Assessment of soil fertility for crop planning in flood affected areas of Dhemaji district of Assam

Frequent flash floods have converted highly productive agricultural lands of Dhemaji district of Assam into sand/silt laden uncultivable lands. An investigation was carried out in Lalung, Samarajan and Dafalagaon village of Dhemaji district to assess the soil fertility for crop planning. After delineating the sand/silt deposited areas, soil samples were collected from representative sites. Physico-chemical properties of the soil samples were estimated. The study showed that the damage was caused by rivers Gainadi and Jiadhal which affected 516 ha areas out of the total geographical area of 1047 ha. The affected soils were found low in fertility and moisture retention. The texture varied from sandy to loamy sand, Bulk density was high, organic carbon content was low and pH was almost neutral. The climatic parameters showed that the length of growing period was more than 300 days. Soil management activities and short term land use planning was suggested for the affected areas. In the areas where sand deposition is < 30 cm, a deep ploughing with tractor drawn MB plough is suggested for increasing the infiltration of water and penetration of roots and green manuring for increasing the organic matter content. In the areas with > 30 cm sand deposition, deep rooted crops like arecanut, coconut and arhar are suggested. Crops like watermelon, muskmelon, pumpkin, pointed gourd etc. may be suggested to grow in pits and areas with < 15 cm sand for normal cropping after a deep ploughing. Oilseed crops like rapeseed and mustard, niger, castor and groundnut are suggested for areas with < 15 cm sand deposition.