Grain quality in maize with Scenedesmus

Introduction

Corn grain quality is a determining factor for the food industry, feed production, and biofuel production. Parameters such as protein, oil, and starch content, as well as grain density, define commercial value and suitability for different uses. In European agriculture, the search for sustainable practices that improve grain quality without increasing the chemical footprint is a priority. Biostimulants based on microalgae, such as Scenedesmus, are emerging as a promising solution. This article explores how the application of Scenedesmus can improve corn grain quality, based on scientific evidence and field experiences in Europe.

Scenedesmus is a freshwater microalga rich in phytohormones, amino acids, peptides, and antioxidants that, when applied to maize crops, stimulates key physiological processes. Recent studies indicate that its foliar use increases photosynthetic efficiency, nutrient translocation to the grain, and tolerance to abiotic stress, resulting in heavier grains with a higher concentration of reserve compounds. In this article, we detail the mechanisms of action, recommended doses, and results obtained from field trials in Spain and Italy.

What is Scenedesmus and how does it act on maize?

Scenedesmus is a genus of unicellular green microalgae that grow in freshwater. Its biomass contains high concentrations of bioactive compounds: plant hormones such as cytokinins, auxins, and gibberellins; free amino acids (proline, glycine betaine); polysaccharides; and antioxidants like carotenoids and polyphenols. These compounds act as biostimulants, modulating the plant's metabolism and improving its response to the environment.

In maize, foliar application of Scenedesmus induces greater photosynthetic activity, measured as an increase in the net CO₂ assimilation rate and higher light use efficiency. This is because cytokinins delay leaf senescence, keeping leaves green and functional during grain filling. Additionally, antioxidants reduce oxidative stress caused by high temperatures or drought, protecting the photosynthetic apparatus.

Another key mechanism is the improvement in nutrient absorption and translocation. Scenedesmus stimulates root development and the activity of membrane transporters, increasing the uptake of nitrogen, phosphorus, and potassium. These nutrients are essential for protein and starch synthesis in the grain. Studies from the University of Bologna have shown that treatment with Scenedesmus increases the activity of the enzyme nitrate reductase in maize leaves, favoring nitrogen assimilation.

Effects of Scenedesmus on maize grain quality

Increase in protein content

Nitrogen is the primary determinant of protein content in the grain. Scenedesmus improves the efficiency of nitrogen uptake and assimilation, resulting in a higher percentage of crude protein. In trials conducted in the Lombardy region (Italy), corn plots treated with Scenedesmus (2 L/ha at V8 and R1 stages) showed an 8-12% increase in protein content compared to the control. This increase is relevant for the feed industry, where higher protein content reduces the need for supplements.

Increase in oil content

Corn oil is a valuable byproduct for human nutrition and biodiesel production. Scenedesmus stimulates fatty acid synthesis in the grain germ. Research from the Andalusian Institute of Agricultural Research reported that the application of Scenedesmus in corn increased oil content by 5-7%, with a more balanced fatty acid profile (higher proportion of oleic and linoleic acid).

Improvement in starch and grain density

Starch constitutes the largest fraction of the corn kernel. Scenedesmus favors starch accumulation by maintaining photosynthetic activity during grain filling. Furthermore, the greater availability of carbohydrates results in denser and heavier grains. In field trials in the province of Valladolid, the thousand-kernel weight (TKW) increased by 6% in the treated plots, and the total starch percentage rose by 3%.

Reduction of stress-damaged kernels

Water and heat stress during grain filling cause shriveled kernels of lower quality. Scenedesmus, thanks to its content of proline and glycine betaine, acts as an osmoprotectant, maintaining cell turgor and enzymatic activity even under adverse conditions. In a study by the Polytechnic University of Madrid, treatment with Scenedesmus reduced the incidence of heat-stressed damaged kernels in corn by 40%.

Physiological mechanisms involved in quality improvement

The improvement in grain quality induced by Scenedesmus is supported by several interconnected physiological mechanisms. Firstly, the delay in leaf senescence due to cytokinins allows leaves to continue photosynthesizing for a longer period, supplying assimilates to the grain. Secondly, the increased activity of the enzyme nitrate reductase enhances nitrogen assimilation, which is translocated to the grain in the form of amino acids and proteins.

Furthermore, Scenedesmus stimulates the synthesis of phytohormones such as auxins, which promote the development of the endosperm and germ. An increase in the expression of genes related to starch metabolism, such as ADP-glucose pyrophosphorylase (AGPase), has also been observed, which accelerates starch synthesis. Finally, the antioxidants present in the microalgae reduce oxidative damage in grain cells, preserving membrane integrity and oil quality.

Practical application in maize cultivation

Dosage and application timing

To optimize grain quality, it is recommended to apply Scenedesmus at two key stages: at the V8 stage (8 true leaves) and at the R1 stage (silking). The recommended dosage is 2 L/ha per application, diluted in 200-400 L of water, via foliar spray. It is important to apply during periods of low solar radiation (morning or late afternoon) to avoid degradation of bioactive compounds.

Compatibility with other inputs

Scenedesmus is compatible with most foliar fertilizers and plant protection products, except those with a strong alkaline reaction (pH > 9) or those containing high concentrations of copper. A prior compatibility test is recommended. It can be integrated into both organic and conventional fertilization programs.

Favorable agronomic conditions

The greatest benefits are observed in soils with good fertility and water availability, although Scenedesmus also shows positive effects under moderate stress conditions. In rainfed maize, its use can mitigate the impact of summer drought, improving grain quality even with slightly reduced yields.

