Four soils from the Army Corps' Adobe Dam project in central Arizona were compared chemically and for seeding responses. Results demonstrated the ability of subsoil fill materials to support seeded species, but in lower densities than topsoiled areas. Seeding date proved crucial in establishment and later seeded topsoils supported significantly lower densities of most seeded species than fill soils seeded earlier. Significant vegetation-soil correlations demonstrated relationships of species densities and both nitrate-nitrogen and total nitrogen. Significant negative correlations of Salsola paulsenii and the seeded species Atriplex canescens are reported. Regression of seeded species and seven soil variables yielded equations explaining sizable variations in seeded species densities. Nitrate-nitrogen was the major factor in these equations, followed by pH, electrical conductivity, percent clay, percent gravel, surface roughness and total cations. Seeding in favorable moisture periods on roughened subsoil seedbeds amended with nitrogen is recommended for similar sites. (Author)
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