Soil testing in vegetable crops provides a snapshot of soil properties and nutrient levels to identify any deficiencies, imbalances, or excessive levels.
By quantifying these nutrient levels and comparing those to the optimum levels for a chosen crop, we can determine which nutrients need to be added to achieve the desired levels. All this information helps create a fertiliser programme specific to that crop in the designated paddock.
Testing in autumn allows time for results to be received and fertiliser plans created and implemented. Once autumn and winter fertiliser applications are made, there is also time for some of the nutrient adjustments in the soil to take effect before spring planting. For example, pH can take a significant period to be adjusted through liming. The lime itself requires water to activate in the soil, so calculating its requirements and applying it over autumn and winter ensures sufficient moisture availability to get the most from lime’s activity during this period.
The sampling method is the greatest contributor to variability in test results. The sampling method should include taking a representative sample across the block, at the correct depth and taking into account the changes in soil type, previous land use, etc.
A standard recommended test for vegetable crops includes pH, phosphorus, cation levels, cation exchange capacity and base saturation. Available nitrogen, sulphate sulphur and boron are also important for vegetables. Boron is known to play a crucial role in maintaining the internal cell integrity in several crops including potatoes and onions, as well as helping prevent carrots and parsnips from cracking.
Test also for soil organic matter as it influences numerous soil properties and processes such as soil structure, biological activity and nutrient availability. If organic matter levels are sub-optimal, steps may be taken to gradually improve this.
More information on organising soil sampling and interpreting your test results is available from your local Fruitfed Supplies Technical Horticultural Representative.