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Open Access
Silicon availability of tropical soils with respect to rice nutrition
(Department of Soil Science and Agricultrural Chemistry, College of Horticulture,Vellanikkara, 2016) Arya Lekshmi, v; KAU; Jayasree Sankar, s
Silicon (Si) is the second most abundant element in soil. The amount of silicon in soil depends on parent material, soil type, pedogenic process and landscape. In soil solution, Si is present as monosilicic acid which is the only form that the plant can absorb from soil. The productivity of rice is comparatively low in soils of Kerala. As a ̳Si – accumulator‘, rice can benefit from Si nutrition. The application of Si can enhance growth and yield of rice. With this background, studies were conducted to categorize major rice growing soils of Kerala according to plant available silicon and to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. The release of silicon from different soils added with various silicon sources under different water regimes was also monitored. Soil samples were collected from five different locations representing major rice growing regions of Kerala viz., Kuttanad, Kole land, Pokkali, sandy and lateritic to categorize them according to plant available silicon. The available Si ranged from 7.70 mg kg -1 (sandy soil) to 34.91 mg kg -1 (Kole land soil) in the order Kole land > Pokkali > lateritic > Kuttanad > sandy soil. All the soils under study were categorized as low in available Si. The available Si had positive correlation with organic carbon, available N, Ca, Mg, Fe, Mn, Zn, exchangeable K, Ca, Mg and CEC and negative correlation with available boron, AEC and silica-sesquioxide ratio. These soils were subjected to fractionation of silicon. The major fractions of Si were mobile, adsorbed, organic, occluded, amorphous and residual Si. The percentage distribution of fractions of Si in these soils were in the order; residual Si > amorphous Si > occluded Si > organic Si > mobile Si > adsorbed Si. Quantity – intensity relationship of five major rice growing soils at two temperatures viz. 25 0 C and 40 0 C were studied. The highest buffer power was indicated by Kuttanad soil followed by Pokkali and sandy soils at 25 0 C. It clearly indicated that these soils have a higher power to retain Si on solid phase and replenish its concentration in soil solution as and when it is depleted through plant uptake or leaching. The equilibrium Si concentration and the amount of Si adsorbed by each soil were used to test the fitness of data to the adsorption isotherms viz., Langmuir, Freundlich and Temkin. The data obtained from the adsorption experiments fitted into Freundlich and Temkin equations, but not to Langmuir equation at 25 0 C. At 40 0 C no adsorption equations were obtained for any soil.An incubation study was conducted to know the extent of release of Si on addition of different sources of silicon such as rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate in five rice growing soils under submerged water regime (SWR) and field capacity water regime (FCWR). Addition of Si significantly increased the release of available Si in all soils except Kole land soil after a month. Kole land soil showed higher release of available Si after two months. The highest release of available Si was at SWR in case of Kole land and Kuttanad soil, where as Pokkali, sandy and lateritic soils showed more release of available Si at FCWR. Irrespective of soils, treatment with sodium silicate showed higher release of available Si. Total Si showed a decreasing trend over the period of incubation for three months in all the soils. A field experiment was conducted at Agronomic Research Station, Chalakudy to evaluate the efficacy of different sources of silicon including rice straw in wetland rice. Rice husk ash, biodecomposed rice husk, calcium silicate and sodium silicate were used as source of Si along with fertilizers as per package of practice recommendation (NPK alone). The maximum number of panicles per hill, number of spikelets per panicle, thousand grain weights and minimum number of unfilled grains per panicle were recorded in treatment with calcium silicate application. The maximum grain yield of 6.90 t ha -1 was recorded in treatment T 5 (T 2 + Calcium silicate) and significantly superior (fig.54) over all other treatments. This increase in yield may be due to the effect of application of Si on soil fertility, nutrient uptake, and plant growth. The direct effect of Si fertilization on increased number panicle per hill, number of spikelets per panicle, and thousand grain weight and decreased number of unfilled grains per panicle might be the reason for increased grain and straw yield in treatment with calcium silicate. The treatment with POP + sodium silicate showed the highest uptake of Si by grain and straw of rice. The sources of Si had no residual effect on grain and straw yield of succeeding rice crop. In general, sandy soil low in available Si had a high response to applied Si in achieving higher grain yield.
