Browsing by Author "Sureshkumar, P"

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Anionic equilibria in major soil types of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2020) Reshma, M R; Sureshkumar, P
Availability indices for stressed nutrients for coconut (Cocos nucifera L) in an ultisol
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2003) Priya, P; Sureshkumar, P
The present study was conducted with an objective to analyse the soil-plant system, the levels and interactions of nutrient ions in soil, soil solution and plant thereby / finding out the contributing factors to yield. The importance of the term relative intensity lies in the fact that the contribution of mineral elements to growth and yield of plants depend much on the relative amount of one element with respect to the others rather than the absolute content of individual elements. To study the ionic interactions and to unravel the role of Net Ionic Equilibrium based on Ratio Law on soil plant system, a sample of fifty phenotypically identical palms varying in yield from 14.4 to 84.4 nuts palm" year"! grown under an Ultisol were selected. Index leaf samples were collected during pre and post monsoon seasons from 25 palms each from high yielding and low yielding groups. Soil samples were also collected from the basins of these palms during the same seasons at 30 cm (surface) arid 60 cm (subsurface) depths. Soil solutions at saturation point were extracted from the surface samples by centrifugation technique. These leaf, soil and solution samples were analysed / . for different nutrient ions, and the NIE ratios in these three phases were worked out with respect to K and Na. The soil samples were acidic in nature and the variation in rhizosphere pH must have definitely influenced the solubility as well as absorption of different nutrient ions. In the case of available nutrients, the micro nutrients showed significant direct relation with yield both for high and low yielding populations. This might be due to their restricted availability due to aerobic oxidised condition where Fe and Mn might have been precipitated and got into unavailable forms. The BaCh exchangeable ions and the CEC derived from summing up of these exchangeable ions influenced yield directly. Exchangeable K had got a significant dominance in deciding the NIE ratio in soil, solution and in index leaves. Exchangeable K controlled the soil solution concentration of K which in turn controlled the NIE ratio in solution and the ratios in plant. Exchangeable K directly controlled the plant K content and plant K was positively and significantly correlated with the NIE ratios in plant and these ratios were positively and significantly correlated with yield. The negative significant correlation of exchangeable K with plant Mn and Zn revealed the antagonistic effect of exchangeable K in restricting the absorption of Mn and Zn by plants. Among the ionic concentrations in soil solution, Fe was positively and significantly correlated with yield in both the seasons. Soil solution concentrations of Ca and Mg were antagonistically and significantly related with plant Mn content. Potassium content and the NIE ratio in index leaves were found to have a significant direct relation with yield in the pre-monsoon season. Potassium, Ca and Mg were the dominant cations in plant deciding the total cation concentration in index leaves. The NIE ratios between the exchangeable ions, the ions in soil solution and the ions in index leaf samples were mutually, .positively and significantly correlated among themselves. This lead to the conclusion that there exists a constancy in the relative proportion of nutrient ions in the entire soil-plant system which followed Ratio Law. The study lead to the conclusion that the soil test values of the individual ions alone or the plant content of individual ions alone can't give a clear picture of optimum nutrient requirements for the plant. The relative concentration of K in soil through the ~ concentration in soil solution was found to govern the relative concentration in plant which in turn influenced the yield.
