Getting it right from the start

Making sure you have the correct soil fertility to support crop growth is critical to achieving your yield goals. Soil testing prior to sowing is a fundamental part of this process and is essential for the development of an effective and economical fertiliser programme.

Soil testing for brassicas

Brassicas are grown on soils often planted as part of the pasture renovation process, so frequently go into poorer performing paddocks, including those with lower fertility. Soil testing should be used to see how the paddock fertility needs to be adjusted to support the growth of your brassica crop, and also to set up the right conditions for successful pasture establishment once the crop has finished. Consider using the Ballance Brassica Soil Test, which has been developed specifically for brassica crops.

Soil testing, to a depth of 150mm, should be carried out well before the crop needs to be sown so that there is sufficient time to correct any pH issues. Applications of lime will take somewhere between six months and a year to work, so soil testing a year before planting is the preferred strategy.

Once you have your soil test results you can start to formulate your fertiliser strategy. The table below details the target levels for various soil test results.

Phosphorus is needed for root development and early plant growth, and is best applied close to the seed for shallower rooting crops (like turnips) as this has been shown to give better results than broadcasting. Brassicas need good levels of potassium, but in most cases this requirement will be filled by existing soil reserves. They rarely respond to sulphur applications and this nutrient should only be applied if soil levels are very low (sulphate-sulphur <2). The key micronutrient they require is boron - deficiencies can result in plant health issues such as brown heart in swedes.

Starter fertiliser options include cropzeal DAP boron boost, DAP, serpentine super and cropzeal 15P. Of these, the product of choice is cropzeal DAP boron boost, as it supplies the nitrogen, phosphorus and boron needed by brassicas. Nutrient spread through the crop is even, as this is a compound fertiliser, with every granule containing the same ratios of each nutrient. If you are interested in using cropzeal DAP boron boost, then speak to your Farmlands or Ballance representative promptly, as there are limited supplies available.

Soil testing for cereal crops

Soil testing is also good practice prior to sowing cereal crops. Soil tests should be taken to a depth of 150mm. When deciding on the target levels of soil nutrients a range of factors should be considered including paddock history, the amount of nutrients removed with the crop and the crop rotation. You may want to adjust nutrient additions to account for the paddock use after the cereal crop, for example, if you are going into pasture you might aim for a higher Olsen P than if you are going back into another crop.

The following table shows target soil test levels for four common cereal crops. If soil test results are lower than this, there will be a likely yield response to adding these nutrients. Phosphorus is needed for root development and sulphur for growth; these can be applied at planting. Potassium and magnesium requirements are likely to be met from soil reserves, although potash may need replenishing if it has been removed in previous crops.

Nitrogen is a key nutrient for cereal crops too, and the timing of applications is important. In wheat, the availability of nitrogen in the early stages of growth encourages the production and survival of tillers. However, too much nitrogen early on can encourage the plant to produce too many tillers, which it will be unable to support through to maturity, so getting the right balance is important. Barley requires less nitrogen than wheat, but does better when it is applied earlier, with larger amounts often applied prior to drilling. Soil test results will help to determine the rates of nitrogen that are required.

The cropzeal range of fertilisers has been developed specifically to meet crop nutrient requirements. In many cases cropzeal 16N, applied as a starter fertiliser, is sufficient to meet demands; however, it is best to soil test and then talk to your Farmlands or Ballance representative to develop an appropriate strategy for your particular crop.

Article provided by Ballance