PRODUCTIVITY, ECONOMICS, AND SOIL QUALITY OF ORGANIC QUINOA CROPPING SYSTEMS IN THE PACIFIC NORTHWEST, USA

Abstract

Volatile crop prices and desire for sustainability have farmers considering alternative practices to increase revenue diversity and protect soil health. Organic management is a rapidly expanding alternative to conventional agriculture, and quinoa is a potential new crop for organic systems in the Pacific Northwest. To improve the competitiveness and adoption by growers of organic quinoa and grain cropping systems, more detailed information is needed regarding the agronomic impacts, economic performance, and effects on soil quality of such systems. A 5-year study was conducted to evaluate these metrics in eight 3-year crop sequences in the Palouse region of Washington State. The 3-year sequences compared quinoa to spring wheat, each in rotation with barley and chickpea, and were part of a longer 8-year rotation with alfalfa. While crop sequence affected yields and crop quality, larger differences were caused by weather across years. Cumulative yields were higher when sequences started with chickpea compared to barley, which also led to higher economic returns. Organic quinoa yields were lower than the yield potential for the region, but some sequences with quinoa had similar economic returns to sequences with wheat. The organic cropping systems (total 8-year crop rotations including 5 years of alfalfa) were more profitable than a typical conventional rotation with county average yields during the same 8-year period. Soil nitrogen (N) decreased with time through the 3-year sequences, but there was sufficient N to support high grain yields in the last year of the sequence when weather conditions allowed. Colonization by arbuscular mycorrhizal fungi (AMF) was lowest in quinoa, and AMF colonization of crops following quinoa was lower than when they followed wheat. However, the moderate rates of AMF colonization observed in quinoa are noteworthy as quinoa is generally thought to be non-mycorrhizal. The results show that dryland organic grain systems supported by multiple years of alfalfa can be financially and agronomically viable in the Palouse region due to economic premiums and N cycling through crop residues. Advances in organic weed control and regionally suited quinoa varieties would further reduce the risk for farmers attempting this cropping system diversification.