Steep III - Pacific Northwest Conservation Tillage Systems Information Source

Chapter 2 - Conservation Tillage Systems and Equipment No.16b (pdf format, 3mb)

AUTHORS: Roger Veseth, WSU/UI Conservation Tillage Specialist, Moscow, ID; Baird Miller, WSU Dryland Cropping Systems Agronomist, Pullman; Tim Fiez, WSU Soil Fertility Specialist, Pullman; Tim Walters, WSU Graduate Student, Pullman; Harry Schafer, WSU Research Technician, Ritzville.

Project Leaders:Roger Veseth, WSU/UI Conservation Tillage Specialist, Moscow, Baird Miller, WSU Agronomist, Pullman, and Tim Fiez, WSU Soil Fertility Specialist, Pullman; with support from Tim Walters, WSU Crop Science Graduate Student, Pullman, and Harry Schafer, WSU Research Technician, Ritzville.

Growers - This large-scale on-farm test project has relied heavily on the active participation of growers who helped plan the field trials, provided the land and equipment, and conducted the field operations. Growers involved in CRP take-out trials in 1994 and 1995 included: George Young and David Carlton in Columbia County, George O'Neal and Remie DeRuwe in Franklin County, Lenard Roth in Adams County, Clay Barr in Garfield County, and Jim Richardson and Darrell Roberts in Lincoln County. Growers involved in CRP take-out trials in 1996 included Dale and Gary Galbreath, and Ron Jirava in Adams County, Andy and John Rustemeyer in Lincoln County, and Tony Viebrock and Mike Grande in Douglas County.

Local Trial Establishment and Data Collection -Roland Schirman, WSU Extension Agent, Dayton; Bill Schillinger, WSU Agronomist, WSU Dryland Research Unit, Lind; Dean Brown, Monsanto Sales Representative, Spokane; Mike Sporcic, NRCS Area Agronomist, Othello; Mark Bareither, NRCS District Conservationist, Waterville; Jeff Harlow, NRCS District Conservationist, and Jim Schawley, NRCS Soil Conservation Technician, Pomeroy; David Bragg, WSU Extension Agent, Pomeroy; David Lundgren, Lincoln County Conservation District Manager, Davenport

Herbicide Kill of CRP Grass -Sheldon Blank, Monsanto Research Agronomist, Pasco; Steve Reinertsen, The McGregor Co. Research Agronomist, Colfax

Soil Quality Changes -Ann Kennedy, USDA-ARS Soil Microbiologist, Pullman; Virginia Gewin, WSU Graduate Research Assistant

Root Disease Sample Analysis and Interpretation -R. James Cook, USDA-ARS Plant Pathologist; Monica Mezzalama, Visiting Plant Pathologist working with Dr. Cook

Soil Surface Characterization for Erosion Potential -Bill Pan, WSU Soil Scientist, Pullman; Rhonda Bafus, WSU Soils Research Technician, Pullman

Economic Analysis -Kathleen Painter, WSU Agricultural Economist, Pullman

The Pacific Northwest has over 2.5 million acres of cropland in the Conservation Reserve Program (CRP). In Washington State there is over 1.045 million acres of CRP land. This represents nearly 14% of the 7.6 million acres in a 20 county area of eastern Washington. About 80% of the Northwest CRP contracts are scheduled to expire in 1997, representing over 800,00 acres in Washington State alone.

A majority of the CRP land in Washington and the Northwest is in the low rainfall, winter wheatsummer fallow regions. These areas typically receive from 7 to 14 inches annual precipitation and are susceptible to wind erosion, as well as water erosion. Serious soil erosion problems could result if intensive tillage and residue removal practices are used to return CRP land to crop production.

A Washington State research project was initiated in 1994 to evaluate management strategies for returning CRP land to crop production. It was designed as an umbrella project for a comprehensive, "grass roots" effort to evaluate prospective, locallyidentified management options for specific agronomic zones of the state. The research focus was on the low-rainfall, crop-fallow region where much of the CRP land was located. Crested wheatgrass is the predominant CRP grass in this area.

Washington State University Cooperative Extension was responsible for coordinating the statewide CRP take-out research project, as authorized by the Washington Farm Service Agency (FSA). As indicated earlier in the CRP take-research team description, the project relied on active involvement of growers, extension specialists and agents, researchers, and personnel from agricultural support agencies and industry.

