Mineral nutrient deficiencies in quinoa grown in hydroponics with single nutrient salt/acid/chelate sources

Major crop nutrient symptoms are well documented. In contrast, there is often minimal or no similar information for minor crops, including quinoa (Chenopodium quinoa Willd.). This knowledge gap can be efficiently filled by using hydroponic systems. However, creating multiple nutrient deficiencies with plants in the same study is challenging because nutrients are often added as dual nutrient salts. For example, if potassium sulfate is the potassium (K) source, varying K concentration also impacts sulfur (S) concentration, possibly creating dual deficiencies or other interactions. A new hydroponic system was created to impose nutrient deficiencies using single nutrient sources: ammonium nitrate; phosphoric, sulfuric, hydrochloric, and boric acids; potassium, calcium, magnesium, zinc, and copper carbonates; manganese acetate; sodium molybdate; iron EDDHA, with HEDTA as an additional chelate. Fourteen treatments were established including a positive control with nutrient concentrations anticipated to be optimal compared with individual deficiencies of nitrogen (N), phosphorous (P), K, S, calcium (Ca), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), copper (Cu), boron (B), molybdenum (Mo), and chloride (Cl). The deficient treatments were created by reducing concentrations by 80% for N and 90% for the others. The solution proved to be mostly effective as quinoa plants were grown to maturity. Stem size, plant height, and shoot and root biomass were impacted, especially for treatments with reduced N, P, and K. Unfortunately, the predicted adequate levels of some nutrients were likely excessive, especially B and Mn. Additional fine tuning is required to create a solution optimal in all nutrients.