Open Access
Nutrient interactions in soil test crop response studies on cucumber ( Cucumis sativus L) in the laterite soils of Kerala.
(Department of Soil Science and Agricultural Chemistry,College of Horticulture, Vellanikkara, 2011) Sajnanath, K; KAU; Hassan, M A
A comprehensive approach has to be adopted for efficient fertilizer use, incorporating soil test, field research and economic evaluation of the results for providing a scientific basis for the process of enhancing and sustaining food production as well as soil productivity with minimum environmental degradation, it needs more. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop. In Kerala, many studies have been conducted to get a fertilizer prescription equation for targeted yield in various crops like rice, banana etc. A programme was formulated to investigate the nutrient interaction in soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of Kerala. In this, the field works were conducted as per the pattern of soil test crop response correlation studies. A gradient crop experiment was conducted in the experimental field of AICRP on STCR using maize. The purpose is to create a fertility gradient in the field by applying different doses of fertilizers. The area was divided into three strips and the doses of nutrients were applied as per STCR pattern of fertilization for maize. The crop was harvested and the plant samples were taken for analysis. The pre and post experimental soil samples were analysed. It was found that fertility gradients were developed in the field. Using the data on dry matter production in various strips, the nutrient uptake was also determined. A test crop experiment was designed in the same field where the gradient crop was raised. There were 24 treatments with three control plots. The treatments included four levels of nutrients and three levels of farm yard manure. The crop, cucumber (Var.: AAUC-2), popularly known as salad cucumber, was raised and managed as per package of practices of KAU. The soil samples were collected before, at flowering and harvest stages during the experiment. The plant samples were collected at flowering and harvesting stages. The total dry matter production and yield were taken treatment wise at the harvest. The soil samples were analysed for various chemical parameters. The data on yield, uptake of nutrients, nutrient status, nutrient requirement, quantity of farm yard manure applied were used for formulating the fertilizer prescription equations for cucumber. Using these equations, the quantity of fertilizers to be used to get a target of yield can be calculated if the available nutrient status is known. The equations thus developed were verified in farmers' field at four locations; Pallikandam, Maraikkal, Ayiloor and Vithanassery. The fields were laid out with five treatments and four replications. The treatments were (i) farmers' practice (ii) KAU package, (iii) soil testing laboratory method, (iv) STCR method with a target of 30 t ha-I and (v) STCR method with a target of 35 t ha-I. The soil samples were analysed before raising the crop and the quantities of fertilizers to be applied were computed for various treatments. The plant and soil samples at flowering and harvest stages were analysed for pH, EC, CEC, Organic Carbon, available N, P, K, Ca, Mg, and micronutrients such as Fe, Mn, Cu and Zn. The total dry matter production and yield were taken treatment wise at the harvest. The data were used for- statistical analysis for assessmg direct and indirect effect of nutrients on yield and nutrient interactions. A positive correlation was observed between organic carbon' and soil parameters at flowering stage. At the harvesting stage, there was a positive correlation was found between yield and major nutrients. The interaction between available P in the soil and Nand K in the plant was observed. The availability ofP in plant was negatively correlated with Fe in the soil. The targeted yield equations for cucumber could produce the yields of 30 and 35 t ha-I from the verification experiments conducted at the different locations. The B:C ratio also was higher in the STCR methods over the farmers' practices, blanket recommendations and STL recommendations. The information generated in the project will help in making the soil testing programme scientifically sound in terms of achieving predicted yields, maintaining soil fertility and helping the extension agencies in ensuring balanced fertilizer use according to the soil fertility status and crop requirement.