Bamboo based agroforestry systems in Kerala, India: performances of turmeric (Curcuma longa L.) in the subcanopy of differentially spaced seven year -old bamboo stand
(2015) Kittur, B. H; Sudhakara, K.; Mohan Kumar, B; Kunhamu, T. K.; Sureshkumar, P
Carbon: nitrogen dynamics in acid sulphate and acid saline rice soils of Kerala
(Department of Soil Science and Agricultural Chemistry, Vellanikkara, 2019) Irene Elizabeth John; Sureshkumar, P
The present study was undertaken to unravel the chemistry of Carbon: Nitrogen dynamics in submerged acid sulphate and acid saline soils, to identify the labile fractions of these elements contributing to soil fertility and to modify the organic carbon based fertility ratings for nitrogen recommendation in Kale lands. Forty-five representative soil samples from 4 different rice growing acid saline and acid sulphate soils of Kerala were collected and characterized for pH, EC, OC, total carbon, total nitrogen, available nutrients (N, P, K, Ca, Mg, S, Fe, Cu, Mn, Zn and B) and microbial biomass carbon. The soil samples were analysed as such after sampling on wet basis and the results were expressed on moisture free basis to have uniformity. The organic carbon status of the soils varied from 0.81 to 7.58 per cent. Soils from Kaipad recorded the lowest and soils from Vechoor Kari of Kuttanad recorded the highest value of organic carbon. The total nitrogen ranged from 0.05 per cent in upper Kuttanad to 0.42 per cent in Vechur Kari. The highest available nitrogen content of281.38 kg ha' was recorded in sample from Vechoor Kari and the lowest of 19.84 kg ha in Purakkad Kari. The C:N ratio varied from 13:1 to 24:1. Widest C:N ratio was recorded in soils of Upper Kuttanad and the lowest in soils from Thrissur Kale. The organic carbon was significantly and positively correlated with total nitrogen and available nitrogen status. Total nitrogen was the single most independent factor explaining 94 per cent variability of organic carbon. Soil samples were subjected to fractionation studies (both physical and chemical) to quantify the carbon and nitrogen that is associated with different inorganic and organic constituents in soil. In physical fractionation, soil carbon and nitrogen preferentially recovered from the sand, silt and clay size fractions were estimated. Of this, carbon recovered from clay size fraction was the dominant independent variable that explained 64.6 per cent variability of organic carbon. The different chemical carbon fractions studied were water soluble carbon (WSC), hot water extractable carbon (HWEC) and permanganate oxidizable carbon (POC). The water soluble carbon being derived from completely decomposed organic matter was not associated with nitrogen in soils. The HWEC being the most labile pool of carbon had significant influence on mineralisation process thereby contributing to total and available nitrogen content. The permanganate oxidizable carbon being a stabilized pool might not undergo further decomposition to release nitrogen and hence, its contribution to available pool was negligible. Among the organic pools of nitrogen, the total hydrolysable nitrogen contributed significantly to mineralizable N. Among the inorganic fractions of nitrogen, ammoniacal nitrogen was contributing more to the available pool of nitrogen than nitrate nitrogen fraction probably because of high solubility and losses of latter by leaching. A field experiment was conducted to investigate the response of rice to different levels of nitrogen in Adattu Kole with an initial C:N ratio of 20:1. The treatments with increased levels of nitrogen based on C:N ratio (treatments Ts-TlO) produced significant effect on plant height, number of productive tillers, number of grains per panicle, straw yield and grain yield. The total nitrogen content both in soil and plant were significantly influenced by higher doses of nitrogen fertilizers prescribed as per the C:N ratio. Among the carbon fractions, hot water extractable carbon contributed more to the mineralizable pool than water soluble carbon. The direct effect of total hydrolysable nitrogen on total and available nitrogen was very high. Ammoniacal nitrogen being a dynamic and time dependent variable, though contributing significantly to available N content, its effect on total nitrogen was negligible. This was in conformity with the results of experiment in characterization of soil samples collected from 45 locations. The maximum grain yield of 8.22 Mg ha" was recorded in the treatment where nitrogen was applied based on C:N ratio (wet analysis). An increase of 1.15 Mg ha of grain yield was recorded over the treatment where soil test based fertilizer recommendation was applied. The highest straw yield of 17.47 Mg ha was recorded in treatment where nitrogen applied was double that of C:N ratio based recommendation. The highest net return was obtained in treatment where nitrogen was applied as per the C:N ratio in soil.
