A recent Italian study found that food industry by-product’s function as “biostimulants” and increase tomato yields. The scientists compared the production of organically fertilized tomatoes grown in pots with various treatments including the following (each tested individually and in various combinations):
- fennel processing residues (leaves and cull bulbs),
- lemon processing residues (pulp, seeds, cull lemons),
- brewer’s spent grain (husk and outer layer of barley after brewing), and
- commercial humic extract of leonardite.
Yields were higher under all four treatments than the control (i.e., no treatment). Application of all three processing residues was linked with a yield increase of 35 per cent compared to the control; the humic extract led to a 14 per cent increase.
The levels of nutrients (N, P, Ca, Na, Fe, Mn and Zn) were also higher in all the treatments, and again the waste products led to a greater increase than the humic acid. The specific effects varied among the waste products with only fennel waste having a significant effect on growth, and the spent grains and lemon waste having the most significant increase in levels of fruit phenols (often linked with flavour).
The food waste was applied to plants in liquid form in small amounts. In this way, it served as a “biostimulant,” defined by the authors as material containing substances and/or microorganisms “able, when applied in small amounts, to stimulate nutrient uptake and use efficiency by plants, increase plant tolerance to abiotic stress and improve crop quality.”
The overall conclusion of the study is a positive message for farming -- a waste product can be used to produce greater yields and higher quality crops—a great success story.
Source: Biostimulants from food processing by‐products: agronomic, quality and metabolic impacts on organic tomato (Solanum lycopersicum L.) Lara Abou Chehade, Ziad Al Chami, Sandra Angelica De Pascali, et al., Journal of the Science of Food and Agriculture. 2018. Volume 98, Issue 4, pp: 1426-1436.
- Janet Wallace