Vertical Tillage Special Project

Transcription

1 Understanding Shallow Vertical Tillage Use and Soil Disturbance Vertical Tillage Special Project Fall 2011 Kevan Klingberg and Dennis Frame, UW Extension/Discovery Farms Curt Weisenbeck, Agronomic Consulting Introduction Crop consultants and farmers recognize the value of conducting some type of tillage to size existing crop residue; incorporate manure, lime or other nutrients into the soil; and condition seedbeds prior to planting. Each of these tillage functions (size residue; incorporate nutrients; and prepare seedbed) play an important role in crop produc tion, soil conservation and water quality protection. How ever, management activities and interactions between crop production and environmental protection are critical to agricultural producers who live and work with the land. Producers are always looking for ways to improve their farming systems for profitability, as well as to reduce environ mental impacts of soil erosion and nutrient loss to surface and/or groundwater that could be attributed to their operation. Some farmers have implemented 1-pass no-till planting systems with various attachments immediately in front of the planter unit that provide for residue management and limited in-row seedbed preparation. This planting system has been used successfully for many years in portions of Wisconsin. Other areas of the state where soils are slow to dry and warm, like the red clays in eastern Wisconsin, have had less success with no-till crop planting. Nutrient stratification (high concentration of nutrients at the soil surface) as a result of prolonged applications of manure or fertilizers to the soil surface has also been identified as a concern in regards to increasing soluble phosphorus loss. Wisconsin farmers have been looking for a method that provides the crop production benefits of tillage, along with the soil conservation benefits of no-till. In many portions of the state, farmers have begun using a new generation of vertical tillage implements, designed to conduct shallow tillage and provide for better crop residue distribution. This paper reviews this relatively new tillage technology and provides a framework for future discussion and research on its advantages and disadvantages. Vertical tillage Vertical tillage implements typically combine gangs of coulter blades with additional rear attachments to cut and distribute crop residue more evenly and to condition a shallow seedbed. Their main working component is a set of straight and/or wavy coulters, which directs soil disturbance downward in slots, a couple of inches wide by a couple of inches deep (Fig. 1). Many implement manufacturers market their own uniquely designed vertical tillage tools. Some machines have aggressive blades, gangs angled at greater than 180 degrees and aggressive rear attachments such that they disturb soil and crop residue more than other machines. With the advent of combination tillage tools, characterizing each component is a challenge, especially as each manufacturer adds uniqueness that sets them apart in terms of soil and residue disturbance, even though these machines are all commonly called vertical tillage implements. For the sake of characterizing soil loss and impact upon soil and residue disturbance, it can be difficult to lump all vertical tillage implements into a set of Figure 1: Straight coulters direct soil disturbance downward. field operations contained within the Natural Resources Conservation Service (NRCS) RUSLE2 soil loss model.

2 Understanding the challenges A representative appointed by the Wisconsin Soybean Board to the University of Wisconsin Discovery Farms steering committee requested that the program evaluate the soil and water conservation impacts of vertical tillage implements. Crop producers intuitively believe that vertical tillage tools cause less soil and residue disturbance, compared with other commonly used implements. Vertical tillage implements cut down into the soil. They do not lift, invert, or shatter the soil profile, making their impact different when compared to disks, field cultivators and chisel plows. As the use of shallow vertical tillage implements increases, their impact on soil and water conservation, as well as nutrient management needs to be evaluated and better understood. Soil conservation Soil conservation practices that minimize soil disturbance and maintain surface residue after planting allow producers more flexibility with crop rotations and field management. This is especially true on sloping landscapes where producers may be looking for more years of corn or soybeans and less years of hay. As farmers consider modifying their no-till planting system to a full width tillage system by including 1-pass shallow vertical tillage on some or all fields, questions arise on the actual amount of tillage being done by these machines. Crop producers who work with professionals in soil and water conservation to update their conservation plans have noticed that the NRCS Revised Universal Soil Loss Equation, Version 2 (RUSLE2, ), predicts soil loss to be higher than anticipated for 1-pass shallow vertical tillage. This has resulted in times when soil loss predictions define that producers must consider additional soil conserving practices for conservation compliance and/or participation in voluntary stewardship incentive programs. Residue management Maintaining residue on top of the soil from previous crops is beneficial for soil and water