Chemistry and transformation of boron in soils of Kerala
(Department of Soil Science & Agricultural Chemistry, College of Horticulture, Vellanikkara, 2013) Santhosh, C; Sureshkumar, P
Sixty five representative soil samples from 23 agro ecological units under five agro ecological zones of the state were collected and characterised with respect to the available boron status for the present study on “Chemistry and transformation of boron in soils of Kerala”. The samples were characterised for pH, EC, CEC, PBS, exchangeable cations, total sesquioxide and available nutrient status (organic carbon, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu) along with available boron.. Among these soils 18 per cent of samples which included samples from southern and northern coastal sandy plains were deficient in boron (< 0.5 mg kg-1) while the acid saline soils of Pokkali and Kaipad have recorded highest levels of available boron (> 3.0 mg kg-1). The availability of boron was found to increase with soil acidity and electrical conductivity. Thirty one soil samples selected from 65 characterised samples representing all the AEUs and ensuring variability in physico-chemical properties and available boron were subjected to fractionation of soil boron. The different fractions, readily soluble, specifically adsorbed, organically bound, oxide bound and residual boron accounted a mean status of 0.59, 0.86, 1.79, 2.31 and 94.45 per cent of total boron respectively in soils of different AEUs in Kerala. All the fractions except residual boron were significantly and negatively correlated with soil pH, and positively correlated with electrical conductivity. The oxide bound and residual boron were highly positively and significantly correlated with the content of sesquioxide and clay and the organically bound boron was significantly correlated with organic carbon content indicating the influence of organic matter, oxides and hydrous oxides dominated amorphous clay minerals of tropical soils in retention and solubility of boron. Among the six soils included for adsorption studies (lateritic soil from Pattambi, wet land soil from Elavampadam, sandy soil from Onattukara, black cotton soil from chittoor, Kole land soils from Thrissur and Kayal land soil from Kuttanad), only two soils ie. Onattukara and Kayal land soils followed Langmuir adsorption isotherms at 250C. The adsorption data for all the soils except Onattukara sandy soil could be fitted in to Freundlich adsorption isotherm both at 25 and 400C. The amount of boron adsorbed at unit equilibrium concentration ( Freundlich K: KF) decreased with increase in temperature from 25 to 400C. The intercept of Quantity-Intensity curve decreased to negative values at higher temperature indicating desorption of boron from the sites when solution concentration fell below equilibrium concentration. The decrease in free energy with a positive enthalpy and a positive entropy in Pattambi, Elavampadam, Onattukara and Kole soils revealed that the adsorption of boron were spontaneous and endothermic. The reverse was the case with black soils of Chittoor and Kole land soils where adsorption was exothermic and non spontaneous. The incubation experiment conducted for a period of three months with different levels of organic matter and borax in three soils ie. Onattukara sandy, lateritic upland and low land of Elavampadam revealed the clear role of organic matter in adsorption, retention and release of boron. Either organic matter or borax independently could increase available boron substantially after one month of incubation and maintained almost a constant level during the further course of incubation. However higher levels of organic matter reduced the available boron after one month incubation as a result of adsorption by organic matter. At highest level of organic matter and borax (15 t and 12 kg ha-1 respectively), adsorption of boron was highest. The field experiment to optimize the boron nutrition for rice in low land lateritic soils in central Palakkad plains (Elavampadam) revealed the clear role of boron in improving the productivity of tillers, number of grains per panicle, thousand grain weight and ultimately yield. The response curve fitted to find out the optimum dose of boron for grain yield showed that application of borax @ 5.5 kg ha-1 would result in yield improvement to the tune of 1 t ha-1. The fractionation of soil boron at panicle initiation and harvest stage indicated that both readily soluble and specifically adsorbed boron in soil increased with the levels of borax up to 6 kg ha-1 while the other fractions increased linearly with the levels of borax up to 12 kg ha-1. The correlation studies and path analysis clearly indicated that plant absorption of boron mainly take place from readily soluble, specifically adsorbed and organically bound boron in that order due to the existence of dynamic equilibrium between these fractions.
