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Open Access
Influence of applied nutrients and stage of harvest on the yield and physicochemical properties of essential oil of palmarosa (Cymbopogon martini Stapf var. motia)
(Department of Soil Science and Agricultural Chemistry , College of Agriculture, Vellayani, Trivandrum, 1985) Chinnamma, N P; KAU; Aiyer, R S
Palmarosa, an essential oil crop introduced in Kerala, from Maharashtra, nearly two decades ago, is spreading steadily la the pialas and midland regions of North Kerala. Several agro-techniques have yet to he standardised for the commercial cultivation of this crop in the State. The present studies were undertaken at the Aromatic pnfl Medicinal Plante Research Station, Odakkaly during 1980-'8 4 to obtain information on the nutrition of palmarosa, optimum harvest intervals to ensure maximum herbage and oil yields and the factors influencing the quality of oil. The treatments in the major field experiment (1980-'82) consisted of three levels of N, and KgO, each at 25, 50 And 75 kg/ha along with six intervals of harvest at 40, 45, 50, 55, 60 and 65 days. The total number of treatment combinations wore 162 in a 3^ x 6 confounded asymmetrical factorial design. Tho main experiment was continued for another two yoaro limiting tho observations, to the yield of herbage and oil. This was then followed by an observation trial with intervals of harvest longer than tho maximum of 65 doye tried in the main experiment. In the main experiment the herbage yield vns significantly increased by application of P2°5 ^2°* Nitrogen did not have any eignifioant offeot on herbage yield poaeibly due to tha medium level etatua of soil N in the ABSTRACT ^erimental plots. The oil yield was Bignifioantly enhanced by P205 application at 50 kg/ha. Different levels and K showed no significant influence on the yield of oil. Harvest intervals showed significant influence on herbage yield, oil yield and oil content and the maximum value was recorded by the 65 day interval. A path analysis of the herbage yield with related cnaracters has shown that the height of the plant is the most important yield attribute influencing directly the yield of herbage. Path analysis of oil yield showed that oil yield is mainly dependent upon herbage yield. The direct effects on oil yield by yield attributes are found to be in the decreasing order of number of tillers with inflorescence, height of the plants and length of inflorescenoe. Maximum indirect affect via herbage yield is expressed by the height of the plant and length of inflorescence. All these directly and indirectly contributing factors arc soon to be markedly influenced by tho applioation of phosphorus and intervals of harvoat* Herbage yield and oil yield for various harvest lntorvalo obtained In the flrot two years wore fit tod In a Cobb-Dcughlua reoponoo function and tha expooted values «leulat«d were found to be very olooe to tho actual observed values• In thethird and fourth year of the experiment, the ghest herbage and oil yields were recorded by 60 day interval followed by the interval of 65 days, A quadratic Sanction for the data pooled over for four years was fitted to see if the data show a diminishing return with an increase in harvest interval and it was found that the optimum herbage yield and oil yield were obtained when the harvest was done at 62 and 63 days interval respectively. The final observational trial also indicated that the herbage and oil yields were maximum for a harvest interval of 65 days beyond which it decreases. Increase in the levels of both N and P tended to increase the content of geraniol and to decrease the content of geranyl acetate which are the price determining quality attributes of the essential oil. But the maximum interval of harvest viz., 65 days tried in the main experiment was not sufficient for moot of the physico-chemical properties of oil ouoh os specific gravity, refractive index, geraniol content, geranyl acotato content etc. to reach the minimum limit prescribed by 131. The observational trial showed that the oil obtained at intervale of 95 days and above satisfied the 131 specification with respect to all the phyalco-ohemioal properties of the oil. However, at thle herveat Interval the yield Itself wae considerably depressed compared to the yield at 65 day Interval. Th, eoonomloe worked out for different Intervale of harveab baaed on the ourrant market prloe of the oil paeein« as above the I SI limits as fe. 240/- per kg (oil from harvest intervals at and above 95 days) and those below them at Fs.220/- per kg (oil from harvest intervals of 55, 65, 75 and 85 days) it has been found that a wider cost benefit ratio and net return per rupee investment are obtainable for harvest intervals ranging from 65 to 85 days. However, 65 day interval has the advantage of early returns from the investment. Application of 50 kg PgO^/ha in view of its significant effect on herbage yield, oil yield and oil quality increase the net profit per rupee invested for the harvest interval of 65 days. The average removal o f II, P, K, Ca and Mg from the s o i l by palmarosa per h ecta re per year lias a lso been worked o u t . The optimum f e r t i l i s e r le v e l fo r palmarosa i s 25 kg II, 50 kg P?05 and 25 kg K20 per h ectare over an a p p lic a tio n o f spent g ra ss at 5 tonnes per h ectare per y e a r . The optimum h arvest in to r v a l i s 65 days. TIiIb would give maximum horbago y io ld , o i l y io ld ond ea rly return from in v e stm e n ts.
