THE EFFECTS OF GROWER PRACTICE AND AGRONOMIC FACTORS ON THE PERFORMANCE OF SUCCESSIVE TOMATO CROPS

Australian growers are adopting practices that involve re-cropping of fields with processing tomatoes over multiple successive seasons. This raises a number of problems, which are reflected in crop performance. Barriers to the re-use of land for tomato cropping were identified through a census of farmers, which focussed on their growing methods and sustainability issues. Twenty-one field sites, selected to contrast management practices (irrigation type, years of cropping and planting system), were also monitored during the 1999/2000 season to establish correlations between growing methods and crop performance. Weeds, diseases and fear of long-term decline in productivity were listed by farmers as major barriers to the re-use of land for tomato production. A break phase of 5 or more years (after tomato cropping for one or more years) was used by 57% of growers using drip irrigation and 40% of growers using furrow irrigation. The lack of suitable soil-types was identified as a major limitation to production by 42% of respondents. Data from the field sites was highly variable, and over all sites, the only significant factor correlated with yield was time of planting (P=0.06), which was thought to be a consequence of seasonal conditions. In drip irrigated crops, yield was inversely related to the incidence of diseases (P<0.001) and weeds (P=0.03), and productivity declined and became more variable with repeated cropping.