Soil fertility evaluation of rice soils of Lumbajong block of Karbi Anglong district under hill zone of Assam through nutrient indexing

Abstract

The Lumbajong block of Karbi Anglong district of Assam is characterized by undulating topography comprising of hillocks and lowland paddy fields. Cultivation of rice in traditional ways for years without adequate and balanced use of chemical fertilizers and with little or no use of organic manure have caused severe fertility deterioration resulting in stagnating or even declining productivity of the paddy field soils. Spatial distributions for organic carbon, available N, available P and available K were examined in the soil samples of selected rice fields in 102 different locations covering six villages in the block to evaluate the fertility status of the block. The study revealed that there is much variation in soil fertility status of soils developed on various land forms in the area as the soils were having low to high in organic carbon (0.42 to1.12 %), low to medium in available nitrogen (175.62 to 376 kg/ha) content; low in available P (3.86 to 28.29 kg/ha) and low to high in available K (71.68 – 439.04 kg/ha) contents. The soils of Lumbajong block were characterized as medium-medium-low-medium (MMLM) category based on the nutrient index calculated with respect to organic carbon, available N, available P and available K.