4 Biostimulant Studies Produce Growers Should Know
August 26, 2020 Most studies on crop inputs are a numbers game. If you apply this active ingredient, does it increase your yield? But a fairly recent trend in the produce industry raises the bar on what qualifies as an improvement: measuring nutritional content.
The current grading system is a physical assessment. Labs like Texas A&M’s Vegetable and Fruit Improvement Center tests for nutritional content, giving growers another bargaining chip when negotiating with buyers.
If you’re considering adopting this business strategy, you’ll want to know about several studies, many out of Europe, that examine how biostimulants impact fruit and vegetable quality.
Biostimulants Increase Vitamin C and Antioxidants in Peppers
A group of Croatian researchers chose to study how biostimulants impact yield and fruit quality on pep-per (Capsicum annuum L.). The group also focused on reduced fertilization conditions.
The results showed that natural biostimulants had a positive effect on the vitamin C and total phenolic contents in pepper fruits during the hot summer season. There is a strong correlation between total phenolic contents and antioxidants. Other antioxidant indicators also were significantly higher in treated plants and correlated strongly with all measured quality parameters except total phenolic content.
Study: Effect of natural biostimulants on yield and nutritional quality: an example of sweet yellow pepper
(Capsicum annuum L.) plants – 2011
Researchers: Nada Paradiković, Tomislav Vinković, Ivana Vinković, Vrček, Irena Žuntar, Mirza Bojić, and Marica Medić-Šarić
Fertilizer and Biostimulant Combo Increases Leafy Green Quality
Italian researchers studied how Trichoderma-based biostimulants affected leafy greens in different fertilizer levels (low, normal, and excessive). They focused on two types of leafy vegetables: iceberg lettuce (Lactuca sativa L.) and rocket (Eruca sativa Mill.). The two have markedly different nutritional content, allowing researchers to see how crop selection plays a role. The researchers conducted the study in greenhouses.
The team inoculated the crop with Trichoderma strains T. virens (GV41) or T. harzianum (T22) and compared the results with non-inoculated plants.
Vitamin C Impacts: When it comes to nutritional content, each crop reacted differently. Iceberg had a relatively low vitamin C content, where rocket had a much higher level.
The team found rocket recorded its highest vitamin C content with GV41 and normal nitrogen fertilizer rates. Interestingly, they did not find biostimulants having an impact on vitamin C when applied to unfertilized crops.
Yield Results: Trichoderma-based biostimulants, in particular GV41, increased lettuce and rocket yield in the unfertilized plots.
“Lettuce grown in absence of N fertilization demonstrated a significant yield increase when inoculated with GV41 (by 34% and 24% for total and marketable weight, respectively), and a moderate increase with T22 (by 16% and 17% for total and marketable weight, respectively),” the re-searchers report in their peer-reviewed journal article.
The highest marketable lettuce fresh yield was recorded with either of the biostimulant inoculations when plants were supplied with optimal levels of N.
Another important finding: the biostimulants did not visibly harm the plant. They found no visible chlorosis and/or necrosis symptoms.
Researchers: Nunzio Fiorentino, Valeria Ventorino, Sheridan L. Woo, Olimpia Pepe, Armando De Rosa, Laura Gioia, Ida Romano, Nadia Lombardi, Mauro Napolitano, Giuseppe Colla, and Youssef Rouphael
Spent Mushroom Substrate Boosts Tomato Nutrients
An international team of researchers, primarily from India, found earthworm grazed and T. harzianum biofortified spent mushroom substrate (SMS) had a big impact on the nutritional content of ripe tomatoes.
The application induced a significant increase in antioxidant capacity, total soluble sugars, carotenoids (lycopene, lutein, and b-carotene), total polyphenols, flavonoid contents, and mineral composition (P, K, Ca,Mg, Fe, Mn, and Zn).
SMS is a byproduct of the mushroom industry, the team says. It’s rich in organic matter and other essential nutrients for plant growth.
Researchers: Udai B. Singh, Deepti Malviya, Wasiullah Khan, Shailendra Singh, N. Karthikeyan, Mohd. Imran, Jai P. Rai, B. K. Sarma, M. C. Manna, Rajan Chaurasia, Arun K. Sharma, Diby Paul, and Jae-Wook Oh
Biostimulants Improve Vitamin C and Antioxidants in Onions
Egyptian researchers found biostimulants improved antioxidant activity, vitamin C, and higher pigment levels in leaves of vegetables compared to non-treated plants.
The group compared seven different groups of biostimulants and found three had the most positive impact on onions.
“Foliar application of yeast, seaweed, and licorice extract treatments greatly improved onion bulb contents of the percentage of nitrogen, protein, and dry matter compared with those of control and other foliar applications in the two seasons,” the team wrote in its study report.
They speculate the yeast extract’s beneficial effect stems from the way it promoted plant hormones. An earlier study from 1983, they say, showed the natural cytokinins in yeast stimulates cell division and enlargement as well as synthesis of protein, nucleic acid, and chlorophyll.
Here are the seven natural biostimulants the team compared to the control (tap water):
1. Foliar application with seaweed extracts (1 g /l)
2. Foliar application with garlic oil (2ml/l)
3. Foliar application with licorice extracts (25 ml/l)
4. Foliar application with limonene oil (2ml/l)
5. Foliar application with yeast extracts (25 ml/l)
6. Foliar application with bee pollen extracts (5 g/l)
7. Foliar application with potassium humate (0.5 g/l)
Researchers: Shafeek, M.R., Y.I. Helmy and Nadia M. Omar
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