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ThesisItem Open Access Exchangeable aluminium as an index of liming for the acidic upland soils of Kerala(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1987) Meena, K; KAU; Alice, AbrahamAluminium toxicity is the major factor limiting crop production in the acidic soils and the usual practice of alleviating aluminium toxicity is liming* / The present investigation was carried out to find out the distribution of water s dluhle and exchangeable aluminium in the acidic upland soils of Kerala and to test the suitability of exchangeable aluminium as an index for liming them* It was further programmed to find out the growth, yield and nutrient uptake pattern of two acid sensitive crops namely cowpea and fodder maize in soils under different levels of exchangeable aluminium brought out by the use of different levels of lime* Chemical analysis of eighty soil samples representing the five major upland soil types of Kerala viz* laterlte, alluvial, red loam, sandy and forest a oil have indicated the highest amount of exchangeable aluminium and percentage aluminium saturation in the laterite soils* The soil with 3 high level of exchangeable aluminium and percentage aluminium saturation was selected for conducting a pot culture experiment to test the suitability of using exchangeable aluminium as an index of liming* The exchangeable aluminium content of this soil was maintained at different levels by applying different levels of lime and the performance of these crops in this soil was compared by making biometric observations and by chemically analysing plant and soil samples* From the results of the study it was seen that higher levels of exchangeable aluminium adversely affected the growth, yield and nutrient uptake In cowpea and fodder maize* Maintenance of exchangeable aluminium at 1*26 me/100 g with a corresponding percentage aluminium saturation valua of around 30, by the use of 500 kg lime/ha appeared to be the optimum for maximising the yield of cowpea* But in fodder maize this level of lime was found to be insufficient and complete elimination of aluminium toxicity appeared to be essential for maximising production* Since the critical levels of exchangeable aiuainiua appears to be different for different crop3, it is desirable that lias levels to reduce exchangeable aluminium to such a critical level alono be applied. The results of the present study thus point to the advantage in adopting the exchangeable aluminium level of soil as a better index of liming for various crops grown in the upland acidic soils of Kerala.ThesisItem Open Access Characterisation of laterite soils from different parent materials in Kerala(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1987) Stella Jacob; KAU; Venugopal, V KIn the present investigation, an attempt has been made to evaluate the morphological, physical, chemical and mineralogical characteristics of laterite soils occurring in different regions of Kerala in relation to the parent rock. Six soil series representing laterite soils identified by the Soil Survey Unit of Department of Agriculture, Kerala State were selected for the investigation. The soil series identified were Thonnackal, Kootala, Anjur, Kanjikulam, Mannur and Nenmanda located in Trivandrum, Trichur, Palghat and Calicut districts. Soil samples representing the different horizons were collected for laboratory studies. The physico-chemical characteristics of the soils, behaviour of iron and phosphorus fractions of samples were investigated with a view to study the interrelationship between various properties and to relate these characteristics to the genesis of the soils. Mineralogy of the fine sand fraction was also carried out. Placement of these soils under soil taxonomy was also attempted based on the available data. The salient findings are summarized below. The soils from different locations had striking similarity in colour with reed hues predominating. Coarse fragments formed a predominant portion of the soil and was mainly concentrated in the subsurface horizons. Most of the elements were found to be concentrated to the gravel as compared to the soil. Sand formed the predominant size fraction but the textual class of the soils was mostly clay. Increasing clay content with depth was a characteristic feature. The slit/clay ratios were very low indicating the highly weathered nature of the soils. The available water capacity was poor and the variations observed closely followed the distribution of clay. Kootala series had the highest available water capacity while Thonnackal recorded the lowest. The soils were in general acidic with very low electrical conductivity. The content of C, N and C/N ratios were very low. Silica formed the predominant fraction followed by Fe2O3 and AI2O3. The total reserves of CaO, MgO, K2O, P2O5 were very low and is a reflection of the mineralogy of the fine sand fraction which was dominated by quartz. The cation exchange capacities of the soils were very low. The CEC5 recorded still lower values as compared to NH4OAc method. The exchangeable bases were in the order Ca> Mg>K>Na in the case of Anjur, Mannur and Nenmanda series while in Thonnackal, Kootala and