1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Dynamics of exchange equilibria and management of magnesium nutrition in lateritic soils of Kerala
    (Department of Soil Science and Agricultural Science, College of Agriculture,Vellanikkara, 2024-11-29) Soniya, V P.; Bhindhu, P S
    Lateritic soil occupies more than fifty per cent of total geographical area of Kerala and is characterized by acidic pH, low cation exchange capacity and dominance of low activity clays. Deficiency of magnesium is a common nutritional disorder in these soils due to leaching of bases under humid tropical conditions. The study aims at characterization of soil samples from midland laterites of Kerala with respect to magnesium fractions, thermodynamics of magnesium adsorption, determination of critical level of magnesium and comparative evaluation of different magnesium sources. Georeferenced composite surface soil samples were collected from fifty-five locations covering four agro-ecological units representing midland laterites (AEU 8- southern laterites, AEU 9- south central laterites, AEU 10- north central laterites, and AEU 11- northern laterites) and characterized for physico-chemical properties and fractions of magnesium. Soil pH varied from 4.26 to 6.40 with forty five per cent of the samples in strongly to very strongly acidic category. Sixty five per cent samples were found deficient in available Mg (< 120 mg kg-1 ). Cation exchange capacity of soils varied between 1.71 and 13.52 cmol (+) kg-1 . Dominance of cations on soil exchange surface followed the order Ca > Mg > Na > K. The soil samples were found to occupy five textural classes namely sandy clay loam, sandy clay, sandy loam, clay loam and clay. The mean per cent contribution of different fractions to total magnesium was in the order: mineral > exchangeable ≥ acid soluble > organic complexed > water soluble. Available magnesium was found to have positive correlation with available potassium, available calcium, cation exchange capacity, percentage base saturation, exchangeable calcium, exchangeable magnesium, exchangeable potassium and exchangeable sodium. Among different fractions of magnesium, the exchangeable fraction showed significant positive correlation with pH, available potassium, calcium, and magnesium, cation exchange capacity, percentage base saturation, exchangeable calcium, potassium and sodium in soil. A significant negative correlation was observed between exchangeable magnesium and exchangeable Al and Fe. The quantity - intensity relationship of magnesium at 25⁰C and 40⁰C was studied in eight soil samples varying in pH and CEC. Linear pattern of adsorption was observed at both temperatures over the range of magnesium concentration added (0-60 mg L-1 ). An inverse relationship was observed between equilibrium activity ratio and potential buffering capacity. The adsorption data of magnesium at 25⁰C and 40⁰C were best explained by Freundlich adsorption isotherm indicating the process of adsorption on heterogeneous sites in soil. The potential buffering capacity was found to decrease and the constants in Langmuir, Freundlich and Temkin adsorption isotherms associated with bonding strength was found to increase with rise in temperature implying stronger bonding of magnesium at higher temperature. The change in free energy of adsorption was negative in all soils signifying spontaneous nature of adsorption. The enthalpy change of adsorption was found positive indicating the process to be endothermic. Competitive adsorption of cations in a binary system for Mg-K, Mg-Ca and Mg-Al exchange was studied to investigate the dynamics of exchange equilibria in soil. Preferential retention of a cation relative to others is described in terms of selectivity coefficient which is the ratio of activity of adsorbed cations to the activity of cation in soil solution. Gapon, Vanselow and Gaines and Thomas selectivity coefficients for preferential retention of Mg over K was found less than one for all exchanger phase composition signifying the preference for K over Mg in soil. In the Mg - Ca exchange system, the preference for Mg was shifted to calcium with increase in concentration of Mg in equilibrating solution (and vice-versa). In the Mg - Al exchange system, the values of Gapon and Vanselow selectivity coefficients were less than one in all the studied soils indicating preferential retention of aluminium over magnesium. Based on the values of selectivity coefficients of the binary exchange systems studied, the preferential retention of cations followed the order aluminium > potassium > calcium when compared against magnesium. Pot culture experiment was conducted in August 2021 at Water Management Research Unit Farm, Vellanikkara, to validate critical level of magnesium in lateritic soils of Kerala with cowpea as test crop. The experiment consisted of forty treatments with the combination of twenty soils collected from the four AEUs and two doses of magnesium (0 and 10 mg kg-1 ). Bray’s per cent yield is the ratio of yield at zero level of a nutrient to that of potential yield with addition of the nutrient. The soil with lowest available magnesium status (48.60 mg