Variations in Soil Carbon and Nitrogen Contents under Different Land Uses in Sub-Temperate Highland of Azad Kashmir

摘要

Land use type affects the soil organic carbon (SOC) which is an important indicator of soil quality. Current study was aimed to investigate land use type and seasonal impact on soil properties, soil organic carbon and total nitrogen under three land use types i.e. cropland (CL), grassland (GL) and forestland (FL) of a sub-temperate highland of Azad Jammu & Kashmir. Soil samples were taken from the depths of 0-15 and 15-30 cm depths in summer, winter, autumn, and spring. Cropland was more alkaline (7.13) than grassland (7.0) and forestland (6.64) indicating higher pH values of about 2-7%. Similarly, soil bulk density was higher in cropland than in grassland and forestland. Particle-size distribution among land use type showed that grassland and forestland had 9-16% less and 10-20% higher clay contents than cropland. Soil organic carbon (SOC) and total nitrogen (TN) content were inversely proportional to soil depth, mainly concentrated in surface soil and were higher in forestland than grassland and cropland. Most of the soil organic carbon and total nitrogen was associated with macroaggregates (Ma) in 0-15 cm and with microaggregates (Mi) in 15-30 cm soil layers, whereas silt + clay fraction had least SOC and TN contents irrespective of land use and soil depth. Bulk density and soil particle-size distribution didn't change during the year. However, soil pH, soil organic carbon and total nitrogen significantly varied between seasons. The present study indicated that soil properties were greatly influenced by the land use type than by seasons. Therefore, the study reinforces the need for developing and devising suitable soil management practices for croplands. Incorporation of organic inputs and retaining the land cover with natural vegetation, or mulching should be promoted in the area.