TY  - BOOK
AU  - Suraj John 
AU  - Subramonia Iyer S (Guide)
TI  - Characterisation of the Gravels in the Major Soil Series of Trivandrum District
U1  - 631.4 
PY  - 1996///
CY  - Vellayani
PB  - Department of Soil Science and Agricultural Chemistry, College of Agriculture
N2  - Soil gravels are different in their morphological, physical, chemical and mineralogical features; as well as in their origin.  In the major soil series of Trivandrum district, soil gravel inclusions make up a considerable part of the soil mass.  Presence of soil gravels interferes with the cultivation operations, reduce soil volume and quantity of available water.  In soil textural determinations and the soil fertility evaluation, presence of soil component greater than 2mm is usually disregarded and ignored.  In order to gather information on the nature and properties of soil gravels, their genesis and distribution and their specific contribution to soil fertility; an integrated and systematic morphological, physical, chemical, mineralogical and micromorphological characterisation and interpretation of soil gravels of the representative profiles of the major soil serious of Trivandrum district namely Palode, Nedumangad, Varkala, Thonnackal and Trivandrum series were attempted.
	All the series except Thonnackal were gravelly throughout; Palode, Varkala, and Trivandrum series showed an increase in gravel content with depth but no specific profile pattern was observed at Nedumangad and Thonnackal.  Palode series is unique with all the different gravel fractions (2mm to 2.5 cm, 2.5 to 7.5 cm and 7.5 to 25 cm).  Another uniqueness of the Palode series is the presence of gneissic cobbles.  Cobbles were absent in all the other series.  Combination of grayels different in morphology and genesis are present at Palode and Trivandrum series.  Gravel consolidation and soil hardening were observed maximum at Varkala series and least at Thonnackal series.  Higher total phosphorus and potassium content of gravels indicate that gravels are the potential source of phosphorus and potassium for crop production.
	Acid insoluble content of gravels are in the increasing order Varkala<  Trivandrum <Nedumangad <palode <Thonnakal.   Acid solubles increase in fine fraction in the order Thonnackal <Varkala< Nedumangad <Palode< Trivandrum, while in the coarse fractions, the maximum content was reported in Varkala and the least by the Trivandrum series.  Sequioxide and total iron content were in the increasingorderThonnackal<Palode<Nedumangad<Trivandrum  <Varkala.  The potential of gravels to supply nitrogen is 1/4th of the soil while in the case of phosphorus and potassium it is about 1 ½ to 2 times.  The contribution of total calcium by gravels are about half the contribution by the respective soil while the mean contribution of total magnesium by both the soil and gravels are uniform throughout.
	Quartz content of the finer gravels are in the increasing order at Varkala<Nedumangad<Palode< Trivandrum <Thonnackal while those for coarse gravels are in the increasing order at Thonnackal<Varkala< Trivandrum <Nedumangad<Palode.  The plinthite granules of the finer gravels are in the increasing order atTrivandrum<Thonnackal<Nedumangad<Palode<Varkala, while that of coarse gravels are in the increasing orderThonnackal<Trivandrum<Varkala<Palode<Nedumangad.  Goethite content of gravels fraction was maximum at Nedumangad and least in the Thonnackal series.  Investigations on the soil fine sand mineralogy reveal that the quartz content is increasing in the soils ofVarkala<Trivandrum<Palode<Nedumangad<Thonnackal.  Plinthite gravels were observed only in the soil of the second horizon of Varkala.  Ilmenite content increased in the order Palode <Varkala <Nedumangad <Thonnackal< Trivandrum.
	Palode and Nedumangad series contain multiglaebular microgravels and multimicrogravelly coarse gravels and cobbles.  The gravels of Varkala are dominantly nodular than concretionary.  The uniqueness of the Thonnackal series is the presence of rubefied less hard kaolinitic gravels.  The gravels of the Trivandrum series are nodular, plinthic to petroplinthic with bigger angular skeletons.
	The preponderance of gravels with geodic internal morphology in the lower horizons and pseudomorphic in the surface horizons are direct expressions of geogenic and pedogenic origin of gravels.  The observation of nucleic type of gravels in the last horizon of Thonnackal series is indicative of its detrital origin from microgravels of nearby landscapes.  The preponderance of quartz both in the soil and gravels is obviously due to the acid igneous and metamorphic parent material.  The hardened plinthite gravel ie., the petroplinthite gravel is proposed in the soil taxonomy to differentiate Entisols and Inceptisols from Oxisols and Ultisols.
	The comparative gravel contribution to available nitrogen content of the soil is in the increasing order Palode<Nedumangade<Thonnackal<Varkala< Trivandrum : for available phosphorus, it is in the order Nedumangad<Trivandrum<Varkala<Palode<Thonnackal ; for exchangeable potassium, in the order Nedumangad<Varkala<Trivandrum<Palode<Thonnackal; for exchangeable calcium, in the order Trivandrum <Varkala<Nedumangad<Palode<Thonnackal and for exchangeable magnesium, in the order Trivandrum <Nedumangad<Varkala<Palode<Thonnackal.
	A multilocational field experiment based on the information gathered in the present study is desired to be taken up to reveal the effect of gravels on the performance of crops in the actual field situation.


UR  - https://krishikosh.egranth.ac.in/handle/1/5810156030
ER  -