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
Land evaluation and suitability rating of the major soils of Onattukara region
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1998) Premachandran, P N; KAU; Subramonia Iyer, M
The need for a scientific approach in inventorying and utilizing land resources most economically and efficiently is now universally accepted. Agricultural prosperity, to a great extent, depends on judicious use of soils and rational application of soils data. A reconnaissance soil survey of Onattukara region was undertaken to study the extent and distribution of the different soils for soil classification, land capability and irrigability classification and for subsequent land evaluation. The study reveals that Onattukara region extends over an area of 40,948 ha. The soil map showing the distribution of the identified twenty soil series has been prepared. The climatological data reveals that the soil moisture regime is , ustic and the soil temperature regime is isohyperthermic. The soils have been classified as per Soil Taxonomy (U.S. Soil Survey Staff, 1975) and Keys to Soil Taxonomy( U.S. Soil Survey Staff, 1994 and 1996). Ten series were classified under Entisols, SIX under Inceptisols, three under Ultisols and one under Alfisols. Based on the inherent soil characteristics and landscape features, the soils have been grouped into three land capability classes, nine capability subclasses and land capability map prepared. The soils were classified into five land irrigability classes, eight land irrigability subclasses and land irrigability map prepared. The soils were evaluated based on principles of land evaluation and rating of productivity parameters. The productivity rating of the soil propertIes agamst the productivity index for nee, coconut, sesamum ,cassava and banana were made and conclusions arrived at. Productivity rating shows that Kottakakam series is best suited for rice, Palamel, best for coconut and banana, Artuva and Mahadevikad, for sesamum and Palamel and Vallikunnam, for cassava. On the basis of the studies carried out, a land use is proposed for the twenty soil series of Onattukara region based on crop suitability ratings and crop suitability map prepared for the five crops taken for study. A proper soil survey interpretation provides information on soil potential, productivity and limitations in their sustained use. Soil survey information forms the major basis for land evaluation. A thorough knowledge of the potentialities and limitations of every piece of land is a prerequisite in its efficient utilization. A systematic survey is essential for the evaluation and classification of the soils based on their inherent soil characteristics, land capability, land irrigability and land suitability. A systematic survey and evaluation of the soils of Onattukara region was taken up to study, interpret, classify and to show their location and extent on base maps. It is hoped that the present study would open up avenues for further investigations on land evaluation, crop suitability and other management aspects for sustained use of soil resource data to the best advantage. This will also form the basis for microlevel planning for integrated and sustainable development of the region under Panchayat raj.