Open Access
Site specific nutrient management for bitter gourd (Momordica charantia L)
(Department of Soil Science & Agricultural Chemistry, College of Agriculture, Vellayani, 2013) Neenu, S; KAU; Sudharmai Devi, C R
A study entitled ‘Site specific nutrient management for bitter gourd (Momordica charantia L.) was conducted in College of Agriculture, Vellayani during 2007-12 with the objective of formulating a site specific nutrient recommendation for enhancing the bitter gourd production in Kalliyur village of Kerala. The experiment set up included three steps namely Omission trial, SSNM field study and validation of results. All the experiments were conducted in farmer’s fields of Kalliyur village. Kalliyur village, located in Thiruvananthapuram district with an area of 17.23 km is one of the major vegetable growing tracts and bitter gourd is a popular vegetable in the locality. Spatial variability studies conducted revealed that remarkable variations existed in the soil properties across the village. Data on irrigation water analysis showed that the water used for irrigation was slightly acidic but safe for irrigation as it did not contain significant amount of soluble salts and other elements. Nutrient omission trial conducted in a farmer’s field at selected location showed that the indigenous supply of major nutrients in the locality is limited. The growth and yield parameters were the highest in (+) NPK treatment. Though the highest yield was recorded in (+) NPK plots, yield reduction in P omission plot was less compared to N and K omission owing to the higher supply of indigenous P in soil. The SSNM experiment revealed that site specific nutrient recommendations for high yield target with soil application of micronutrients recorded the highest values for all the growth and yield attributes of bitter gourd. Nutrient uptake and harvest index were also the highest in this treatment. The lowest value of harvest index was recorded by absolute control. In the case of nutrient balance sheet the highest value of N and K balance sheet was obtained in site specific nutrient recommendations for high yield target with soil application of micronutrients while the highest value of P balance sheet was obtained in farmer’s practice II. The correlation study revealed that bitter gourd yield was highly correlated with nutrient uptake as well as dry matter production and harvest index. Economic analysis showed that the SSNM practice is beneficial to farmers as it is able to provide more income than the usual farmer’s practice. The validation trial of the best treatments SSNM treatments with high yield target showed that the yield increase was consistent and hence can be prescribed to other farmers in Kalliyur village. The study thus conclusively proved that the present rates of fertiliser recommendation are not at all sufficient for getting maximum yield and profit to farmers. A site-specific nutrient prescription of 123: 59: 160: 30: 40: 25: 10 kg N P K Ca Mg Zn B ha -1 was found to produce 24 t of fruits ha -1 and a dose of 123: 59: 160: 30: 40 kg N P K Ca Mg + 1 per cent Zn foliar + 0.5 per cent B foliar ha were found to yield 22 t fruits ha -1 . The farmers in the area could get a monetary benefit of 601604/- and 542104/- ha -1 respectively by adopting these recommendations. Adoption of SSNM prescriptions is advantageous not only from the point of view of increasing profitability to farmers but also minimizing environmental degradation.