Kanjikulam series. Exchangeable Na was slightly higher than K. Among the acid generating ions extractable aluminium was very low. The percentage base saturation was low and did not show appreciable variation between soil series. The Fed formed the predominant iron fraction and based on the degree of freeness of iron in soils, Kanjikulam series was the oldest followed by Anjur, Kootala, Mannur, Nenmanda and Thonnackal. The active iron ratio (Feo/ Fed) recorded very low values for all the soils. Among the inorganic P fraction Fe-P was dominant in all the soils except Thonnackal series. Nenmanda series had the lowest content of Ca-P. All the soils were highly weathered based on the behaviour of P fraction. Silica was the dominant fraction of clay. Based on Sio2/Ai2o3 ratio, Thonnackal and Nenmanda were designated as ferralitic or true laterites. The Sio2/R2o3 ratio was the lowest among the molar ratios. The rocks were siliceous in nature with poor content of bases. The fine sand fraction of the soil also revealed a predominance of quartz and very little weatherable minerals. The heavy graction consisted of mainly opaques, zircon, sillimanite, mica, rutile and sphene. The soils did not reveal contrasting characteristics in their composition that can be attributed to the parent material. Under the influence of the high temperature and heavy rainfall conditions existing in the state, the effect of parent material has been obliterated and properties of the soils appear to be mainly governed by the dominating climatic factor conditioned by the relief of the area. Based on the available data Thonnackal series was classified under fine loamy kaolinitic isohyperthermic family of Typic Haplorthox while others belong to the clayey, kaolinitic isohyperthermic family of Typic Haplorthox.ThesisItem Open Access Continuous use of municipal sewage on soil physical and chemical properties(Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, 1987) Karunakaran Nair, G; KAU; Aiyer, R SAn investigation was conducted on the physical and chemical properties of the sewage farm soil, Valiyathura in Trivandrum District. The sewage farm soil represents the loose sandy coastal alluvium. The area of the farm extends to 33 hectares under sewage water irrigation. From the farm area/6 blocks were selected representing 20 years and another 6 blocks representing 15 years of sewage irrigation.A comparative study was also made by choosing an adjacent block irrigated with well water. The whole area is cultivated with Napier and guinea grass Profile soil samples from different depths (0-15, 16-30, 31-45,. 46-i/70 cm) were collected for the determination of physical parameters such as bulk density, aggregate stability, stability index, hydraulic conductivity, water holding capacity and capillary and non capillary porosity. The soil chemical properties such as soil reaction electrical conductivity, organic matter content, total ammonical and nitrate nitrogen, total and available major nutrients, secondary nutrients micronutrients, cation exchange capacity and exchangeable cations were also determined from the soil samples collected at different depths. The plant nutrient content due to 15 year and 20 year sewage irrigation were also examined.ThesisItem Open Access Effect of different mulches on soil temperature and soil water retension in relation to seedling emergence and crop growth(Department of soil science and agricultural chemistry, College of Agriculture, Vellayani, 1987) Jayasree, P; KAU; Pushkala, SThesisItem Open Access Chemistry of coconut rhizosphere(Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 1987) Anilkumar, K S; KAU; Wahid, P AAn investigation on the root activity pattern of coconut palm (Cocos nucifera Linn.) and the influence of long term application of NPK fertilizers was conducted at the College of Horticulture, Vellanikkara. The coconut variety West Coast Tall was invariably used for the study. It was found that major portion of the active roots of coconut were within an area of 2 m radius around the palm. The vertical distribution of active roots was mainly confined to a depth of 30-60 cm and the root activity decreased sharply at 90 cm depth. The surface 25 cm soil layer is practically devoid of roots. Based on these results it is suggested that the fertilizers may be applied to an area of 2 m radius around the palm for their maximum utilization. Root activity was positively correlated with organic carbon, available P, available K, available Mn and Zn and negatively correlated with exchange acidity. Studies on the effect of long term NPK fertilization on soil chemical characteristics revealed that regular application of ammonium sulphate reduced the soil pH markedly (from 4.88 in N0 plots to 4.38 in N2 plots). A decrease in available Mn and an increase in available S also observed with continuous N fertilization. Continuous P fertilization, improved available P status of soil from 5.65 ppm in P0 plots to 146.45 ppm in P2 plots. Heavy build up of available P also noticed in lower layers with continuous P fertilization. Application of superphosphate reduced K status of soil probably due to replacement by Ca in exchange sites. Continuous application of muriate of potash