Direct Seed Systems for Grain Legumes – Pursuing Improved Erosion Control, Water Storage, Yields and Profitability

Chapter 2 – Cropping Systems and Equipment, May 1999

Pacific Northwest Conservation Tillage Handbook Series No. 26 (Update of No. 20, May 1997)

Authors: Roger Veseth, WSU/UI Conservation Tillage Specialist; Stephen Guy, UI Crop Management Specialist; Duncan Cox, UI/WSU Project Support Scientist; Donn Thill, UI Weed Scientist; John Hammel, UI Soil Scientist, Moscow, ID; Tim Fiez, WSU Soil Fertility Specialist; and Joe Yenish, WSU Weed Scientist, Pullman, WA.

Direct seeding of grain legumes offers exciting potential benefits in improved soil erosion control, soil quality, yield and profitability. Innovative growers and university scientists have combined efforts to accelerate the development of integrated management systems for direct seeding in the cereal-legume-winter wheat cropping sequence. The following is a brief description of why changes are needed in spring grain legume production practices and preliminary results on these new direct seed systems.

The Need for Change

In the Inland Northwest, soil erosion can be a serious problem in crop rotations with grain legumes followed by winter wheat. Intensive tillage traditionally has been used to bury the previous cereal crop residue and incorporate soil-active herbicides. Today, there are a number of herbicides available for grain legumes that do not require soil incorporation. Another reason for preparing a finely-tilled, low-residue seedbed for spring grain legumes in the past has been to facilitate the use of “lifters or pea bars” to pick up the lodged crop on the soil surface at harvest. However, the increasing availability of semi-leafless pea varieties that remain upright and can be harvested with the standard grain header will reduce the need for a smooth, low residue seedbed in the future.

Spring field operations when soils are wet can result in significant soil compaction from tractor traffic and tillage implements. The combination of little or no residue from the previous cereal crop retained on the soil surface after legume planting and the smooth compacted soil from the spring tillage operations can leave legume fields vulnerable to soil erosion during intense rainstorms in the spring and early summer. Spring soil compaction alone also can directly reduce crop yield potential.

Grain legumes produce relatively little crop residue, which is fragile and shatters easily during dry harvest conditions, and decomposes rapidly under moist conditions. Without carryover cereal residue preceding the legume crop and the reduction of soil compaction from spring tillage operations for legume establishment, fields with winter wheat after grain legumes can be highly vulnerable to erosion during the critical November to April period, when about 70% percent of the yearly precipitation occurs. Winter wheat is typically seeded later in the fall (October) to reduce the risk of a number of weed, insect and disease problems, and/or because of dry soil conditions earlier in the fall. Consequently, the wheat crop usually over-winters as small plants and provides little erosion protection. Even though growers have made a significant shift towards minimum tillage or direct seeding of winter wheat, surface residue cover from the legume crop alone is often inadequate for erosion control.

Surface runoff and soil erosion can cause yield losses in both the grain legume and winter wheat crops. Water running off the fields or lost to evaporation is water not stored for grain production. The greatest impact occurs on upper slopes and ridgetops where yields are most limited by available water. Erosion can reduce current crop yields by loss of plant stands and reduced plant vigor. Soil loss will also reduce future crop yields due to loss of soil fertility, water holding capacity, rooting depth and other soil quality and productivity factors.

Direct Seeding Grain Legumes — A Promising Solution

Some innovative Northwest growers have been experimenting with direct spring seeding of grain legumes with no prior tillage or with minimum tillage the previous fall. To build upon their efforts, beginning in 1996, a 3-year research project by scientists from University of Idaho and Washington State University was initiated to assist growers in developing integrated management systems for direct seeding of grain legumes. The project is partially supported by collaborative UI and WSU grants from the Pacific Northwest STEEP III (Solutions To Environmental and Economic Problems) conservation farming research program in Idaho, Oregon and Washington. This direct seed grain legume research is a combination of researcher-managed experiments on university research farms and grower fields, and grower-managed field experiments with their field-scale equipment. The research effort includes comparisons of direct seeding and more intensive tillage systems in the cereal – legume – winter wheat sequence.

