This article was written by Jorge Luis Alonso G., an information consultant specializing
in the potato crop.
Researchers at Washington State University completed a research study to assess 27 non-traditional crop treatments with 32 products to determine their effects on potato growth. The researchers involved in the study are Colton R. Thurgood, Francisco Gonzalez-Tapia, Zachary J. Holden, and Mark J. Pavek. Their study was published as a scientific paper in the Agronomy Journal in 2022, titled “Nontraditional production additives fail to improve potato yield and economic return“.
We summarize the findings of the study in this article.
Unproven, non-traditional crop inputs are widely used and promoted despite a lack of impartial research. Many peer-reviewed articles have found that these non-traditional crop production inputs do not provide an adequate return for the grower. In addition, conducting research on non-traditional crop inputs is often costly and requires significant land and resources, which may contribute to the limited research in this area.
For this study, field trials were conducted near Othello, Washington, from 2016 to 2019, evaluating 27 non-traditional additive treatments with 32 products to determine their effects on potato (Solanum tuberosum L.) growth. Treatments were applied using a variety of methods, including in-furrow and surface bands, foliar sprays, and chemigation/fertilization, in addition to standard practices. Conventional nutrients were applied to promote optimal potato growth. Economic returns were calculated using a mock processing contract, with product costs ranging from $15 to $889 per hectare.
Non-traditional additives are categorized into seven groups, but for simplicity, this study focuses on characterizing five of these categories to test non-traditional additives: microbial inoculants, biostimulants, humic acids, specialty fertilizers and fertilizer additives, and surfactants.
Research on microbial inoculants shows mixed results. Field trials in Maine showed a reduction in stem canker and black scurf and increased soil microbial activity with an arbuscular mycorrhizal (AM) inoculant, but there was no significant effect on potato yield. In the Andean trials, AM inoculation provided no benefit, and in one trial yield was actually reduced, possibly due to high fertilizer levels. High soil phosphorus levels negatively affected AM colonization in onions. Bacterial inoculation research showed improved tuber yields; however, in some cases, crop rotation had a greater effect on yield than treatment. Results from potato plots inoculated with bacterial strains require further verification due to variability, and it is critical to consider economic returns adjusted for costs when evaluating feasibility for growers.
Research on biostimulants, particularly seaweed extracts, is also inconsistent. Some studies indicate improved plant growth, root development, and potato yield, while others suggest that benefits may depend on the growing season. Variety and environmental interactions, as well as physiological differences among potato varieties, may influence responses to biostimulant applications. Comparative economic analyses of treatments are generally lacking. For other crop biostimulants such as Megafol and Employ, there are conflicting results, with some studies showing positive effects and others showing no significant differences. In the absence of adjusted gross income data, the impact of these biostimulants on economic outcomes remains uncertain.
Humic acid has been evaluated both as a standalone crop amendment and in combination with fertilizer mixtures. In one trial in Idaho, increased humic acid rates significantly increased potato yield, while no yield response was observed at other locations. Large-scale trials showed that humic acid treatments resulted in reduced nitrogen, phosphorus, and water requirements, although yield increases were not statistically significant. In fertilizer mixtures, humic acid had no effect on yield but increased nutrient levels in some cases. Soil physical properties may influence the yield response to humic substances, with increased uptake and yield observed in sandy-textured soils but not in clayey-textured soils. The effect on economic returns has not yet been reported.
Specialty fertilizers and fertilizer additives
Research on enhanced specialty fertilizers is mixed. Some studies indicate improved potato yield parameters when P fertilizers are combined with AVAIL (maleic-itaconic copolymer), while others show no response. Alternative N fertilizers, when used on corn and wheat, have not consistently increased grain yields compared to standard urea ammonium nitrate. Response to specialty fertilizers likely depends on the soil’s physical and chemical conditions. Potato yield response to AVAIL is more likely in alkaline, calcareous soils with low soil test P; however, in some studies, AVAIL failed to improve yield or economic return under similar soil conditions.
Surfactants in agriculture aid in water infiltration and product distribution, but laboratory research has not found significant differences in water infiltration or holding capacity. One study found no significant change in potato yield from a wetting agent, and its economic return was not reported.
The majority of studies on non-traditional products did not report economic impacts or included treatments alongside standard practices.
● Although the 32 non-traditional products in this study claimed to improve plant characteristics and increase growth, none significantly affected economic returns or yields. One-up, NutriCal, and Reclaim showed small benefits in certain areas, but these factors did not have a significant impact on overall yields or economic returns. Some products showed trends of higher or lower yields compared to the control group, but additional field trials are needed to determine significant differences.
● To understand why One-up, Reclaim, NutriCal, Trafix ES Cal Eight, and KelpXpress showed significant differences from the control, an extensive literature review and additional research is needed. OneUp may have produced favorable results due to its low salt index, low treatment cost, and inclusion of humic acid. The reason for the increase in specific gravity with NutriCal remains unclear, but further research is needed to determine the factors that influence its effect on tuber solids content and decay.
● KelpXpress, which contains kelp extract, requires further investigation to understand why it led to an increase in tuber rot. Reclaim, which contains chelated copper and other ingredients, may have reduced tuber rot due to copper’s ability to suppress bacterial and fungal diseases. Further research is needed to verify this hypothesis.
● Although the non-traditional additives affected specific aspects of the plants, none had a significant effect on potato yield or economic return. This result may be due to the fact that standard grower inputs adequately meet crop needs or the lack of efficacy of the additives in potato production. In addition, the high yields in Washington’s Columbia Basin may make it difficult for these additives to enhance already optimal plant nutrition and irrigation.
● Growers who have experienced positive results with these additives may attribute their success to the product; however, it is important to consider other factors such as ideal growing and weather conditions. A comparison of additive inputs with standard inputs could provide greater insight into the observed lack of plant response associated with certain products.
● While manufacturers claim that their additives are compatible with pesticides and fertilizers, there is no evidence that these additives do not interfere with the active ingredients in pesticides. As a result, “free use” could ultimately result in crop damage and yield loss for the grower.
● Ongoing research is essential to inform growers’ decisions about non-traditional additives. However, the sheer scope of this task is challenging. Researching these 32 products over four years took considerable time, money, and effort. Under the right circumstances, non-traditional additives could reduce the need for traditional fertilizers or irrigation water, but their effectiveness warrants further investigation.
● Before using untested non-traditional additives, growers should conduct replicated trials on smaller sections of the farm or request product-specific information from university extension personnel to avoid the significant expense associated with full-scale application.
In summary, the 27 non-traditional additive treatments, which included 32 products, did not provide significant economic advantages over standard grower practices for potato production near Othello, WA. As a result, there is no compelling argument for potato growers to include these non-traditional additives in their crop management plans.
Source: Thurgood, C. R., Gonzalez-Tapia, F., Holden, Z. J., & Pavek, M. J. (2023). Nontraditional production additives fail to improve potato yield and economic return. Agronomy Journal, 115, 801– 816.
Photo: Credit Myriams-Fotos from Pixabay