Characterization of Rice Growing Soils of Lower Brahmaputra Valley Zone (LBVZ) of Assam, India

An experiment was conducted to characterize and classify the physico-chemical properties of different rice growing soils namely Ahu, Sali and Boro rice of Boko block of Assam. A total of sixty (60) geo-referenced and representative (0-15 cm) samples of soil were collected from the three different rice growing soils (20 each) viz., Ahu, Sali and Boro. The soils were then tested for their different physico-chemical properties. Soil textural classes varied from sandy loam to clay loam for Ahu and Sali rice while clay loam in Boro rice with strongly acidic to moderately acidic in their reactions (pH 4.52 to 5.85). Soil organic carbon was found to be medium to high in Ahu and Sali rice but high in Boro rice growing soils. The clay content was found to be significantly more in Boro rice growing soils as a contrary to Ahu and Sali rice growing soils. The EC values represented the non-saline nature of the soils and the CEC of all the rice growing soils of Boko block was invariably low with the mean values of 8.66 cmol (p+) kg-1 for Ahu rice growing soils, 8.80 cmol (p+) kg -1 for Sali rice growing soils and for Boro rice growing soils it was 8.90 cmol (p+) kg-1. All the available primary nutrients were medium in their status except available phosphorus which was low to medium. Exchangeable Ca2+ was the dominant basic cation followed by Mg2+.