Open Access
Investigations on the efficacy of biochar from tender coconut husk for enhanced crop production
(Department of soil science and agricultural chemistry, College of agriculture, Vellayani, 2015) Mariya Dainy, M S; KAU; Usha, P B
An investigation was carried out at College of Agriculture, Vellayani to characterize biochar from tender coconut husk and to assess its effects on soil properties, growth and yield of yard long bean (Vigna unguiculata subsp. sesquipedalis). The experiment consisted of production and characterization of biochar, laboratory experiments on nutrient sorption- desorption studies, carbon dioxide emission studies and a field experiment. Biochar was produced from tender coconut husk by the process of pyrolysis and it was crushed, sieved and the 2 mm sieved samples were used for further studies. The produced biochar had an alkaline pH (9.13), high CEC (15.26 cmol kg-1) and C: N ratio (68.86). Electrical Conductivity, total C, N, P, K, Ca, Mg and S contents in the prepared biochar were 1.73 dS m-1, 72.3 per cent, 1.05 per cent, 0.38 per cent, 2.27 per cent, 0.40 per cent, 0.20 per cent and 0.27 per cent respectively. The produced biochar recorded very high water holding capacity (226 per cent), low bulk density (0.14 Mg m-3) and high Brunauer Emmett Teller surface area (157.93 m² g-1) A laboratory experiment was conducted to study the desorption and sorption of nutrients like N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu using biochar. 32.35 per cent NH4+, 75.65 per cent PO42-, 45.14 per cent K+, 46.00 per cent Ca2+, 23.45 per cent Mg2+, 74.38 per cent SO42-, 36.80 per cent Fe2+, 30.20 per cent Mn2+, 26.75 per cent Zn2+ and 26.72 per cent Cu2+ were found to be desorbed from biochar after 7 rinses using de-ionized water in 1:100 ratio. The highest per cent of nutrient desorbed was P (75.65 per cent), followed by S (74.38 per cent) and the lowest per cent of nutrients desorbed were Zn (26.75 per cent) and Cu (26.72 per cent) within 72 hours. Sorption experiments were performed using rinsed biochar at different concentrations of nutrients and at different time intervals in 1:100 ratio. The results of the study indicated that biochar could sorb 100 per cent NH4+, 90.70 per cent PO42-, 92.00 per cent K+, 87.00 per cent Ca2+, 86.15 per cent Mg2+ and 91.82 per cent SO42- when it was equilibrated with 100ppm solutions within 24hours. For micronutrients, when 50 mg l-1 Fe2+, Mn2+, Zn2+ and Cu2+ solutions were given, biochar could sorb 99.67 per cent, 100 per cent, 99.12 per cent and 99.12 per cent respectively. Biochar from tender coconut husk is a good sorber and slow releaser of nutrients. An incubation study was carried out to estimate and study the pattern of carbon dioxide emission by the application of biochar into soil and it was compared with that of common organic amendments viz. FYM and vermicompost. The experiment consisted of 7 treatments with 3 replications and the study revealed that the cumulative amount of carbon dioxide emitted was highest for FYM @ 2 per cent (1014.05 mg CO2 100 g-1) and biochar @ 2 per cent registered an emission of 87.17 mg CO2 100 g-1 after 6months of incubation. There observed 91.40 per cent reduction in CO2 emission when soil was incubated with biochar @ 2 per cent compared to 2 per cent FYM. A field experiment was carried out with biochar and other commonly used organic manures at different doses using yard long bean variety Vellayani Jyothika as the test crop during January 2013 to April 2013, at the Instructional farm, College of Agriculture, Vellayani. Yield (1358 g plant-1) and yield attributes like pod length (54.50 cm), pod girth (3.90 cm), number of pods per plant (51), nutrient uptake and B: C ratio were significantly superior for the treatment T8 which received biochar @ 20 t ha-1 with 2 per cent PGPR and NPK as per POP. Physical properties chemical properties of the soil were significantly improved by the application of biochar @ 30 t ha-1. Biochar application reduced the bulk density, increased water holding capacity, water stable aggregates, pH, Cation Exchange Capacity, organic carbon status and nutrient availability. From the investigations, it can be concluded that application of biochar @ 20 t ha-1 along with 2 per cent PGPR and NPK as per POP which resulted in the yield of 1358 g plant-1 (20.12 t ha-1) can be considered as the economically viable and the best treatment. Biochar from tender coconut husk can be used as a good soil amendment which can improve soil health and enhance crop production.
