Vegetable production in the dry tropics - Nutrient and soil management strategies from Queensland Australia

Abstract

Agricultural industries located in coastal catchments adjacent to the Great Barrier Reef Marine Park in Queensland, Australia, are facing increasing pressure to demonstrate that their production systems are environmentally sustainable. Our experiences show that research and technology to improve productivity and profitability can also address environmental issues associated with off-site movement of nutrients. Due to limited water availability, vegetable farmers in the region utilise trickle irrigation and fertigation, often combined with polyethylene mulch film and seedling transplant technology. This system conserves water and allows for accurate and timely placement of fertiliser. The challenges for vegetable production systems in a dry tropical environment are: periods of high summer rainfall on fallow land; inherently low soil carbon with associated impacts on soil health properties (nutrient cycling, resistance to soil erosion); potential for denitrification under mulches; and salinisation of the soil profile. Fertiliser recommendations are based on empirical data rather than calibrated soil and plant tissue diagnostic indices. There is a need to develop science-based tools for objectively assessing and facilitating improved best practice nutrient management on a soil-, site- and crop- specific basis. In collaboration with local vegetable growers, we are modifying a decision support tool from the sugarcane industry for assessing the risk of off-site movement of nitrogen and phosphorus for the horticulture industry. This process is identifying large gaps in available input data (critical soil P test levels, crop growth cycles, nutrient uptake and removal data) for a number of vegetable crops but confirming the potential of the package to deal with the complexity and variability needed to support best management practices for nutrients in vegetable cropping systems.