Southern region grain growers are advised to take extra care with seed and fertiliser placement this year due to the dry sowing conditions.
Dry soils increase the risk of harm to germinating seeds by fertiliser, especially when it is placed too close to the seed or at rates that are too high.
Norton Agronomic director Rob Norton said growers needed to be mindful of the soil conditions in their paddocks when applying fertiliser at sowing.
‘‘The dry lead in to winter sowing in 2018 means last year’s strategy might not be safe this year,’’ he said.
Dr Norton encourages growers to use a seed damage calculator to check how much fertiliser they can apply with seed through the same chute.
The calculator does not address fertiliser placed below or to the side of seed, but Dr Norton said separation of seed and fertiliser at about 3cm to 5cm was usually enough distance to protect the seed.
‘‘The risk of fertiliser damage increases with drier and sandier soils,’’ he said.
‘‘Conditions that cause stress or slow germination prolong fertiliser-seed contact, and this increases the chance of damage.’’
Crop type is another factor, with canola and lentils being more sensitive, while wheat and barley are relatively tolerant.
Fertilisers can affect germinating seeds in at least two ways, with the first relating to salt index.
Most fertilisers are salts and, as such, too much fertiliser salt can burn the seedling or stop seedlings from absorbing water.
Ammonia formation potential is the second consideration and Dr Norton said free ammonia could be toxic to seed.
‘‘Placing urea-containing fertilisers in-furrow is risky because they produce ammonia,’’ he said.
‘‘A fertiliser with polymer coatings or urease inhibitors may slow the rate of ammonia production enough to protect seed. These fertilisers are still considered risky to place near seeds.’’
In terms of placement, Dr Norton said the safe rate of fertiliser per hectare increased as row space narrowed.
He said the seed damage calculator included several liquid fertilisers.
■The seed damage calculator is available at: goo.gl/NT8vmB
■Tables for fertiliser/crop combination thresholds are on the International Plant Nutrition Institute website at: http://anz.ipni.net/article/ANZ-3074.
■More information on seed and fertiliser placement in dry soils is available on the eXtensionAus website at: goo.gl/ZuYKPJ