conservation. Large corn stalks and cobs, as well as smaller soybean stalks, alfalfa stems and even livestock manure play a role in absorbing raindrop impact when they exist as cover over the soil. Soil erosion is minimized by maintaining a residue covering over the field surface in the early season, prior to crop canopy. The pool of residue that exists in a crop field is a combination of residue either standing up, laying flat and/ or buried. Tillage impacts residue by knocking it down to the soil surface, continuing to break it into smaller pieces, and burying it or resurfacing it. Management of prior year crop residue before planting a new crop is one of the main reasons producers in western Wisconsin have begun using vertical tillage. Producers are interested in shallow vertical tillage to size and distribute the large amount of stalk residue associated with current high yielding, strong stalked corn hybrids. Large amounts of previous year(s) corn residue in no-till planting systems can sometimes reduce yields due to cool wet soils, slow seed germination and the physical challenge of planting into prior year crop residue. Particulate and dissolved phosphorus loss Agricultural phosphorus enters surface water through two main transport methods: 1) deposited sediment from cropland where phosphorus is tightly attached to, and travels with soil sediment in runoff water; and 2) water soluble phosphorus materials at the soil surface (organic matter, livestock manure, commercial fertilizers, other) that mix with surface water runoff and transport dissolved phosphorus away from cropland. Ten years of field edge surface water monitoring by the UW-Discovery Farms Program on private Wisconsin farms (Stuntebeck, et al.) has shown: Surface water runoff is nearly equally distributed between time periods of frozen ground and unfrozen ground. When the ground is not frozen, surface water runoff was highest in May and June. Runoff that occurred in May and June contributed more than 80 percent of the total annual sediment loss. Annual total-phosphorus yield was about 2.0 lb/acre. Phosphorus loss was highest in February, March, May, and June, corresponding with highest runoff months. Particulate phosphorus was more prevalent in runoff during unfrozen-ground time periods; Dissolved phosphorus was more prevalent in runoff during frozen-ground periods. Overall, half of the lost phosphorus was in the dissolved form, un-attached to sediment.

3 Water quality results from a no-till crop and dairy farm (Cooley, et al.) show that although no-till crop systems can greatly minimize soil loss and corresponding particulate phosphorus loss, more than 75% of phosphorus loss through surface water runoff in no-till cropping systems can be in the dissolved form. Soil and water conservation practices that minimize soil erosion and slow surface water runoff help keep phosphorus on the land where it can be utilized by crops, and out of surface waters. Decreasing sediment loss through no-till cropping systems reduces particulate phosphorus loss. On livestock farms, dissolved phosphorus losses can be lowered with proper manure application timing and rates. Surface applied manure and phosphorus fertilizers can result in high concentrations of phosphorus in upper layers of the soil in no-till systems. Finding a way to mix the top layers of soil with a conservative tillage pass that also maintains large amounts of crop residue may play a role in reducing dissolved phosphorus loss in these systems. Study During April of 2010, UW Discovery Farms worked with a private crop consultant on 5 farms in western Wisconsin to collect data and evaluate the amount of soil disturbance and residue remaining on 14 crop fields after one pass of a vertical tillage implement. Staff worked with the Natural Resources Conservation Service on this study design because soil disturbance and residue remaining are critical parameters used within the RUSLE2 soil loss model. Farm location and vertical tillage equipment The crop consultant identified cooperating farms, and worked with Discovery Farms staff to collect field data and summarize findings. The study farms were located in western Wisconsin, in Buffalo, Pepin and Trempealeau Counties (Fig. 2). Field data collected included soil disturbance and surface residue remaining within five days after a single-pass shallow vertical tillage operation, conducted before planting. Participating farmers used their own tillage implement, operated at their usual speed (6-8 mph) and depth. All implements had two gangs of forward-facing nonconcave blades, either straight or waved. Blades were spaced at ten inches, with the back gang off-set from the front by five inches. None of the rear attachments were power driven. Three of the farms used a Great Plains Turbo- Till equipped with an angled rolling spike harrow, followed by a rolling reel (TT) (Fig. 3). Both the front and rear blades on the Great Plains Turbo-Till were waved (20 diameter, 0.25 thick, 20 forward angled waves with 1¼ total working width). All of the Great Plains Turbo-Till machines had the same style of rear attachment. One farm used a Summers Supercoulter Plus equipped with a similar rolling spike and reel (SCP1) (Fig. 4). The remaining farm used a Summers Supercoulter Plus with a more aggressive rolling Figure 3: Great Plains Turbo Till with rolling spike and reel (TT). Figure 2: Unglaciated western Wisconsin landscape. Figure 4: Summers Supercoulter Plus with rolling spike and reel (SCP1).

