Trellis tomato production is still relatively new to northern Victoria, the primary source of fresh tomatoes the markets of eastern Australia during the Summer and early Autumn. As such, great uncertainty exists in the industry as to optimal fetiliser application. Sap nutrient levels in a number of trellis tomato crops in the Goulburn Valley were monitored during 2001/2002 season and were related to fertigation practices and crop productivity. The results of the study have been used to create guidelines on efficient fertigation of trellis tomatoes as well as to introduce local growers to the benefits of nutrient monitoring via sap analysis. The growers now have the tools required to match their fertiliser applications with crop requirements in order to produce in the most cost-effective manner possible as well as to minimise the environmental impacts of tomato production. However, results have been obtained for one season only and further validation of the recommendations is required.

It is recommended that trellis tomato growers use sap analysis and compare their results to the benchmarks developed in this project. The amount of a nutrient fertigated should match its removal by the crop less that already in the soil. It is estimated that 228kg N/ha less any residual available nitrogen should be applied to the crop to make up for the nitrogen removed by a 194 t/ha tomato crop. Application of nitrogen should be timed to meet the demand of the crop to avoid excessive fruit set leading to smaller fruit. Currently, excess nitrogen is applied when the crop is young and cannot be utilised. Nitrogen, potassium, and calcium are commonly applied through fertigation. While the benefits of applying nitrogen are evident, the local soils are rich in potassium and large amounts of calcium are applied pre-planting in the form of line, gymsum, and superphosphate. Excess calcium is detrimental to phosphorus uptake and this limits yield. It is recommended that less calcium nitrate is applied through fertigation but a study is needed to compare the effect of using alternative nitrogen forms. These recommendations should be made available to fertiliser and agricultural service providers and used to develop decision support system for growers.