Determination of physical, water retention and transmission properties of soil of paddy fields in the vicinity of Nirjuli (Arunachal Pradesh)

This study shows the importance of physical, water retention and transmission properties of soils in relation to water management/hydrological studies of paddy fields in the vicinity of Nirjuli (Arunachal Pradesh). Soil samples were collected at various depths (0-15, 15-30,30--45 and 45-60 cm) at Nirjuli village, Modern village, Doimukh and Banderdewa. The mechanical composition of the soils at all sites reveals that soils were sandy in texture at all depths. The value of dry density, specific gravity and porosity increased for 0--45 cm depths for most of the sites. For Modern village (15-30 cm depth), Doimukh (15-30 em, 30--45 cm depth) and Banderdewa (30--45 cm, 45-60 depth) coefficient of uniformity (Cu2) which indicated that soil was uniformly graded. Except Doimukh, at all other sites and soil depths the value of Cc was lying in the range of 1 to 3 which indicated that soil was well graded. Generally soil moisture available to plants varies in between 1/3 bar to 15 bar. At 1/3 bar pressure, the moisture content in the paddy fields of D-sector, Modern Village, Doimukh and Banderdewa varied 28.2-35.1%,19.0-29.2%,19.0-28.3%,12.5-28.4% at 0-15 em, 15-30 em, 30--45 cm, 45-60 em soil depths respectively. At 15 bar pressure the moisture content in the paddy fields of D-sector, Modern Village, Doimukh and Banderdewa varied 10.4-22.2%, 10.0-18.8%, 6.9-17.0%, 3.9-14.6% at 0-15 em, 15-30 em, 30--45 em, 45-60 em soil depths respectively. As the soil depth increased, the moisture content also decreased at 1 and 15 bar levels at all sites. For Doimukh and Banderdewa sites the value of hydraulic conductivity are 1.831 x 10-7-1.831 x 10-4 em see' and 1.721xl0-7-1.721xl0-4 em sec-' respectively. The value of hydraulic conductivity decreased as the soil depth increased for both the sites. For D-sector the value of hydraulic conductivity varied between 7.20xl0-s-7.43xl0-4 em see'. In this site the value of hydraulic conductivity increased as the soil depth increased.