4 chopper rear attachment (SCP2) (Fig. 5). Both Summers Supercoulter Plus machines used in this study had straight blades on the front gang (22 diameter, 0.25 thick, no waves with 1/2 total working width) and waved blades on the back (22 diameter, 0.25 thick, 13 waves with 2 1/8 total working width). This report is not an endorsement of any of these machines, nor was this study designed to characterize anything other than the way these particular machines were being used in western Wisconsin. Figure 5: Summers Supercoulter Plus with rolling chopper (SCP2). Data collection The line-transect method was used to estimate percent crop surface residue cover (Wollenhaupt and Pingry, 1991) (Fig. 6). Soil disturbance was evaluated using parameters of the NRCS Soil Tillage Intensity Rating (STIR) (USDA-NRCS 2005). Trenches were dug perpendicular to the tillage travel line to measure individual coulter tillage depth and width, as well as associated non-disturbance areas (Fig. 7). Available soil moisture was estimated using the ball and ribbon feel and appearance test (USDA-NRCS 1998). Three representative soils from within the study were used to compare NRCS RUSLE2 soil loss predictions and STIR values for three tillage systems (no-till planting; shallow vertical tillage + planting; and tandem disk + field cultivate + planting). The predicted soil loss and STIR values for each scenario were based on a 6-year crop rotation of corn grain, followed by corn silage, followed by alfalfa + brome grass direct seeding, followed by 3 years of hay. Figure 6: Line transect residue determination. Figure 7: Observation trench. Results Soil disturbance and residue remaining on the surface after 1-pass shallow vertical tillage varied by field and farm based on soil type, machine characteristics and operating depth. Sandier soils, more aggressive blades, and deeper operation all resulted in more soil disturbance and less surface residue. Table 1 contains information on field site, soil type, slope, soil moisture, implement used, previous crop, residue remaining and soil disturbance for 14 crop fields where single-pass shallow vertical tillage was conducted within the previous five days. Table 1 shows the Go farm consistently operated their Turbo Till (TT) implement at the shallowest soil depth. This farm also had high levels of residue remaining (90 94%), with the one exception being after soybeans, on the Sparta loamy sand. This soil type also exhibited deeper and wider soil disturbance with the same equipment and operating

5 Table 1. Crop residue remaining and soil disturbance after 1-pass shallow vertical tillage Farm Soil Slope Soil Implement * 2009 Residue Tillage Moist Crop Remaining Depth Width (%) (% avail) (%) (inches) Go1 Downs silt loam 4 80 TT cgr Go2 Sparta loamy sand 4 70 TT sb Go3 Eleva sandy loam 9 70 TT cgr Go4 Boaz silt loam 2 75 TT cgr Go5 Gale silt loam TT cgr Gr1 Rowley silt loam 2 75 TT cgr Cr1 Drammen loamy sand 2 70 TT cgr Cr2 Garne loamy sand 4 70 TT cgr Ha1 Meridian loam 4 75 SCP1 cgr / 3 Ha2 Billett f. sandy loam 9 75 SCP1 cgr / 3 Ha3 Seaton silt loam SCP1 cgr / 3 Ol1 Downs silt loam 8 75 SCP2 cgr / 3 Ol2 Hixton f. sandy loam 4 75 SCP2 cgr / 3 Ol3 Downs silt loam 8 75 SCP2 cgr / 3 * TT = Great Plains Turbo Till with rolling spike and reel; SCP1 = Summers Supercoulter Plus with rolling spike and reel; SCP2 = Summers Supercoulter Plus with rolling chopper. speed. The Gr and Cr farms both used a similar Turbo Till implement, and both consistently operated it deeper (2.5 inches versus 1.5 inches) than the Go farm. The Drammen and Garne loamy sand soils on the Cr farm were the coarsest soils in the study, and the 70-75% surface residue is attributed to moderate 2009 corn yields which produced less stalk material. Table 1 also shows that the SCP1 and SCP2 tillage implements used on the Ha and Ol farms cut alternating 1 inch and 3 inch wide tillage strips due to their straight front blades and waved back blade design. The Ol farm consistently operated the SCP2 machine deeper than the other farms. The larger diameter and larger total working width blades on Summers Supercoulter Plus machines were more aggressive than blades on the Turbo Till implements. Similarly, the rolling chopper rear attachment on the SCP2 machine was sharper and more aggressive than the rolling spike and reel attachments on the TT and SCP1 machines. The Ol farm conducted two vertical tillage passes on some fields prior to planting. Subsequent visits back to that farm showed that a more homogeneous 3 inch tillage depth across the whole field resulted from two passes with the SCP2 implement. On all farms, sandy soils displayed deeper tillage depth, and it was harder to find distinct coulter slots (Fig. 8). Sandy Figure 8: Sandy soil after 1-pass TT. Figure 9: 1-pass SCP1. White pins are middle of coulter depth, colored pins are disturbance width.

