Soil quality assessment in Aquilaria malaccensis Lamk. (Agar) growing localities of three districts in upper Assam, India with respect to natural infection

摘要

A total of six pedons were studied from the Aquilaria malaccensis Lamk. (Agar) growing areas of upper Assam and in these areas natural infection of agar trees occur. The objective of research work was to study the relationship of soil quality with natural infection of agar trees. Pedon 1 and 2 are in Nahorani, Golaghat district of Assam. Pedon 3 and 4 are in Sotai and in Jorhat district, Pedon 5 and 6 are from Namti, Sibsagar district. Available soil nitrogen was recorded within low (102.42 kg ha-1) to medium (326.41 kg ha-1) range in all the six pedons and variations are found to be statistically insignificant. Available phosphorous was ranged low (15.12 kg ha-1) to high (75.71 kg ha-1 ) in Nahorani soils, low (21.40 kg ha-1) to medium (48.10 kg ha-1) for Sotai soils and also low (15. 23 kg ha-1) to medium (46. 37 kg ha-1) for Namti soils. Available K was within the range of low (56.11 kg ha-1) to medium (336.00 kg ha-1). Secondary soil nutrients such as Ca and Mg are found low for all the studied sites. Wide variation was observed in soil textural class, soil pH and soil organic carbon content among the three sites. Presence of clay fractions differ significantly between the pedons in all the depths. Soil pH was strongly acidic in Namti (4.4-5.2) and Nahorani ((4.3-4.9) soils. Soil pH was found moderately acidic in Sotai soils (5.0-5.6). Soil organic carbon was recorded low in Sotai soils whereas it was in medium range in both Nahorani and Namti soils and it showed a significant difference among the pedons. This study reveals that there is a strong relationship between the natural infections of agar trees with soil parameters. Maximum natural infection was found in soils with pH between 4.3-5.2, finer soil texture class particularly clay loam to loam and medium to high soil organic carbon.