The project goal was to identify management strategies that optimize agronomic performance and profitability of the first crops following CRP take-out, while providing effective soil erosion control and preserving soil improvements gained during CRP. There were two primary research thrusts in this statewide project: 1) evaluate management strategies for returning CRP land to winter wheat production following summer fallow; and 2) evaluate management strategies for returning CRP land to spring crop production.

Criteria evaluated to determine the relative success of different CRP take-out systems included: soil water storage efficiency; crop establishment and development; soil erosion potential; pest incidence; crop yield and quality; and economics.

This research project was funded in part by two grant programs from the USDA Cooperative States Research, Extension and Education Service (CSREES) through WSU: STEEP II (Solutions To Environmental and Economic Problems) and the Columbia Plateau Wind Erosion/Air Quality Project.

Before field experiments were initiated, a series of local planning meetings were conducted in six counties with high CRP acreage. Each meeting included four to six growers, county extension agents, researchers and personnel from USDANRCS, conservation districts and the agricultural service industry. This group identified prospective tillage and residue management systems to be studied in the CRP take-out field research trials. The tillage systems in most 1994 and 1995 trials relied primarily on commonly available tillage equipment within the different cropping regions. Direct seeding was also evaluated in one 1995 field trial in Columbia County and in three 1996 field trials in Adams and Douglas Counties.

This field research project used the large-scale, replicated, on-farm testing approach with farmscale equipment operated by the growers. This approach increases grower confidence in the research results and facilitates rapid grower adaptation of research results. Treatment area for each plot were generally 30 to 50 feet wide, depending on the implements used, and 800 to 1,000 feet long. Each treatment was replicated four times. Most trials included 4 to 6 management systems (treatments) and were 12 to 30 acres.

The project leaders and cooperators worked with growers to design and lay out the field experiments, and collecting the data. The growers performed all of the crop production operations. Yield measurements are made using the growers combine and portable truck scales or weigh wagons.

Data collection included initial grass biomass, soil water content in the spring and at fall planting, soil fertility analysis for fertilizer application, surface residue cover and surface roughness for evaluating soil erosion potential, pest incidence, plant stands, and crop yield. Comparative crop enterprise budgets were generated to evaluate the profitability of the different systems. Some of the trials were followed through the next crop rotation to evaluate the longer term effects of take-out treatments on soil erosion potential, pest incidence and soil quality.

In cooperation with other university and industry researchers, experiments were also conducted to evaluate alternative spring crop choices, fertility management in CRP take-out, nonselective herbicide rates and timings for killing CRP grass before direct seeding, root disease interactions, and changes in soil quality under different take-out systems.

To give the reader a better understanding of surface residue cover and surface roughness data presented in this report, the following is a brief explanation of their relative effectiveness for reducing wind erosion potential in low-rainfall, crop-fallow regions. Measurements of surface residue cover and surface roughness were made on CRP take-out field trials to evaluate the comparative effect of different take-out systems on wind erosion potential. In addition to reducing wind erosion, surface residue cover and roughness are also very important in reducing water erosion potential.

Surface residue cover was measured as percent surface cover using the line-point method, the standard residue measurement method of the USDA-NRCS. Surface roughness was estimated using reference roughness photos developed by the USDA-ARS in the Northwest for use by NRCS staff in the region. The surface roughness, called "random roughness" refers to surface soil cloddiness and is measured in inches as the average variance (standard deviation) from the mean height of soil clods above the soil surface. For comparison, a random roughness of less than 0.25 inches is a smooth field surface that could be highly susceptible to wind erosion, while a random roughness of 1.0 inch is about the roughest field surface possible after seeding without significantly reducing agronomic performance. Random roughness does not include the furrow and ridge patterns created by implements in field operations. That is a separate roughness measurement called "oriented roughness" which was not collected in these field trials, but generally enhances the erosion protection of random roughness.

Fig. 1. Wind erosion potential (soil loss ratio) as affected by surface residue cover (left) under three levels of random surface roughness (Horning, Stetler and Saxton, 1996, USDA-ARS, Pullman, WA). Fig. 2. Wind erosion potential (soil loss ratio) as affected by surface random roughness (right) under three levels of surface residue cover. (Horning, Stetler and Saxton, 1996, USDA-ARS, Pullman, WA).