In direct spring seeding of grain legumes, integrated crop and pest management systems for grain legumes must optimize yield, quality and residue production and minimize soil compaction. In addition, winter wheat planting systems must then continue to retain surface residue from the legume and previous cereal crops, and maintain soil physical conditions for effective water infiltration. The overall goal is to improve erosion control, yield potential and profitability in the cereal – legume – winter wheat rotational cycle.

Rotation Consideration — An important point to keep in mind is that direct seeding establishment of grain legumes will be much more successful in a crop rotation of three years or longer, such as winter wheat-spring cereal-legume, than in the common 2-year winter wheat-legume or fallow rotation in the region. The additional year of spring crop, or a winter non-cereal crop, in the rotation is very important in reducing the potential for soilborne diseases and winter annual grass weeds that can be problems under direct seed systems in a 2-year rotation. In addition, direct spring seeding of grain legumes after spring cereals is easier than after winter wheat because residue levels are usually much lower.

This publication primarily focuses on 1997-1999 field trials comparing spring pea production under direct seeding and other tillage and residue management systems. Preliminary results from other related university trials are available in the 1997 and 1998 STEEP III Research Progress Reports (see References at the end).

University Research Farm Trials

A 1997-1999 field trial on comparing four tillage systems for spring pea establishment following spring cereals is being lead by Stephen Guy, UI Crop Management Specialist, at the UI Kambitsch Research Farm near Genesee, ID, which is in a 20-inch precipitation zone. The trial is evaluating the tillage system effects on cereal residue carryover through the pea crop and winter wheat establishment, as well as effects on performance of the pea and winter wheat crops (Table 1). Both spring wheat and spring barley were included in the study, but only the results following the spring wheat barley crop will be reported here. Plots are 16 ft. wide and 600 ft long, with four replications of each treatment.

After harvest of the 1997 spring cereals, three fall tillage treatments were established: plow, chisel, and paratill (low disturbance subsoiler). A fourth treatment included undisturbed stubble overwinter for direct seeding in the spring. In the spring, the plow and chisel treatment were cultivated twice and Roundup was applied to the three other treatments two weeks before seeding all the plots with a Haybuster 1000 no-till disc drill. Pursuit was applied pre-emergence for broadleaf weed control. After pea harvest, fertilizer was directly injected without prior tillage (Ripper-Shooter) and winter wheat seeded using a Great Plains no-till drill with coulter/offset double disc openers. Residue groundcover was measured after the 1997 fall tillage treatments through the spring pea crop and winter wheat establishment.

In all cases, surface residue cover with direct spring seeding without any previous tillage was significantly greater than with the fall Paratill – direct seed, which was greater than or similar to the fall chisel – direct seed treatment. Surface residue in the plow treatment was lowest after planting both the pea and winter wheat crops. There were no differences in pea population among tillage treatments. Pea yields were highest in direct seed and Paratill treatments and lowest in the plow treatment. This trials show the effectiveness of direct seeding and minimum tillage systems in carrying spring cereal residue through pea and winter wheat establishment. In the plow treatment, there was inadequate surface residue retention for erosion control after planting of both crops. The pea crop alone did not provide adequate residue for erosion control in the following winter wheat crop, even with a low-disturbance, shank fertilize-and-seed system for winter wheat planting.

Table 1: Effects of tillage practices following a 1997 spring wheat crop on surface residue retention and performance of the 1998 spring pea crop and establishment of winter wheat. UI Kambitsch Research Farm, Genesee, ID -- 20- to 22-inch rainfall zone.