6 soils have less structure to resist the physical manipulations of tillage. The sandy soil fields appeared to receive a more comprehensive horizontal soil disturbance. This was more pronounced on fields with less initial surface residue, and also more pronounced when using machines with waved coulters. In general, it is safe to say that a single-pass by the vertical tillage machines used in this study created slices of disturbed soil in the same direction of travel, such that every five inches of field width had, approximately, a two inch wide by two inch deep tilled area and three inches of width with less soil disturbance (Figs. 9 and 10). A conservative, shallow single-pass use of these implements on silt loam soil was equivalent to 40% of the field area being coulter tilled to a two inch depth, while 60% remains physically untouched by coulters and disturbed only by rear attachments. Machines with wavy coulters can be expected to contribute additional horizontal soil disturbance outside of the immediate tillage strip. The combined amount of tillage observed from the TT, SCP1 and SCP2 machines Figure 10: 1-pass TT. Every 5 is a 2x2 coulter tilled slot. in this study, although minimal, does not meet the NRCS definition of consolidated soil, which is the basis for soil savings attributed to no-till planting systems within RUSLE2. Impact on residue remaining Similar to soil disturbance, the amount of surface residue remaining after 1-pass with a shallow vertical tillage implement varied from field to field and farm to farm based on soil type, machine blade characteristics and operating depth. Post emergence observations showed that onepass shallow vertical tillage did not bury much residue, yet residue was sized smaller to move through high residue planters (Fig. 11), leaving 70-80% of previous corn residue in place, as well as 80% of last year s corn roots intact and still in the ground (Fig. 12). Observations showed that when the previous crop was corn grain, corn stalk residue was as much as 95% ground cover for land that had not yet been tilled (Fig. 13). Areas where 1-pass shallow vertical tillage was conducted resulted in most stalks broken down from the initial standing position with 70 95% surface residue remaining, depending on farm, soil type, and machine used. The remaining residue will be less when using vertical tillage on fields where previous crops were fine stemmed plants like alfalfa or soybeans, or when corn has been harvested as silage. Most surface residue was cut into pieces 12 inches or smaller and distributed into a layer, up to three inches deep, sitting on top of the soil. Some larger residue pieces were seen pinched into the tillage slots, yet the amount of residue that actually gets incorporated was minimal, involving only pieces smaller than 2 inches (Fig. 14). An interesting phenomenon was observed in corn fields Figure 11: 80% surface residue after 1-pass TT, post planting. Figure 12: 70-80% previous corn residue in place after planting.

7 where 1-pass shallow vertical tillage was conducted. After tillage, a significant amount of the prior year s corn plant roots remained intact, anchored and still in place, with stalks knocked down and a small stalk stub remaining. This was observed in all fields, regardless of soil type. The number of remaining plant roots ranged from 22,000 25,000 in-place corn roots per acre (Fig. 15), based on traditional population count methods for defined row widths. These anchored corn roots represented as much as 80% of the initial corn planting rates. We anticipate these intact prior year corn roots to have soil and water conservation value that would help minimize soil loss and positively impact soil quality and soil organic matter. Figure 13: Corn stalk residue without tillage. Figure 14: Pinched residue, SCP2. Figure 15: Corn roots, intact and anchored after 1-pass SCP1. The conservation conundrum Sometimes vertical tillage machinery is equated with tandem disking when discussing soil disturbance. The concave configuration of most disk blades, along with angled gangs, moves soil laterally, cuts and buries residue and dislodges most prior year root systems (Fig. 16). Tandem disks create complete lateral soil movement, compared with what this project showed to be very limited lateral soil movement with non-concave coulter, shallow 1-pass vertical tillage. Subsequent visits to study fields revealed that as soon as producers begin making 2 or more passes with vertical tillage implements, similarities with tandem disking become more apparent as soil disturbance increased and residue amounts decreased (Fig. 17). Similarly, it is not out of the question that certain aggressively designed vertical tillage implements will move soil laterally, even during 1-pass operations. Figure 16: Ejected corn roots after 1-pass tandem disk. Figure 17: Comprehensive tillage after 2-pass SCP2.

