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Open Access
Taxonomy and organic carbon-nutrient interactions in selected wetland soils of Kerala
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2019) Nideesh, P; KAU; Sreelatha, A K
A study was undertaken with the objective to classify wet land soils in the agro ecological units AEU 10 (north central laterite), AEU 5 (Kole lands) and AEU 6 (Pokkali lands) of Kerala and to assess the organic carbon stocks and CNPS stoichiometry. The study also aimed in finding out the organic carbon - nutrient interactions and to predict the organic carbon turnover in these soils. Extensive field traverse was conducted to select sites for profile excavation in the lateritic, Kole and Pokkali wetlands. The excavated profiles were studied for their morphological, physical and chemical properties. Based on the results of the study, soils of lateritic wetlands were classified as fine loamy, mixed, super active, acid isohyperthermic, Fluventic Dystrustepts. Soils of Kole lands were classified as loamy, mixed, euic, isohyperthermic, Terric Sulfihemists and Pokkali soils as coarse loamy over sandy, mixed, active, isohyperthermic, Typic Sulfaquepts. Total soil organic carbon (SOC) stock in the north central laterite region (Fluventic Dystrustepts) was 218 Mg ha-1 up to the depth of 120 cm of which maximum amount was stored in the surface 30 cm (86 Mg ha-1). In the Kole land soil (Terric Sulfihemists) maximum SOC was stored in the 90-120 cm layer (1016 Mg ha-1) and a total SOC of 2261 Mg ha-1 was stored up to 120 cm depth. Pokkali soils (Typic Sulfaquepts) stored 209 Mg ha-1 SOC up to 120 cm depth which was almost uniformly distributed in the entire profile. The C/N, C/P and C/S ratios decreased with depth in lateritic soil profile, whereas in the Kole land soil these ratios except C/S ratio increased significantly in the sub surface horizons. In the Pokkali soils the CNPS stoichiometry suffered irregular variation with depth. An incubation experiment was conducted to study the organic carbon nutrient interactions in the three wetland soils. Treatments included control (T1), POP based fertiliser and lime application (T2), soil test based fertiliser and lime application (T3), FYM substituting nitrogen in the T3 treatment (T4) and soil test based fertiliser and dolomite application (T5). In the lateritic soils. the active carbon and organic reserves of N, P and S were high in T3 treatment. The organic N, P and S pools increased in treatment T5 whereas organic P and inorganic S increased in treatment T4. In the Kole land soils, active carbon, organic nitrogen, inorganic P, organic S and inorganic S increased in T3; inorganic N and organic P increased in T4 and organic P and S pools increased in T5. In the Pokkali soils, active carbon content was high in T2 compared to other treatments while active carbon, organic N and inorganic N decreased in treatment T3. Liming decreased organic P in Pokkali soils due to conversion to available forms and higher utilisation. Application of FYM increased organic S in Pokkali soils and inorganic S in all soils. Temporal variation of the nutrient content (mg kg-1 soil) per organic carbon content (g kg-1 of soil) indicates the change in nutrient supply per unit change of organic carbon content. Treatment T1 favoured higher inorganic nitrogen per carbon content in laterite and Pokkali soils, where as in in Kole soils it was increased in T4. Inorganic phosphorus content per carbon was highest in laterite and lowest in Kole soil in control (T1). Inorganic sulphur per carbon content was highest in T4 for laterite, Kole and Pokkali soils. Organic nitrogen per carbon content was highest in the Kole land and minimum in the Pokkali land in the T3 treatment. Organic phosphorus per carbon content was maximum in FYM treatment in Kole and Pokkali soils and was minimum in T2 treatment in laterite and Pokkali soils. Treatment T3 had the highest organic sulphur per carbon content in the laterite and Kole soils and the treatment T1 gave the highest content in Pokkali soil. Wetland DNDC model was used to simulate the organic carbon turn over in the three wetland systems using the climatic data predicted by MarkSIM software. The results of modelling simulated for the year 2050 indicated that application of 100 per cent NPK along with FYM @ 5t ha-1 will ensure maximum organic carbon content in the Kole, Pokkali and lateritic wetlands. Fertiliser application improves the organic carbon storage in lateritic and Kole land soils. But in the Pokkali soils, fertiliser addition will not cause change in the organic carbon turn over processes whereas FYM application can improve the carbon content. Results of the study indicate that cultivation without any fertiliser and lime application causes gradual depletion of all organic and inorganic pools of nutrients in Kole land and lateritic wetland soils. Soil test based fertiliser and lime application along with FYM @ 5t ha-1 is appropriate in these soils for increased sustainability. The Pokkali soils are self-sufficient and can sustain its fertility status without any fertiliser application. However liming and FYM application may be considered as management options to improve sulphur availability and organic carbon turn over processes in these soils.
