Broadleaf Incorporation in an Intense Direct Seed Cereal Rotation

The objective of this on-farm test is to better understand the value of yellow mustard as an alternative crop in an intense cereal grain cropping rotation under direct seeding conditions in the intermediate rainfall cropping region of eastern Washington. Yellow mustard in rotation may have benefits because of opportunities to control grassy weeds, suppression of cereal root diseased, or interactions with soil microbial activity that benefits subsequent cereal crops. Specifically with regards to disease, three conditions are required

1. Presence of a virulent pathogen in adequate population and level of energy
2. Presence of a susceptible crop species and variety
3. A favorable environment

Crop rotations with mustard may reduce economic damage by minimizing one or more of these factors.

Locations: 5-7 miles NW of Wilbur, WA.
Annual precipitation: 12 inch.
Soil type: Bagdad silt loam.
Soil depth: 6 feet plus.

This experiment compared replacing spring barley with yellow mustard in an intensive cereal rotation. Table 1 shows the cropping history at each location for each year. During the “spring barley” year of the rotation plots of yellow mustard and spring barley were sown. The trial is a randomized complete block design with 4 replications each of the 3 site-years, and plot size was 43 feet wide and 1000 feet long. Plots were seeded in the spring with a Flexi-Coil 5000 direct seed drill on 12-inch row spacing. Roundup® was applied for burn-down weed control about 10 days prior to seeding. Barley was seeded at 70-lb/ac and mustard was seeded at 10-lb/ac each year. Fertilizer rates varied each year based on soil tests results, but both mustard and barley received the same rate. Aqua ammonia was applied as the primary N source and 16-20-0-14 was applied with the seed at 50-lb product/acre each year. In-crop herbicides were not applied in any year. Plots were harvested with the grower’s combine and weighed using portable weigh pads. The prevailing market price for each year was used to calculate gross revenue.

Subsequent spring cereal crops (wheat or barley) in the study were direct seeded with the same drill used to seed the treatments. Roundup® was applied 7-10 days prior to seeding. In-crop herbicides were not applied because of low weed pressures. The cereal crops following each treatment were harvested with the grower’s combine and weighed using portable weigh pads. Grain samples were collected to determine grain protein and test weight.

Treatment Crop Yield
Yields of spring barley and yellow mustard for each year are presented in Table 2. Spring barley produced greater yields than yellow mustard during each season; averaging 1,640 lb/ac compared to yellow mustard which produced an average yield of only 647 lb/ac. Site 2, when precipitation was near average (Figure 1), had the greatest yield averaging nearly 1,500 lb/ac between the treatments. Other years, when precipitation was more than 2 inches less than average, yields were around 1,000 lb/ac.

Soil Samples
Soil samples were taken in 1 foot increment to a depth of 4 feet in spring of the year after the treatment crop and prior to seeding the cereal crop. Samples were analyzed for NO3, NH4, K, P, S and H2O in the top foot and NO3, S and H2O from 2-4 feet to detect differences between treatments. Averaged over the 3 years, subtle differences were detected between the two treatments (Table 3). Greater amounts of ammonia and nitrate nitrogen remained in the top 1foot following mustard (19 lb N/ac combined). This was consistent over the duration of the study. Less soil water was measured in the top 2 feet of the soil profile following yellow mustard; however this difference was greatest at Site 2 where yellow mustard had ½ inch less in water in the top 2 feet and 1.3 inches less water in the 4 foot profile (Figure 2).

Weed Population
Grassy and broadleaf weeds were counted in the spring after burn-down herbicide application and prior to seeding subsequent spring cereal. Barley as the previous crop had more broadleaf and grassy weeds in comparison to yellow mustard (Figure 3). Overall yellow mustard as the previous crop had an 82% reduction in weed population compared to spring barley (Photo Page 7). The decrease in weed population may be due to glucosinolates in mustard residue, which are potential inhibitors of weed seed germination.

Subsequent Crop Production
Small differences were detected in the subsequent spring crop production following either spring barley or yellow mustard. Stand establishment, grain protein, and test weight were not different between the two treatments over the 3 years (data not presented). Spring cereal following spring barley produced the greatest yield at 1,854 lb/ac compared to only 1,625 lb/ac following yellow mustard (Figure 4). However, the yield differential was not consistent over the 3 years and was mostly from Site 2 where spring wheat following spring barley yielded 38 bu/ac compared to 28 bu/ac following mustard. There was no difference in subsequent crop yield at Site 1 and Site 3.