increased the available K content as well as organic carbon content of soil. The effect on exchangeable K in soil is found to be N-dependent as revealed from the significant N x K interaction. Significant positive correlations were observed between soil available K in the 0-25, 50-75 and 75-100 cm depths and the levels of K in 6th and 14th fronds. Available K in the 0-25, 50-75 and 75-100 cm soil layers is positively correlated with yield. Organic carbon at 0-50, 25-50 and 75-100 cm soils depths also showed positive correlation with yield. Among the micronutrients studied Fe and Cu (25-50 cm soil layer) and Zn (50-75 cm soil layer) showed positive correlations with yield. Foliar Mg and Mn levels decreased with increasing rates of K fertilizations, while N fertilization increased foliar Mn content. Nitrogen fertilization also increased foliar N and Ca contents. Potassium levels in 6th and 14th fronds showed significant positive correlations with yield (r’values 0.500** and 0.544** respectively). The critical K level found by Fremond et al.(1966) (0.8 to 1.0%) need a revision as significant yield increase was observed even at foliar K levels of 2.15 to 2.62 ppm in 14th and 6th leaf respectively of the experimental palms.ThesisItem Open Access Effect of sodium chloride on soil characteristics, yield and quality of coconut grown in a laterite soil(Department of Soil Science and Agricultural Chemistry, College of Horticulture, 1987) Prema, D; KAU; Jose, A IThe coconut palms of the sodium chloride trial conducted at the Regional Agricultural Research Station (K. A. U.), Pilicode, Kasaragod district, Kerala were made use of for the present study. At the Reegional Agricultural Research Station, Pilicode there are two field experiments laid out in 1976, in order to evaluate the effect of NaCl on coconut palms. The soil type of the experiment site is laterite. The design, layout and treatments were the same for both the experiments. It is randomized block design with six treatments and four replications retaining six palms per plot. Treatments T1 control T2 1000 g K2O/palm/year T3 750 g K2O + 250 g Na2O/palm/year T4 500 g K2O + 500 g Na2O/palm/year T5 250 g K2O + 750 g Na2O/palm/year T6 1000 g Na2O/palm/year Potassium was applied as KCI and sodium as NaCI. In both experiments the crop is rainfed and the area receives an average annual rainfall of 3200 mm. The present study was conducted with soil and leaf samples drawn from these two experimental sites. The first experiment was conducted with 24 year old stock of hybrid palms (TxD) which received N, P and K as per the recommended dose till 1976 after which the above treatments were superimposed. Thus the palms received the treatments only for the last 10 years from 1976 to till the time of sampling for this study (January, 1986). The second experiment was laid out with newly planted coconut seedlings (DxT) and therefore the treatments were given from planting to till the date of sampling. The soil, leaf and nut samples were collected from the first experiment for chemical analysis to find out the effect of NaCI on soil characteristics, nutrient uptake, yield and quality of copra. In the second experiment, as the palm had not reached the bearing stage only the soil and leaf samples were collected. Data on the yield and morphological characteristics of the palms were collected from the R. A. R. S., Pilicode. In the second experiment as the palms have not reached stabilized yield, the yield data were not collected. The nutrient contents of leaf and copra were analysed and the quality of oil was estimated. The soil samples were subjected to physical and chemical analysis. The fertilizer treatments did not differ significantly in respect of the number of functioning leaves retained by the palms in the experiment No.1. Yield was significantly correlated with the number of functioning leaves and a unit increase in number of leaf would correspond to an increase in yield of 5.045 nuts per palm. In the second experiment, the number of functioning leaves was significantly influenced by the fertilizer treatments. The maximum number of leaves (18.48) was recorded by treatment No.4 (50% substitution of K2O by Na2O) and the minimum number of leaves (15.3) was registered by T1 (control). The treatments did not differ significantly in their influence on the total number of leaves produced per palm per year in the case of the first experiment and on the total number of leaves produced so far by the palms of the second experiment. Differences between treatments were not significant with regard to the number of female flowers produced per palm in the first experiment or the early flowering nature of the palms of the second experiment. Observations on yield, in the first experiment revealed that yield of the palms increased continuously with progressing period of time and the maximum increase in yield was in T4 (50% substitution of K2O by Na2O). Though there was 104.15 per cent increase in yield in T4 as compared to T1, the difference was not found statistically significant, the significance being lost by marginal difference. When the data were subjected to the analysis of covariance the adjusted treatment mean values varied