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1999 STEEP III Final ReportTITLE: Impact of direct
seeding on crop water use efficiency, soil physical and microbial properties
and quality of soil organic matter. INVESTIGATORS: David Bezdicek, WSU; Steve Albrecht, ARS, Pendleton; Mary Fauci, WSU, Pullman; Marcus Flury, WSU, Pullman; John Hammel U of ID. INTERIM REPORT:
OBJECTIVES:
KEY WORDS: direct seed, soil quality, carbon sequestration, crop rotation STATEMENT OF PROBLEM: Many growers are asking about costs and benefits from DS systems in the long term and in the transitional period. Long-term benefits are best understood, but short-term benefits are less certain given the current depressed commodity prices and the cost of getting into DS. One short-term benefit is increased soil water storage and water use efficiency under DS. Another is the change in soil pore size distribution from old root and earthworm channels under DS. In spite of greater compaction under DS systems, water infiltration seems to be increasing. Soil organic matter (SOM) increases at the surface of DS and is the property most talked about by growers and researchers alike because it holds the key to so many vital functions in soil. Total SOM tells us little about the quality of SOM, but the POM and light fractions of SOM accumulate quickly under DS and can be used as indicators of soil quality in the transition period. ZONE OF INTEREST: Studies will take place in high, intermediate, and low rainfall zones. ABSTRACT OF RESEARCH FINDINGS: Winter soil water storage and water consumption by crops grown under DS and conventional tillage was the same in 1998 at Palouse and Touchet, but water use efficiency was greater for DS. Maintaining surface cover in annual cropping and eliminating fallow are key reasons for improved water use efficiency. Soil organic matter was increased under DS compared to conventional tillage. At previous STEEP III research sites, the greatest increase in SOM of 50% was noted at Palouse, with a slight increase noted at the wheat-fallow site at Touchet. Similar trends are found at Pendleton. Preliminary field estimates suggest different crops may influence earthworm populations. RESULTS AND INTERPRETATION: Research locations for our studies are as follows: High rainfall zone: Palouse, WA: 25+ years of DS wheat-barley-lentil compared to conventional and 3 years transition into DS; Colfax, WA: 9 years of NT, mostly spring wheat, lentil, and barley compared to conventional rotation using mold board plow; Intermediate rainfall zone: Long-term plots at the Columbia Basin and Columbia Plateau Research Centers, Pendleton, OR; Northwest Crop Project; and Low rainfall zone: Touchet, WA: 14 years continuous DS spring wheat compared to conventional wheat-fallow. Crop water use efficiency, seed zone temperature, soil profile winter water storage, and N use efficiency under DS and conventional systems at the Palouse and Touchet are part of Juan Pablo Fuentes's M.S work. Winter soil water storage and water consumption by crops grown under DS and conventional tillage was the same in 1998, but water use efficiency was greater for DS. Maintaining surface cover in annual cropping and eliminating fallow are key reasons for improved water use efficiency. The Cropsyst model was calibrated for winter wheat growth for both tillage systems in Palouse. Given the approximation of growth yields to a normal distribution, yield seems to be mainly influenced by the climatic conditions simulated. Soil nitrogen (ammonium and nitrate) was collected at monthly intervals to determine crop N use efficiency and develop apparent N bugdets and will be analyzed. Our previous STEEP III research had found increased SOM under DS compared to conventional tillage. The greatest increase in SOM of 50% was noted at Palouse, with a slight increase noted at the wheat-fallow site at Touchet. Many of the above measurements were highest for direct seed compared to conventional at the soil surface 0-5 cm (0-2 inches), but were lower at the 5-20 cm depth due to the lack of surface soil inversion. At the Palouse site we are able to follow a transitional period as an adjacent parcel has been under DS for three years now. However, the Palouse site is unreplicated and may be unique. Therefore we are sampling replicated tillage plots from the Pendleton Research Station for additional soil C measurements. Baseline soil organic matter determinations were made at the seven sites in the Northwest Crop Project. After a complete crop rotation the site will be resampled to evaluate the accumulation of SOM under DS with various crop rotations. Earthworms were sampled
in the long-term DS plots from our STEEP III study in the spring of 1998
and 1999. Earthworms were found at the Pullman, Palouse, Colfax, and Lewiston
sites, but infrequently at the drier sites at St. John and Touchet. We
conducted a preliminary survey of worms in other areas in Eastern WA and
Northern ID in the spring of 1999. Most worms were in the Apporectodea
genus. Canadian research has shown increases in earthworm populations
after a broadleaf crop in rotation, such as canola, mustard, flax, pea,
and lentil. With the current interest in expanding crop rotation our dryland
region, we have an opportunity to study the differences in cereal and
broadleaf residues on earthworm populations. Earthworm sampling rings
were installed in November 1998 at the Ruark's plots near Pomeroy, WA.
These plots are part of the NW Crop Project. We placed 8-inch diameter
rings in plots representing each of the residues from the four-year rotation.
We sampled twice in spring 1999 and plan to continue sampling over the
next two seasons to follow the crop effect on earthworms. Preliminary
results are shown in Figure 1. Laboratory studies also show better worm
growth in soil amended with pea compared with wheat residues. COOPERATORS: Dennis Roe, NRCS,
Colfax; David Huggins, USDA-ARS; Stewart Wuest and Dale Wilkins, ARS,
Pendleton PUBLICATIONS AND PRESENTATIONS (current year): Mary Fauci, David Bezdicek, and Kent Gephart. Earthworm Research in the Palouse Region. Northwest Direct Seed Cropping Systems Conference and Trade Show, Jan. 5-7, 1999, Spokane WA. David Bezdicek, Mary Fauci, and Dennis Roe. Earthworm Dynamics and Soil Biology in Direct Seed Systems. In 1999 Field Day Proceedings: Highlights of Research Progress, WSU Technical Report 99-1. David Bezdicek, Mary Fauci, Steve Albrecht, and Katherine Skirvin. Tillage Effects on Soil Carbon in Pacific Northwest Dryland Cereal Production. American Society of Agronomy Meetings, Nov. 4, 1999, Salt Lake City, UT. Mary Fauci, Steve Albrecht, Katherine Skirvin, and David Bezdicek. Labile Carbon from Particulate Organic Matter: Soil Depth and Tillage Effects. American Society of Agronomy Meetings, Nov. 4, 1999, Salt Lake City, UT.
Figure 1. Worm populations
in crop residues from the previous years crop at Ruark's NW Crops Project
plots near Pomeroy, WA . ACKNOWLEDGEMENTS:
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