After Twelve Years of Dryland Organic Wheat Research, What Have We Learned?.

In 2002, Washington State alone produced 10% of conventional winter wheat grown in the U.S., but accounted for less than 1% of all organic wheat grown nationally. The lack of organic adoption in the state in the face of a rapidly growing organic industry prompted Washington State University researchers to initiate a transition-to-organic study to support profitable dryland organic wheat production. Conservation tillage was used throughout the duration of the study, to minimize soil erosion and maximize the soil health benefits of organic management. Winter pea green manure and an alfalfa-oat forage mix grown during the three-year transition period resulted in the greatest spring wheat yields (3870 to 4290 kg ha^-1) the year following the end of the transition period. Certified organic hard red spring wheat contained ~12% grain protein and did not meet the 14% market standard, indicating that supplemental fertility may be needed to meet grain quality standards. These lessons were applied during a certified organic wheat production study where winter wheat was rotated with alfalfa and winter pea and poultry manure was incorporated into one rotation as a supplemental fertility source. Organic winter wheat yields were greatest (5660 kg ha^-1) when following winter pea and fertilized with poultry manure, and soil inorganic N levels were similar between soils fertilized with poultry manure and conventional fertilizer. Organic hard red spring wheat receiving poultry manure achieved grain protein levels of 11.9 to 14.1%, but contained less protein on average than conventional grain. Competition from perennial weed species was high, but was mitigated by growing perennial forages. Maintaining soil fertility resulted in decreased weed populations, whereas low soil N levels led to poor crop competitiveness with weeds. In organic systems, maintaining adequate soil fertility and N levels is key to limiting weed pressure and producing yields competitive with conventional systems.