Open Access
Leaf litter dynamics in acacia and eucalyptus plantations
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1997) Moossa, P P; KAU; Venugopal, V K
An investigation entitled “Leaf litter dynamics in Acacia and Eucalyptus plantations” was undertaken to study the leaf litter production, litter decomposition and nutrient release characteristics, and impact of Eucalyptus and Acacia monoculture plantations on the soil physico-chemical and biological characteristics during 1994-97. One hectare each of Acacia auriculiformis, Eucalyptus tereticornis and a moist deciduous forest coming under the Kulathupuzha range of Kerala Forest Department were selected for the study. Field experiment were conducted to determine the leaf litter production and decomposition characteristics of plantation and natural forest. Leaf litter collected at monthly intervals showed that highest litter production was in Acacia (9.4 t ha-1 year-1) followed by natural forest (6.67 t ha-1 year-1) and Eucalyptus (4.68 t ha-1 yaer-1). Pattern of litter production was unimodal in Acacia and natural forest while in Eucalyptus it was bimodal. Chemical analysis of litter samples of plantations and natural forest revealed that with respect to nutrient content fresh and leaf litter of Acacia and Eucalyptus is superior to natural forest whereas litter quality in terms of water soluble components, polyphenols, lignin and cellulose were superior in natural forest. Annual dry matter loss of leaf litter by decomposition followed the order natural forest > Acacia > Eucalyptus. Nutrient release pattern of major and micro nutrients were also worked out for the leaf litter during the process of decomposition and natural forest litter recorded the highest mobility for all the nutrients on decomposition. Improvement in soil physico-chemical properties were noticed due to leaf litter decomposition in the monoculture plantation and natural forest. Biological activity in terms of earthworm and nematode under monoculture plantation was significantly lower than that of adjacent natural forest. Microbial content of soil below the litter bag during different months of decomposition were low in Eucalyptus and Acacia. Chemical analysis of the profile samples of various plantations revealed lower nutrient status in respect of major and micronutrients compared to natural forest. The physical properties of the soil also recorded as unfavourable change in the monoculture plantations as compared to the adjacent natural forest. Proximate anlysis of soil organic matter and humus characterization of the soil organic matter separated from various plantations indicated a low rate of humification and condensation under Eucalyptus. Low humic acid and fulvic acid content in humus and dominance of fulvic acid over humic acid was also noticed in Eucalyptus plantations. Functional group analysis of humic acid and fulvic acid showed that humic material separated from natural forest contained higher quantity of total acidity, contributed by COOH and phenolic group compared to plantation soils. UV, IR, DTA and TGA analysis of humic acid and fulvic acid separated from various plantations showed no variation with respect to natural forest. Allelopathic effect of fresh leaf and leaf litter extract of various plantations on the germination and growth of rice and cowpea followed the order Eucalyptus > Acacia > natural forest and as the concentration decreased from 1: 2 to 1: 10, the allelopathic inhibition also decreased significantly. Allelopathic effect of soil extract also followed the order Eucalyptus > Acacia > natural forest. Thus it can computed that though the leaf litter production and litter quality of monoculture plantations are comparable with that of natural forest, leaf litter decomposition and nutrient released were significantly lower than that of natural forest. Soil physico-chemical properties, soil fertility and biological activities were also adversely affected by monoculture plantations.
Open Access
Nitrogen losses from the rice soils of Kerala with special reference to ammonia volatilization
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1989) Anila Kumar, K; KAU; Rajaram, K P
In order to get a deeper insight in to the N dynamics of selected submerged rice soils, an investigation entitled “Nitrogen losses from the rice soils of Kerala with special reference to ammonia volatilization” was carried at the Regional Agricultural Research Station, Pattambi during 1985 – 87 with the following objectives. 1. To estimate the magnitude of ammonia volatilization losses from submerged rice soils, representing major rice growing tracts of Kerala. 2. To study the factors which are responsible for accelerating the rate of ammonia volatilization under flooded soil conditions. 3. To evaluate the effect of submergence, organic matter application, complementary effect of P and K on ammonia volatilization from the rice soil ecosystem. 4. To identity suitable N carriers capable of reducing the loss of N due to ammonia volatilization from submerged paddy soils. 5. To find out the effect of continuous application of organic and inorganic manures in lateritic submerged paddy soils on the quantum of N loss through ammonia volatilization. 