Treating Tomato Nutrient Deficiencies with Biostimulants

Tomatoes, like other heavy-feeding crops, are particularly susceptible to nutritional deficiencies. Depending on soil types, fertilization programs, and environmental conditions, it can be a challenge to supply tomato crops with adequate macronutrients (nitrogen, phosphorus, and potassium), along with many key micronutrients. 

However, tomato nutrient deficiencies are often not the result of inadequate supply via conventional fertilization, but inadequate nutrient availability. With appropriate growing practices and fertilization programs in place, biostimulants can improve that availability and help growers treat deficiencies sustainably and cost-effectively.

Identifying Common Tomato Nutrient Deficiencies

Let’s start by quickly summarizing the symptoms and effects of common tomato nutrient deficiencies. 

  • Nitrogen deficiency begins with older leaves turning yellow, progressing up through younger leaves. Left untreated, nitrogen deficiency results in spindly, stunted tomato plants and limited fruit development.
  • Phosphorous deficiency results in leaves on young tomato plants turning purple. In mature plants, the undersides of leaves will turn a reddish-purple. Fruiting will be delayed and tomatoes will be smaller.
  • Potassium deficiency results in yellowing at the edges of leaves, which eventually become brown and leathery. Insufficient potassium can delay ripening and produce yellow shoulders on tomatoes.
  • Magnesium deficiency is a particularly common problem for tomatoes. It starts with interveinal yellowing on older leaves and progresses up to newer growth. Midribs remain green as the rest of the leaf dies. Untreated deficiencies can lead to defoliation and reduced yields.
  • Iron deficiency can result in iron chlorosis, with similar symptoms and effects as magnesium deficiencies. Tomatoes prefer acidic soil, and cannot properly absorb iron in alkaline soils, even if iron levels are adequate.

Because symptoms of different nutrient deficiencies can overlap with each other and with unrelated disorders, consider combining visual assessments with professional soil testing and plant tissue analysis for an accurate and comprehensive understanding of crop nutrient status. This will ensure any changes to your fertilization program are aligned with the actual needs of your tomato plants.

Adjusting Tomato Fertilization Practices

In an effort to address specific tomato nutrient deficiencies, it can be easy to overcorrect in counterproductive ways by adding excess fertilizer—as a nutrient surplus is not necessarily better than a deficiency. For example, excess nitrogen fertilizer will result in lush, green tomato plants, but limit fruit development.  

Excessive fertilization can also affect the availability of other nutrients: too much potassium can inhibit magnesium absorption, while too much phosphorus interferes with iron and zinc. So, in some cases, overapplying all-purpose NPK fertilizers exacerbates nutrient deficiencies. Further, chemical fertilizers typically have a low use efficiency. This means that only a portion of their nutrients is taken up by plants, while much is leached into groundwater or precipitates into less plant-available forms. Excess fertilization is a serious environmental problem, and is quite often simply a waste of money, too 

All that to say, in many cases the root problem of many tomato nutrient deficiencies is actually not about supply, it is about availability.

Biostimulants for Tomato Nutrient Deficiencies

Biostimulants can treat tomato nutrient deficiencies by unlocking nutrients already in your soil or growing medium. They are capable of improving nutrient uptake, use efficiency, and availability, all without supplying additional nutrients through conventional fertilization. They do this through various mechanisms, which include promoting root development, chelating minerals into plant-absorbable forms, and fixing nitrogen out of the atmosphere.  

Biostimulants are a diverse category of amendments, including everything from bacteria to inorganic elements. Here, we will focus on amino acids and beneficial microbes—two classes of plant biostimulants proven effective in addressing common tomato nutrient deficiencies.

Amino Acids

Amino acids are the building blocks of proteins, and fundamental to all biological life. Plants need amino acids to build cellular structures, regulate metabolic processes, and facilitate nutrient transport. They are also themselves an important source of nitrogen.  

