Intercropping, Precision Weed Management, and Pea Breeding for Organic and Conventional Cropping Systems

Research conducted in the 2009-10 and 2010-11 growing seasons had three main components: a winter wheat-winter pea intercropping study, developing an inter-row cultivator with precision guidance for in-season weed management, and a new pea breeding project. (1) Intercropping: The potential use of winter peas as a nitrogen (N) resource for winter wheat was evaluated in a two-year study, 2009-10 and 2010-11. Peas were intercropped with wheat and removed at different times to determine the optimal time of removal. This was a weed-free study, led by Kristy Ott-Borrelli, a doctoral student. The winter pea intercrop did not compete with winter wheat for soil moisture or inorganic N either year and wheat yield, test weight and protein levels were unaffected by any intercrop treatments. Pea biomass yield and total N as well as grain yields decreased with the inclusion of a wheat intercrop. Soil inorganic N and moisture were often greater when peas were grown alone or when wheat intercrops removed at an early growth stage. Greater than average spring precipitation likely resulted in low competition for soil moisture and N both seasons. However, results indicate that wheat may out-compete peas for soil resources. (2) Precision Inter-Row Sweep: The inter-row sweep with precision guidance was tested in 2010. A number of problems arose and modifications were made including adding coulters to cut through residue and modifying the guidance method. The final test in 2010 was successful and it was used as a management tool in Ott-Borrelli’s study in 2011. (3) Pea Breeding: A significant new pea breeding effort by Dr. McGee was initiated to (i) develop a spring pea for organic and low-input systems, and (ii) develop a multi-purpose winter pea for green manure N, forage, and feed and food value when taken to maturity. Thirty spring varieties were evaluated in a replicated trial 2010. Crosses were made to transfer the superior disease resistance of several spring lines into winter elite breeding lines that have long vines and normal leaves. We have also obtained winter germplasm from Europe that has improved levels of winter-hardiness that we are incorporating into our elite winter material. An autumn-sown trial was planted at the Boyd Farm in October, 2010; winter survival was excellent but seed weevil infestation in 2011 rendered seed quality unacceptable.

Grant Information

  • Project ID: 093
  • Project Status: Complete


  • Principal Investigator(s): Fuerst, P.
  • Investigator(s): Burke, I., Koenig, R., McGee, R.
  • Student(s): Ott-Borrelli, K.
  • Grant Amount: $40,000
  • 2010 Progress Report (PDF)


  • Principal Investigator(s): Fuerst, P.
  • Investigator(s): Burke, I., Koenig, R., McGee, R.
  • Student(s): Ott-Borrelli, K.
  • 2011 Progress Report (PDF)


Borrelli, K.A., R.T. Koenig, I.C. Burke, E.P. Fuerst and R. Gallagher. 2011. Nitrogen dynamics in nine rotation systems from transition to certification of organic dryland grain production. [Online]. Available at 13 December 2011).

Borrelli, K.A., I.C. Burke and R.T. Koenig 2011. Timing the removal of a legume intercrop to optimize soil nitrogen and moisture in an organic dryland wheat system. [Online]. Available at (Accessed 13 December 2011).

Borrelli, K.A., I.C. Burke, R.T. Koenig, D.R. Huggins and S.H. Hulbert. 2011. Timing the removal of winter peas intercropped with winter wheat to optimize available soil nitrogen and moisture in a dryland small grain system. [Online]. Available at (Accessed 13 December 2011).

Borrelli, K.A., R.T. Koenig, I.C. Burke, R. Gallagher and E.P. Fuerst. 2010. Crop and soil nitrogen dynamics of nine rotation systems during the transition and certified organic phases of dryland grain production. [Online]. Available at (Accessed 13 December 2011).

E. Fuerst, I.C. Burke, D. Huggins, R. Gallagher, K. Borrelli, D. Pittmann and R. Koenig. 2010. Dryland organic weed management strategies in Eastern Washington. [Online]. Available at (Accessed 13 December 2011).

Borrelli, K.A., R.T. Koenig, R.S. Gallagher, D. Pittmann, A. Snyder, I. Burke, L. Hoagland, and E.P. Fuerst. (in press). Alternative strategies for transitioning to organic production in direct-seeded grain systems in eastern Washington II: Nitrogen fertility. J. Sust. Ag.

Burke, I.C., R.T. Koenig, K. Painter, K.A. Borrelli, M. Manuchehri and S. Machado.  2011. Nuts and bolts of organic dryland farming. Oral presentations by each author listed at Washington State University’s Dryland Organic Agriculture Symposium, Yakima, WA. November 11, 2011.

Gallagher, R.S, D. Pittmann, A. M. Snyder, R.T. Koenig, E. P. Fuerst, I.C. Burke and L. Hoagland. 2010. Alternative Strategies for Transitioning to Organic Production in Direct-Seeded Grain Systems in Eastern Washington I: Crop Agronomy. J. Sustainable Agric. 34:483-503.

E. P. Fuerst, I.C. Burke, D. Pittmann, R.T. Koenig, D. Huggins, D. Collins, C. Cogger, A. Corbin, and C. Benedict. 2010. Organic Conservation Tillage Practices – Innovations and Implications for Grain, Vegetable, and Conventional Farming Systems. Poster at Pacific Northwest Direct Seed Association Annual Meeting, January 20-21, 2010.

Additional Funds Leveraged

In the future, Dr. Burke plans to include this implement and precision weed management strategies as central themes for a NIFA-OREI proposal.


Following the presentation on the inter-row cultivator at the Boyd farm field day, Eric Nelson, an organic farmer from Pendleton OR, purchased a cultivator with the same guidance equipment and has implemented it on his farm; he presented information and video on his experience at the Dryland Organic Conference in November. In the future, we expect this research to lead to significant increases in utilizing legumes in rotations and using precision weed management for organic and resistant weed management; this will lead to decreases in chemical fertilizer and herbicide use. These practices will also increase soil conservation by reducing the use of inversion tillage currently used for weed control in organic systems. The pea breeding will have long-term impacts on winter peas as a nitrogen and protein resource in organic and conventional crop and livestock operations.