6. To find out the transformations and extent of mineralization of applied urea. With these objectives, in view, a serious of laboratory incubation studies, followed by pot culture trials were carried out and the results were finally verified under field experiment also. Besides these, the plots of permanent manorial trial (dwarf indica) were utilized for estimating the N loss through ammonia volatilization on long term application of organic manures and inorganic fertilizers. In the incubation study for estimating the magnitude of N loss though ammonia volatilization, eight rice soils of kerala viz., sandy, karapadam, kayal, kari, pokkali, kole, poonthalpadam and laterite soils representing the major rice growing tracts of Kerala were incubated with no N and 27 g N m-2 as urea. Air train and acid trapping device was utilized to collect the volatilized ammonia. The results showed that sandy soil collected from Onattukara region registered an increased N loss through ammonia volatilization, whereas in the kole soil of kattukampal, the process was retarded to the lowest level. More than 75 per cent of the volatilization loss was observed within 9 days after urea application. Significant negative correlation was observed between ammonia volatilization and organic matter content, clay fraction and cation exchange capacity of the soil, whereas the coarse sand fraction showed significant positive correlation. Soil sterilization had little influence on ammonia volatilization in any of the soil under study. Another incubation study to assess the impact of quantity of urea applied on the quantum of N loss through ammonia volatilization was carried out using four soil types (sandy, kayal, poonthlpadam and laterite soils) with four rates of N application (9, 18, 27 and 36 g N m-2 ). The results indicated that the N loss through ammonia volatilization had a positive relationship with increased rates of urea application, though not linear. The complementary effect of phosphorus and potassium on the extended loss of N through ammonia volatilization was estimated in another incubation study utilizing the same four soil types with treatment as N alone, N and P, N and K and N, P, K @ 27:13.5:13.5 g N, P, K m-2 respectively as urea, superphosphate and muriate of potash. The results revealed that combind application of urea and muriate of potash was found to be significantly better in reducing the volatilization loss to be significantly better in reducing the volatilization loss of ammonia compared to the treatments, N alone and N and P. The incubation study to find out the influence of depth of submergence on the rate of volatilization of ammonia was conducted using the same soil types and four treatments (soil saturation, 5,10 and 20 cm submergence). The results showed that the soil samples maintained at saturation point recorded double the values for ammonia volatilization, compared to samples kept under submergence of 20 cm depth. The effect of application of organic matter on N loss through ammonia volatilization was studied in the same four soil types with the treatments as no organic matter, 0.25, 0.50, 0.75 kg organic matter m-2 as farm yard manure. The results indicated that application of organic matter was found to reduce volatilization losses considerably in all the soils studied and the lowest value recorded was for the treatment receiving farm yard manure @ 0.75 kg m-2. The relationship between N sources and the extent of volatilization of ammonia was investigated in another incubation study employing the same four soil types and ten different N carriers to supply 27 g N m-2. The relative efficiency of different N carriers in reducing the ammonia volatilization loss was in the order sulphur coated urea > urea mudball > gypsum coated urea > rock phosphate coated urea = neem cake coated urea = ammonium sulphate = ammonium chloride > urea : coconut pith: soil = urea. The pot culture study to trace the pathway of transformation and extent of mineralisation of urea under flooded soil condition consisted of three soil types (laterite, kari and poonthalpadam soil) and two levels of N (no N and 90 kg N ha-1 as urea). The rate of mineralisation of applied urea followed the soil reaction and the mineralisation stopped at the stage of NH+4 formation and hence chances of N loss through denitrification is meagre, unless the soil is aerobic. The second pot culture experiment was conducted with a view to identify the different ways that result in minimum loss of N through ammonia volatilization in sandy and laterite soils. The study showed that the decreasing order of N loss through ammonia volatalization from different N carriers followed the order, urea basal = urea; coconut pith: soil = coaltar coated urea = gypsum coated urea = rock phosphate > coated urea > urea split > urea super granule > urea mudball > sulphur coated urea. The five treatments selected from this experiments viz., urea split, urea mudball, urea super granule, gypsum coated urea and rock phosphate coated urea on reduced ammonia volatilization and high grain yield were compared in another pot culture trial and finally it was verified under field experiments in trial and finally it was verified under field experiments in laterite soil. The results revealed that urea mudball placement in the anaerobic layer of soil was found to reduce the n loss through ammonia volatilization to negligible level. Treatments with surface application of rock phosphate coated urea and urea in split dose ranked second and third position respectively in reducing the volatilization losses. Treatment receiving split application (top dressing of urea at 20 and 40 DAT) reduced ammonia volatilization considerably. Significant positive correlation was found between the cumulative N loss through ammonia volatilization and flood water pH measured at 0800 hrs and 1400 hrs, flood water NH4 – N content and flood water bicarbonate content. The pH of flood water measured at 1400 hrs were significantly higher than the value recorded at 0800 hrs and highest diurnal variation was observed for treatment with urea super granule deep placement. The urea super granule deep placement treatment resulted in increased grain yield in both the pot culture trials and field experiment. However, in field experiment the effect of different N carriers on grain yield was found to be uniform. The periodical N uptake by plants as well as N accumulation in grain and straw at harvest were found to be higher in the case of treatments receiving USG deep placement and urea split application. The effect of long term application of organic and inorganic nitrogen sources in soil on the rate of n lose through ammonia volatilization was studied utilizing the permanent manorial experiments. Plots receiving combined application of cattle manure + green leaves + NPK @ 45:45:45 kg N, P2 o5, K2 o as ammonium sulphate, super phosphate and muriate of potash were recorded the lowest value of n loss via ammonia volatilization when compared to other treatment plots.
