Developing Organic Quinoa Cropping Systems for Utah.

Most of the Western United States could face increasing water shortages in the coming years, which will prove to be a major challenge in maintaining sustainable farms. In the Intermountain West, quinoa may be an ideal alternative crop to meet such a challenge. Quinoa grows well in drought conditions and marginal soils and the demand and price for organic grain has risen dramatically in recent years. The objective of this study was to evaluate the efficacy of different organic cropping systems for quinoa. A field trial was established as a random complete block (RCBD) with split plot and four replicates. The whole plot factor was cropping system [three levels: strip crop with hairy vetch + winter wheat mowed and blown into the crop row (SC), undersown clover (UC), and tillage only (T)]. The split plot factor was fertility [compost added (+C) or no compost added (-C)]. Steer manure compost was added prior to the first year of quinoa production at a rate sufficient to supply readily available phosphorous (P) for 2 years (11.2 Mg DM ha^-1). Quinoa did not set seed in 2013 due to high summer temperatures; in 2014, total seed yield was greater in quinoa +C than –C and greater in SC than UC, with T intermediate. Main effect of compost and year were significant for total above ground biomass averaged over both years. Quinoa total biomass was greater in +C than -C treatments and greater in 2014 than 2013. Readily mineralizable carbon, soil respiration and microbial biomass, as measured by substrate induced respiration, were greater in +C than –C and were unaffected by cropping system. Extractable soil nitrate (NO₃^-) was lower in SC+C and higher in T-C than other treatment combinations, demonstrating complex interactions between readily available nitrogen and carbon. Results suggest compost increased quinoa growth and soil microbial activity while cropping system influence was mixed. Quinoa’s apparent sensitivity to high summer temperatures may pose a problem for widespread production in the Intermountain West.