Influence of different types of fertilisers on the major antioxidant components of tomatoes

The objective of this study was to investigate the effect of three different mineral nutrient solutions (nitrate: ammonium ratios of 4:1 or 1:4), chicken manure and grass-clover mulch on the major carpometric and antioxidant components of greenhouse grown tomatoes. The mean plant shoot biomass was significantly higher ( P < 0.05 ) for the plants grown with mineral nutrient solutions (mean plant fresh weight, 1.05 kg) compared with chicken manure and grass-clover mulch (0.80 kg). However, there was no significant difference in the yield, dry matter content, or soluble solids of tomatoes grown with different forms of fertilisers for the duration of the experiment. The titratable acidity of tomatoes grown with nitrate-dominant solution was significantly lower ( P < 0.05 ) than tomatoes grown with other treatments. The mean total phenolic and ascorbic acid content of tomatoes grown using chicken manure and grass-clover mulch was 17.6% and 29% higher, respectively, than the tomatoes grown with mineral nutrient solutions. The mean lycopene content was 40% lower in tomatoes grown with high chloride levels and grass-clover mulch (11.5 mg/100 g dry matter) compared with other treatments (19.2 mg/100 g dry matter). The mean antioxidant activity of the ammonium-treated plants was 14% lower compared with other treatments. These results show that the nutrient source plays a major role in determining the levels of titratable acidity and antioxidant components in tomato.