Open Access
Nutrient dynamics in the rice based cropping systems
(Division of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1989) Sundaresan Nair, C; KAU; Subramonia Aiyer, R
The experiment consisting of five cropping sequences viz. rice - rice – rice (A1), sweet potato – rice – rice (A2) cowpea – rice – rice (A3) daincha – rice – rice (A4) and fallow – rice – rice (A5) and six treatments with varying doses of N P and K were conducted to study the performance of the sequences in relation to the nutrients required for optimising the out put from the sequences. The field experiment was laid out at R.R.S., Pattambi in 1980 – 81 and the experiment was conducted for two consecutive years ie. For six seasons. The experiment was started with the summer crop of 1981, namely summer rice (Triveni), sweet potato, cowpea, daincha and a summer fallow wherein the land was ploughed twice and left as such without any crops. The component crops were raised with five treatment variations modified from the recommended doses for each crop. The biometric observations for the summer crops, virippu and mundakan crops were recorded. The indications were that treatments have a significant effect on summer crops virippu and mundakan rice crops of 1981 and 1982. The yield shows that both treatments and sequences have a significant effect. The sequence daincha – rice – rice and the cowpea – rice – rice sequence gave the highest yield. The chemical analyses of plant parts of the summer crops, virippu and mundakan rice crops of both 1981 and 1982 show that the treatments have no effect on the NPK content. The soil study shows that the cropping sequences have a significant effect on soil pH. A pH decrease was noticed in all the sequences, the highest decrease being in the rice – rice – rice sequence. The organic carbon level of the soil is also affected due to the cropping sequence. The rice – rice – rice sequence shows a maximum decrease in organic carbon level and the daincha – rice – rice – rice shows a gain in organic carbon level of the soil. The total nitrogen of the soil shows a decrease in all the sequences and maximum decrease was noticed in sweet potato – rice – rice sequence. The available nitrogen level also was influence both by the sequences and treatments. A decrease in available nitrogen was noted to be a maximum in the rice – rice – rice sequence. The total P and available P levels show an increase in all the sequences and were high in daincha – rice – rice and cowpea – rice – rice sequences. The treatments also have a significant effect in maintain the P level in soils. The total K status of the soil as well as the exchangeable status of K shows a decrease after two year of cropping. The nutrient uptake studies reveal that the maximum NPK uptake takes place in the sequences sweet potato – rice – rice followed by rice – rice – rice and cowpea- rice – rice – rice followed by rice – rice – rice and cowpea - rice – rice. The balance sheet of nutrients reveals that nitrogen and available phosphorus in all sequences show a decrease and increases with decrease in fertilizer levels. The balance sheet of K shows that the soil maintains K levels. The sequence daincha – rice – rice is the best in maintaining a high K status in the soil. An analysis of the economics of cropping sequences reveal that the sequence sweet potato – rice – rice with full recommended dose of fertilizers gave the highest net return, which was followed by Cowpea in – rice – rice and rice – rice – rice. From nutrient balance studies, yield and economic analysis it is clear that any attempt in reducing the quantity of fertilizer for the component crops of the sequences affects the yield, besides deleteriously affecting the fertility of the soils. Any decrease in the fertilizer doses in the sequences will not be economical. With a long range view of enhancing crop output from cropping sequences and maintaining soil fertility, it becomes necessary to enhance and maintain higher fertility levels.