8 Soil loss and tillage intensity estimates The Natural Resources Conservation Service has developed the RUSLE2 software model to predict long term, average annual soil erosion potential caused by water running off from cropland. NRCS updates and maintains the database components for RUSLE2, pertinent to assigning values that impact soil loss for unique soil features, landscapes and farm management. Many NRCS incentive programs and practices have defined target Soil Tillage Intensity Rating (STIR) values, as well as tolerable soil loss levels (T), both calculated within RUSLE2. Within RUSLE2, measurements of the amount of soil disturbance and the amount of surface residue remaining after tillage are two of the many parameters used to predict cropland soil loss. Soil disturbance from a tillage pass is weighted heavier and contributes more toward predicting soil loss than the amount of surface residue remaining after that same tillage pass. Similarly, the soil consolidation feature associated with long term no till planting systems greatly minimizes RUSLE2 soil loss predictions. Soil Tillage Intensity Rating (STIR) values are numerical calculations within RUSLE2 that reflect the type and degree of soil disturbance caused by tillage operations. STIR values range from with smaller numbers indicating less soil disturbance. Specific components of STIR values include: 1) operational speed; 2) tillage type (inversion, mixing, etc); 3) tillage depth; and 4) soil surface area disturbed. For this study, three representative soils (6-12% slope) soils were compared by showing the tolerable soil loss values (T), RUSLE2 predicted soil loss and STIR values for three different tillage systems. Predicted soil loss for each soil is based on a 6-year crop rotation of corn grain, corn silage, alfalfa + brome grass direct seeding and 3 subsequent years of hay. Tillage systems used in this analysis include: 1) no till: 1-pass plant with no tillage; 2) shallow vertical: first pass implement comprised of coulter caddy with fluted coulters, rotary harrow and rolling basket incorporator, second pass plant; and 3) disk + field cultivate: first pass tandem disk, second pass field cultivator with sweeps, third pass plant. Table 2 shows that RUSLE2 predicts a large difference in soil loss between the no-till system and the two tillage systems. In this example, the soil loss estimates for a shallow vertical tillage system and a disk + field cultivate tillage system were 4 6 times more predicted soil loss through the 6-year crop rotation, when compared to no-till. RUSLE2 also predicts a smaller difference in soil loss between the shallow vertical tillage system and the disk + field cultivator tillage system. In this example, a shallow vertical tillage system had 90% (~ ½ ton less) of the soil loss compared to a disk + field cultivator tillage system Table 2. RUSLE2 soil loss and STIR value estimates for 3 tillage systems through a 6-year corn hay rotation. Soil T No Till Shallow Disk + Field Vertical Cultivate tons / ac / yr and (STIR value) BlC (2) 2.7 (14) 3.0 (25) DdC (2) 4.8 (14) 5.3 (25) ElC (2) 3.0 (14) 3.3 (25) through the same 6-year crop rotation. This is similar to other comparisons that have been done between vertical tillage and disk + field cultivate systems. It is not clear why the two systems have such similarly predicted soil loss when field observations suggest that a conservative 1-pass vertical tillage causes much less soil and residue disturbance compared to a disking system. The STIR values for all no-till, all shallow vertical, and all disk + field cultivate tillage systems in this comparison were 2, 14, and 25, respectively. STIR values do not change based on the soil type. STIR values change with crop management systems and are a function of tillage machines or individual components / attachments, and their characteristics, as well as their operation through a defined crop rotation. It should be noted that the estimated soil loss and STIR values shown in Table 2 would increase for the same soils and tillage managements if the crop rotation had the three non-tillage years of hay removed. Table 3 shows the default soil disturbance and residue component values within RUSLE2 used to predict soil loss for the shallow vertical tillage system and the disk + field cultivator tillage system. Tillage type identifies how a soil disturbing operation vertically distributes surface residue when it is buried. Tillage type also identifies how the operation redistributes existing buried residue and dead roots. For most agricultural tillage operations, tillage type categories include: 1) inversion + some mixing (moldboard plowing); 2) mixing + some inversion (tandem disks, chisel plows, field cultivators); and 3) mixing only (rotary powered tillers). Table 3 shows that the 3 component operations that describe shallow vertical tillage (coulter, harrow, and basket) are collectively defined as mixing + some inversion. Both operations of the disk + field cultivator tillage system are also defined as mixing + some inversion within RUSLE2. The observations in this study showed that 1-pass shallow vertical tillage mixes minimal amounts of very small residue pieces within the 2 inch wide by 2 inch deep tillage slot. This does officially match the mixing + some inversion tillage type definition within the RUSLE2 model; yet the

