity coefficient, all the other coefficients (KKDO, KV and KN) increased upto a certain value of base saturation and then decreased. The value of KG increased with increase in base satuation. Among the various selectivity coefficients, KN was found to be the most dependent one and KG the least dependent. The dependence followed the order KN > KV > KKDO > KG. The negative values of free energy change for different cationic systems suggested the preferential adsorption of potassium, calcium and magnesium over aluminium. Among these cations potassium was found to be adsorbed with more energy, followed by calcium, magnesium, and then by aluminium. The values of free energy change showed the following order of preference for the competing cations: K > Ca > Mg > Al. From the study it can be concluded that potassic fertilizers can be effectively used in acid soils of Kerala, because of its high retention and minimum leaching loss. Compared to potassium, calcium and magnesium were adsorbed with less bond energy and hence to maintain a higher concentration of these cations in the soil exchanger, a considerable amount of calcium and magnesium should be supplied by frequent application of lime. To evaluate correctly the response of applied potassic fertilizers and liming material in different soils, efforts should be made to relate exchange behaviour of potassium, calcium and magnesium to the nature and relative proportion of different soil clay minerals. Similarly, the extension of the predictive approach essentially meant for binary system need special attention in order to make the studies on cation exchange equilibria more realistic and field oriented.ThesisItem Open Access Environmental planning of two selected river basins of western ghats based on investigations on land use planning and land capabilities(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1987) Binoy Cherian, T Kau; Aiyer, R SRapidly changing socio economic structure puts tremendous pressure on human society to find additional resources for its sustenance. Indiscriminate exploitation of the natural resource with scarce concern for the ecological balance has caused disturbances and sometimes total destruction of important portions of the biosphere with immediate or delayed effects being evidenced on a global scale. Land and soil are not resources that are infinite and cannot be exploited for ever. This fragile epidermis of the earths crust is severely affected due to drastic changes in vegetation cover resulting in destruction of soils and losses of nutrients and fertility. The quality and quantity of terrestrial biosphere depends on the soil and land. For studying the extent and state of an environmental impact a well defined natural unit has to be selected. Being a natural physical system where the land and water act as definite determinants of land use, and since it is a well defined natural unit, river basins were chosen as the units for study. The sub water sheds and micro water sheds are the accepted units for ecodevelopment planning. There is a need for detailed studies in natural and agroeco systems in different water sheds in relation to the physical features of the land and soil characteristics. Such studies are required to plan microlevel aspects of eco restoration, and eco development of water sheds especially in Kerala where environmental degradation has reached alarming proportions. The main objectives of the work is as follows: 1. A study of the sub water sheds of Bharathapuzha and Aralampuzha for relief, morphology, drainage, geology, vegetation, climate, soil and land use. 2. A land capability assessment of both the river basins based on details soil studies and traversing of the area. 3. To evolve a set of recommendations for management of the two river basins. The basic approach in the present study is to investigate individual components and bring out their relationship with present land use, that would help to maintain the ecological balance while sustaining human needs. For this two river basins Mangalam-Gayatripuzha and Aralam-Bavalipuzha were selected. The former highly influenced by man and the latter relatively less interfered were chosen for making a comparative study. Environmental components like relief, slope, morphology, drainage, geology, vegetation, climate and soil have been analysed by using standard methodology with respect to individual variables. On the basis of these studies land capability was assessed for each geomorphic unit and the present land use was also studied. Finally a set of recommendations were evolved for the judicious use of each geomorphic unit. With minimum degradation to it. From the study it was found that the Mangalam-Gayatripuzha basin has a mature landscape in comparison with Aralam-Bavalipuzha basin with more diverse geomorphic units. The soil is mainly alluvial in Mangalam-Gayatripuzha basin whereas it is lateritic in Aralam-Bavalipuzha basin. Soil fertility is moderate with no marked variation in both cases. High population density, smaller land holdings and low per capita income have put the land to great stress. Ecologically viable land use based on land capability has become subservient to subsistence land use. Food crops dominate the agricultural scenary in the Mangalam-Gayatripuzha basin whereas cash crops take more area in the Aralam-Bavalipuzha basin. Both the basins are suspectible to erosion and this has been aggravated by large scale deforestation and cultivation of tuber crops on the hill sides. On the basis of these findings it is recommend that deforestation should be completely stopped and afforestation programmes expedited in order to conserve the ecology of both basins. Soil conservation measures should be taken up on a war footing in the Aralam-Bavalipuzha basin with the entire cost borne by the government. Comprehensive programmes must be formulated to bring the catchment of the rivers under good perennial tree and fodder vegetation. Tapioca cultivation requiring greater tillage on slopes should be discouraged or prohibited. A detailed land capability assessment based on natural land use determinates should be worked out for the two basins since large section of the people in the hilly areas are poor with no alternative means of subsistence. Imaginative hill slope agricultural programmes that guarantee subsistence for these people should be evolved.