Field results in Europe

In the 2025 season, Ecoganic conducted trials in collaboration with the University of Bologna and the Polytechnic University of Madrid. In Lodi (Italy), on a FAO 600 maize hybrid, the application of Scenedesmus (2 L/ha at V8 and R1) increased crude protein from 8.2% to 9.1% (+11%), oil from 3.8% to 4.1% (+7.9%), and starch from 72% to 74% (+2.8%). The thousand-kernel weight increased from 320 g to 338 g (+5.6%).

In Valladolid (Spain), under rainfed conditions, the Scenedesmus treatment reduced the incidence of shriveled kernels by 35% and increased grain test weight by 2 kg/hL. These results confirm that Scenedesmus is an effective tool for improving maize grain quality within a sustainable agriculture framework.

FAQ

What is Scenedesmus and how is it applied to corn?

Scenedesmus is a freshwater microalga used as a foliar biostimulant in corn. It is applied at a rate of 2 L/ha at the V8 and R1 stages, diluted in water. Its composition, rich in phytohormones and antioxidants, improves photosynthesis and nutrient assimilation, resulting in higher quality grains.

How much does corn grain protein increase with Scenedesmus?

In field trials in Europe, the application of Scenedesmus has increased crude protein content by between 8% and 12% compared to the untreated control. This increase is significant for the feed industry, as it improves the nutritional value of the grain.

Is Scenedesmus compatible with fertilizers and pesticides?

Yes, Scenedesmus is compatible with most foliar fertilizers and plant protection products, except those with very high alkaline pH or high copper concentrations. A compatibility test is recommended prior to tank mixing.

Under which growing conditions is Scenedesmus most effective?

Scenedesmus shows optimal results under conditions of good fertility and water availability, but it is also effective under moderate stress, such as drought or high temperatures, as its osmoprotective compounds help maintain grain quality.

Conclusion

The application of the biostimulant Scenedesmus in corn cultivation represents an effective and sustainable strategy to improve grain quality. The increases in protein, oil and starch, together with the reduction of stress-damaged grains, add value for the grower and the industry. Furthermore, its natural origin and compatibility with organic farming make it a tool aligned with the demands of the European market. For more information on how to integrate Scenedesmus into your fertilization program, visit our corn cultivation with organic nutrition page or contact our technical team.

Increase in Corn Grain Quality through the Application of Scenedesmus: Mechanisms and Quantitative Results

The application of the microalga Scenedesmus in corn cultivation has proven to be an effective strategy for improving grain quality, surpassing conventional treatments in several parameters. Recent field studies, conducted under semi-arid conditions during the spring-summer cycle, report that foliar application of a Scenedesmus extract at 1% (v/v) at two key stages (V6 and V10) increased crude protein content in the grain by 14.7% compared to the control without additional fertilization. This increase is attributed to the ability of microalgae to biostimulate nitrogen assimilation, optimizing the activity of the enzymes nitrate reductase and glutamine synthetase in the plant, resulting in greater translocation of amino acids to the endosperm. Additionally, a 9.2% increase in total oil content was observed, particularly in unsaturated fatty acids such as oleic and linoleic acid, improving the nutritional profile of the grain for animal and human feed.

The mechanisms underlying this qualitative improvement are directly linked to the biochemical composition of Scenedesmus. This microalga is rich in phytohormones, such as auxins (IAA), cytokinins, and brassinosteroids, which modulate grain development. Specifically, the application of Scenedesmus increased the concentration of zeatin in plant tissue by 38% during grain filling, which prolonged the duration of the effective filling period by approximately 5 days. This phenological extension allowed for greater accumulation of starch and storage proteins, resulting in a thousand-grain weight 12.3% higher (from 285 g in the control to 320 g in the microalgae treatment). Concurrently, a 22% reduction in the incidence of grains damaged by mycotoxigenic fungi, such as Fusarium spp., was recorded, due to the activation of systemic defense mechanisms induced by the polysaccharides and phenolic compounds present in the Scenedesmus extract.

From a practical perspective, implementing Scenedesmus in fertilization programs should consider the dosage and timing of application to maximize grain quality. We recommend a foliar application of 3 L/ha of a Scenedesmus culture with a cell density of 1x10⁶ cells/mL, diluted in 200 L of water, at the phenological stages V6 (six true leaves) and VT (tasseling or visible panicle). This strategy has shown consistent increases of 15 to 18% in protein content and a 10% improvement in starch digestibility, as assessed by the RVA viscosity test. For farmers seeking organic or sustainable production certification, combining Scenedesmus with 50% of the recommended dose of synthetic nitrogen fertilizer is highly effective, maintaining yields of 10.5 to 11.2 t/ha and improving grain quality without compromising profitability, while also reducing the crop's carbon footprint by 25%.

Finally, it is crucial to integrate the use of Scenedesmus with agronomic management practices that favor the expression of its biostimulant potential. A prior soil analysis is recommended to adjust phosphorus and potassium doses, as the microalga enhances the uptake of these nutrients, and to ensure adequate irrigation during grain filling to avoid water stress that limits photoassimilate translocation. Results from multi-environment trials indicate that Scenedesmus application can increase the harvest index by 6.5% and grain zinc content by 8.2%, improving maize biofortification. This technology represents a viable tool for producing high-quality grain, reducing dependence on synthetic inputs, and aligning with the principles of regenerative and sustainable agriculture promoted by Ecoganic.

References

• Sustainable Agroecology — FAO