Surface residue cover and surface roughness are important components in predictions of wind erosion potential. Figures 1 and 2 illustrate the effectiveness of different combinations of surface residue cover and surface roughness for controlling wind erosion. They were developed from actual soil erosion measurements using a large portable wind tunnel in extensive field evaluations across the crop-fallow regions of eastern Washington from 1993-1996. The research was conducted by ARS agricultural engineer Keith Saxton, with ARS research associates Lance Horning and Larry Stettler, as part of the Columbia Plateau Wind Erosion/Air Quality Project.

Figures 1and 2 shows wind erosion potential as a "Soil Loss Ratio". The soil loss ratio is calculated from the field-measured soil erosion during the wind tunnel tests under specific surface residue and roughness levels, divided by the soil loss measured from an adjacent "standard" field condition site with no surface residue and a smooth surface with soil clods removed. For example, the soil loss ratio of 1.0 would be the highest wind erosion potential on a site with no effective protection from surface residue or roughness. In contrast, a soil loss ratio of zero would mean no wind erosion potential because of effective protection by surface residue and/or surface roughness.

One way to help visualize the wind erosion potential from the two figures is to view the soil loss ratio under different levels of surface residue and roughness as a percentage of the erosion potential without residue or roughness protection. The following are two examples to help illustrate the effectiveness of surface residue cover and surface roughness for wind erosion control.

Example from Figure 1 on Surface Residue Cover Effectiveness-- Example 1 illustrates how a moderate level of surface cover of 25%, under a low random roughness of 0.3 inches, would have a soil loss ratio of about 0.25, or a 75% reduction in erosion potential compared to that under a field with no surface residue or roughness. Erosion potential could be reduced further to about 85% (soil loss ratio of 0.15) with a moderate roughness of 0.6 inches at the same 25% surface residue cover.

Example from Figure 2 on Surface Roughness Effectiveness --Example 2 illustrates how a moderate surface random roughness of 0.6 inches, under a low surface residue conditions of 5% cover, could reduce erosion potential by about 65% (soil loss ratio of 0.35) compared to a smooth soil surface. If surface residue cover was increased to 30% with the same 0.6 inch random roughness, the soil erosion potential could be reduced further to about 87% (soil loss ratio of about 0.13). As surface residue cover increases, random roughness becomes less important for erosion control. Surface roughness is less effective than surface residue in reducing wind erosion in the low-rainfall, crop-fallow regions, but can still be an important component of a wind erosion management strategy.

Ten large-scale on-farm trials were conducted, primarily in crested wheatgrass CRP fields. Three trials in Adams, Franklin, and Lincoln Counties evaluated different tillage and residue management systems for CRP takeout with summer fallow and were planted to winter wheat in 1995. Spring take-out trials for spring wheat were completed in Columbia County in 1994 and 1995, along with a small plot satellite study on spring crop choice under high and low residue systems in 1995. A direct seeding trial with spring barley was also conducted in Columbia County in 1995. Four small plot research trials on non-selective herbicide use for killing CRP grass were conducted in Franklin and Adams Counties in 1994-95 by Monsanto. Another study on nonselective herbicide use in CRP take-out was conducted by the McGregor Company in 1995, adjacent to a large scale trial in Columbia County.

Three trials on spring take-out with hard red spring wheat were conducted in 1996. Each trial compared 3-5 direct seeding systems with a tillage comparison. Two were located near Ritzville and one near Waterville. A fourth spring 1996 take-out trial evaluated several tillage and residue management systems for spring barley in tall wheatgrass CRP near Sprague.

Three large-scale trials were initiated in fall 1994 in Adams, Franklin, and Lincoln Counties to evaluate fall versus spring CRP take-out and management practices for summer fallow and winter wheat planting.

The trial site was north of Lind on the Lenard Roth farm in a 10-inch annual rainfall zone. The field had been in crested wheatgrass for 8 years. Ritzville and Willis silt loams were the dominant soil series. Grass residue averaged about 4,700 lb/A. Primary tillage and residue management treatments are listed in Table 1.

Table 1. Primary tillage and residue treatments in a fall versus spring CRP take-out trial with summer fallow - winter wheat in Adams County - Lenard Roth, grower cooperator.