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 management in coconut based cropping system utilizing products from rapid conversion technology of biowastes
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2019) Priya, U K; KAU; Sudharmai Devi, C R
The study entitled “Nutrient management in coconut based cropping system utilizing products from rapid conversion technology of biowastes” was carried out at the Department of Soil Science and Agricultural chemistry, Vellayani and Farmers field in Onattukara , Kayamkulam ,Alapuzha during May 2016 to August 2018. The major objective of study was the nutrient management in coconut intercropped with banana (Njalipoovan) and tuber crop elephant foot yam (Amorphophallus paeoniifolius ) variety Gajendra using different products that are produced from rapid conversion technology of biowastes in AEU 3 of Kerala. In development and characterization of liquid formulation produced by rapid conversion technology, the segregated, ground biodegradable waste was subjected to thermochemical process and extracted using five concentrations (1%,2%, 3%, 6%, 10%) of four extractants KOH (0.1 N), KOH (0.25 M), KCl (2M), distilled water. The best extractant was chosen after screening for shelf life and phytotoxicity test using germination bioassay. KOH 0.25M, 2% and KCl 2M ,3% promoted seed germination, seedling vigour of okra and cow pea were selected. The two concentrations were then tested for their performance in pot culture using amaranthus and tomato. The results indicated that KOH 0.25 M, 2 % was superior to the KCl 2M, 3% solution. KOH 0.25 M 2 % was then fortified using modified Hoagland medium and GA3 1ppm. In banana and amorphophallus 0.1% dilution was given as foliar spray and in coconut 0.5% dilution was given as root feeding. Customisation of organic fertilizer was carried out on the basis of initial soil test results and crop requirements. 227 In order to find the effect of treatments in coconut intercropped system a field trial was conducted in RBD with eight treatments and 3 replications. The treatments had significant effect on the soil bulk density and WHC. There was lowering of bulk density in banana and amorphophallus for treatments that received POP and POP +STB. The highest WHC in coconut was for the treatment that received POP+STB. In banana and amorphophallus the WHC was highest for treatment that received POP and POP +STB followed by FFOF. There was a slight increase in the pH, for the treatments that received FFOF, QFOF+LF, HFOF +LF and LF alone. The second and third depths remained unaffected in terms of physical properties due to treatment effects. In soil carbon pools dynamics the results showed that TOC % was highest in surface soils for the treatments that received POP, POP +STB and FFOF in all the three crops. The labile carbon content was highest for treatment that received FFOF and LF, HFOF+LF, QFOF+LF in coconut for all the three depths. In amorphophallus and banana, the highest was for FFOF followed by the POP and POP+STB. Similar trend was followed in the case of oxidizable carbon, LI and CPI. The dehydrogenase activity was also high in treatments receiving FFOF ad those receiving LF. The earth worm count was mostly related to the rainfall pattern and not the carbon pool dynamics. There was a gradually increasing trend for soil available nutrients for subsequent years. In the case of coconut the primary nutrients shows a gradual increase in the April -May followed by a hike in August September in surface samples. the treatments that received FFOF was superior or on par with HFOF+LF or LF, POP, POP+STB. Second and third depths nutrient values were usually highest for treatment that received foliar fertilization and root feeding. In banana and amorphophallus POP, POP +STB and LF were either superior or comparable to FFOF. There was an initial increase in nutrient content of soil followed by a gradual decrease. In the case of micronutrients and secondary soil nutrient status FFOF was superior to all other treatments in terms of soil nutrient 228 availability that was mostly on par with POP+STB or HFOF +LF treatments for coconut, banana and amorphophallus. The foliar nutrient concentration in coconut showed a significant change only during the third season of treatment application. The highest foliar concentration was for treatment receiving FFOF, POP, POP+STB followed by the HFOF +LF, QFOF +LF, LF that was on par. In case of banana and amorphophallus a similar pattern was observed. The yield and yield contributing parameters in coconut showed a significant change during the third observation period of treatment application. The highest yield in terms of nut yield was highest for treatment receiving FFOF, followed