Title:

Soil Biological, Chemical, and Physical Dynamics During Transition to Nonthermal Residue Management Grass Seed Systems

Objectives:

1. Determine the effects of chopped straw, straw removal and crop rotations on biological, chemical, and physical properties.

2. Evaluate biological indexes as temporally sensitive indicators of soil quality.

3. Relate changes in soil properties to N accumulation and yield of grass seed crops.

Principal Investigator:

R.P. Dick, Associate Professor of Soil Science
Department of Crop and Soil Science Oregon State University

Cooperators:

W.C. Young, III, Grass Seed Extension
R.A. Christ, Faculty Research Assistant
Department of Crop and Soil Science
Oregon State University

J.J. Steiner, Research Agronomist
S.M. Griffith, Plant Physiologist
L.F. Elliot, Soil microbiologist
USDA-ARS

Abstract:

As field burning is phased out for grass seed production, alternative nonthermal practices (e.g. straw removal or return to soils; diverse crop rotations) are being developed but impacts of these systems on crop productivity is not well understood. At three sites in Western Oregon, the effects of these systems on soil dynamics and quality are being investigated in tandem with other agronomic factors. After two years cropping, physical measurements were insensitive to management effects. Preliminary interpretations suggest that microbial biomass and particularly some soil enzyme activities are the most sensitive to soil management effects. These appear to be precursors of organic matter accumulation because positive effects by high straw or the legume rotation on soil biology paralleled a trend of increases in organic carbon at two of the three sites. These methods offer potential for growers to have early predictors of long-term impacts of cropping on soil quality. Further work is in progress to relate the soil data to agronomic performance of grass seed. Preliminary results have been disseminated to farmers, ag. professionals, and scientists.

Justification:

As field burning of grass seed straw in Oregon is phased out, alternative nonthermal practices such as post harvest straw residue removal or incorporation to the soil, and crop rotations (e.g. legumes and cereals) are being developed. There is little information available on the practicality and impacts of nonthermal systems on productivity, pests and soil properties. Consequently, in 1992, the multidisciplinary Non-Thermal Cropping Systems Project was initiated at three diverse sites in the Willamette Valley, Oregon. Studying the effect of these new systems on soil dynamics is critical for cross comparison with parallel studies on entomology, plant pathology, and crop production. Furthermore, this provided an excellent opportunity to evaluate soil quality indexes for their potential to be sensitive discriminators of soil management effects which are needed to aid farmers as early indicators of changes in soil management.