`Fall 1994`	`Spring 1995`
`Disc`	`Cultivate`
`2X Harrow and chisel`	`Skewtread - cultivator`
`Flail with combine`	`Sweep`
`-`	`Disc - cultivator`
`-`	`Sweep - disc`

Fall tillage and residue management treatments were established in early October and spring treatments on March 28. After the initial tillage operations, all treatments were managed as one field. Subsequent field operations included the following implements: skewtreader, rotary hoe, shank fertilizer injector, rodweeding three times and seeding to Eltan soft white winter wheat August 24 at 35 lb/A with a John Deere HZ deep furrow drill.

Soil test results in April of the fallow season showed a total of 94 lb N/A -- 10 lb/A ammonium-N in the top foot and 61 lb/A nitrate nitrogen to 6 feet, plus an estimated N mineralization of 23 lb/A from the 1.1 % soil organic matter. Based on the soil test results, a 40 bu/A yield goal and nitrogen requirement of 2.7 lb N/bu, a N fertilizer application of 40 lb N/A was made in June with a conventional shank fertilizer applicator. The fertilizer and applicator were provided by the Lind Grange Supply.

Results from the trial through winter wheat establishment in 1995 are shown in Table 2. One of the most striking difference between treatments was in plant-available soil water to a 6-foot depth in March 1995 before spring tillage operations. Fall discing reduced overwinter water storage by about 2 inches compared the undisturbed grass cover in spring take-out treatments. The fall harrow-fall chiseling treatment caused a smaller but still significant water loss, whereas fall flailing did not.

The loss of soil water in the two fall tillage treatments was still evident at winter wheat seeding time in September, although the differences were not as great as in the spring, ranging from 1.8 to 3.3 inches available water to 6 feet. All of the treatments showed substantial water loss during the summer fallow period. A total of 11.2 inches of precipitation occurred from the late August planting through the following June. However, most precipitation amounts were less than 0.5 inches so effective precipitation was much lower. Based on an estimation of 4 inches of water needed for crop development to the reproductive stage and 5 bu/A yield of winter wheat per inch of additional water, yield potential was about 47 to 54 bu/A.

Although differences in surface residue levels between treatments after seeding were not always significant, fall discing and fall harrowing/chiseling resulted in the lowest residue levels, about 12 percent cover. The fall combine flail-spring sweep resulted in the highest residue level of 15 percent. However, the surface residue level on all the treatments is relatively low, indicating that each of the primary tillage and residue management combinations and/or the following secondary tillage operations should have been less intensive.

Surface random roughness after seeding was similar in all the treatments. The secondary tillage operations with the skewtreader and rotary hoe significantly reduced soil cloddiness, consequently eliminated earlier differences in soil roughness between treatments.

The lower soil water storage in the fall disc treatment may have caused the slightly lower plant stand, about 5.4 plants/square foot compared to 6.0 to 6.6 plants/square foot in the other treatments.

Table 2. Data through wheat establishment on the 1994-96 fall versus spring CRP take-out with summer fallow - soft white winter wheat in Adams County - Lenard Roth, grower cooperator.

Table 3. Harvest data on the 1994-96 fall versus spring CRP take-out with summer fallow - soft white winter wheat in Adams County - Lenard Roth, grower cooperator.

`Treatments`	`Yield (bu/A)`	`Test weight (lb/bu)`	`Protein (%)`	`Initial tillage cost ($/A)`	`Total cost`^.`** ($/A)`	`Average annual returns * over total cost($/A/yr)`**
`Fall disc`	`53.5 c`	`58.2 a`	`7.4 a`	`13`	`136`	`51 b`
`2X fall harrow - chisel`	`55.8 b`	`57.9 b`	`7.3 ab`	`18`	`145`	`51 b`
`Fall combine-spring sweep`	`59.9 a`	`57.8 bc`	`7.0 bc`	`18`	`142`	`58 a`
`Spring disc`	`56.9 ab`	`57.9 b`	`6.9 c`	`12`	`136`	`59 a`
`Spring sweep - disc`	`57.2 ab`	`57.7 c`	`6.9 c`	`13`	`135`	`60 a`
*`LSD (5%) `**	`2.1`	`0.2`	`0.3`	`--`	`--`	`--`

