Carbon - nitrogen relationship in laterite soils of Kerala

Abstract

Surface soil samples from 490 sites representing upland laterite areas of the different districts of Kerala were analysed in order to establish precise relationships between organic carbon and total as well as available nitrogen in these soils. As the acidity increased, the content of organic carbon, total nitrogen and available nitrogen (aN) in soils also increased. The content of organic carbon in soil was found to be significantly and positively correlated with the clay content (r=0.i282*). Organic carbon content had positive and significant correlation with total nitrogen (r=0.4008*) of soil. The C N ratio for low, medium and high organic carbon soils were 8.1 9. 9.63 and 1 1 .26 respectively. Simple linear equation for calculating total nitrogen based on organic carbon content of soil was worked out as N %=0.0803 C% + 0.03 8- C/aN ratio had positive and significant correlation with organic carbon (r —0,6128**) and total nitrogen (r=0.32Q9**). On an average, 10.82 percent ^ftotal nitrogen in soil was retained in available form. The N/aN ratio increased with increase in organic carbon, but not in linear proportion.