Open Access
Potassium supplying capacity of Neyattinkara- Vellayani soil association and its relationship with potash nutrition of major crops on them
(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1989) Valsaji, K; KAU; Subramonia Aiyer, R
Detailed study on the potassium supplying capacity of Neyattinkara-Vellayani soil association and its relationship to potash nutrition of major crops on them namely coconut and cassava has been made. This soil association represents the red loam soil type and consists of Neyattinkara series tentatively classified under Typic Eutropepts and Vellayani series under Typic Tropudalfs. Soil samples were collected from selected fields under coconut and cassava for the dominant soil types namely sandy clay loam and sandy loam soils under Neyattinkara and Vellayani series. To find the most suitable depth and location of soil sampling for coconut samples were also drawn at two different depths of 0-30 and 30-60 cm from basins and interrows. Empirical methods, quantity intensity studies, electro ultrafiltration studies and foliar diagnostic techniques were employed to decide on the most suitable method for plant available K. The various intensity, quantity and capacity factors which relate the readily available, difficultly available and storage or buffer capacity were assessed for a proper appraisal of the K status and supplying capacity. The various soil K parameters such as total K, water soluble K, exchangeable K, available K, nonexchangeable K, HNO3 extractable K, H2SO4 extractable K, sodium tetraphenylboron extractable K and percentage K saturation were found to be low. The water soluable K formed higher proportion of available K than exchangeable K. Interrelations showed that water soluble K, exchangeable K and available K are in dynamic equilibrium. Nonexchangeable K did not show any relationship with available K indicating that it is a poor source of available K. Quantity-intensity studies showed that the shape of the Q/I curve was similar in all types of soil since they belong to a group of related soils. The Q/I parameters like Are.K, Ko, Kx. KL and potential buffering capacity values were low. The KL values were higher than NH4OAc.K. The free energy values were found to be high indicating easy release rates of K. For both coconut and cassava, the leaf K did not show any consistent relationship with the soil K parameters. Among the Q/I parameters, KL had significant relation with leaf K of coconut. EUF 10 and EUF 35 showed significant relationship with leaf K of both coconut and cassava. Electro-ultrafiltration studies showed that the easily desorbed K was more than the strongly desorbed K indicating easy supply rate. The EUF 30-35 values were related to HNO3.K showing that this fraction included some initially nonexchangeable K. EUF 10 had significant relation with exchangeable K and EUF 35 had significant relation with exchangeable and available K. The buffer parameters BK (EUF 10/EUF 30) and EUF.Q (EUF 30-35/EUF 30) values were low indicating low buffer capacity. The EUF desorption pattern showed that the first peak was within 10-20 minutes and prominent than the second peak. This indicated low reserve K but easy supply rates. The EUF desorption curve of soils with high NH4OAc.K was above that of soils with low NH4OAc.K. This indicated that with increase in NH4OAc.K the easily desorbed K also increased. The yield of coconut and cassava were related to the various K parameters to evaluate the suitability of different methods for available K. In most of the cases NH4OAc method was found to be suitable for both coconut and cassava. Leaf analysis was also found to be suitable. For cassava the result obtained after 41/2 months is meaningless for the current crop. For coconut collection of index leaf is laborious. It was also found that the Q/I and EUF were suitable for coconut. But these methods cannot be followed in routine soil testing because of the high input of laboratory work involved. Considering these aspects it was found that NH4OAc method is the most suitable one because it is simple, cheap and easy to adopt. Based on the NH4Ac.k content the fertility status was found to be low to medium. The various intensity, quantity and capacity factors of soil K, Q/I and EUF parameters revealed that this soil association has low K supplying capacity. Hence heavy dose of K fertilizers is required. Split application is preferable especially in sandy loam soils to reduce leaching losses. NH4OAc.K which was found as a suitable indicator of plant available K varied significantly in basin and inter-row samples of sandy clay loam soils. This K fraction did not vary with depth in both sites. In general, the K nutrient index indicated that the basin samples had a higher level than inter-row and surface samples. Thus basin sampling at 0-30 cm depth was found to be the ideal site of soil sampling for coconut tree.
