Carbon-nitrogen stocks and structural stability of a tropical loamy sand soil as influenced by Tithonia diversifolia (L.) and other fertilizers

Abstract

This study investigated the residual effects of Tithonia diversifolia (wild Mexican Sunflower) incorporated as green manure and also composted with poultry manure and other organic-based and inorganic fertilizers on C-N storage and structural stability (SI) of a loamy sand soil in South-western Nigeria. Treatments applied include fresh Tithonia diversifolia (GM), Poultry Manure (PM), Tithonia diversifolia composted with PM (CP), Organo-Mineral Fertilizers (OMF), Neem fertilizer (NF), NPK (20-10-10) and control (C) while soil samples were collected at different depths (0-15, 15-30 and 30-45 cm). Results show that OC were stored most in OMF plots while total nitrogen was occluded most by green manure. The overall trend was OMF>PM>GM>CP>C>NF>NPK irrespective of sampling depth. The SI varied between 11.59-18.63% at 0-15 cm soil depth, 4.26-9.13% at 15-30 cm depth and 4.39-9.19% at 30-45 cm depth, while highest SI values were obtained in plots amended with only PM. The SI values for the surface soils were >9% considered to indicate sufficient accumulation of soil carbon to maintain structural stability. In conclusion, Tithonia diversifolia when incorporated fresh into soil or applied as compost and OMF are good sources of amendments to improve soil quality than inorganic fertilizers alone.