SOIL PROPERTIES AND CROP YIELD AMONG 4 TILLAGE SYSTEMS IN A WHEAT PEA ROTATION

Tillage systems that address soil conservation and sustainable crop yield need to be developed. Research was conducted on a Walla Walla silt loam (Typic Haploxeroll) to determine the long-term (19 years) effect of four tillage systems on soil properties and crop yield in a green pea (Pisum sativum L.)-winter wheat (Triticum aestivum L.) rotation that was started in 1968. The experimental design was a split plot with four replications. Wheat and peas were grown each season. The primary tillage systems were: (T1) fall moldboard plow after wheat and after peas (control); (T2) fall rototill after wheat and fall sweep after peas; (T3) spring moldboard plow after wheat and fall moldboard plow after peas; (T4) no tillage after wheat and fall sweep after peas. Soil measurements included bulk density, pH, organic carbon, penetration resistance, and saturated hydraulic conductivity. Profiles of bulk density, penetration resistance and pH revealed unique differences among treatments. However, there were no consistent differences in yield among the four tillage systems, in either green peas or wheat. From a crop production viewpoint, changes in soil properties on these tillage plots were inconsequential. From a soil erosion viewpoint, spring plowing (T3) and conservation tillage (T4) have an advantage over T2 and T1 because surface cover is maintained during the first winter following wheat harvest. Results show the importance of testing tillage systems over long periods of time and that the traditional system of fall moldboard plowing after wheat and after peas can be replaced by conservation systems without yield loss.