Open Access
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; KAU; Sureshkumar, P
Field experiments on aerobic and flooded systems of rice were conducted in second crop season with the objectives to study the nutrient dynamics and transformations in these systems in second crop season with rice (variety Jyothi), in farmer’s field, at Nellikkattiri, Thirumittakode panchayat, Palakkad district. The treatments with two doses of fertilizers (as per Package of Practices Recommendations, KAU and based on soil test) and three doses of lime (as per POP, as per ΔpH and as per SMP buffer method) were imposed in plots of 20m2 area in Randomized Block Design with four replications. Under flooded condition, two field experiments were conducted to standardize the method of sampling and analysis for soil test based application of lime and fertilizers. One was based on sampling and soil testing on wet basis keeping the anaerobic environment unchanged, while the other was based on routine sampling and analysis after air drying. Better correlations with respect to available nutrients and plant nutrient content were obtained for wet analysis based recommendation and hence the data from this experiment were considered for comparison of the nutrient dynamics with that of the experiment on aerobic rice. In situ measurement of pH, electrical conductivity and redox potential was done under both systems of rice cultivation. Redox potential was measured from three different depths under flooded system (15, 30 and 45 cm) and from two different depths under aerobic system (30 and 45 cm). The soil and plant samples were collected at three stages viz. at active tillering, panicle initiation and at harvest of the crop. The soil samples collected were analysed for pH, EC, OC available nutrients (P, K, Ca, Mg, S, Fe, Cu, Mn Zn and B), and were also assayed to estimate fractions of soil phosphorus, iron, zinc and boron. The plant samples were analysed for N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu and B. At harvest straw and grain samples were analysed separately. The increase in pH in both systems was in proportion to the quantity of lime applied. Higher rate of increase in pH was observed under aerobic system. Increase in EC was in proportion to the quantity of lime and fertilizers added, and it was more in aerobic system due to less dilution. The redox potential became negative due to reduced environment in flooded system within two weeks of transplanting while it was consistently positive under aerobic system. The organic carbon content was higher under aerobic environment at active tillering and panicle initiation due to quicker decomposition of applied organic matter especially in presence of lime while it was lower under flooded condition initially due to slower rate of decomposition. Available P was highest under flooded system due to release of bound P from Fe and Mn by reduction of these elements to their respective soluble forms. Under aerobic condition, the available P recorded at active tillering and panicle initiation was lower than that of the initial value, due to its precipitation as tri calcium phosphate [Ca3 (PO4)2]. The available K status was higher under aerobic condition throughout the crop growth because of reduced rate of leaching under this environment. The rate of increase in available K was concurrent to the quantity of fertilizer added under both systems of rice cultivation. Highest K content in plant was recorded under aerobic rice system. The highest available Ca was recorded at active tillering and panicle initiation in flooded system of rice cultivation, because of the solubilization of applied lime. At harvest, the available Ca became precipitated as tri calcium phosphate which decreased the availability of both Ca and P under flooded condition. The transformation of tri calcium phosphate to mono calcium phosphate occurred only under aerobic condition during later stages. The highest Mg in plant was recorded in treatment where fertilizer application was done based on soil test under both systems of rice cultivation. The available sulphur status was higher under flooded condition during all the stages of sampling because of the increased solubility of applied factomphos and MgSO4. The status of available Fe was higher under flooded environment because of the reduction of Fe3+ to soluble Fe2+, while the available Fe status was found to decrease under aerobic condition due to oxidation of Fe2+ to insoluble Fe3+. The available Mn status under flooded environment decreased when compared to that of aerobic condition because of enhanced absorption by rice. The lower status of available Zn under aerobic condition resulted from more absorption of Zn by the crop, because of decreased competition from cations such as Fe3+ and Mn4+ under aerobic condition. The available boron status and boron content in plant was high under flooded condition because of the enhanced solubility of applied borax. Ultimately, aerobic rice recorded significantly higher grain and straw yield (6.23 t ha-1 and 6.35 t ha-1 respectively) than that under flooded system (5.12 t ha-1 and 5.52 t ha-1 respectively). The treatment with fertilizer application based on soil test and with lime as per SMP buffer method under aerobic situation recorded significantly higher grain yield of 6.8 t ha-1 because of balanced nutrition in this treatment combination. Higher root CEC, root mass, shoot mass root volume and root length were recorded under aerobic system. The decline in productive tillers during active growth phase was observed under flooded environment. Well developed aerenchymatic tissue in the roots was observed only under flooded environment. The water requirement was reduced by 57 % in aerobic rice, than that in flooded rice.