9 Table 3. Soil and residue disturbance values within RUSLE2 operational database for shallow vertical and disk + field cultivate tillage system implements. Coulter Rotary Rolling Tandem Field Units Caddy Harrow Basket Disk Cultivator mix + some mix + some mix only mix + some mix + some Tillage type inversion inversion inversion inversion Tillage intensity fraction Rec. till depth in Min. till depth in Max. till depth in Ridge ht. in Initial roughness in Final roughness in Surface area disturbed % Rec. speed mph Corn residue flatten % mass Corn residue burial % mass Corn residue resurface % mass degree of this vertical residue distribution, compared to disk + field cultivate, is relatively small; small enough that a significant amount of prior year corn root systems remain intact, post-tillage. Project observations for tillage depth ( inches) were in line with the defined maximum operational depth for the shallow vertical tillage components ( ). Similarly, project observations for surface area disturbed (40% of the field area coulter tilled, while 60% remains untouched by coulters and disturbed only by rear attachments) were in line with defined surface area disturbance for the shallow vertical tillage components (55 100%). The residue (flattened, buried or resurfaced) shown in Table 3 is defined as percent of pre-operation mass. This is different than percent of surface cover remaining after an operation, as measured in this project. This project did not weigh surface residue. Fields that had 1-pass shallow vertical tillage consistently had at least 70-80% surface residue cover, which appears to be generally consistent with values listed in Table 3, as estimated below: Vertical tillage. Assuming 45 lbs of corn stover/bu of grain, a 150 bu/ac corn grain crop will leave behind 6,750 lbs/ac of corn residue. Table 3 implies that a vertical tillage implement can leave 64% of the initial residue unburied, as follows: 6750 x.11 burial by coulter = 742 buried = 6008 left x.15 burial by harrow = 901 buried = 5107 left x.15 burial by basket= 776 buried = 4331 left after operation lbs / 6750 lbs = 0.64 = 64% left unburied after operation. Disk + field cultivator. Again, assuming 45 lbs of corn stover/bu of grain, a 150 bu/ac corn grain crop will leave behind 6,750 lbs/ac of corn residue. Table 3 implies that disking + field cultivating can leave 32% of the initial residue unburied, as follows: 6750 x.55 burial by disk = 3712 buried = 3038 left x.3 burial by field cultivator = 911 buried = 2127 left after operation lbs / 6750 lbs = 0.32 = 32% left unburied after operation. Project observations were that on fields with large amounts of prior year residue, 1-pass shallow vertical tillage sized the residue with coulters, and that the rear attachments rolled on top of the residue mat at a shallower depth into the soil than listed as assumed for rotary harrow and rolling basket within RUSLE2. For vertical tillage implements, a comparison of the RUSLE2 soil disturbance and residue parameter database with project observations suggest that RUSLE2 characterization of coulter caddy and rear attachment finishers are generally consistent and appropriately represented. It is unclear just where within the soil loss model that adjustments might be necessary to best predict soil loss from vertical tillage implements. We anticipate some adjustments may be needed within the field operation and tillage intensity database.

10 Conservation programs and tillage Soil and water conservation practices that agricultural producers implement for stewardship and compliance programs are defined by NRCS technical standards. The tillage practices referred to as no till and mulch till both have formal NRCS definitions and standards. No till cropping practices involve a direct planting into untouched soil and residue from the previous year (STIR < 10) or a direct planting into a prepared strip where the crop row will get planted, and where no more than 30% of the row width has been tilled with coulters or row cleaners (STIR 10-15). Mulch till cropping practices involve full width tillage, more comprehensive and in areas more than just where the crop row will be planted, such that more than 30% of the soil surface is disturbed (STIR 15-30) The tillage configuration created by a single pass with vertical tillage implements falls into the NRCS definition for full width mulch tillage, conducting mixing with some inversion within the soil. This study shows that the represented vertical tillage implements (TT, SCP1, and SCP2) can create slices through the field such that 40% of the area is coulter tilled and 60% of the area remains untouched by coulters and disturbed only by rear attachments. In this scenario, more than 30% of the field area is tilled and the resulting tillage strips are created so that up to five additional strips are placed between 30 inch crop rows. This is more intensive than strip tillage planting systems allowed within NRCS Code 329: Residue and tillage management no till, strip till, direct seed. Many producers believe that single pass, shallow, conservative vertical tillage is a complementary practice that could be added and periodically used within their established no till cropping systems. At this time, for NRCS stewardship and compliance programs, any field with a planned and established no till cropping system will get redefined for program purposes as full width mulch till when vertical tillage is conducted. This is important to know when considering conservation requirements associated with tolerable soil loss and producer chosen cost share practices like continuous no till with high residue cropping systems, available within the current NRCS-Conservation Stewardship Program. Conclusion This study evaluated the soil disturbance and surface residue remaining within 5 days after a single-pass shallow vertical tillage operation at 14 crop fields on 5 farms in western Wisconsin. Three different non-concave bladed vertical tillage implements and their unique operation by farmer participants were evaluated. Soil disturbance and remaining surface residue after 1-pass shallow vertical tillage varied by field and farm based on soil type, machine characteristics and operating depth. Sandier soil, more aggressive machinery, and deeper operation all resulted in more soil disturbance and less remaining surface residue. A single-pass by the machines in this study created slices of disturbed soil in the same direction of travel, such that every five inches of field width had, approximately, a two inch wide by two inch deep tilled area and three inches of width with less soil disturbance. A conservative single-pass use of these implements on silt loam soil was equivalent to 40% of the field area being coulter tilled to a two inch depth, while 60% remains physically untouched by coulters and