Effects of compost, coal ash, and straw amendments on restoring the quality of eroded Palouse soil

Ridgetops in the dryland farming region of eastern Washington suffer from low productivity and poor soil quality from years of erosion. Two studies investigated the effectiveness of soil amendments in restoring soil quality. Study 1 treatments were two rates of compost and a control. Study 2 treatments were compost, coal ash, wheat straw, three rates of inorganic N, and a control. A wide array of soil biological, chemical and physical parameters were measured from 1995 to 1997 and yield of spring barley, spring pea, and winter wheat were measured in different years from 1995 though 1998. In study 1, compost plus N increased barley yield and soil pH. Compost without N in study 2 increased total soil C and continued to immobilize soil N 2 years after incorporation because of the high C:N ratio of the compost. Total soil N, available P and K, some micronutrients, and cation exchange capacity were increased by the compost. Compost reduced soil bulk density and soil impedance, while increasing water-stable aggregates and improving infiltration. Coal ash slightly suppressed phosphatase activity, while tending to increase pH and soil B, and improving infiltration. Straw decreased soil bulk density and microbial activity in 1996 only. Barley grain trace element uptake, barley yield, and pea yield were uninfluenced by amendments. In 1998, 3 years after application of the amendments, winter wheat yield was significantly higher from the compost application than from any other treatments. Compost had the greatest benefit to improving soil quality and crop yield.