Chemistry and transformations of calcium and magnesium in tropical acid soils of kerala
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Thrissur, 2017) Bhindhu, P S; Sureshkumar, P
Calcium and magnesium are indispensible as secondary nutrients for plant growth. Availability of these nutrients to plants depends on the form and quantity present in soil. Soils of the tropics normally pose the problem of acidity due to high rainfall and leaching of bases causing widespread deficiency of these nutrients. The study aims at characterization of soil samples from 23 agro ecological units of Kerala with respect to supplying power, chemistry, dynamics, transformations and availability indices of calcium and magnesium and also to optimize the level of calcium and magnesium for rice nutrition in lateritic soils. Sixty four representative soil samples from 23 agro ecological units under five agro ecological zones of the state were collected and characterised for physico-chemical properties. Among these soils, ninety two per cent were acidic in reaction, of which sixty three per cent were strongly to very strongly acidic (4.5-5.5). Lowlands of Kuttanad, Pokkali and Kaipad were extremely to ultra acidic. Twenty seven per cent of samples were deficient (< 300 mg kg-1) in available calcium, while sixty seven per cent samples were deficient in available magnesium (< 120 mg kg-1). Deficiency was negligible in soils from Attapady hills (AEU 18 and 19), Palakkad central and eastern plains (AEU 22 and 23) and the lowlands of Kuttanad, Pokkali, and Kaipad (AEU 4, 5 and 7). The availability of calcium and magnesium increased with pH, cation exchange capacity and decreased with increase in exchangeable aluminium. Forty one soil samples from different agro ecological units were subjected to sequential fractionation. The mean per cent contribution of different fractions to total calcium was in the order exchangeable > mineral > acid soluble > water soluble > organic complexed, whereas in the case of magnesium, it was observed as mineral > acid soluble > exchangeable > water soluble > organic-complexed. Exchangeable calcium and water soluble magnesium were the sole forms contributing directly to the available pool. The quantity-intensity relationship of calcium and magnesium in twenty- three soils belonging to different AEUs of Kerala were studied at 25oC and 40oC. Potential buffering capacity or the supplying power of soil had significant positive correlation with CEC and exchangeable cations in soil. The adsorption data of both calcium and magnesium at 25oC and 40oC were best explained by Tempkin adsorption isotherm indicating that the affinity for adsorption decreases linearly with degree of saturation. The change in free energy of adsorption for calcium and magnesium was negative in all the soils studied signifying the spontaneous nature of adsorption. The change in enthalpy (ΔH0) was negative in most of the soils indicating the process to be exothermic. The close correlation of enthalpy change with change in entropy proved that as the enthalpy change becomes more negative, stronger is the bond and more orderly is the adsorption. The incubation experiment conducted to study the effect of organic matter on the adsorption of calcium and magnesium revealed a positive influence of organic matter on availability of calcium and magnesium. The addition of organic matter improved the supplying power with respect to calcium and magnesium either through mineralization or formation of stable soluble complexes especially at higher pH. Two field experiments to optimize the level of calcium and magnesium nutrition for rice in low land of north central laterites (Pattambi) revealed the clear role of calcium and magnesium in improving the yield and yield attributing characters of the crop. Application of dolomite as per ΔpH was found to be effective in increasing the yield and maintaining optimum level of calcium as well as magnesium in soil. Application of lime was not found to influence the in situ soil pH. The response of crop to magnesium showed yield improvement to the tune of 1.18 t ha-1 by application of magnesium sulphate @ 120 kg ha-1. Residual effect of dolomite had significant influence on the yield of rice whereas no residual effect of applied magnesium sulphate was evident. The correlation studies and path analysis clearly indicated that plant absorption of calcium mainly takes place from exchangeable fraction and that of magnesium from water soluble fraction.
Nutrient dynamics and transformation in aerobic and flooded systems of rice in lateritic soils of kerala
(Department of soil science and agricultural chemistry, College of Horticulture, Vellanikkara, 2015) Geetha, P; Sureshkumar, P
Phosphorus dynamics in an ultisol
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2005) Smitha, M S; Sureshkumar, P
A pot culture experiment was carried out at Radiotracer laboratory of College of Horticulture, Vellanikkara, using laterite soil (Ultisol), from the main campus of Kerala Agricultural University with the objectives to trace the fate of fertilizer P and to study the dynamics of P by the addition of amendments. The experiment included 13 treatments of three levels of P and four amendments and an absolute control. Amendments were added to the respective treatments and kept for wetting and drying cycles for two weeks 32P labelled KH2PO4 (32P @ 0.4mCig-1 P) was added as per the treatments. Seeds of cowpea @ 3 seeds pot -1 were sown. Application of Phosphorus at different levels significantly contributed to available P status different P fractions i.e. non occluded Al-P and Fe-P, P sorbed by carbonate, occluded P and Ca-P in a linear fashion at all the stages of crop growth i.e. just before sowing, flowering and harvesting. The amendments also contributed to the above pools. Among the amendments Pongamia leaves was found to have better influence in contributing to the above pools except for Ca-P, where lime was found to have a better influence. This was supported by the data on plant P content, where the increasing levels of P and amendments improved the plant P content at 15 DAS, flowering and at harvest. Further Ca-P fraction was dominantly contributing to the available P suggesting that applied P might get transformed to non occluded Al-P and Fe-P, occluded P as well as P sorbed by carbonate, which might be slowly transformed to Ca-P fraction probably Ca (H2PO4)2, the soluble form which is contributing to available P. It was observed that, non occluded Al-P and Fe-P was contributing to plant P as time proceeded due to solubilisation of this fraction. Application of P at increasing level and amendment significantly increased the dry weight of pods and haulm. Radioactive 32P labelled with the applied phosphorus could be traced out in the available pools and fractions of P only at just before sowing, flowering. Percentage of P derived from applied P were the highest for higher level of P and amendment sodium silicate.
