Yield and quality of sequentially grown cherry tomato and lettuce under long-term conventional, low-input and organic soil management systems

Summary Aside from conventional fertilizers, organic and low-input technologies are being increasingly used for soil management in vegetable production. However, different factors operating during crop growth (i.e. the preharvest factors) and related to soil properties may affect yield and quality of vegetable crops. The present research aimed to study how different soil management regimes influence soil physical and chemical properties and how these affect yield and some quality traits of two major vegetable crops. We focused on lettuce, a major crop in the area under both conventional and organic production, and on cherry tomato, which is increasingly grown in organic vegetable systems. The soil management systems were: conventional (CM), following recommended fertilizer rates; low input (LI), using minimum fertilizer rates as needed; and organic, including manure application (MA) and incorporation of oat as green manure (GM) and of maize residues (MR). Preliminary results indicate that after 7 years of rotating vegetable crops, soil properties tended to improve with some systems: e.g. lower bulk density and higher porosity with MA; higher cation exchange capacity (CEC) with MA and CM. After these 7-year pretreatments, significant differences in crop growth and yields were observed for cherry tomato and lettuce grown under different production systems, but not for the overall quality indicators. The highest yields of cherry tomato were achieved with CM and MA, due to the increased number of fruits per plant, with no differences in fruit weight. Lettuce yields were generally higher with CM compared to LI, although the effect was different for different types of lettuce: the leafy type produced higher yields per area whereas the Latin type produced heavier individual plants. Under organic soil management systems, the relative survival and the visual quality of the Latin type was reduced by Botrytis cinerea infections. The results of the study indicated that plots that underwent long-term applications of 15 t ha -1 manure every two years produced similar yields than conventional systems and had comparable soil fertility attributes. However, the visual quality of the end product may be affected under organic systems. As observed for lettuce, cultivar choice may also play a role, since some lettuce types appeared to be more suitable for such systems than others.