b'All biostimulants come with a cost.This increase in cost has to be covered by either an increasein yield or a decrease in inputs, usually N. CARL ROSENIn 2019, Carl Rosen, professor and head of the Department of Soil, Water,Based on our research, there may be a slight yield increase some years, but and Climate at the University of Minnesota, along with colleagues there andthere are no silver bullets, he says. All biostimulants come with a cost. This at the United States Department of Agriculture-Agricultural Research Service,increase in cost has to be covered by either an increase in yield or a decrease in published a study on biostimulants in potatoes. They found potatoes con- inputs, usually N. Based on the literature, you will not find many field-scale stud-taining an amino acid blend (AAB) with and without nitrogen-fixing microbesies published, and those that are published usually report inconsistent results. (NFM) produced modest improvements in tuber yield, under limited conditions,The most positive results with biostimulants are usually based on greenhouse compared to urea alone.experiments, but these results do not often translate to the field. Effects on yield were generally positive but inconsistent, says Rosen.Rosen and his colleagues stress that field trials with biostimulants should For example, in the first year, yield increased with NFM and AAB at thenot only assess yield but also show how the nutrients in the environment low N rate but there was no effect at the high N rate. In the second year,fare, particularly nitrogen. He believes biostimulants research should involve biostimulants had no effect on yield at the low N rate but increased yield overfertilizer rates, especially for nitrogen and phosphate, which are lower than urea alone at the high N rate. We suggest that more field research is neededrecommended to determine if biostimulants can reduce fertilizer inputs, to identify conditions (soil, climate, fertilizer, cropping system etc.) whereincrease fertilizer use efficiency and reduce nutrient losses.biostimulant applications may be beneficial.Blaylock thinks growers need to be cautious with biostimulants until more research is done. He suggests on-farm experiments are a good way for growers LOOKING FORWARD to test a product as the trials will involve each growers chosen varieties and There are numerous biostimulants now on the market but Rosen says itsgrowing conditions. He also advises the most informative and reliable trials difficult to evaluate the effectiveness of all the products available. Studies ofuse paired strips with and without the product of interest replicated in differ-them need to be based on replicated field studies over multiple years.ent areas of a field, rather than comparing one field with another. 34 SPUDSMART.COM FALL 2020'