Open Access
Partial substitution of muriate of potash by common salt for cassava (Manihot esculenta crantz) in oxisols of Kerala
(Department of Soil Science & Agricultural Chemistry, College of Agriculture, Vellayani, 1995) Sudharmai Devi, C R; KAU; Padmaja, P
Field experiments were carried out in the College of Agriculture, Vellayani during 1991 to 1994 to study the possibility and extent of substitution of K of Muriate of Potash with the Na of common salt in Cassava variety M4 used as the test crop. Substitution of K was tried at 4 levels viz. 25, 50, 75 and 100 per cent of the recommended dose. Muriate of potash, replaced by wood ash and a combination of KHCO3 and NaHCO3 (eliminating chlorine source) also were included in the experiment. Plant growth characteristics like plant height and number of leaves did not vary significantly as a result of substitution. The maximum LAI was observed in the case of 50% K as MOP + 50% Na as CS treatment at all the growth stages. An increase in chlorophyll content was observed with NaCl substitution. In the early growth stages there was no significant variation in the production of roots, but at the later stages there was significant difference in this aspect. The root volume at 2 MAP varied significantly between treatments. In general, there was an increase in total weight of plant with NaCI substitution upto 50% and thereafter a decrease with higher levels of substitution, at all growth stages. Significant treatment difference could be observed in tuber yield in both the years of the experiment. T3 (50% MOP +50% CS) registered the highest tuber yield and T5 the lowest. The bulking rate and Utilisation Index also differed significantly among treatments. The cooking quality of the tubers from T3 was as good as that of T1. Significant differences could be observed in total sugars, reducing sugars and sucrose content of fresh tubers under different treatments. With increasing levels of substitution, the content of total sugars increased. Sucrose content was found to increase with Na application upto 75% substitution of K by Na. Significant variation was observed in the crude protein, total amino acid and free amino acid content of tubers. Hydrocyanic acid, total phenols and crude fibre also differed significantly between treatments. The keeping quality studies revealed that tubers from T3 could be stored fresh up to 35th day in moist soil, whereas tubers from T1 could be stored only upto 12th day, without deterioration. Enzyme studies revealed significant difference in the activity of starch synthesising enzymes, but NRA at 6 MAP was not affected by different treatments. The uptake of N was highest in T1 and P and K in T3. Na uptake by T1 which received no Na was generally higher than other treatments receiving Na. Ca and Mg uptake also differed significantly between treatments. Changes in soil organic carbon, available P, available K and available Mg were statistically significant between treatments but that of Ca was significant only from 4 MAP onwards. Yield of tubers was positively and significantly correlated to the uptake of N, P, K, Na, Ca and Mg. Yield at harvest was positively and significantly correlated to the root weight and root volume and also to the bulking rate at 2 MAP. Path coefficient Analysis revealed that the maximum direct effect on yield was contributed by the drymatter of roots at 2 MAP. From the results, it can be concluded that in soils having low to medium status of K, the K of MOP can be substituted up to 50% by Na of commonsalt in cassava without affecting the quality and quantity of tubers.
Open Access
Morphological, physical and chemical characterization of the soils of North Kuttanad
(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1997) Manorama Thampatti, K C; KAU; Jose, A J
An investigation was carried out at the College of Horticulture, Vellanikkara during 1992 to 1995 to evaluate the morphological, physical and chemical characteristics of soils of North Kuttanad and to assess the extent of toxic factors that pertained in the soil due to restricted movement of water under the influ- ence of Thanneermukkom regulator. The study was carried out in three parts, viz., (1) Morpho- logy and physicochemical characteristics, (2) Fertility characteristics and (3) Toxicity chara- cteristics. Fifteen soil profile were drawn from North Kuttanad to study the morphology and physicochemical characteristics of the area. The fertility characteristics were studied by collecting 97 surface soil samples (0-15 cm depth) from 27 padasekharams of the area during rainy and summer seasons (before and after the closure of Thanneermukkom regula- tor). Toxicity characteristics of the area were studied by collecting bulk soil samples (0-25 cm depth), surface water and ground water from the above sites during the same period. Morphological and physicochemical properties of the soils showed great degree of variation. Soils were dark brown to black in colour, sticky and plastic, subangular blocky in structure and sandy to clayey in texture, with random deposits of lime shells and humus. Presence of faint to prominent reddish yellow or brown mottles, rice roots and root canals were some of the special characteristics observed in the soil profiles. Soils of the area were highly acidic and mildly saline. Both soil acidity and salinity increased with depth. Organic carbon, CEC and ECEC of the area were higher compared to other parts of Kerala, but the base