by POP, POP+STB and HFOF +LF. A similar trend was seen in banana (18.01 kg) and amorphophallus (7 kg) wherein the yield was highest for treatment receiving FFOF followed by that receiving POP+STB, POP, that was comparable with yield in treatment receiving HFOF +LF. The Benefit cost ratio in coconut was highest for the treatments that received POP and POP+ STB, followed by the treatment that received half dose of FOF along with root feeding that was comparable with treatments that received QFOF +LF or LF alone. In the case of banana highest B:C ratio of 2.72 was for treatment receiving foliar fertilization alone, followed by FFOF, 2.60 during the first season. The second season the treatment with FFOF was on par with the treatment that received foliar fertilization. In amorphophallus the treatment that received FFOF was having the highest BC ratio followed by the treatment that received HFOF+LF during the first season. The same trend was found in second season. Hence it can be concluded that application of FFOF will increase the yield, soil nutrient availability and uptake in coconut and inter crops. Half dose of FOF along with LF was equally beneficial for annual crop. In case of coconut when the B:C ratio was calculated despite of the comparatively low yield in treatments that received liquid fertilization and POP, was on par with the treatment that received 229 FFOF, due to the high cost of FFOF. Therefore, if the unit cost of FOF is reduced can increase the B:C ratio for the treatment that receives FFOF, which can be recommended to the farmers for economic and ecologically sustainable intercropping of coconut with banana and amorphophallus.
Open Access
Organic nano NPK fomulations for enhanching soil health and productivity
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2019) Nibin, P M; KAU; Ushakumari, K
The present investigation entitled “Organic nano NPK formulations for enhancing soil health and productivity” was carried out from July 2017 to February 2019 in the Model Organic Farm under the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani. The objectives of the study were to characterize organic nano NPK formulations, assess the nutrient release pattern under laboratory conditions and study the effect of soil and foliar applications of organic nano NPK formulations on crop growth, yield, quality and soil health using okra as direct test crop and amaranthus as residual test crop. The first part of the experiment comprised characterization of granular and liquid nano NPK formulations. During characterization study physical, physico-chemical and biochemical properties of nano NPK formulations were estimated. The particle size of granular and liquid nano NPK formulations were 83.20 nm and 71.79 nm, respectively. The surface area of granular nano NPK formulation was 138.95 m2 g-1. The pH of granular nano NPK was neutral and that of liquid nano NPK was slightly acidic. Primary, secondary and micro nutrient contents (Cu, Zn, Fe, Mn and B) in both granular and liquid nano NPK formulations were analysed. Heavy metals such as As and Cd were not detected in the nano NPK formulations and Pb, Ni and Cr detected were below the permissible limit. Organic carbon, total amino acid and organic matter fractions of granular nano NPK were also determined. The second part of the experiment was a laboratory incubation study, conducted to assess the nutrient release pattern of granular nano NPK formulation for a period of 75 days. The study comprised of 8 treatments with 3 replications. Treatments included Soil alone (T1), Soil + FYM (12 t ha-1) (T2), Soil + nano NPK 12.5 kg ha-1 (T3), Soil + FYM (12 t ha-1) + nano NPK 12.5 kg ha-1 (T4), Soil + nano NPK 25 kg ha-1 (T5), Soil + FYM (12 t ha-1) + nano NPK 25 kg ha-1 (T6), Soil + nano NPK 50 kg ha-1 (T7) and Soil + FYM (12 t ha-1) + nano NPK.50 kg ha-1 (T8). In general, pH, EC and organic carbon content of incubated soil significantly increased throughout the incubation period. There was a significant difference in the available nutrient status of primary, secondary and micronutrients throughout the period of incubation. In general all the available nutrients increased upto 45th day of incubation and thereafter showed a decreasing trend except for K, where K showed an increasing trend upto 60th day and thereafter declined on 75th day. In the case of available Fe, Mn and Cu, the nutrient release increased upto 45th day of incubation and then declined. Zn showed a varying pattern of release. T1 (Soil alone treatment) recorded the least nutrient release pattern throughout the incubation period. The third part of the study consisted of four field experiments to study the efficacy of organic nano NPK formulations on crop growth, yield, quality