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Subject: Soil Sciences × Author: Kalita, Pallabi × End date: 2018 × Start date: 2018 × Type: Thesis ×
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    ThesisItemOpen Access
    DISTRIBUTION OF PEDOGENIC IRON AND ALUMINIUM IN RELATION TO SOIL ACIDITY COMPONENTS UNDER DIFFERENT LAND USES IN GOLAGHAT DISTRICT OF ASSAM
    (AAU, Jorhat, 2018) Kalita, Pallabi; Dutta, Marami
    An investigation was carried out to study the pedogenic distribution of Fe and Al, the soil acidity components and to assess the relationship of pedogenic Fe and Al with soil acidity components under different land uses in Golaghat district of Assam. Five pedons were selected representing five land uses viz., Forest cover (P1), Paddy cultivation (P2), Tea plantation (P3), Bamboo plantation (P4) and Vegetable cultivation (P5) from Nambor Doigrung Reserve Forest, Borjan, Doria, Dergaon and Danichapori respectively. The dominant hue of soil colour was 10YR. Value ranged from 4 to 7 and chroma ranged from 1 to 6. Texture varied from sandy loam to clay loam in the surface and loam to clay in the sub-surface horizons. The structure of the soils varied from massive in the surface to sub-angular blocky to angular blocky in the subsurface. The clay content and bulk density increased with soil depth. The highest amount of organic carbon was recorded in A horizon of forest soil (P1) with 2.2 per cent. The pH were in acidic range in all the pedons and in all the cases ΔpH (pHKCl – pHH20) was negative. Among the exchangeable cations Ca2+ was the dominant followed by Mg²⁺, Na⁺ and K⁺. CEC ranged from 7.5 to 10.8 in the surface and 5.8 to 15.9 cmol (p⁺) kg⁻¹ in the sub-surface horizons. The percent base saturation generally tended to increase with depth with some exceptions in P1. Soils were classified as Typic Dystrudepts (P1, P3 and P4), Oxyaquic Hapludalfs (P2) and Aquic Udifluvents (P5). Dithionite extractable Fe (Fed) and Al (Ald) constituted the highest amount among the pedogenic iron and aluminium. Fed tended to increase with soil depth with few exceptions. On the weighted average, paddy soil (P1) recorded the highest Fed. Oxalate extractable iron (Feo), amorphous inorganic iron (Feo – Fep) was irregularly distributed in all the pedons. On the weighted average vegetable soil (P5) and paddy soil (P2) recorded highest (Feo) and (Feo – Fep) respectively. The distribution of (Fed – Feo) was irregular in all the pedons except P1. On the weighted average forest soil (P1) recorded the highest (Fed – Feo). The surface horizons recorded comparatively higher amount of pyrophosphate extractable iron (Fep) than the subsurface horizons in all the pedons. The amount of KCl extractable iron (FeKCl) was low which ranged from 0.001 to 0.002 per cent in all the pedons. The ammonium acetate extractable iron (FeNH4OAc) was below detectable limits in all the pedons. On the weighted average, Paddy soil (P2) recorded the highest dithionite extractable aluminium (Ald). Oxalate extractable aluminium (Alo), crystalline form of aluminium (Ald – Alo) and amorphous inorganic aluminium (Alo – Alp) followed inconsistent trend with soil depth whereas pyrophosphate extractable aluminium (Alp) decreased with soil depth. Bamboo soil (P4) recorded the highest Alo, bamboo soil (P4) and vegetable soil (P5) recorded highest Alp. Bamboo soil (P4) recorded highest (Alo – Alp) and forest soil (P1) recorded highest (Ald – Alo). The amount of ammonium acetate extractable aluminium (AlNH40AC) at pH 4.8 was low but was higher than that extracted by KCl solution. Profile weighted mean of forms of acidity under various land uses depicted that the paddy soil (P2) exhibited maximum extractable, non-exchangeable and hydrolytic acidity, tea soil (P3) exhibited maximum total acidity, exch. H+, exch. Al3+ and exchange acidity and bamboo soil (P4) exhibited maximum pH dependent and total potential acidity. It was observed that the soils under forest cover (P1) and vegetable cultivation (P5) exhibited lower acidity compared to other land uses in the present study. Principal component analysis of the 27 soil characters revealed that different forms of Fe and Al contributed towards development of soil acidity irrespective of land use. Among the physico-chemical parameters clay contributed positively and significantly and pH (pHH2O and pHKCl) contributed negatively and significantly towards soil acidity.