Quantity - intensity relations of phosphorus with reference to its bioavailability in lateritic soils
(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellakikkara, 2008) Geetha, P; Sureshkumar, P
Soil resource inventory of the main campus Kerala Agricultural University Vellanikkara: Part 1 (east)
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2000) Seena, E; Sureshkumar, P
Wet soil analysis for nutrient prescription in paddy soils
(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 2014) Irene Elizabeth John; Sureshkumar, P
Three locations from 7 agro ecological units dominated by rice crop were identified namely, Onattukkara sandy soil(AEU 3), Kuttanad(AEU 4), Pokkali(AEU 5), Kole(AEU 6), north central laterite(AEU 10), Palakkad central plains (AEU 22) and Palakkad eastern plains (Black soils )(AEU 23). Geo-referenced soil samples were collected at 3 stages: before cropping season, at active tillering and visual panicle initiation. Plant samples were also collected during the above stages and analyzed for nutrient contents. Initial characterization was done with air dried samples while samples during crop growth period were collected by maintaining the wet anaerobic conditions and analyzed as such as well as after drying. Submergence resulted increase in pH both under wet and dry analysis. The pH on the basis of wet analysis was higher than that by dry analysis. EC decreased during flooding and dry analysis gave higher values than by wet analysis. The (C: N) 1 ratio (based on total carbon and total nitrogen) varied from 9.32 :1 in Onattukarasandy soil to 18:1 in Kuttanad on the basis of wet analysis. Analysis after drying recorded a (C: N) 1 ratio ranging from 10.84 inPalakkad central plains to 22 in Kuttanad. Comparison of wet and dry analysis of other available nutrients indicated that higher values were recorded for P, K, Ca, Mg and Fe in wet analysis while the values for availableS, Mn, Zn and B were higher in dry analysis. Data on analysis after drying, recorded significant negative correlation of pH with organic carbon (0.36**) and available S (-0.37**) due to accumulation of organic acids and SO 42-ions under aerobic condition. Antagonistic interaction of available P with available Ca was attributed to significant negative correlation obtained between them in dry analysis. Wet analysis gave significant positive correlation of pH with available Ca (0.35**) and significant negative correlation with available S (-0.28*). All the C: N ratios computed on the basis of, total carbon and total nitrogen (C: N) 1, total carbon and available nitrogen (C: N) 2, organic carbon and total nitrogen (C: N) 3 and organic carbon and available nitrogen(C: N) 4 were significantly correlated with total and available nitrogen at different stages both under wet and dry analysis. Four soil types namely, Onattukara sandy, Kuttanad, north central laterites and Palakkad eastern plains were used for an incubation study to unravel the pattern of decomposition of added organic matter and to identify the C: N ratio at equilibrium. Changes in pH and redox potential during submergence indicated slight increase in pH after 7 days of submergence and redox potential was constantly decreasing with increasing period of submergence. The (C: N) 1 ratio was found to stabilize at 9.6:1 after 3 months of incubation with organic matter while it was stabilized at 7.6:1 without organic matter in Onattukara soil. In Kuttanad soils it was 18.3:1 and 17:3 respectively. In Chittor soils it stabilized at 10:1. The (C: N) 3 also showed similar trends. However, available nutrient did not give any significant correlationwith the corresponding plant content of the respective nutrient. This focusesto the importance of future studies with more number of samples from eachAEU’s as each of the fertility parameters are highly varying in these units.