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Foliar Fertilizers and Sugars in Soybeans

In the absence of plant nutritional deficiency symptoms, foliar fertilizers did not increase yield. While the application of sugar-based products helped to alleviate crop injury symptoms caused by Cobra herbicide, it did not increase yield.

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Updated:

December 15, 2025

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Photo was taken standing between 30-inch no-till planted soybeans around the V3 growth stage.

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Principal Investigator and Co-Investigator

Daniela Carrijo, Ph.D., Penn State Grain Crop Production Extension Specialist
Assistant Professor; Paul Esker, Ph.D., Penn State Field Crop Pathologist and Professor

Background

Farmers are increasingly exposed to new products broadly classified as biostimulants. In the US, there are currently over 350 companies offering products in this category, including foliar fertilizers, biologicals, organic acids, and others. Locally, there has been an increased interest in applying sugar-based products to crop foliage as a rapid means to alleviate crop stress. Unlike pesticides, there is no national standard for registering biostimulants, and research on product efficacy is often lacking.

Objective

We aimed to evaluate the efficacy of several biostimulant products applied to soybean foliage.

Methods

Products were selected from a statewide survey conducted in 2024 and included foliar fertilizers, applied alone or tank-mixed with a fungicide, and sugar-based products, which were tank-mixed with Cobra herbicide, known to cause crop injury symptoms in soybeans (Table 1). The study was conducted at the Penn State Southeast Agricultural Research and Extension Center in Manheim, Pennsylvania, during the summers of 2024 and 2025.

Table 1. List of Treatments Evaluated
Treatment	Product	Rate	Product description	Spray timing**
T1	Untreated control	-	-	-
T2	Priaxor	4 fl. oz/A	Fungicide (fluxapyroxad + pyraclostrobin)	R3
T3	Fertileader Gold	3 pt/A	Fertilizer (B, Mo)	R3
T4	ENC Flex	3 qt/A	Fertilizer (N, P, K, B, Co, Cu, Fe, Mn, Mo, Zn)	R3
T5	Power Ag Alpha Power	2 qt/A	Fertilizer (N, P, K, B, Cu, Fe, Mg, Mo, Zn, organic compounds)	R3
T6	Priaxor + Fertileader Gold	See above	See above	R3
T7	Priaxor + ENC Flex	See above	See above	R3
T8	Priaxor + Alpha Power	See above	See above	R3
T9*	Cobra	10 fl. oz/A	Herbicide (lactofen)	R1
T10*	Cobra + Dextrose	4 lb/A	Herbicide (lactofen) + pure sugar	R1
T11*	Cobra + Molasses	2 gal/A	Herbicide (lactofen) + organic solution high in sugar	R1

*Non-ionic surfactant was added as adjuvant.
**R1 occurred on 6/28/2024 and 6/27/2025, and R3 occurred on 7/25/2024 and 7/15/2025.

Results

Across study years, none of the treatments evaluated increased soybean yield compared to the untreated control (Figure 1). However, soybeans sprayed with the Fertileader Gold + Priaxor mixture (T6) yielded 10% higher than those sprayed with Fertileader Gold alone (T3), indicating a potential synergy between the two products. Priaxor is a strobilurin-based fungicide marketed for plant health even in the absence of disease, which was minimal in this study, as evidenced by the fact that soybeans sprayed with Priaxor only (T2) yielded comparably to the untreated control (T1). Fertileader Gold is a foliar fertilizer that, compared to the other fertilizers and in the rates used in this study, delivered a relatively high amount of boron (approximately 2.7 compared to 0.1 fluid ounces per acre). Therefore, the synergy between these two products may have been driven by the high boron content in Fertileader Gold.

Based on visual scoring data, the application of Cobra herbicide resulted in crop injury symptoms observed around seven days after application. Crop injury was more pronounced in 2025 than in 2024, likely because the 2025 application coincided with relatively high temperatures (85°F) during and in the days following application. Tank-mixing Cobra with either dextrose or molasses helped alleviate crop injury symptoms in 2024 but not in 2025. Still, in both years, crop injury symptoms appeared to be cosmetic and did not affect yield (Figure 1).

A bar chart shows soybean yield in bushels per acre on the vertical axis, with treatments 1 through 11 shown across the horizontal axis. Minimal yield differences are seen across treatments, and none of the treatments significantly increased yield over the control. — Figure 1. Treatment average yields (2024–2025). Error bars are the standard error of the means. Different letters indicate significant differences between treatments based on Analysis of Variance (p<0.05).

Conclusion

None of the foliar fertilizers evaluated in this study, applied alone or in combination with a fungicide, increased soybean yield. Therefore, the use of these products in the absence of visual symptoms of plant nutritional deficiency is not recommended. Similarly, the use of sugar-based products to alleviate herbicide-induced crop injury symptoms, as practiced in this study, did not affect soybean yield and is thus not recommended.

Acknowledgements

Funding provided by the Pennsylvania Soybean Board (Pennsylvania Soybean On-Farm Network). Thanks to SEAREC staff, Tyler McFeaters, Ethan Whitmoyer, Levi Showalter, and others who supported this work.