Influence of humic acid applications on soil physicochemical properties

7 Soil structure is often said to be the key to soil productivity since a fertile soil, with desirable 8 soil structure and adequate moisture supply, constitutes a productive soil. Soil structure 9 influences soil water movement and retention, erosion, crusting, nutrient recycling, root 10 penetration and crop yield. The objective of this work is to study, humic acid (HA) 11 application on some physical and chemical properties in weak structured soils investigated. 12 The approach involved establishing a plot experiment in the laboratory conditions. Different 13 rates of HA (control, 0.5%, 1%, 2% and 4%) were applied to soil at three incubation periods 14 (21, 42 and 62 days). At the end of the each incubation period, the changes in 15 physicochemical properties were measured. Generally, HA addition increased EC values at 16 the all incubation periods. HA applications decreased soil modulus of rupture. Application of 17 HA at the rate of 4% was significantly increased soil organic carbon contents. HA 18 applications at the rate of 4% significantly increased both mean soil total nitrogen content and 19 aggregate stability after at three incubation periods (p<0.05). Therefore, HA was potential to 20 improve structure of soil in short term. 21