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United States Department of Agriculture

Agricultural Research Service

Title: Temporal Changes in Tall Fescue Straw Residue Degradation

Authors
item Griffith, Stephen
item Gavin, William - OREGON STATE UNIVERSITY

Submitted to: Seed Production Research at Oregon State University
Publication Type: Experiment Station
Publication Acceptance Date: March 31, 2007
Publication Date: April 30, 2007
Citation: Griffith, S.M., Gavin, W.E. 2007. Temporal Changes in Tall Fescue Straw Residue Degradation. Seed Production Research at Oregon State University. Department of Crop & Soil Science Ext/CrS 126 P 19-21.

Interpretive Summary: In grass seed agriculture, straw residue is a byproduct. Traditionally it has been thought of as a “waste” product yielding little additional net income to the grower. Straw residue can be baled and sold to Asian or local markets, open field burned, or flailed and left on the soil surface or incorporated into the soil. All practices are in current use by Willamette Valley grass growers to varying degrees and the method chosen is based on a number of decisions that factor into a grower’s crop and field management plan. Straw moved off-site removes nutrients that would otherwise be returned to the soil. In contrast, straw remaining allows carbon (C), nitrogen (N), and other nutrients to return to the soil food web that reduce future nutrient supplementations by the grower. Shortages of certain plant nutrients can result when straw is continuously removed. Aside from a nutrient role, straw residue might also play a role in weed suppression, preserving soil moisture, improving soil tilth, and protecting soil from erosion. Off-site straw removal can benefit the live stock industry, be used in erosion control, or even as a biofuel feedstock. The primary focus of this study was to quantify the amount of straw that is degraded through the a season, the amount of C and N contained in the straw, and temporal changes in these chemical constituents during the degradation process. Our study found that flailed straw remaining on the soil surface can lose as much as 80% of its original mass between fall and spring under western Oregon climate conditions. Further, there is a substantial amount of C and N and other chemical constituents that are released during this degradation process that would have direct and indirect influences on soil tilth, soil nutrient status, and soil physical properties. Future studies are underway to help understand the role straw residues play in affecting soil quality in grass seed production systems.

Technical Abstract: In grass seed agriculture, straw residue is a byproduct. Traditionally it has been thought of as a “waste” product yielding little additional net income to the grower. Straw residue can be baled and sold to Asian or local markets, open field burned, or flailed and left on the soil surface or incorporated into the soil. The focus of this study was to quantify the amount of straw that is degraded through the a season, the amount of C and N contained in the straw, and temporal changes in these chemical constituents during the degradation process. This study was conducted on-farm in a tall fescue seed production field located in the south Willamette Valley, Oregon. The perennial crop was in its fourth (2003-2004) and fifth (2004-2005) seed production years. The field was managed and seed harvested by the grower. Following seed harvest, the remaining straw residue was flailed and spread across the field after seed harvest (July). From fall to spring, chopped straw samples were collected from six randomly selected areas measuring 20 cm in diameter The straw biomass was returned to the laboratory, dried, weighed, and assayed for total carbon (C) and nitrogen (N). Total C and N analysis was performed using a Perkin-Elmer Series II 2400 total C/N analyzer. Our study found that flailed straw remaining on the soil surface can lose as much as 80% of its original mass between fall and spring under western Oregon climate conditions. Further, there is a substantial amount of C and N and other chemical constituents that are released during this degradation process that would have direct and indirect influences on soil tilth, soil nutrient status, and soil physical properties. Total straw C and N amount varied by the amount of biomass produced. Total C and N ranged from 3102 kg C/ha in fall 2004 to 6742 kg C/ha in fall 2003 and 75.2 kg N/ha in fall 2004 to 163 kg N/ha in fall 2003. This is a substantial amount of nutrients that could potentially enter into the soil biota and crop food web during the following season when the straw degrades. In addition, other nutrients are present in straw biomass and released during the degradation process. If successive years of straw residue removal occur (e.g., baling), then soil deficits of some nutrients can occur over time. Future studies are underway to help understand the role straw residues play in affecting soil quality in grass seed production systems.

Last Modified: 8/22/2014
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