and soil health using okra as the direct test crop and amaranthus as residual test crop. The field experiment on okra followed by amaranthus was repeated once again for confirmatory results. The field studies were carried out in a lattice design with 16 treatments and 3 replications. Treatments consisted of soil application of granular nano NPK at 3 levels (12.5 kg ha-1, 25 kg ha-1 and 50 kg ha-1) with and without FYM, foliar application of liquid nano NPK at 2 levels (0.2% and 0.4%) with and without FYM and combined application of granular and liquid nano NPK formulations with and without FYM. Growth, physiological and yield attributes of okra (direct test crop of first and third field experiment) viz., plant height, LAI, DMP, chlorophyll content, days to 50 % flowering, fruit length, fruit girth, number of fruits per plant, average fruit weight and total fruit yield were significantly influenced by the soil and foliar applications of organic nano NPK formulations. Treatment that received FYM + soil application of granular nano NPK formulation 12.5 kg ha-1 along with foliar application of liquid nano NPK formulation 0.4 per cent was found to be the best with respect to yield and yield attributes. Quality parameters of the fruit viz., crude protein, crude fibre and ascorbic acid contents were influenced by the application of organic nano NPK formulations. Post harvest analysis of soil for physical, chemical, biological and biochemical properties after the first and third experiments was done and was found to be significantly influenced by the treatments except for the bulk density of the soil. Highest NUE of 30.81 % and 31.38 % was recorded by the treatment T12 for the first and second direct crop, respectively. In general, microbial load viz., bacteria, fungi and actinomycetes were significantly influenced by the application of organic nano NPK formulations. With respect to nutrient uptake by the plants, T12 recorded the highest uptake of N, P, K, Ca, Mg, S, Fe, Mn, Zn and Cu for first and second direct test crop (okra). The highest B:C ratio of 2.27 was also recorded by T12 for both the okra crops. The residual effect of nano NPK formulations on growth, yield, quality and soil health was studied by raising amaranthus as test crop in the same field after the harvest of the direct test crops (okra). Highest plant height, DMP and yield were recorded in T12 in both residual crops. Quality parameters of residual crop were analysed and T12 registered the lowest oxalate and nitrate content. The highest vitamin C was recorded by T12. Post harvest analysis of soil revealed that pH, OC, labile carbon, available N, P, K, Ca, Mg, micronutrients and enzymatic activities were significantly influenced due to the residual effect of organic nano NPK formulations by soil and foliar application. Regarding the uptake of nutrients, T14 (FYM (12 t ha-1) + soil nano (25 kg ha-1) + foliar nano NPK (0.2%)) recorded the highest uptake of N, P, K, Ca, Mg, S and micronutrients (Fe, Mn and Zn). The highest B: C ratio of 1.99 was registered in T12 in first residual experiment. Similarly B:C ratio of 1.81 was recorded in the treatment T12 in second residual experiment. The present study revealed that both granular and liquid nano NPK formulations satisfied nano specifications having particle size less than 100 nm and high surface area. Organic nano NPK formulations contained primary, secondary, micronutrients, organic carbon, amino acid, humic acid etc. From the incubation study, in general, it was revealed that granular nano NPK formulation was found to be capable of releasing nutrients slowly for a period of 45 days and thereafter showed declining trend. Treatment which received Soil + FYM (12 t ha-1) + nano NPK (25 kg ha-1) was superior with respect to the nutrient release. Among the different treatments, application of FYM (12 t ha-1) + soil nano NPK (12.5 kg ha-1) + foliar nano NPK (0.4%) was found to be the best resulting in highest growth, yield and yield attributes of okra, the direct test crop. Similar trend was observed with respect to residual crop (amaranthus) also. But for the nutrient uptake of the residual crop, FYM (12 t ha-1) + granular nano NPK (25 kg ha-1) + foliar nano NPK (0.2%) showed a significant influence over the other treatments. From the study it was concluded that combined application of granular organic nano NPK at 12.5 kg ha-1 with foliar application of liquid nano NPK 0.4 per cent at biweekly intervals can substitute conventional fertilizers for sustainable crop production and healthy environment. Organic nano NPK formulations are ecofriendly and organically certified which can totally substitute conventional fertilizers and are considered as a boon for organic farming.
