Growers looking to improve their onion yields get the best return on investment costs by sticking to conventional fertilizer inputs. That is the conclusion of a two year study which examined the effects of 11 different “nonconventional” fertilizers or crop stimulants under standard production conditions in Oregon. The nonconventional products tested included various humic acid formulations, seaweed extracts, plant growth regulators and several foliar feed formulations. All nonconventional products were applied according to their label recommendations to onions otherwise supplied with standard inputs of fertilizer and pesticides. None of the nonconventional products improve crop yields or quality – and several were clearly detrimental to the crop. None of the organic fertilizer formulations tested met crop nutrient requirements – yields from the organic regimes were consequently substantially lower than with a standard fertility program. At a cost of $ 10 – 200/acre for basic materials plus the added cost of application – none of the non-conventional products improved the net profitability of onion production in this study. Growers interested in trying these products should carefully examine their effectiveness in small replicated trials before investing in large scale applications.
Source : Feibert, Shock and Saunders (2003). Nonconventional additives leave onion yield and quality unchanged. HortScience 38: 381-386.