Grower On-Farm Trials

Eight grower on-farm tests are being conducted during 1996-99 to evaluate spring pea establishment in a cereal – pea – winter wheat rotational sequence under direct seeding compared to more intensive tillage and residue management practices. These are large-scale trials established and managed by collaborating growers with their field equipment. All the trials are being conducted for a 2-year period beginning in the fall after harvest of a spring or winter cereal, through a pea crop and the subsequent winter wheat crop. Nearly all the trials compare a spring direct seed system without prior tillage with some type of fall minimum tillage and direct seeding in the spring without any spring tillage. Some of the trials included additional tillage and residue management treatments to address specific grower’s interests and equipment available. All trials have four replications of each treatment and individual plots range from 30 to 50 feet wide and 700 to 1,500 feet long. Surface residue evaluations were conducted after fall tillage of the cereal crop, before and after pea planting, after pea harvest and after winter wheat planting. Other data collection included pea plant stand and yield, and finally winter wheat yield.

Wayne Jensen – Genesee, ID — A 2-year on-farm trial comparing two tillage practices for spring pea following a 70 bu/A hard white spring wheat crop was completed in 1998 on the Wayne Jensen farm northwest of Genesee, ID in a 20- to 22-inch rainfall zone (Table 2). The two treatments following spring wheat were 1) Fall Plow – Spring Cultivate – Seed – fall (1996) moldboard plow with trash boards – spring Pursuit herbicide application followed by two field cultivator operations – seed; and 2) Fall Chisel/Cultivate – Spring Direct Seed – fall chisel – late fall cultivate/harrow – spring Roundup-Pursuit herbicide application (2 weeds before seeding) – spring direct seed. Both treatments were seeded with a John Deere 455 offset double disc drill. The soft white winter wheat crop was direct seeded in fall 1997 with a Yielder double disc no-till drill.

Table 2. Tillage comparison following 1996 spring wheat through 1997 spring pea and 1998 winter wheat crops, Wayne Jensen, Genesee, ID -- 20- to 22-inch rainfall zone.

The results from this trial show that the minimum fall tillage – direct spring seed system resulted in greater erosion protection with higher surface residue levels after seeding peas and the subsequent winter wheat crop than with the fall plow treatment, 34 vs. 6% and 47 vs. 30%, respectively. There were no differences in plant establishment, pea yield or yield of the following winter wheat crop. The results of this trial are very similar to the results of Jensen’s first trial with these two treatments in 1995-97. In the first study, surface residue levels after seeding peas and the subsequent winter wheat crop were 59% and 51%, respectively, in the fall chisel/cultivate – direct spring seed treatment versus 10% and 24% with the fall plow treatment. There also were no significant differences in spring pea and winter wheat yields between the treatments.

Nathan and Steve Riggers – Nezperce, ID — Four tillage and residue management systems were compared following a 65 bu/A hard red spring wheat crop west of Nezperce, ID in a 24- to 26-inch rainfall zone (Table 3). Treatments included: 1) Direct Spring Seed; 2) Spring Burn – Direct Spring Seed; 3) Fall Disc – Direct Spring Seed; 4) Fall Moldboard Plow – Spring Cultivate – Seed

The two treatments with overwinter stubble received a late October application of Roundup. In early April, all treatments except the plow treatment received a second Roundup application about 2.5 weeks before planting. All treatments were seeded with a Flexi-Coil 5000 no-till hoe air-seeder on May 4 with Karita peas, a semi-leafless variety that stand upright and can be harvested with a standard grain header. All the plots were harrowed with a tine harrow after seeding. All treatments received separate post-emergence applications of Basagran and Assure II. Winter wheat was direct seeded in the fall with the same Flexi-Coil 5000 no-till hoe airseeder.

Residue groundcover levels and pea yield was highest in the non-burn, direct seed systems (Table 3). Surface residue cover after pea and winter wheat planting were highest in the non-burn, direct seeded pea treatments at 72 and 60%, respectively. Pea emergence was not significantly different among the treatments, but lower than expected because the low seed lot germination (<85%) was not known at planting. Direct seed pea yield was significantly higher than burn-direct seed and plow treatments, with yields in the trial increasing with increasing surface residue levels.