Longer term crop rotation impacts were examined in 2005 at both Site 1 and Site 2 (data not presented). Overall no difference in yield or grain quality was detected in the winter triticale at Site 1. At Site 2 no differences were detected as well in the winter wheat crop despite significant differences in spring grain production the previous year.

The economic performance is presented as gross economic return between the two treatments as the production costs in this study are nearly equal between spring barley and yellow mustard. Averaged over the 3-years yellow mustard had greater value than spring barley but spring cereal following spring barley had greater value (Table 4). Averaged over the three years, yellow mustard followed by a spring cereal had the highest 2-year total return at $186/ac compared to only $175/ac for barley followed by a spring cereal; however these differences varied among years.

At Site 1 no differences in gross economic return were significant between treatments crops, subsequent cereal crops and the two-year total.

Large differences were detected at Site 2 in both the treatment crops and subsequent cereal crop. Yellow mustard had a gross return of $167/ac compared to only $96/ac with spring barley. The subsequent spring wheat crop following spring barley had returned $133/ac compared to $98/ac for spring wheat following mustard. Despite less value in the subsequent crop, yellow mustard followed by spring wheat had the greatest 2-year gross return at $264/ac compared to only $229/ac for spring barley followed by spring wheat.

At Site 3 some differences were detected. Similar to Site 2, yellow mustard produced greater economic returns than spring barley at $64/ac compared to only $50/ac for spring barley. Similar to Site 1, no differences were detected in subsequent cereal averaging $67/ac. Overall yellow mustard followed by spring cereal had the highest 2-year average at $128/ac compared to $118/ac for spring barley followed by spring cereal.

Conclusions:

Yellow mustard has value as alternative crop in an intense cereal grain cropping rotation under direct seeding conditions in the intermediate rainfall cropping region of eastern Washington. Despite lower than average precipitation in each the four years of the study, yellow mustard in rotation produced $11/ac more gross economic return than spring barley included in rotation. However gross economic return is both a function of crop production and market price.

Table 5 is a price matrix that utilizes the crop production data collected over the duration of this project to help determine the most profitable crop between yellow mustard and spring barley at a given market price. This included the value of the treatment crop as well as the value of the subsequent cereal crop. It does not include any potential value in weed control and seeding date.

As an alternative crop, yellow mustard did not appear to reduce economic damage by limiting root and crown diseases in comparison to spring barley as subsequent cereal crop performance appeared to be mostly soil moisture related. Yellow mustard may have more had a more positive impact on subsequent cereals crops if precipitation was average or above average. One of the potential advantages not captured by this study was the low weed populations following yellow mustard in the spring. Having low weed populations reduced the potential for “green bridge”, thus burn down herbicide application and time of seeding interval can be reduced allowing for earlier seeding dates for spring cereal following yellow mustard. Research shows early spring seeding provides yield advantages over delayed seeding under most conditions.

Examples: If barley is selling at $95/ton barley and mustard is $0.12/lb, barley will return an                   estimated $13.26/ac more than mustard. If barley is selling at $95/ton barley and mustard is $0.16/lb, mustard will return an estimated                   $12.64/ac more than barley.

1 Smiley, R., R.J. Cook, T. Paulitz. 2002. Controlling Root and Crown Diseases of Small Grain Cereals. OREM8798.

Recognition:
The authors would like to extend a special thanks to Dan McKay, McKay Seed Company, for support and seed donations throughout the duration of the project.

The authors would also like to extend a special thanks to the Otto and Doris Amen Dryland Research Fund, and USDA/CRSEES funded Columbia

The authors would like to extend a special thanks to Dan McKay, McKay Seed Company, for support and seed donations throughout the duration of the project. The authors would also like to extend a special thanks to the Otto and Doris Amen Dryland Research Fund, and USDA/CRSEES funded Columbia Plateau PM10 Project for their economic support.

Thanks to all cooperators who make these Lincoln-Adams On-Farm Testing Program possible.

For additional information, please contact:

Aaron Esser
Area Agronomist
WSU Extension
210 W. Broadway, Ritzville, WA 99169
Phone: 509 659-3210
E-mail: aarons@wsu.edu