SOIL DEVELOPMENT AND VEGETATION ESTABLISHMENT ON AMENDED SALINE DREDGED MATERIALS 1

Crop establishment on saline-source fine textured dredged materials is challenging due to the adverse physical properties of the material (e.g. fine texture and lack of structure) and short-term salinity. Two approaches to improve crop establishment and soil properties on such dredged materials on an upland deposition site in Virginia were tested: (1) a topsoil cap plus fertilizer (approximately 20 cm; TS) and (2) incorporation of 30% sand by volume into the surface plus fertilizer (30%S). Each treatment was compared to a Control where only fertilizer was added based on soil fertility testing. A greenhouse study was initiated prior to the installation of field experimental plots. In the greenhouse study, German millet (Setaria Italica L.) yields and average plant height from highest to lowest were Control > TS > 30%S after three months. Large aggregation (250-8000 μm) was highest on the Control (68-70% total soil) followed by the TS (56%) and 30%S (48%) treatments; however, salinity was also higher on the Control treatment vs. the other two. The field experiment was installed in the spring of 2009 with an additional compost treatment added to the plots in splits. Plots were seeded to German millet in May 2009 and no-till drilled to Triticum aestivum (winter wheat) in October 2009. Weed control and a second application of N fertilizer in the spring of 2010 were impossible due to extremely wet soil conditions; therefore, only total biomass (wheat+weeds) data are presented for 2010. Millet yields (4382 kg ha -1 ) and total biomass (4319 kg ha -1 ) were higher on the 30%S treatments followed by the Control and TS treatments. Large aggregation was higher in the Control (70-80% total soil) than the 30%S (40-60%) and TS (20-30%) treatments in 2009 and 2010. Salinity declined with time across all treatments with suitable levels for crop production attained in the amended plots (30%S and TS). Compost additions stimulated microbial biomass and soil C concentrations, but did not significantly increase crop yields or aggregate formation relative to the non-compost treatment. Overall, yields and soil salinity were significantly improved when 30% sand by volume was incorporated into the dredge sediment, making this a feasible remediation strategy in the short-term, provided it is cost-effective.