The effect of flood water spreading on soil physico-chemical change in flood water spreaders

Conversion of the Gareh Bygone Plain, a sandy desert, into a verdant scenery through tloodwater spreading (FWS) for the artificial recharge of groundwater (ARG) has raised many questions concerning how each ofthe soil constituents has changed due to the sedimentation of the suspended load on to the waterspreaders and the soil enrichment by the dissolved nutrients carried in floodwater. There has been an ll fold increase in forage production of native and introduced species, and also a large yield of Ecrzlyyirus cnmrzldulensis wood due to FWS. This study was implemented to discover some measurable changes in a few soil physical and chemical properties which have occurred during the l983- 1996 period. Each of A the first 3 waterspreacler in the Bisheh Zard l ARG system was selected as a sampling site. Soil samples were collected plots in each waterspreader. One plot of waterspreader, which due to its higher position had remained out of floodwater, was taken as the control. Analysis of variance of the measured factors assumed a split plot experimental arrangement with flooded (treated) and non flood (control) as main plots and the 3 depths as subplots. The 3 waterspreader were assigned as replicates, FWS has significantly increased clay content, Zn concentration, EC, pH, SAR and soluble Na, soil salinity increased significantly in O-l5 cm layer. Organic matter and total nitrogen have increased significantly in the 0-15 cm layer relative to 30-45 cm thickness. There has been a significant increase in the concentration of soluble Na, Ca and Mg in the 0-15 cm layer, SAR has also significantly increase there, this applies to the C:N ratio as well. Sand content has increased and silt content has increased significantly in the O-15 cm layer relative to the lower depths. Although statistical analyses do not point to other significant changes in the rest of studied characteristics, FWS has improved them all. Micronutrient concentrations have increased due to an increase in the organic matter content and silt and clay percentage. It seems that enhancement in soil quality has improved the micro flora and fauna of the waterspreader. Moreover determination of the environmental quality, which usually follows development, has not happen here. Therefore as exponential population growth rates urge us to find environmental friendly ways and means of food production, the merits of FWS, particularly for the ARG, become more apparent.