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Fertilizer Type Found to Affect the Growth and Antioxidants in Tomatoes, but Not Yields
Tomatoes are known to be an important source of antioxidants such as lycopene, phenolics, and vitamin C (ascorbic acid). While other studies have looked at the difference between conventionally and organically grown foods in terms of macronutrients, vitamins, and minerals, this study looks at levels of secondary plant metabolites such as antioxidants.
Previous studies had shown that different fertilizers release nutrients differently, leading to varying carbon/nitrogen ratios in plants, which in turn effects the production of secondary metabolites. Additionally, taste, color, vulnerability to pests, and nutrient qualities of tomatoes can be affected by their antioxidant content.
The researchers studied greenhouse grown tomatoes treated with five different fertilizers: three inorganic (varying mineral nutrient solutions) and two organic (chicken manure and grass clover mulch).
Looking at the carpometric characteristics of their crop, they found that the plant shoot biomass was significantly higher in the inorganic treatments. However, "there was no significant difference in the yield...of ripe tomatoes from different treatments."
In terms of antioxidant components, they found that "the use of chicken manure and grass-clover mulch has ... been found to improve the levels of total phenolics and ascorbic acid in tomatoes."
This study concludes that organic fertilizer sources can increase antioxidant levels in tomatoes, while producing yields comparable to conventional production systems and fertilizers.
Source: "Influence of different types of fertilisers on the major antioxidant components of tomatoes"
Authors: R. K. Toor, Geoffrey P. Savage, Anuschka Heeb
Journal: Journal of Food Composition and Analysis, Volume 19, pp 20-27, 2006.