disturbed only by rear attachments. Most crop residue was cut to 12 inches or smaller and distributed into a layer on top of the soil. Post emergence observations showed that onepass shallow vertical tillage did not bury much residue, yet residue was sized to move through high residue planters, leaving 70-80% of previous corn residue in place, as well as 80% of last year s corn roots intact and still in the ground. This project showed very limited lateral soil movement with non-concave coulter, shallow 1-pass vertical tillage. As soon as producers began making 2 or more passes with vertical tillage implements before planting, similarities with tandem disking became more apparent as soil disturbance increased and remaining residue amounts decreased. When comparing 3 tillage systems through a 6 year corn and hay crop rotation, RUSLE2 predicts a large difference in soil loss between the no-till system and the two tillage systems. In this example, a shallow vertical tillage system and a disk + field cultivate tillage system had 4-6 times more predicted soil loss through the 6-year crop rotation, compared to no-till. RUSLE2 also predicts a smaller soil loss difference between the shallow vertical tillage system and the disk + field cultivator tillage system. In this example, a shallow vertical tillage system had 90% (~ ½ ton less) of the soil loss compared to a disk + field cultivator tillage system through the same 6-year crop rotation. Within the RUSLE2 field operation database, project observations for tillage depth were in line with the defined maximum operational depth for the shallow vertical tillage components. Similarly, project observations for surface area disturbed were in line with defined surface area disturbance for the shallow vertical tillage components. Fields that had 1-pass shallow vertical tillage consistently had at least 70-80% surface residue cover, which also appears to be

11 generally consistent with the interpretation of RUSLE2 database values. The tillage configuration created by a single pass with vertical tillage implements falls into the NRCS definition for full width mulch tillage, conducting mixing with some inversion within the soil. This study shows that the represented vertical tillage implements created slices through the field such that 40% of the area is coulter tilled and 60% of the area remains untouched by coulters and disturbed only by rear attachments. In this scenario, more than 30% of the field area is tilled and the resulting tillage strips are created so that up to five additional strips are placed between 30 inch crop rows. This is more intensive than strip tillage planting systems allowed within NRCS Code 329: Residue and tillage management no till, strip till, direct seed. Tillage has numerous functions, including residue management, soil mixing and weed control. Most crop producers in Wisconsin have dramatically reduced tillage to save soil, time and fuel. Some have implemented 1-pass no-till planting systems with various attachments for residue management in front of seed placement. Still others want to maintain the soil and water conservation benefits of high residue planting systems, yet desire prior season residue to be cut smaller and/or they desire a small degree of soil mixing. Agricultural producers and crop consultants believe that conservative operation of vertical tillage implements has less of an impact on soil disturbance and residue management than disking or field cultivating. Producers who are serious about using these tillage tools as a 1-pass + plant system should invite their agronomist and conservation planning professionals to do field observations with them to properly evaluate the depth and width of soil disturbance, along with remaining prior season residue. An accurate definition of tillage implement used based on RUSLE2 guidance and realistic crop residue levels that a producer is able to consistently maintain will provide the most representative soil erosion estimate. In light of numerous designs and individual components of vertical tillage implements, on-farm field observations can define farm specific use of the machine and identify any operational changes necessary for best crop production, as well as soil and water conservation. In cropping scenarios where the desired rotation depends on very limited or no tillage in order to maintain conservation compliance, conservative 1-pass shallow vertical tillage might be an option, on a site specific basis. Producers should consult their local NRCS for tillage and cropping system requirements that pertain to their individual program participation. It is not out of the question that certain aggressively designed vertical tillage implements can and will disturb more soil and surface residue than other machine designs. Conservative and shallow are key phrases when considering the use of these implements on cropland landscapes that have high soil loss potential. As soon as producers begin making 2 or more passes with vertical tillage implements before planting, similarities with tandem disking become more apparent as soil disturbance increases and remaining residue decreases. Future research needs Three observations from within this project need additional study: 1) evaluate the soil quality and conservation value of maintaining intact prior year root systems after 1-pass shallow vertical tillage; 2) evaluate the assigned RUSLE2 field operation database values for vertical tillage implements to confirm or adjust modeled tillage characterization and soil loss predictions; and 3) field-validate the comparative similarity of soil loss prediction between shallow vertical tillage and tandem disking + field cultivating systems. Additional studies should be initiated to evaluate the impact and effectiveness of shallow vertical tillage for: 1) minimizing soil loss; 2) water infiltration; 3) fertilizer, lime and manure incorporation; 4) redistributing nutrients when stratified near the soil surface; 5) season of operation; 6) early season soil drying and warming; 7) use on tile drained preferential flow critical sites.