Table 3. Comparison of four tillage and residue management practices following 1997 hard red spring wheat through 1998 spring pea and 1999 winter wheat crops, Nathan and Steve Riggers, west of Nezperce, ID - 24- to 26-inch rainfall zone.

Randy and Larry Keatts – Lewiston, ID — Five tillage and residue management practices were compared for spring pea following a 1997 soft white spring wheat crop south of Lewiston, ID in a 12- to 16-inch rainfall zone (Table 4). Previous crops were winter wheat (1996), and spring pea (1995). Treatments included: 1) Spring Direct Seed; 2) Spring Burn – Spring Direct Seed; 3) Fall Disc – Spring Direct Seed; 4) Fall Subsoil/Disc – Spring Direct Seed – fall R & R subsoiler – fall disc – direct seed; 5) Fall Chisel – Spring Direct Seed – fall chisel/harrow – direct seed.

The trial received mid-October and early March applications of Roundup. All treatments were seeded to Columbia pea (common type) on March 18 with a Tye no-till disc drill, then harrowed and rolled. Winter wheat was seeded in the fall with a 2-pass system of direct-shank application of fertilizer and then seeding with the Tye no-till disc drill.

Pea plant stand in the direct seed treatment was lower that most of the other treatments and a difference in seeding depth between fall-tilled treatments and the direct seed treatment in undisturbed residue probably caused the reduced plant stand. The field trial was seeded as one field and it was difficult to set seeding depth accurately for all treatments. Consequently, direct seed plots in undisturbed residue were seeded shallower than desired (0.5-1 inch) and tilled plots were seeded slightly deeper than desired (2-3 inch). Reduced seed-to-soil contact from shallower seeding in the direct seed treatment in standing stubble contributed to the lower stand.

Pea yield was not significantly different among treatments. A hail storm shortly before harvest resulted in approximately 60-70% seed loss. The direct seed treatment maintained the highest percent surface residue for erosion control after pea and winter wheat planting, 83 and 49%, respectively.

Table 4: Comparison of tillage and residue management practices following a 1997 soft white spring wheat crop through 1998 spring pea and 1999 winter wheat crops. Randy and Larry Keatts, Lewiston, ID - 12- to 16-inch rainfall zone.

Art Schultheis – Colton, WA — Two tillage systems were compared for establishing a 1998 spring pea crop following a 90 bu/A 1997 winter wheat crop just northwest of Colton in a 20- to 22-inch annual rainfall zone (Table 5). Previous rotation crops were lentils in 1996 and spring barley in 1995. Treatments include: 1) Fall Disc-Subsoil – Spring Direct Seed – fall (1997) John Deere disc-ripper – spring harrow – direct seed; and 2) Spring Direct Seed. The winter wheat stubble was flailed after harvest when the residue was dry. Roundup was applied on the direct seed treatments in the fall and on both treatments in the early April. The trial was seeded in late April to Columbia pea with a Flexi-Coil single-disc air seeder. The disc-rip treatments were harrowed after seeding. Basagran and Thistrol were applied post emergence to the disc-rip treatments only (no weeds observed at that time on the direct seed treatments). Assure II was applied to both treatments for grass weed control. Winter wheat was direct seeded with a John Deere 750 single disc no-till drill in the fall.

Direct seeding provided more residue groundcover and better soil erosion protection in both the pea and winter wheat crops. The percent residue cover was significantly higher after planting pea and winter wheat, 96 vs. 19 and 84 vs. 41, respectively. Pea plant stands and yields were not significantly different.

Table 5: Comparison of tillage practices following a 1997 soft white winter wheat crop through 1998 spring pea and 1999 winter wheat crops. Art Schultheis, Colton, WA - 20- to 22-inch annual rainfall zone.

