Robert S. Gallagher

Resistance of a Prickly Lettuce (Lactuca serriola) Biotype to 2,4-D

Abstract Dose-response experiments were conducted on a biotype of prickly lettuce collected from Whitman County, WA, to determine the level of resistance to 2,4-D. Initially, progeny of prickly lettuce that survived two applications of glyphosate and 2,4-D in mixture were collected to determine if antagonism of the 2,4-D or glyphosate was occurring. Prickly lettuce survival was determined to not be due to antagonism of 2,4-D or glyphosate when the two herbicides were applied in mixture. The doses required to reduce growth 50% (GR50) for resistant and susceptible field-collected prickly lettuce were 150 and 6 g ae/ha 2,4-D, respectively, indicating the resistant biotype was 25 times more resistant to 2,4-D than the susceptible biotype. The resistant biotype expressed injury but produced regrowth following application. A dose of 2,4-D at 220 g/ha was required to reduce regrowth frequency 50% (FR50) for resistant field-collected prickly lettuce. Regrowth was also observed with the susceptible biotype, although the FR50 was much lower (10 g/ha), resulting in an R/S ratio of 22 based on the respective FR50 values. A rate of 4,300 g/ha 2,4-D (10 times the maximum labeled rate in wheat) was required to reduce the regrowth frequency in the resistant biotype to zero. Nomenclature: 2,4-D; glyphosate; prickly lettuce, Lactuca serriola L. LACSE; wheat, Triticum aestivum L.

Alternative Strategies for Transitioning to Organic Production in Direct-Seeded Grain Systems in Eastern Washington I: Crop Agronomy

Organic grain production is not common to eastern Washington, but offers attractive market opportunities if systems can be developed that are compatible with regional production constraints. Erodible soils make tillage-intensive systems unsustainable, and there are limited alternative fertility options. Given these constraints, the objective of this study was to evaluate nine cropping systems during the transition to organic grain production under reduced tillage and relying on legumes as the primary source of crop nitrogen. The experimental transition systems ranged in the degree in which legume grain crops or legume green manures/forages were present in the rotation. We found that spring pea grown for grain to be a poor choice for organic production due to the susceptibility of this crop to insect pests and weeds, which generally resulted in crop failure. Likewise, bell bean was poorly suited as a legume green manure crop due to its low productivity in our region. In contrast, alfalfa and winter pea-based systems achieved the best legume biomass production, weed suppression, and crop yields in the subsequent crops. Winter wheat substantially out-yielded spring wheat, but the yields of both of these crops were well below the yield potential typically achieved under conventional production. Competition from annual weeds, such as wild oat and prickly lettuce, and the perennial weed field bindweed was difficult to manage under the reduced tillage regimes employed in this study.

Conservation agriculture on steep slopes in the Andes: Promise and obstacles

Small-scale farming in Ecuadors highlands is associated with excessive soil erosion, degradation of soil health, and agricultural productivity loss. Conservation agriculture (CA) offers promise in these areas. Minimum disruption of soil and maintenance of permanent groundcover, two CA pillars, reduce erosion and can increase soil health and productivity. Despite its promise, CA has not been widely adopted by Andean region farmers, and factors such as uncertainty about CA benefits, risk aversion, and high discount rates have been offered as explanations for lagging adoption. This paper combines an analysis of CA trial data from farmer fields and an analysis of two farm-household surveys to measure potential benefits from adoption and identify correlates of adoption. The analysis reveals actions to promote more widespread adoption of CA. Data are from a unique five-year research project in Bolivar Province, Ecuador. Yield and cost of production data from on-farm trials are used to estimate costs and benefits of CA, household data are used to analyze the determinants of CA adoption, and data from a choice experiment help estimate willingness to pay for CA attributes, such as increased yield and reduced erosion. We find that CA practices yield more and cost slightly less (over five years) than conventional practices, but differences are not large. The adoption analysis shows that farm size and labor access are not associated with adoption, but farmers who perceive soil loss on their farm to be severe are much more likely to adopt. This aversion to soil loss is examined in the choice experiment, which finds that farmers are most interested in economic considerations, such as increasing yields and saving increasingly costly labor. CA holds promise in such systems, but diffusion efforts must be carefully tailored to address farmer needs.

Alternative Strategies for Transitioning to Organic Production in Direct-Seeded Grain Systems in Eastern Washington II: Nitrogen Fertility

The nitrogen (N) dynamics of nine rotation systems designed to transition dryland cereal to organic production in eastern Washington State were examined. Systems combined cereal and legumes for grain, forage (FOR), and green manure (GRM). Few differences in N balances and soil inorganic N levels were found among transition systems when poor spring crop establishment resulted in competition from weeds. However, FOR and winter GRM crops produced adequate stands that were competitive with weeds and increased residual soil inorganic N in the final year of the transition. Winter legumes and continuous FOR systems demonstrated the greatest potential to provide a sustainable inorganic N source to subsequent organic cereal crops.