Amino acids are known for their chelating effects and help treat nutrient deficiencies by transforming vital micronutrients into more plant-available forms. Calcium, iron, magnesium, manganese, and potassium—common deficiencies for tomato plants—are some of the minerals effectively chelated with amino acids. Studies show that amino acid application can improve tomato yields at different fertilization levels, and help sustain yields in nutrient-limited growing conditions. 

Amino acid fertilizers like Impello’s Lumina™ can complement any organic or conventional fertilization program. Tomato growers can use Lumina™ to boost nutrient availability, improve plant stress tolerance, and enhance the function of beneficial microbes—effects that all work to correct and protect against many common nutrient deficiencies.

Beneficial Microbes

Beneficial microbes refer to bacteria and fungi that encourage plant growth and development. Like amino acids, beneficial microbes improve the bioavailability of essential nutrients in the soil. They improve nutrient uptake and efficiency when used alongside conventional fertilizers by encouraging root development and solubilizing nutrients into plant-available forms. Certain bacteria even “fix” more nitrogen in the soil by converting atmospheric nitrogen (N2) into plant-available ammonia (NH3) and/or ammonium (NH4+). 

In addition to improving nutrient bioavailability and use efficiency, beneficial microbes can address nutrient deficiencies by stimulating root development and increasing root surface area, allowing plants to access a larger volume of soil and absorb nutrients more effectively.  

Impello’s newest microbial inoculant, Continuum™, contains a blend of plant growth promoting rhizobacteria (PGPR) from the Bacillus and Paenibacillus genera, chosen for their ability to promote root development, improve nutrient uptake, and solubilize potassium, phosphorous, and other vital micronutrients into bioavailable forms. Nutrient deficiencies, nutrient leaching, and fertilizer overuse can all be mitigated simultaneously with the help of these beneficial microbes.

Start Using Biostimulants on Your Tomato Plants

Plant biostimulants are a holistic and environmentally friendly strategy for treating nutrient deficiencies in tomatoes and other heavy-feeding crops. Impello’s Lumina Amino Acid Fertilizer™ and Continuum™ Microbial Inoculant are formulated to work synergistically to improve nutrient availability, uptake, and use efficiency. They are compatible with any growing system and fertilization program.

The use of biostimulants helps address nutrient deficiencies while aligning with sustainable agricultural practices. By improving nutrient availability and uptake efficiency, biostimulants can significantly reduce the overall need for chemical fertilizers. This reduction not only minimizes environmental impact but also contributes to cost-effectiveness in the long run.  

The holistic benefits of biostimulants extend beyond nutrient management. They promote stress tolerance, encourage a healthy soil microbiome, and support overall plant health, leading to healthy, high-quality yields—for tomato crops and beyond.

Impello biostimulants integrate into any growing system and fertilization program as a comprehensive solution for treating and preventing nutrient deficiencies. Browse our online store to get started today!



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Eltlbany, N., Baklawa, M., Ding, G., Nassal, D., Weber, N., Kandeler, E., Neumann, G., Ludewig, U., Van Overbeek, L., & Smalla, K. (2019). Enhanced tomato plant growth in soil under reduced P supply through microbial inoculants and microbiome shifts. FEMS Microbiology Ecology, 95(9). 

Klokić, I., Koleška, I., Hasanagić, D., Murtić, S., Bosančić, B., & Todorović, V. (2020). Biostimulants’ influence on tomato fruit characteristics at conventional and low-input NPK regime. Acta Agriculturae Scandinavica Section B-soil and Plant Science, 70(3), 233–240.

Koukounaras, A., Tsouvaltzis, P., & Siomos, A. S. (2013). Effect of root and foliar application of amino acids on the growth and yield of greenhouse tomato in different fertilization levels. Journal of Food Agriculture & Environment, 11(2), 644–648. 

Tian, J., Ge, F., Zhang, D., Deng, S., & Liu, X. (2021). Roles of Phosphate Solubilizing Microorganisms from Managing Soil Phosphorus Deficiency to Mediating Biogeochemical P Cycle. Biology, 10(2), 158.

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