Harvest data and economics are shown in Table 3. The fall disc treatment yield was significantly lower than the other treatments. The yield reduction was probably due the lower water storage over winter and reduced plant population in fall 1995. Yield with the 2X fall harrow - fall chisel was also lower than spring tillage treatments. The highest yielding treatment was the fall combine - spring sweep, which was the lowest tillage intensity system resulting in the highest surface residue level and a high surface roughness after seeding. There were only small differences in test weight and protein between treatments. Profitability ranking of the take-out systems was similar to the yield results, with spring tillage take-out systems being more profitable. Although fall flailing increased initial tillage and total costs of the flail - sweep systems over spring take-out systems, there was no difference in profitability.

A fall versus spring CRP take-out trial with summer fallow - winter wheat was established on the George O=Neal and Remie DeRuwe farm north of Connell on the edge of Franklin County. It was in a 9-inch rainfall zone and the field had been in crested wheatgrass for 8 years. Shano and Burke fine sandy loams were the dominant soils. These soils have weak soil structure and are susceptible to wind erosion. Grass residue averaged 4,700 lb/A.

Table 4 describes the primary treatments included in the trial. Fall tillage and residue management treatments were established in 1994 (disc - Oct. 10; flail and harrow - Nov. 2). Roundup RT was applied at a 1-pint per acre rate to all the plots before spring field operations. After the initial spring tillage operations were established (March 24), the trial was managed as one field. Subsequent field operations included a conventional shank fertilizer applicator, rodweeding three times during the summer and seeding Hatton hard red winter wheat on August 29 with an International Harvester deep furrow drill.

Table 4. Treatments in the fall versus spring CRP take-out trial with summer fallow - winter wheat in Franklin County - George O'Neal and Remie DeRuwe, grower cooperators.

`Fall 1994`	`Spring 1995`
`Disc`	`Disc`
`2X Harrow`	`Disc`
`Flail`	`Sweep`
`-`	`Burn - Sweep`
`-`	`Disc - Disc`

Soil test results in April 1995 of the fallow season showed a total of 87 lb N/A -- 10 lb/A ammonium-N in the top foot and 63 lb/A nitrate nitrogen to 6 feet, plus an estimated N mineralization of 14 lb/A from the 0.7 percent soil organic matter. Based on the soil test results, a 35 bu/A yield goal and a N requirement of about 3 lb N/bu, a fertilizer application of 40 lb N/A, 10 lb P²O⁵/A and 5 lb S/A was made in June with a conventional fertilizer applicator.

Table 5 summarizes the trial results through winter wheat establishment. Soil samples were taken to a 6-foot depth before spring tillage operations. All tillage and residue management treatments in the fall resulted in significantly lower overwinter water storage because of greater water loss by evaporation. Where the grass residue was left undisturbed over winter for the spring burn and spring disc treatments, there was just over 4 inches of plant-available soil water to a 6-foot depth before the spring treatments were established. Both of the fall residue treatments of harrowing and flailing resulted in slightly lower soil water contents of 3.6 inches. The fall disc treatment resulted in the greatest loss of water over winter, with only 2.2 inches of available water, which was 2 inches lower that under undisturbed grass cover over winter. This was similar to the soil water loss with fall discing in the Adams County trial.

Six-foot soil samples were again taken just after winter wheat seeding. All of the treatments lost about half of the water content present in the spring, ranging from 0.9 to 2.2 inches/6 feet. As in the spring sampling, the fall discing still had the lowest water content (0.9 inch), which was just over 1 inch less than the spring take-out treatments. There was 11.4 inches of precipitation from winter wheat seeding through the following June. However, most precipitation amounts were less than 0.5 inches so effective precipitation was much less. Based on an estimation of 4 inches of water needed for crop development to the reproductive stage and 5 bu/A yield of winter wheat per inch of additional water, yield potential was roughly 42-48 bu/A.

Surface residue cover was measured through the fallow season and after seeding. Although surface residue levels in all the treatments were low, the fall flail - spring sweep treatment resulted in the highest surface residue level of about 9 percent. This was one of the least intensive tillage systems. The lowest residue treatment was the spring burn - sweep with about 2 percent cover. The other three treatments with one or two disc operations had surface residue levels of 5 to 6 percent.