Open Access
Heavy metal contamination of laterites by accumulation of solid wastes
(Department of soil science and agricultural chemistry, College of horticulture, Vellanikkara, 2015) Divya Vijayan, V; KAU; Sushama, P K
A heavy metal is defined as a metal that has the atomic number and specific gravity greater than 20 and 5 Mg m-3, respectively. Heavy metals occur naturally in the soil environment from the weathering of parent materials and also as contaminants at the waste disposing sites. Though, the soil acts as a sink for the majority of heavy metals, the excess uptake of any one of them may limit the plant growth. In this background, the research work entitled “heavy metal contamination of laterites by accumulation of solid wastes” was undertaken during the period 2010-2014. The project aims to investigate the extent of distribution of heavy metals (As, Cd, Cr, Pb, Hg and Co) in waste dumping sites of laterite as influenced by soil and climatic conditions using geostatistical technique, to correlate the activity of major soil enzymes with the contents of heavy metals, to explore the potential of phytoremediation as well as aerobic and anaerobic methods of composting for the removal of heavy metals in solid waste and to evaluate the performance of amaranthus under different decontaminated methods adopted. In order to attain the objectives, four experiments were conducted. The effect of soil and climatic factors on heavy metal accumulation was examined with the collection of soil samples at quarterly intervals for a period of one year from two different waste disposal sites located at Laloor and Kalamassery. For the study on phytoremediation, the crops, vetiver, marigold and sunflower were experimented. Both the aerobic and anaerobic methods of composting were tried for the removal of heavy metals in another set of experiment. A pot culture study was also conducted to assess the growth of amaranthus under different decontaminated conditions. The salient findings are summarized as follows: The percentage distribution of Pb, Ni, Co, Cr and Hg at the different sites of Kalamassery revealed that Cr had the highest distribution followed by others. At Laloor, Pb was found to be dominant for the major dumping sites, whereas Cr at the non dumping site. The geo accumulation index for Hg was recorded as above one for all sites at Kalamassery. The average contents (mg kg-1) of Pb, Co, Ni, Hg and Cr was 15.58, 6.06, 43.18, 0.56, 107.9 at Kalamassery and 82.84, 7.79, 35.54, 0.42 and115.67 at Laloor, respectively. Heavy metal contents were found to be higher during summer than rainy season except for Cr and Cd. In general, soil enzyme activities were higher during quarter II of the sampling period. There was a positive correlation between Fe and urease (0.391*) and Pb and phosphatase (0.350*). The phytoremediation study with the three different crops (sunflower, marigold and vetiver) proved vetiver as a good phytostabilizer compared to others. Vetiver was found to be a translocator of Cr, since Ni, Pb, Co and Hg were mostly stabilized in the root. Marigold translocated all these heavy metals from soil except Co, and sunflower translocated Co, Ni and Cr except Pb. Bioconcentration factor (the heavy metal concentration in the plant/ the heavy metal concentration in the soil) was higher for vetiver compared to sunflower and marigold. Vetiver removed the heavy metals from the waste material in the order Cr>Ni> Co> Pb. Compared to aerobic composting, the anaerobic method proved to be better for the removal of heavy metals from the waste material collected from Laloor. The comparative performance of amaranthus grown in soil under different methods adopted for reducing heavy metal contamination showed that the yield was found to be the highest in the treatment with aerobic compost. The lowest yield was reported for amaranthus grown with phytoremediated material, followed by absolute control. The uptake of major nutrients also followed the same trend as yield. The heavy metal content was higher in the shoots of amaranthus grown with waste material and the accumulation followed the order Cr>Pb>Ni>Co>Hg. In all the treatments under study, the presence of Cr was more dominant in the post harvest soil compared to other heavy metals.