Open Access
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; KAU; 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.
Open Access
Characterization and evaluation of on-farm liquid organic manures on soil health and crop nutrition
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2017) Sreya, U Parvathi; KAU; Ushakumari, K
The experiment entitled “Characterization and evaluation of on-farm liquid organic manures on soil health and crop nutrition” was undertaken at College of Agriculture, Vellayani during 2014-2017.The study was envisaged to characterize the on-farm liquid organic manures viz., cow urine, panchagavya, fish amino acid, vermiwash and jeevamrutha, to monitor the nutrient release pattern under laboratory conditions and to evaluate the efficacy of soil and foliar applications of these liquid manures on soil health and crop nutrition using bhindi as test crop. The study consisted of three parts. The first part comprised the preparation and characterization of above said on-farm liquid organic manures. These manures were prepared as per standard procedures and characterization study was conducted to determine the physical, chemical, biological and biochemical properties. Physical properties viz., colour and odour of different on-farm liquid organic manures were recorded. Among the liquid organic manures studied, fish amino acid and panchagavya showed acidic pH and other three liquid organic manures viz., cow urine, jeevamrutha and vermiwash recorded neutral pH. Regarding EC, jeevamrutha recorded the lowest value (1.53 dSm-1).The highest OC content (39.96%) was recorded by fish amino acid followed by panchagavya. Among the major nutrients, the highest N content (0.45%) was found in panchgavya followed by fish amino acid. The highest P content was recorded by FAA (0.41%). Maximum K content (0.17%) was recorded in cow urine followed by panchagavya, vermiwash and jeevamrutha. S content of all the liquid organic manures were higher compared to Ca and Mg content. The highest contents of Ca, Mg and S were recorded by fish amino acid. The Fe content (39.92mg L-1) was highest in jeevamrutha and the lowest in fish amino acid. Cow urine was found to be rich in Mn (0.400 mg L-1) and Cu (21.21 mg L-1).The maximum zinc content (2.00 mg L-1), IAA (6.00μg ml-1) and GA (35.00μg ml-1) were found in fish amino acid. Panchagavya was rich in cytokinin (2.82 mg L-1) whereas, ascorbic acid content (37.50 mg 100g-1) was the highest in vermiwash. Fish amino acid was registered the highest enzyme activities, except for dehydrogenase activity which was found to be maximum in cow urine (371.27 μg of TPF g -1soil 24 h-1) followed by fish amino acid (336.98 μg of TPF g -1soil 24 h-1). The maximum population of bacteria was observed in vermiwash and fungal population was presented in all liquid organic manures except cow urine. The highest azotobacter population was observed in fish amino acid. K solubilizers were found to be the highest in vermiwash whereas E.coli, P solubilizers, azospirillum and Pseudomonas sp. were not detected in any of the above liquid organic manures. The second part of the experiment was laboratory incubation study to monitor the nutrient release pattern from soil treated with the on-farm liquid organic manures for a period of two months. The study consisted of 6 treatments which included soil alone and soil treated with 10 per cent dilution of all the liquid organic manures separately and all the treatments were maintained at 60 per cent moisture level. In general increased pH and EC values were observed in all the treatments received diluted liquid organic manures compared to control. Regarding the release of major, secondary and micronutrients, there was significant difference in available nutrient contents between treatments during the periods of incubation. Regarding the release of N and P during incubation study, soil along with FAA 10 per cent recorded the highest release pattern whereas soil along with cow urine 10 per cent recorded the highest K release throughout the incubation period. There was increased release of Ca in the