The two treatments with the highest surface roughness in July 1995 of the fallow season were the two lowest intensity tillage treatments...the fall flail - spring sweep and the spring burn - spring sweep. All the other treatments included one or more disc operations. This illustrates the well know fact that the disc can reduce soil structure and aggregation, particularly in these light textured soils. There were no real differences in surface roughness after seeding.

There were no significant differences in plant stands between the treatments, except for the fall disc treatment, which contained about half the population of the other treatments. The lower soil water content at seeding probably reduced germination and establishment.

Table 5. Data through wheat establishment on the 1994-96 fall versus spring CRP take-out with summer fallow - hard red winter wheat in Franklin County - George O'Neal and Remie DeRuwe, grower cooperators.

`Treatments`	`Available soil water spring 1995` `(inches/6 feet)`	`Available soil water fall 1995` `(inches/6 ft)`	`% Surface residuecover` `(after seeding)`	`Inches of surface random roughness ` `(July 1995)`**	`Inches of surface random roughness` `(after seeding)`	`Plant stand (plants/ft`²`)`
`Fall disc - spring disc`	`2.2 c`	`0.9 c`	`5.8 b`	`0.75 b`	`0.74 a`	`3.9 b`
`Fall harrow-spring disc`	`3.6 b`	`1.9 b`	`6.5 b`	`0.79 b`	`0.77 a`	`7.7 a`
`Fall flail-spring sweep`	`3.6 b`	`2.0 ab`	`8.8 a`	`0.85 a`	`0.78 a`	`6.9 a`
`Spring burn -sweep`	`4.1 a`	`2.1 ab`	`1.9 c`	`0.87 a`	`0.77 a`	`6.9 a`
`Spring 2X disc`	`4.2 a`	`2.2 a`	`5.8 b`	`0.77 b`	`0.68 b`	`7.1 a`
*`LSD (10%) `**	`0.3`	`0.2`	`1.1`	`0.04`	`0.04`	`0.9`

Table 6 shows downy brome populations and harvest data. It is not surprising that downy brome populations in crop in March 1995 were lower in the fall disc and spring burn treatments,but there was no yield effect due to different populations. Grain yield was significantly lower (about 6 bu/A) and protein was significantly higher (about 1%) in the fall disc treatment compared to the other treatments. This is believed to be largely the result of lower available soil water (about 1 inch) which directly reduced yield potential (Table 5). Winter wheat yields generally increase about 5 bu/A for each inch of additional water available within the normal yield potential for the area. In addition, the lower water content at winter wheat seeding also reduced plant stands, which added to the lower yield potential. Test weight was relatively uniform across treatments.

Table 6a shows the costs and returns for the take-out systems. The fall disc - spring disc treatment resulted in the lowest average annual returns because of the lowest yield and relatively high cost. The two spring take-out systems and fall 2X harrow - spring disc systems resulted in the highest returns. Flailing resulted in lower returns because of the highest initial treatment cost.

Table 6. Downy brome population and harvest data in the 1994-96 fall versus spring CRP take-out with summer fallow -hard red winter wheat in Franklin County - George O'Neal and Remie DeRuwe, grower cooperators.

`Treatments`	`Downy brome``population` `3/25/96 (plants/yd`²`)`	`Yield``(bu/A)`	`Test weight` `(lb/bu)`	`Protein` `(%)`
`Fall disc - spring disc`	`3.1 ab`	`45.4 b`	`64.4 b`	`11.0 a`
`Fall 2X harrow - spring disc`	`4.9 bc`	`51.6 a`	`64.8 ab`	`10.2 b`
`Fall flail - spring sweep`	`7.4 d`	`51.1 a`	`64.8 ab`	`10.0 cd`
`Spring burn - sweep`	`2.6 a`	`51.8 a`	`65.1 a`	`10.1 bc`
`Spring 2X disc`	`5.9 cd`	`51.8 a`	`65.0 a`	`9.8 d`
*`LSD (5%) `**	`1.9`	`1.7`	`0.2`	`0.4`

Table 6a. Economics of the 1994-96 fall versus spring CRP take-out trial with summer fallow - hard red winter wheat in Franklin County - George O'Neal and Remie DeRuwe, grower cooperators.