Richard Druffel and Sons – Pullman, WA – Two tillage practices were compared for establishing a 1998 spring pea crop after a 1997 soft white spring wheat crop south of Pullman in a 20- to 22-inch annual rainfall zone (Table 6). Treatments included: 1) Fall Disc-Subsoil – Spring Direct Seed – fall (1997) John Deere disc-ripper – spring harrow – direct seed; and 2) Spring Direct Seed.

Roundup was applied to all treatments on March 22. There was 4 to 6 inches growth on the volunteer spring wheat at a moderately high plant density in the direct seed compared to a light population of 2- to 4-inch high volunteer in the fall disc-subsoil treatment. All treatments were seeded to Columbia pea on April 10 with a Palouse Zero Till double disc drill. Fargo and Pursuit were applied post-plant pre-emergent with a harrow-sprayer. The harrow was used to incorporate the herbicides on the disc-ripper treatments, but was lifted off the soil on the direct seed treatments. Winter wheat was direct seeded with the Palouse Zero Till drill in the fall.

Percent surface residue was significantly higher in the direct seeding than in the fall disc-subsoil treatment after pea and winter wheat planting, 81 vs. 22% and 54 vs. 36%, respectively. Pea plant emergence and yield were not significantly different between the two treatments.

Table 6: Comparison of tillage practices following a 1997 soft white spring wheat crop through 1998 spring pea and 1999 winter wheat crops. Richard Druffel and Sons, Pullman, WA - 20- to 22-inch annual rainfall zone.

Larry Cochran – Colfax, WA —Two tillage practices were compared for establishing a 1998 spring pea crop after a 1997 spring barley crop northeast of Colfax in a 18- to 20-inch annual rainfall zone (Table 7). Treatments included: 1) Fall Chisel/Cultivate/Harrow – Spring Direct Seed; and 2) Spring Direct Seed. Roundup was applied in late fall and in mid April. All treatments were direct seeded to Columbia peas on May 1 with a John Deere 750 single disc no-till drill then rolled. Winter wheat was direct seeded with the same John Deere 750 no-till drill in the fall.

Direct seeding retained higher surface residue levels after pea and winter wheat planting, 84 vs. 43% and 55 vs. 43%, respectively, although both systems provided good erosion protection. Pea plant stands, yields and residue cover after pea harvest were not significantly different.

Table 7: Comparison of tillage practices following a 1997 spring barley crop through 1998 spring pea and 1999 winter wheat crops. Larry Cochran, Colfax, WA - 18- to 20-inch annual rainfall zone.

Bob Garrett – Endicott, WA — Two tillage practices were compared for establishing a 1998 spring pea crop after 1997 soft white spring wheat (Table 8) and soft white winter wheat (Table 9) crops northwest of Endicott in a 15- to 18-inch annual rainfall zone. Treatments on both the spring wheat and winter wheat fields included: 1) Fall Chisel/harrow – Spring Direct Seed – fall (1997) chisel (with narrow fertilizer knife openers on 12-inch spacing) and attached tine harrow – direct seed; and 2) Spring Direct Seed. Roundup was applied in mid-November and on March 22. Both treatment systems on the spring wheat and winter wheat field trials were direct seeded to Columbia peas on April 16 using a Great Plains no-till drill with coulters directly ahead of offset double discs. All plots were harrowed after seeding. Sencor was applied post-plant pre-emergence and Assure II and Basagran were applied post emergence as a tank mix about 5 weeks after seeding. Winter wheat was established in the fall using a 2-pass system with the same low-disturbance chisel as a direct-shank fertilizer applicator and seeding with the Great Plains no-till disc drill.

Although there were slightly higher surface residue levels pre-plant and post-plant in spring peas under direct seeding compared to fall chisel/harrow – direct seed, no differences were noted later in pea plant stands, pea yield or in surface residue levels after harvest and winter wheat seeding. The fall chisel/harrow was a very low-disturbance operation, so both systems provided effective erosion protection in the pea crop and subsequent winter wheat crop. Seeding depth was generally 0.5 to 1 inch, slightly shallower than planned, contributing to lower plant stands than expected. Although the reasons for the low pea yields are not known, post-emergence herbicide injury is suspected as one factor in reducing plant growth and yield potential in both trials.