treatments received liquid organic manures. The highest Mg release throughout the incubation period was registered by the treatment received cow urine 10 per cent. Available iron content was higher in T5 (soil 5 kg + jeevamrutha 10 %) compared to other treatments. A significant difference was found among treatments with respect to available Zn content. Initially (0th day of incubation), all the treatments were recorded higher values compared to values recorded on 7th ,15th ,30th , 45th and 60th days of incubation. There was increasing trends in the Cu content of soil from 0th day of incubation to 60th day of incubation except in the case of T3 (soil 5 kg + FAA 10 %). Treatment T1 (soil without treatments) recorded the lowest values for all nutrients throughout the incubation period. The third part of the experiment was to evaluate the efficacy of soil and foliar applications of on-farm liquid organic manures in a pot culture experiment using bhindi as test crop. The treatments included were 75 per cent N as enriched vermicompost along with diluted liquid organic manures separately as soil and foliar applications. Plant height, LAI, dry matter production, number of flowers, number of fruits per plant and total fruit yield were found to be the highest in T5 (75 % N as EVC + panchagavya 3 % foliar application). Chlorophyll a, b and total chlorophyll content were the highest in T10 (75 % N as EVC + jeevamrutha 10 % soil application). T1 (KAU PoP) recorded the highest average fruit weight. T4 (75 % N as EVC + FAA 5 % soil application). registered the highest crude protein content while crude fibre content was lowest in T7 (75 % N as EVC + cow urine 10 % foliar spray). Ascorbic acid content was the highest in T5 (75 % N as EVC + panchagavya 3 % foliar spray) and was on par with T7, T2,T9 and T11. The results of the post harvest analysis of soil revealed that pH, EC, organic carbon and labile carbon contents varied significantly among the treatments. The highest organic carbon content of soil was recorded by T4 (75 % N as EVC + FAA 3 % soil application) and T12 (75% N as EVC + vermiwash 10 % soil application). The maximum labile carbon was recorded by T8. T5 (75 % N as EVC + panchagavya 3 % foliar spray) was rich in available N. Soil enzyme activities were influenced by the application of liquid organic manures. The treatment T5 registered the highest plant uptake of major nutrients. The treatment T3 registered the highest plant uptake of secondary nutrients. The highest value of Fe and Zn uptake was noticed in T11.(75 % N as EVC + vermiwash 10 % foliar spray). The highest value of Cu uptake was noticed in T1 (KAU PoP). The highest value of Mn uptake was noticed in T3 (75 % N as EVC + FAA 5 % foliar spray) . The lowest plant uptake of all nutrients were recorded by T13 (Absolute control). Economics of cultivation of bhindi indicated that cost benefit ratio was found higher for treatment T5, 75 per cent N as EVC + panchagavya 3 per cent foliar application (2.83) followed by T7, 75 per cent N as EVC + cow urine 10 per cent foliar spray (2.09). From the above study, it was concluded that the recommended dose of inorganics (KAU PoP) can be substituted with combined application of enriched vermicompost (enriched with azolla 10 %) to get 75 per cent N and foliar application of 3 per cent panchagavya or soil application of 10 per cent cow urine or 5 per cent fish amino acid at 10 days intervals. Soil health, in terms of physical, chemical, biological and biochemical properties of soil was more enhanced in the treatments received soil application of liquid organic manures. Liquid organic manures viz., cow urine, panchagavya, jeevamrutha, fish amino acid and vermiwash were easily preparable in the farmers’ farm, biodegradable, less expensive, eco-friendly and non-hazardous for human health and environment. From the study it was found that above liquid organic manures were very good organic sources for organic farming and sustainable agriculture.
Open Access
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; KAU; 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.