kg-1 ) recorded lowest Bray’s per cent yield (75.35 per cent), and highest per cent increase in yield (32.70 per cent) with the application of magnesium. Scatter plot of Bray’s per cent yield against available magnesium and magnesium content in index leaves of cowpea revealed the critical level of available magnesium in soil to be 80 mg kg1 and that in index leaf tissue at flowering to be 0.34 per cent. Field experiment was conducted at Water Management Research Unit, Vellanikkara, with okra as test crop in the second cropping season (Oct-Nov to Jan-Feb) of 2020-21. Magnesium was applied at three doses (10, 20 and 30 kg ha-1 ) through five different sources (magnesium sulphate, magnesium carbonate, magnesium oxide, magnesium silicate and dolomite) to compare the efficacy in supplying magnesium. Second crop of Okra was raised in the same field to study the residual effect of applied magnesium sources. The ameliorating effect of magnesium sources was found to vary with solubility, neutralizing value and dose of applied magnesium. Application of magnesium oxide and dolomite significantly increased soil pH at flowering (5.38) and harvest (5.39) respectively. However, significantly higher soil pH after second crop was recorded in the treatments with magnesium silicate (5.15) and dolomite (5.17). Magnesium sulphate significantly increased the available Mg status in soil during flowering whereas considerable increase in available magnesium was noted with the application of magnesium oxide and magnesium carbonate at harvest stage. A persistent effect of magnesium silicate and dolomite on available magnesium status in soil was observed till the harvest of second crop. Magnesium dose at 30 kg ha-1 , was found superior in increasing pH and available Mg status in soil at all stages of analysis. Among different fractions of magnesium, significantly higher acid soluble fraction was recorded with the application of dolomite followed by magnesium silicate at flowering and harvest stage of crop indicating their persistence in soil during the crop period. However, the lack of significant variation in acid soluble fraction of magnesium in soil after second crop harvest indicates complete dissolution of applied sources. Treatment with magnesium oxide and magnesium sulphate recorded highest magnesium content in leaves at flowering stage, while the slow release of magnesium from magnesium silicate and dolomite was reflected in higher plant magnesium content at harvest stage. Application of magnesium carbonate, magnesium oxide, magnesium silicate and dolomite at 10 kg ha-1 of Mg were found on par in recording significantly higher crop yield. Whereas, the impact of treatments on yield of succeeding crop was significantly higher with application of magnesium at 30 kg ha-1 through magnesium silicate and dolomite. Among the different treatments, application of magnesium oxide at 10 kg ha-1 of Mg had the highest B: C ratio of 2.27 followed by dolomite (2.24) and magnesium carbonate (2.10) at 10 kg ha-1 of Mg. Magnesium being a frequently ignored nutrient in crop production, an optimal supply through slow soluble source can tackle leaching losses in lateritic soils of Kerala. The interaction of magnesium with major cations in soil also plays a crucial role in retention of the nutrient in soil and its uptake. Moreover, crop wise validation of critical level of magnesium in soil and plant will help to manage crop requirement.
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    Nutritional status of soils in relation to foliar nutrient levels in oil palm
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1988) Solomon Chacko; Abdul Hameed
    An investigation was taken up in oil palm grown in the plantation of oil palm India Limited at Yeroor (Bharathipuram) of Quilon District, with a view to evaluating the nutritional status
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    Response of rice to application of micronutrients
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1992) Muralidharan, P; Jose, A I
    A field experiment was conducted to study the response of rice to application of secondary and micronutrients during the first and second crop seasons of 1991. The experiment was conducted at the agricultural Research Station, Mannuthy using rice variety Jyothi and the soil was sandy clay loam in texture. The treatments consisted of the different micronutrients (Zn, Cu, Mn, B and Mo), magnesium, sulphur, a combination of the above said nutrients and stanes Microfood, a micronutrient formulation, in addition to the control with no micronutrients. Application of N, P and K was done uniformly in all the treatments. Soil and plant samples were collected at the maximum tillering, flowering and harvesting stages of the crop for the determination of uptake and availability of nutrients, pH and specific conductance. The continued effect of the application of micronutrient was studied by repeating the experiment in the second crop season with the same set of treatments applied to the same plots. Observations on the morphological and yield characters and yields of grain and straw were recorded in both the seasons of crop growth.