Table 8: Comparison of two tillage practices following a 1997 soft white spring wheat crop through 1998 spring pea and 1999 winter wheat crops, Bob Garrett, Endicott, WA - 15- to 18-inch annual rainfall zone.

Table 9: Comparison of two tillage practices following a 1997 soft white winter wheat crop through 1998 spring pea and 1999 winter wheat crops, Bob Garrett, Endicott, WA - 15- to 18-inch annual rainfall zone.

Preliminary Conclusions from the Large-Scale Direct Seed Pea Trials

These nine large scale field trials demonstrate that direct seeding of spring peas after cereals can significantly increase surface residue retention for erosion control and water storage through the cereal – grain legume – winter wheat rotation compared to more intensive tillage systems beginning with fall tillage. In addition, pea stand establishment and yield with direct seeding were either not significantly different or were greater than with fall tillage. Spring direct seeding also resulted in the higher pea test weight in five of the 1998 direct seed pea trials, although differences were not always statistically significant. This could indicate that a higher level of soil water may be present at grain filling than under more intensive tillage systems. Yield of winter wheat will be compared in the second year of the field trials in 1999. In the first three project trials completed through the second year with winter wheat harvest, there were no significant differences in winter wheat yield due to the tillage and residue management operations evaluated for grain legume establishment. Economic comparisons have also not yet been completed, but production costs may be reduced with spring direct seeding by eliminating a number of tillage operations.

Other Project Trials Underway

There are several other studies underway that address related management options in direct seed systems for the cereal – grain legume – winter wheat sequence as part of this STEEP III project.

The results of these studies will be reported later in subsequent publications when the data are available.

1. Residue Production and Durability – Stephen Guy, UI Crop Management Specialist, is leading studies at the UI Kambitsch Research Farm to evaluate differences in residue production between spring wheat and spring barley as the cereal crop preceding the grain legume, differences in residue production between pea and lentil, and differences between varieties of each legume crop. In addition to residue production, he is also looking at the durability of residue from the spring cereals and legume crops through different tillage practices for establishing the subsequent crops.
2. Herbicide Options – Donn Thill, UI Weed Scientist, is evaluating the relative effectiveness of different herbicides for pre-plant, pre-emergence or post-emergence applications on grain legumes under direct seeding and other tillage systems. In addition, he is evaluating herbicide crop safety and soil carryover effects on the following winter wheat crop. Joe Yenish, WSU Extension Weed Scientist, is evaluating these issues at Washington locations and is also evaluating fall versus spring applications of herbicides without incorporation for direct seed grain legumes.
3. Fertility – Tim Fiez, WSU Extension Soil Fertility Specialist, is researching the effects of applying 20 lb/acre nitrogen, phosphorus and sulfur (N, P₂0₅ or S) fertilizer alone or in all combinations at pea planting under direct seeding and other tillage systems. These trial have been established across the grower large-scale trials. Fertilizer applications have generally not resulted in pea yield increases from under conventional tillage in the region. It is not known if they will respond to fertilizer applications under the new soil and residue environments of direct seed systems.
4. Soil Water Storage and Crop Use – John Hammel, UI Soil Scientist, is evaluating water storage and grain legume use under direct seed systems compared to more intensive tillage systems.

Additional References on Direct Seed Grain Legumes

Conservation Tillage and Pulse Crop Production — Western Canada Experiences – Adrian Johnston, Perry Miller and Brian McConkey, in Proceedings of Northwest Direct Seed Cropping Systems Conference, Jan. 5-7, 1999, Spokane, WA.

Residue Production and Retention in Small Grain Cereal and Legume Rotational Systems With Different Tillage Practices – S. Guy, D. Thill, R. Veseth, J. Hammel, T. Fiez, J. Yenish and D. Cox, in Pacific Northwest STEEP III 1998 Annual Research Report.