Open Access
Carbon sequestration and soil health under different organic sources in wetland rice
(Department of Soil Science and Agricultural Chemistry, Vellanikkara, 2018) Rajalekshmi, K; KAU; Betty Bastin
In the current scenario of global climate change, wetland paddy fields are considered as major sources of greenhouse gases (GHG), especially methane (CH 4) and carbon dioxide (CO 2) as they experience both dry and wet situations depending on water availability. On the other hand, wetland characteristics promote the accumulation of organic matter in the soil and sediment, serving as carbon (C) sinks and making them one of the most effective ecosystems for storing soil carbon. In this context, the present study was undertaken with the objective to assess the combined effect of organic and inorganic sources on carbon sequestration and soil health under rice –rice cropping system and to compare the carbon distribution and fluxes with that of adjoining fallow land. The experiment was conducted in the farmer’s field at Varadium, Thrissur with rice as test crop in sandy clay loam soil for two continuous cropping seasons viz., Virippu and Mundakan during April 2015 - January 2016. The treatments consisted of different organic sources like farm yard manure (FYM), jack tree (Artocarpus heterophyllus) leaves, daincha (Sesbania aculeata), rice husk biochar and no organic manure. These were applied in combination with four levels of nitrogen (N) viz., 0, 35, 70 and 105 kg ha -1 represented respectively as N 0, N 35, N 70 and N 105. The soil samples from surface (0-15 cm) and subsurface (15-30 cm) and plant samples were analysed at harvest stage in both seasons to assess the impact of treatments. Gas samples were collected during the second cropping season at three stages viz., active tillering, panicle initiation and near harvest of the crop from fifteen treatments (except N 0 level) so as to evaluate the GHG flux (CO 2 and CH 4) from the cultivated land and it was compared with that of adjoining wetland. Soil characterization of cultivated land (biochar treatment with N 0 level) and fallow wetland (1 m depth) was also carried out after the field experiment.Combined use of both organic and inorganic sources improved the physico-chemical properties of soil over inorganics alone. The impact was more pronounced with biochar + N 0 treatment and its effect on increasing soil pH was also note-worthy. The build- up of soil organic carbon (SOC) as well as total carbon (TC) contents were more in the surface layer compared to the subsurface. Irrespective of treatments, the carbon content decreased after Virippu season as a result of high temperature. The high carbon content noted in the biochar with all levels of N had positive effect even in the second season. The soil carbon storage was also high with this organic source. The distribution of organic C among physical pools of soil organic matter viz., coarse particulate organic carbon (cPOC), fine particulate organic carbon (fPOC), light fraction organic carbon (LFOC), intra light fraction organic carbon (iLFOC), heavy fraction organic carbon (HFOC) and mineral associated organic carbon (MinOC) separated on size and density basis using standard procedures were also studied. Though the organic sources had positive effect on various pools, biochar with all levels of N had a strong impact in the carbon content of cPOC, LFOC and iLFOC. The cPOC concentration decreased over time while the reverse happened with fPOC. However, in the density fractions with biochar treated soils, the LFOC had the highest C concentration followed by iLFOC and the effect was more prominent in the surface layer. Combined application of organic sources and inorganic fertilizers significantly increased the cation exchange capacity and nutrient availability in soil than that of inorganic fertilizers alone. The amount of nutrients decreased with increasing soil depth. Levels of N also had varied effect on these contents. The nutrient content in plant parts like grain, shoot and root of rice crop varied among treatments. Adequate improvement in soil physical, chemical and microbiological parameters on application of green manure contributed to increased grain yield at 35 kg N ha -1 in flooded rice soil while the straw yield was maximum in the treatment with biochar at N 105. Measurement of GHG emission during the rice growth stages showed that the level of CO 2 was high in the active tillering phase and near harvest phase of crop growth, while that of CH 4 was found to be higher in the panicle initiation phase. Application of biochar as well as green manure with 105 kg N ha -1 resulted in greatest emission of CO 2, whereas the FYM + N 105 showed highest emission of CH 4. Soil profile study carried out after the field experiment indicated that the soil profile in the fallow land had a depth of 115 cm and five horizons while a soil profile depth of more than 70 cm with six horizons in the cultivated land. The effect of biochar on distribution of carbon and available nutrients within 30 cm depth was maximum in cultivated land in comparison with fallow wetland. The study revealed that the application of biochar without N had great impact on soil pH and various pools of carbon but its effect at this level on soil available nutrients was reverse. The soil available nutrients were higher with FYM and daincha and their effects increased with higher levels of N which subsequently improved the plant nutrient contents and rice yield. However, the organic sources with higher doses of N had enhanced emission of CO 2 and CH 4. Hence a suitable balance between the organic + inorganic N sources is advocated.
