Impacts of farming systems and soil characteristics on processing tomato fruit quality

Field trials were carried out in 1998 and 1999 at the Sustainable Agriculture Farming System Project (SAFS) located on the Agronomy Farm at the University of California, Davis to evaluate the effects of different farming systems on mineral composition and quality parameters of processing tomato fruits. The farming systems included 4-year rotations (processing tomato-safflower-corn-bean/wheat) under conventional, low-input, and organic management systems. The experimental design was a randomized complete block, split plot with four replicates. The three farming systems were main plots, and the crops in rotation were subplots. Total carbon, total nitrogen, soluble phosphorus, exchangeable potassium, calcium, and sodium, were highest in the organic system, Conventional 4-year rotations showed highest electrical conductivity and lowest values for most soil chemical parameters, while the low-input system had intermediate values. Nitrogen and sodium in the conventionally produced fruits were higher than the other systems, while phosphorus had the opposite effect. In 1998, fruit soluble solids, titrable acidity, and color score were highest in the conventional system and lowest in the organic system, while the low-input system showed intermediate values. In contrast, in 1999, no significant differences in fruit quality were found among the farming systems. The differences in environmental conditions and farming practices between the two years may explain the different quality responses. Several correlations were found among fruit quality parameters and soil chemical properties.