Substitution of 1/2 chemical N input with swine manure and straw increases the nutritional quality and species and contents of volatile substances in tomato fruit

Objectives We investigated the effect of partial substitution of chemical fertilizer with swine manure and straw on the nutritional quality and volatile substances of tomato fruit to provide basis for high quality tomato cultivation.

Methods Swine manure and/or straw were applied with chemical fertilizer in ratio of total N input of 1/4 and 1/2. All treatments had the same amount of N, P and K input. The fruit nutrition, volatile species and their contents affected by treatments were analyzed after 9 years continuous application of the fertilizers in a solar greenhouse.

Results The use of swine manure or straw with chemical fertilizer significantly decreased the concentrations of fruit fructose, glucose and lycopene, but did not affect the concentrations of fruit nitrate, Vc and titratable acid. However, the combination of both manure and straw with chemical fertilizers not only did not decrease the nutrient quality, but also improved the fruit aroma. Treatments contained swine manure accumulated more fruity and floral aroma volatile species at higher concentrations, for instance 2-isobutylthiazole, β-ionone, 3-methylbutanol, 3-methylbutanal, 6-methyl-5-heptene-2-ketone and E-2-hexenal. Some of these volatiles, such as 3-methylbutanol, 6-methyl-5-heptene-2-ketone, 3-methylbutanal, 2-isobutylthiazole, β-ionone showed an upward tendency with increasing swine manure substitution ratio.

Conclusions Swine manure and straw substituted for 1/2 chemical N could improve tomato fruit aroma without significant decrease of nutrient quality under long-term substitution of swine manure and straw for chemical fertilizer. Swine manure benefits for the accumulation of more fruity and floral aroma volatile species at higher concentrations, for instance 2-isobutylthiazole, β-ionone, 3-methylbutanol, 3-methylbutanal, 6-methyl-5-heptene-2-ketone, especially when it combines with maize straw. More than 30 volatiles are detected in the fruit, and 12 of them are above the average contribution to the variation among treatments. E,E-6,10,14-trimethyl-5,9,13-pentadecatrien-2-one and 2-methyl-4-pentenal are the two volatiles with the highest contributions.