Open Access
Impact assessment of landfill on soil health and water quality in a waste disposal site
(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 2017) Fasila, E K; KAU; Sam, T Kurumthottical
The study entitled “Impact assessment of landfill on soil health and water quality in a waste disposal site” was undertaken with an objective to assess the impact of dumping Municipal Solid Waste (MSW) on soil and water quality, spatial variability in the level of biological and chemical contamination along the leachate zone and identification of a few bioremediators and their possible effectiveness in decontaminating the landfill materials. As a part of this study, geo-referenced sampling points have been identified initially for dumped waste materials (from the existing two landfill sites), soil (from two depths) and leachate samples along the leachate flow zone at a regular interval of 50 m within the plant area and ground water samples outside the area were collected. All the samples were monitored from these geo-referenced sampling points in three successive seasons, viz., pre-monsoon, monsoon and post-monsoon. The values for all the physico-chemical parameters in landfill materials were high during pre-monsoon period and only a marginal variation observed in heavy metal content in three seasons of study. Soil samples were acidic in reaction and a reduction in N, P, K and heavy metals were observed as the depth of sampling increased. Comparatively high values were observed in all parameters during pre-monsoon period than the other two seasons both in soil and leachate samples. Fe, Al and Hg content in leachates were very high and the concentrations of Fe, Al, Pb, Cd and Hg in ground water exceeded the acceptable level insisted by BIS. The leachate samples also recorded a high value for biological oxygen demand, chemical oxygen demand and coliform count than the ground water samples. Fifteen profusely growing weed species were identified and collected along the leachate flowing zone and the shoot and root portions were analyzed separately for various heavy metals to assess their selective retention capacities. Most of the weed species except Sphagneticola trilobata, Commelina diffusa, Ricinus communis, and Mikania micrantha were found to retain more toxic metal load in the root portion than the shoot portions. Among them, Alternanthera tenella was identified as the best hyper accumulator with respect to its gross uptake of the metals like Mg, Mn, Pb, Cd, Ni, Co and Cr. Hence, this plant was selected for the sand culture study along with other established hyper accumulator plants namely; Indian mustard, sunflower, globe amaranth and marigold analyzed for selective retention capacity under four graded doses of lead, cadmium and nickel. This study identified three best plants species (sunflower, globe amaranth and marigold) showing highest hyper accumulation capacities and hence they were carried forward to another pot culture study employing contaminated and degradable landfill materials for the final revalidation of claims. The experiment consisted of ten treatments and the treatments where the growing medium was re-constituted with different proportions of degradable landfill materials and virgin soil with and without the AMF inoculation. The plants which were grown for three months were analyzed separately for root and shoot portions for the exact quantum of selective retention status of metals like Al, Zn, Cu, Fe, Pb, Cd, Ni, Co, Cr and Hg. Lower levels of metal accumulation was recorded in all the plant parts where AMF had been inoculated in the media than its pairing treatment without inoculation, indicating the specific effect of AMF in preventing the uptake of heavy metals by plants and at the same time permitting the absorption of other ions needed for growth. Sunflower had been adjudged as the best plant that removed maximum load of studied heavy metals from the contaminated growing media except nickel and chromium. Similarly globe amaranth had been specifically identified as an excellent accumulator of nickel. Marigold was identified to be efficient accumulator of chromium. From the investigation it can be concluded that the soil and water bodies near the dumpsite sufficiently contaminated with the heavy metals like Zn, Mn, Cu, Fe, Pb, Cd, Ni, Co, Cr and Hg. As the distance from the dumpsite increased the extent of various chemical and biological contaminations showed a decreasing trend. Sunflower, globe amaranth and marigold were found to be effective hyper accumulators for the area in decontaminating the soils.

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