`Treatments`	`Initial tillage costs` `($/A)`	*`Total costs ` `($/A)`**	`Average annual returns over total costs``($/A/yr)`**
`Fall disc - spring disc`	`15`	`150`	`32 d`
`Fall 2X harrow - spring disc`	`12`	`146`	`48 ab`
`Fall flail - spring sweep`	`18`	`154`	`43 c`
`Spring burn - sweep`	`7`	`142`	`51 a`
`Spring 2X disc`	`14`	`149`	`47 ab`

This trial was located north of Ritzville near the town of Lamona. Grower cooperators were Jim Richardson and Darrell Roberts. The site was in a 10-inch annual rainfall zone on Renslow silt loam soil and had been in crested wheatgrass for 8 years. Initial grass residue averaged about 5,600 lb/A.

CRP take-out treatments compared at the Lincoln County trial are listed in Table 7. Fall tillage and residue management treatments were established in 1994 (harrow - Oct. 5, disc - Nov. 2). Spring flailing was done on March 6. Roundup RT was applied March 28 at 1-pint per acre to all the plots before spring field operations on April 19. Both the disc and sweep had a 3-bar tine harrow attached. After the initial tillage operations, the plots were managed as one field. Subsequent field operations included conventional fertilizer shank applicator, three rodweeder operations during fallow, and seeding Eltan soft white winter wheat on August 24 at 55 lb/A with a John Deere HZ deep furrow drill.

Soil test results in April of the fallow year showed a total of 77 lb N/A -- 10 lb/A ammonium-N in the top foot and 39 lb/A nitrate nitrogen to 6 feet, plus an estimated N mineralization of 28 lb/A from the 1.4 percent soil organic matter. Based on the soil test results, a 40 bu/A yield goal and a N requirement of 2.7 lb/A, a fertilizer application of 50 lb N/A, and 8 lb S/A was made in June with a conventional fertilizer applicator.

Table 7. Treatments in the 1994-96 fall versus spring CRP take-out trial with summer fallow - winter wheat in Lincoln County - Jim Richardson and Darrell Roberts, grower cooperators.

Table 8 summarizes the trial results through wheat establishment. There were no significant differences in overwinter soil water storage between fall and spring take-out treatments in the early spring, in contrast to results at the Adams and Franklin County trials. There were also no differences in soil water content at seeding time, but early fall rains before sampling probably overshadowed treatment differences. Beginning with the 4.9 to 5.3 inches of available water to 6 feet at seeding, there was an additional 11.8 inches of precipitation through June. However, most precipitation amounts were less than 0.5 inches so effective precipitation was lower. Based on an estimation of 4 inches of water needed for crop development to the reproductive stage and 5 bu/A yield of winter wheat per inch of additional water, yield potential was less than about 64 bu/A.

Surface residue measurements in July 1995 of the fallow season showed the spring burn had the lowest percent cover -- about 14 percent. Fall or spring discing resulted in about 49 to 51 percent surface cover. Harrowing or flailing ahead of spring discing further reduced the surface cover to about 40 to 44 percent. In a spring planting system, this surface residue level and soil roughness would have been more than adequate for effective erosion control prior to crop canopy cover with the spring crop.

Surface cover at planting was still lowest in the burn-sweep with 4 percent. The other four disc treatments ranges from 13 to 16 percent cover, with harrowing and flailing treatments still being slightly lower. Surface random roughness after seeding was significantly higher with the spring burn - sweep treatment. The other four treatments with the disc as primary tillage had similar levels of surface roughness. There were no differences in winter wheat plant stands between the treatments. Early fall rains provided uniform seed zone water and crop establishment appeared to be good under all the treatments.

Table 9 shows March 1996 downy brome populations in crop and the trial harvest data. Down brome population in spring 1996 were substantially lower in the spring burn than the other treatments, but a fall metribuzin application and competitive wheat crop minimized weed survival and competitive effects on the crop. Yields, test weight and protein content were nearly identical between treatments. Profitability of the systems was also similar (Table 9a). The main difference was a higher initial tillage system cost with flailing, resulting in a lower average net return.

Table 8. Fallow data and plant stands on the 1994-96 fall versus spring CRP take-out trial for winter wheat on summer fallow in Lincoln County - Jim Richardson and Darrell Roberts, grower cooperators.