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Fertiliser Toxicity, Fertiliser Placement and Timing of Application with Oil Seed and Cereal Crops.

After heavy rains and colder than normal soil conditions, there is confidence that the Eastern States could be looking towards another good season. However there is some evidence to suggest that there has been a loss of nutrients in the root zone, requiring growers to increase the rates of fertilisers applied.

Fertiliser toxicity is a well documented problem that's generally attributed to the "salting index" of the particular fertiliser. The salting index is a measure of the osmotic dehydrating effect, or "burn", the fertiliser has on seeds and seedlings, with nitrogen and potassium fertilisers generally considered more damaging that phosphatic fertilisers.

There are other factors contributing to this problem, with light sandy and dryer soils generally increasing the toxic impact of the fertiliser.

Various planting systems have evolved that place the seed and fertiliser sufficiently apart to avoid the toxicity problem, however recent evidence suggests that poor germination or compromised seedling growth, which may have been attributed to soil or environmental factors, the equipment, the seed or the driver, may be due to fertiliser toxicity.

The GRDC has published some initial results of an ongoing research program that suggests fertiliser toxicity may be the result of fertiliser induced problems other than the "salting index" and some so called safe fertilisers are toxic to seeds and seedlings.

The research suggests that ammoniated fertilisers, such as urea, can negatively impact seedlings at distances of 5cm away from the urea band.

Clearly this is going to be a challenge for smaller seeds, such as canola seed and becomes less of a problem as the seed size increases.

Reducing the Fertiliser Toxicity Impact:

"Up front" fertiliser, particularly nitrogen, is critically important and it is likely that the seed/fertiliser placement recommendations may be reconsidered.

We can say in the meantime that it would be prudent for growers to avoid heavy applications of ammoniated fertilisers close to the seed.

If there is an ability to inject a liquid fertiliser with the seed, they should consider NitrotainTE27, which is 27% nitrogen with potassium, magnesium, sulphur and micronutrients, held in a carbon molecular complex, which is non toxic to plants or soil organisms.

Alternatively, if high rates of nitrogen are required then granulated urea and/or additional NitrotainTE27 can be applied after the crop is established and in the case of grains, when the plants are tillering.

Determine the Crop Fertiliser Requirements:

Growers are encouraged to undertake a soil test to determine the amount of nitrogen the crop is likely to require at planting and post emergence.

A tissue test is recommended at, or about, boot stage in cereal crops and on this basis the probable yields can be estimated and the protein/yield interaction considered and the liquid fertiliser determined. (This subject will be covered in more detail in future newsletters).

If you would like to know more about reducing the fertiliser toxicity impact on your farm, give the team at ECTOL a call and we’ll happily discuss it further.

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