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    Deficiency symptoms of mineral nutrients in clove (Syzygium aromaticum (L.) Merr. and Perry).
    (Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 1989) Nazeem, P A; Sivaraman Nair, P C
    Experiments were conducted at the College of Horticulture on nutritional aspects of clove, to study the nutrient deficiency symptoms as well as the distribution pattern of nutrients in starved clove plants. The deficiency symptoms were induced in clove seedlings in sand culture. The distribution pattern of P, S (anions) and Ca (cation) were studied in the nutrient-starved seedlings employing radio isotopes. Besides, the annual nutrient removal and the seasonal fluctuations in the foliar nutrient concentration were studied in bearing clove trees. Older leaves were the first to exhibit 'hunger signs' due to the stress induced by N, P, K and Mg starvation whereas the symptoms, were manifested on the younger growth due to deficiency of Ca, S, Fe, Mn, Cu, Zn and B. General yellowing of the older leaves and early defoliation were the symptoms expressed by N-starved plants. Phosphorus stress resulted in small brownish spots to appear on older leaves of clove seedlings which later coalesced to form necrotic patches.
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    Fertility investigations on the soils of South Kerala in relation to their physiographic positions
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1986) Wilfred Godwin, G; Alice Abraham
    A study of the soils of South Kerala has been undertaken to investigate the variation in fertility status in relation to their physiographic position. Twelve locations from the districts of Trivandrum and Quilon were selected and from each location soil samples from upper, middle and lower reaches were collected from depths of 0 to 20 cm and 20 to 40 cm. The elevation of the location varied from 20 to 150 meters and the degree of slope from 6 to 27. The lower reaches of all the location were or less level paddy fields. The middle reaches were cultivated to banana, pepper, coconut and tapioca and the upper reaches in addition to the above crop perennials like coconut and rubber.
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    Nutritional status of soil and plant in relation to the incidence of chenthal disease of cardamom
    (Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1983) Dileep Kumar, K N; Alice Abraham
    An investigation was carried out at the College of Agriculture, Vellayani, to study the nutritional status of soil and plant in relation to the incidence of chenthal disease in three major cultivars of cardomom viz., Vazhukka, Malabar and Mysore. Soil and plant samples for the study were collected from the cardamom plantations in the High Ranges of Idukki district of Kearala State during March, 1982 (Pre-monsoon period) and September, 1982 (Post-monsoon period)
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    Studies on a manure supplement containing secondary and trace elements prepared from sea water (Sagar) on the growth, yield, quality and absorption of nutrients by rice
    (Division of Agricultural Chemistry, College of Agriculture, Vellayani, 1975) Chinnamma, N P; Money, N S
    A field experiment was conducted to assess the effect of application of Sagar, a manure supplement prepared from the sea water on the growth, yield and quality of rice and absorption of nutrients from soil. The result obtained are summarised below. 1) Application of NPK increased significantly all the growth characters and these characters were increased steadily with increase in the levels of NPK. Sagar application increased considerably the number of tillers and the number of productive tillers per plant.
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    Potash nutrition of rice with regard to the effect of Calcium, Magnesium and Silicon
    (Division of Chemistry, Agricultural College & Research Institute, Vellayani, 1966) Usha, C; Verghese, E J
    The study of potash nutrition of rice for maximum economic yields of grain and straw of high quality has not so far received adequate attention. In recent years, however, the use of potash in rice production has made remarkable progress in Japan and in India. But sufficient data are not yet available with regard to the need for potash manuring of Rice in Kerala. It is well known that rice soils of Kerala are very poor in lime status due to high rainfall obtained in the State. It has been found that liming affects the available potash contents in the soils.
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    Studies on the effect of silicate fertilization on the uptake of nutrients by rice plant at different stages of growth
    (Division of Agricultural Chemistry, Agricultural College and Research Institute, Vellayani, 1965) Sadanandan, A K; Verghese, E J
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    Soil test based fertilizer prescriptions for tomato (Solanum lycopersicum L.) in magnesium deficient ultisols of kerala
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2017) Remya, K N; Beena, V I