saturation was comparatively lower. The area was rich in almost all the essential nutrients except P. Fe, Al and S were present in toxic concentrations. Potential acidity of the area was very high and more than 70 per cent of it was contributed by hydrolytic acidity and the rest by exchangeable acidity. All the acidity characteristics increased with depth. The profile IX was grouped under order Inceptisol and all others under order Entisol. On evaluating the fertility characteristics of the area it was observed that the area experienced an increase in soil acidity and availability of N, P, Fe and Zn and a decrease in salinity, CEC, ECEC and available K, Ca, Mg, \.10 and Cu. However, the availability of all nutrients except P was above the deficiency level. Fe was present in toxic quantities. On a general comparison with that of pre-barrage period, the area experienced a reduction in salinity and an enhancement in soil acidity and availability of K, Ca and Mg. The Na content was reduced considerably in response to the reduction in salinity. The exchangeable and water soluble cations followed the same trend as that of available cations. Among the exchangeable cations Ca was the dominant basic cation instead of Na which occupied the same place during pre-barrage period. Acidity characteristics of surface samples behaved similar to that of profile samples. Pot- ential acidity and hydrolytic acidity recorded higher values during rainy season while exchangeable acidity was greater during summer. Among the components of exchange- able acidity exchangeable Al3+ dominated during rainy season, and exchangeable H+ dur- ing summer. The overall influence was greater for exchangeable A13+ as evidenced from the higher correlation coefficient (0.862**). The general soil properties and acidity characteristics of the bulk soil samples were similar to that of surface samples, showing a reduction in pH, EC, CEC and available, exchangeable and water soluble cations during summer compared to the rainy season. Among the different fractions of Fe, free and available forms were present in large quantities while exchangeable and water soluble forms were present in negligible quantities. All the fractions expressed a higher concentration during summer indicating more chances for severe Fe toxicity during that period. Mn was also present in large quantities. Compared to Fe, the concentration of different fractions of Mn were very small. The availability of Cu and Zn were also above the critical levels. The area was rich in AI. Reverse to that of Fe the different fractions of Al showed a lower concentration during summer. The free Al content was three times lesser than that of free Fe, while in exchangeable form Al expressed a higher concentration. The water soluble AI was very low. Surface water and ground water of the area were mildly acidic and saline during rainy season and they showed an increase during summer. The acidity exceeded the permissible maximum but the salinity was maintained below the permissible limit for agricultural and domestic purposes. Among the various elements present in water, Na and Cl- were the dominant ions expressing greater concentrations during summer in both surface and ground water. Based on SAR they were rated as moderately unsafe for irrigation during summer. The concentrations of K, Ca and Mg were within the permissible maximum for agricultural and domestic purposes. P was present only in traces. The Fe content was greater for ground water than surface water and it exceeded the permissible limit for drinking water. Though Mn was absent in ground water, it has already reached up to the permissible maximum in surface water. Al content exceeded the permissible maximum for domestic purposes. Cu, Zn, Cd and Pb were not detected in water. SO4-S, NH4-N and NO2+NO3- N contents of both surface and ground water were well below the critical levels suggested, but Cl' contents of both were sufficient to cause specific toxicity effect. The chlorinated hydrocarbon pesticides identi _ fied in the area were (X-HCH, y-HCH and DDT. They showed higher concentration during summer. Among the chlorinated hydrocarbons, DDT was present in larger quantities, though it was banned for agricultural uses, followed by (X-HCH. The concentration of y-HCH was comparatively small. The accumulation of fertiliser residues in the area was not so negligible. The highest concen- tration was observed for NH4-N during addi- tional crop season, at the time of basal dressing, both in soil and water. During punja season, a decrease of 55 to 60 per cent in soil and 10 to 12 per cent in water for NH4-N was observed. The content of N02+N03-N was comparatively low in soil due to continuous submergence. In water it was not as low as that of soil, indicating a major portion of N02+NOrN retained in water. P content of the area was very low. Its loss through drainage water was nil. A sizable quantity of K was also subjected to loss through drainage water, though the extent of loss was well below the level of N. Here also highest concentration was noted during additional crop season at the time of basal dressing both in soil and water. The study indicated that the area is subjected to severe pollution due to the accumulation of native toxic factors as well as residues of pesticides and fertilisers. The closure of Thanneermukkom regulator aggravates the situation by restricting the water movement.

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