Growing nitrogen in the organic orchard

Two on-farm trials were established in 2008 to test different approaches to growing nitrogen within an orchard. The trial at Warren Morgan Orchard (WMO) compared four perennial legume species (ladino white clover, alfalfa, birdsfoot trefoil, kura clover) direct seeded into the existing alley vegetation with or without suppression. All species were successfully established, with better growth in the suppressed areas. A single mowing was done pre-harvest (late August) but total biomass was low. Ladino clover and alfalfa performed best in this initial season. The legumes will be managed for ‘mow and blow’ in 2009 and their N contribution monitored. The trial at Cloud Mountain Farm (CMF) focused on annual legumes planted into the tilled edges of the tree weed strip. A good planting device was not available and seedling establishment was poor. The tillage led to severe weed infestation and little legume biomass was produced. The trial will not be continued in 2009.

Grant Information

  • Project ID: 046
  • Project Status: Complete




  • Principal Investigator(s): Davenport, J.
  • Investigator(s): Granatstein, D.
  • Grant Amount: $15,874


Mullinx, K. and Granatstein, D. 2011. Potential nitrogen contributions from legumes in Pacific Northwest apple orchards. Intl. J. Fruit Sci. 11:74-87.

Granatstein, D.*, Wiman, M., Kirby, E., Mullinix, K. 2010. Sustainability trade-offs in organic orchard floor management. Acta Hort. 873:115-122.

Samples are still being analyzed for Year 3 and manuscripts will be prepared once all data are analyzed.

Additional Funds Leveraged

None – proposals were not funded.


In 2010, the cooperating grower in one on-farm trial expanded the practice we are testing to an additional 80 acres. I personally viewed the fields. A neighboring farm adopted the practice on 20 ac that I personally viewed. The cooperating grower on the other project applied the practices on over 100 acre of orchard. This grower also qualified for $80,000 in EQIP funds for the practices. In a recent grower survey (n=74), 51% of the growers reported use of legume cover crops to supply nitrogen in their orchards, which is the focus of one of the research projects. NRCS is now cost sharing this practice and a training for NRCS staff is scheduled for May 2011.