significantly, the maximum being recorded by T2 (1000 g K2O) and the minimum by T1 (control). Treatment T2 was closely followed by T4 and the difference between T2, T4, T5, T6 and T3 were not significant. The treatments did not differ significantly in their influence on the copra weight per nut. The percentage oil recovery of copra did not differ significantly by the application of treatments. Nitrogen and phosphorus uptake by the palms in both the experiments did not differ significantly by the application of treatments. The potassium uptake was decisively influenced by the treatments in both experiments. Treatments receiving higher levels of K showed a correspondingly higher uptake of this element. The treatment T1 (control) registered a higher uptake of K than T6 (1000 g Na2O). The sodium uptake by the palms in both the experiments was also significantly influenced by the treatments. In general palms receiving higher levels of Na retained higher amount of Na in their leaves. Antagonism between K and Na in leaves was also exhibited in both experiments. The uptake of divalent cations (Ca and Mg) by the palms was not decisively influenced by the application of treatments in both experiments. The treatments did not differ significantly in the uptake of CI by the palms in the case of the first experiment. But in the second experiment, the CI uptake of the palms was decisively influenced by the treatments. The treatment T1 (control) which received no application of CI recorded the minimum value which was significantly lower than all other treatment mean values. All other treatment mean values were statistically on par. The soluble K content of coconut water did not differ significantly by the application of treatments whereas the soluble Na content of coconut water showed significant variation between treatments. The maximum amount of Na was in T6 (1000 g Na2O). The copra analysis showed that the treatments did not differ significantly with regard to their influence on the extent of N, P and K in copra. The sodium content of copra was found to be influenced by the treatments. The Na content increased with increasing application of Na. The differences between treatments in the case of Ca, Mg and CI contents of copra were not statistically significant. The analysis on the quality of oil revealed that there was no significant difference in the specific gravity, Refractive index, iodine number and saponification value of oil, between treatments. The pH and Ec of the soil did not differ between the treatments in both the experiments. The soil physical constants viz., apparent density, absolute specific gravity, percentage pore space, percentage volume expansion and maximum water holding capacity were not significantly different under various treatments in both the experiments. The moisture retension characteristics like field capacity and wilting coefficient and the percentage available water of the soil were not significantly influenced by the substitution of KCI, by NaCI to various extent. The aggregate analysis of the soil of both the experiment sites showed that there was no significant defference between treatments in the percentage aggregate stebility of the soil. Thus the structure of the soil was not found affected due to the application of NaCI at the rate employed in the experiment. The treatments did not differ in their influence on the percentage organic carbon in soil, total N in soil and available P in soil in both the experiments. Available K in soil registered significant difference between treatments in both the experiments. Invariably, treatment receiving the highest amount of K (T2 1000 g K2O) retained the highest amount of this element in soil. In general soil receiving a higher quantity of NaCI recorded higher values for available Na in soil. However, the differences between treatment means were not sufficient to establish statistical significance, in the case of the first experiment. In the second experiment the treatments had significant influence on available Na in soil and the treatment T6 (1000 g of Na2O) registered a significantly higher value of available Na than all other treatments. The available chlorine in soil did not differ significantly due to the application of treatments. The treatments did not differ significantly as far as CEC of the soil in both experiments was considered. Exchangeable Ca and Mg contents in soil in both the experiments did not differ significantly between treatments. The treatments could decisively influence the exchangeable K in soil in the first experiment but failed to do so in the second experiment. The values of exchangeable K registered by individual treatments increased in accordance with the increasing order of application of K to soil in the first experiment. Exchangeable Na as well as exchangeable Na percentage in soil were not significantly different when the treatment means were compared. These results showed that substitution of K2O applied to coconut palms as KCI, by Na2O applied as NaCI to the extent of 50 per cent is possible without a reduction in the yield, quality of soil and adverse effects on soil characteristics, under the climatic and soil conditions comparable to that tried in this experiment