Open Access
Chemistry and transformation of boron in soils of Kerala
(Department of Soil Science & Agricultural Chemistry, College of Horticulture, Vellanikkara, 2013) Santhosh, C; KAU; 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.
Open Access
Assessment and management of micronutrient deficiencies in Onattukara
(College of Agriculture, Vellayani, 2015) Mini, V; KAU; Usha, Mathew
A study on “Assessment and management of micronutrient deficiencies in Onattukara” was undertaken with an objective to assess the available micronutrient status of the Onattukara region to develop a multi micronutrient mixture for balanced crop nutrition and to evaluate the effect of multi micronutrient mixture on growth and yield of okra. Two hundred georeferenced soil samples were drawn at random from twenty soil series of the Onattukara region representing different crop production systems and analysed for 13 soil fertility parameters. The results of the analysis of various soil parameters were integrated in GIS for the preparation of thematic maps. The overall fertility status of this region indicated that the soil was very strongly acidic with high level of phosphorus, low oxidisable organic carbon and available potassium and wide spread deficiencies of calcium, magnesium, boron and zinc. Observational trials were conducted at 18 different locations to assess the response of the okra crop to adhoc recommendations by KAU for micronutrients. Micronutrient application increased the yield up to eighty percent in these trials. Micronutrient fertilizer requirement was computed based on the available micronutrient status of the region and crop requirement. A multi micronutrient mixture having a composition of Zn (9.5%) + B (2.6%) +Cu (1.2%) +Mg (2.4%) +N (0.46%) @ 20kg ha-1 was developed and the effect of multi micronutrient mixture was assessed in the field experiments using okra variety Varsha Uphar as the test crop in two seasons during September- December in 2013 and February -May in 2014. The field experiment consisted of nine treatments and the treatments were T1 (Absolute control), T2 (Package of Practices (POP) ), T3 (Soil test based POP and secondary nutrients), T4 (Treatment 3 + computed dose of micronutrients mixture), T5 (Treatment 3 + 25% less of computed dose of micronutrients mixture),T6 (Treatment 3+ 25% more of computed dose of micronutrients mixture), T7 (Treatment 3+ foliar application of 0.5% solution of computed dose of micronutrients mixture), T8 (Treatment 3+ foliar application of 0.5% solution of 25% less of computed dose of micronutrients mixture) and T9 (Treatment 3 + foliar application of 0.5% solution of 25% more of computed dose of micronutrients mixture). Growth, yield and quality of okra increased significantly due to multi micronutrient mixture. Application of soil test based NPK and secondary nutrients + foliar application of 0.5 per cent solution of computed dose of micronutrient mixture @ 5 kg ha-1 in two splits at 15 DAS and 35 DAS (T7) yielded significantly higher (11.3 tha-1) over rest of the treatments. T7 recorded 80 per cent more yield than T3, which was the soil test based package of practices (POP) and secondary nutrients and more than double the yield of POP. Soil application of this mixture @ 20kg ha-1 (T4) was also significantly superior to the POP recommendations. Soil status of micronutrients in the experiment site before the experiment was Zn (0.27 mg kg-1), Cu (0.21 mg kg-1) and B (0.17 mg kg-1). After two consecutive application of multi micronutrient mixture, the soil status of Zn, Cu and B were in the range of 0.62 to 1.58 mg kg-1, 0.74 to 0.99 mg kg-1 and 0.19 to 0.31 mg kg-1 respectively. Even after continuous application of micronutrients for two seasons the critical status was not attained for Cu and B in soil. So application of micronutrient fertilizers customized for agro ecological units and crops ensures increased yield and sustain soil health. In general the highest nutrient content and uptake in shoot and fruit were recorded by T7. The highest B: C ratio of 3.02 was also recorded by T7. From the investigation it can be concluded that foliar application of micronutrient mixture @ 5kg ha-1 in two splits at 15 DAS and 35 DAS was superior to soil application with respect to yield, quality and B: C ratio. The study revealed that micronutrient deficiency is one of the yield barriers which can be broken down by including micronutrient fertilizers in the nutrient schedule of crops.