12 References and resources Cooley, E., A. Wunderlin, A. Radatz, N. Drummy, and D. Frame Understanding nutrient & sediment loss at Koepke Farms, Inc. Phosphorus loss at Koepke Farms, Inc. University of WI Discovery Farms Program, Pigeon Falls, WI. Great Plains Manufacturing, Inc., Salina, KS. Turbo-Till Series II information sheet. Available at greatplainsmfg.com (verified Oct. 2011). Klingberg, K., and C. Weisenbeck Shallow Vertical Tillage: Impact on Soil Disturbance and Crop Residue. Proceedings of the 2011 Wisconsin Crop Management Conference, Vol. 50: Madison, WI. Schuler, R.T Residue Management Horizontal vs. Vertical Tillage. Proceedings of the 2007 Wisconsin Fertilizer, Aglime & Pest Management Conference, Vol. 46: Madison, WI. Stuntebeck, T.D., Komiskey, M.J., Peppler, M.C., Owens, D.W., and Frame, D.R., 2011, Precipitation-runoff relations and water-quality characteristics at edge-of-field stations, Discovery Farms and Pioneer Farm, Wisconsin, : U.S. Geological Survey Scientific Investigations Report Available at: sir/2011/5008/ (verified Oct. 2011). Summers Manufacturing Company, Inc, Devils Lake, ND. Supercoulter Plus information sheet. Available at (verified Oct. 2011). U.S. Dept. of Agriculture Natural Resources Conservation Services Estimating Soil Moisture by Feel and Appearance. Program U.S. Dept. of Agriculture Natural Resources Conservation Services, WI Residue and Management Mulch Till, Code 345. Available at references/public/wi/345.pdf. (verified Oct. 2011). U.S. Dept. of Agriculture Natural Resources Conservation Services, WI Residue and Tillage Management No Till / Strip Till / Direct Seed, Code 329. Available at (verified Oct. 2011). U.S. Dept. of Agriculture Natural Resources Conservation Services, WI Soil Tillage Intensity Rating (STIR) information sheet. Available at ftp://ftp-fc.sc.egov.usda.gov/ WI/Pubs/STIR_factsheet.pdf (verified Oct. 2011). U.S. Dept. of Agriculture Natural Resources Conservation Services, WI Tillage Practice Guide information sheet. Available at consplan/tillagepracticeguide.pdf (verified Oct. 2011). Wagner, L.E., and R.G Nelson Mass Reduction of Standing and Flat Crop Residues by Selected Tillage Implements. Trans. ASAE 38(2): Wolkowski, R.P Is Vertical Tillage a Practice for Wisconsin Soils? Proceedings of the 2010 Wisconsin Crop Management Conference, Vol. 49: Madison, WI. Wollenhaupt, N. and J. Pingry Estimating Residue Using the Line-Transect Method. University of Wisconsin Extension pub. A3533. Madison, WI. October 14, Special thank you to Pat Murphy and Terry Kelly, WI NRCS for review, comments and edits. This paper can be found on the web at: www. uwdiscoveryfarms.org or by calling the UW- Discovery Farms Office at by the Board of Regents of the University of Wisconsin System. University of Wisconsin-Extension is an EEO/Affirmative Action employer and provides equal opportunities in employment and programming, including Title IX and ADA requirements. Publications are available in alternative formats upon request.