Open Access
Nutrient interactions in soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of Kerala.
(College of Horticulture, Vellanikkara, 2011) Sajnanath, K; KAU; Hassan, M A
A comprehensive approach has to be adopted for efficient fertilizer use, incorporating soil test, field research and economic evaluation of the results for providing a scientific basis for the process of enhancing and sustaining food production as well as soil productivity with minimum environmental degradation, it needs more. Soil testing is one of the best scientific means for quick and reliable determination of soil fertility status. Soil test crop response study in the field provides soil test calibration between the level of soil nutrients as determined in the laboratory and the crop response to fertilizers as observed in the field for predicting the fertilizer requirements of the crop. In Kerala, many studies have been conducted to get a fertilizer prescription equation for targeted yield in various crops like rice, banana etc. A programme was formulated to investigate the nutrient interaction in soil test crop response studies on cucumber (Cucumis sativus L.) in the laterite soils of Kerala. In this, the field works were conducted as per the pattern of soil test crop response correlation studies. A gradient crop experiment was conducted in the experimental field of AICRP on STCR using maize. The purpose is to create a fertility gradient in the field by applying different doses of fertilizers. The area was divided into three strips and the doses of nutrients were applied as per STCR pattern of fertilization for maize. The crop was harvested and the plant samples were taken for analysis. The pre and post experimental soil samples were analysed. It was found that fertility gradients were developed in the field. Using the data on dry matter production in various strips, the nutrient uptake was also determined. A test crop experiment was designed in the same field where the gradient crop was raised. There were 24 treatments with three control plots. The treatments included four levels of nutrients and three levels of farm yard manure. The crop, cucumber (Var.: AAUC-2), popularly known as salad cucumber, was raised and managed as per package of practices of KAU. The soil samples were collected before, at flowering and harvest stages during the experiment. The plant samples were collected at flowering and harvesting stages. The total dry matter production and yield were taken treatment wise at the harvest. The soil samples were analysed for various chemical parameters. The data on yield, uptake of nutrients, nutrient status, nutrient requirement, quantity of farm yard manure applied were used for formulating the fertilizer prescription equations for cucumber. Using these equations, the quantity of fertilizers to be used to get a target of yield can be calculated if the available nutrient status is known. The equations thus developed were verified in farmers' field at four locations; Pallikandam, Maraikkal, Ayiloor and Vithanassery. The fields were laid out with five treatments and four replications. The treatments were (i) farmers' practice, (ii) KAU package, (iii) soil testing laboratory method, (iv) STCR method with a target of 30 t ha-I and (v) STCR method with a target of 35 t ha-I. The soil samples were analysed before raising the crop and the quantities of fertilizers to be applied were computed for various treatments. The plant and soil samples at flowering and harvest stages were analysed for pH, EC, CEC, Organic Carbon, available N, P, K, Ca, Mg, and micronutrients such as Fe, Mn, Cu and Zn. The total dry matter production and yield were taken treatment wise at the harvest. The data were used for- statistical analysis for assessmg direct and indirect effect of nutrients on yield and nutrient interactions. A positive correlation was observed between organic carbon' and soil parameters at flowering stage. At the harvesting stage, there was a positive correlation was found between yield and major nutrients. The interaction between available P in the soil and Nand K in the plant was observed. The availability ofP in plant was negatively correlated with Fe in the soil. The targeted yield equations for cucumber could produce the yields of 30 and 35 t ha-I from the verification experiments conducted at the different locations. The B:C ratio also was higher in the STCR methods over the farmers' practices, blanket recommendations and STL recommendations. The information generated in the project will help in making the soil testing programme scientifically sound in terms of achieving predicted yields, maintaining soil fertility and helping the extension agencies in ensuring balanced fertilizer use according to the soil fertility status and crop requirement.

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