IN THE FIELD with Alan Wright
Hi Fert Agronomist

Sowing finished what now?
With the seeder packed up and back in the shed, and the sleep deprivation remedied by a quiet weekend on the couch, as you would be well aware, the next part of crop management is weed and insect control.

Take the opportunity to do a visual assessment of your crops colour and growth from the cabin while spraying and make a mental note of anything that is out of the ordinary. For example patches where plants are lighter in colour or leaves turning yellow, investigate further and include your agronomist.

Yellow ill thrift on cereal plants can have a number of causes - such as disease (e.g. rhizoctonia), bugs (e.g. red legged earth mites or cockchafers), very deep sowing, and of course nutrition.

Lack of Nitrogen is usually the cause of ill thriftiness and this is usually characterised by - new growth being lighter in colour than a plant with adequate nitrogen and abortion of the older leaves. Inspect the older aborted leaves for signs of leaf diseases and once disease has been ruled out, it is worth weighing up how the season is progressing. Weather forecasts will determine if topdressing with nitrogen is going to be a good return on investment.

How sure are you that nitrogen is the cause? Sulphur and potassium deficiencies are both expressed by cereal plants as ill thriftiness and yellowing, so now might be an appropriate time to consult previous soil test results or do a tissue test.

If potassium, as is most likely, is above the critical level and sulphur is marginal, the best solution is to plan a nitrogen top-dress such as urea (46%N) or GoldN (41%N, 9%S).

Soil sulphur levels are the key to answering this one. If sulphur levels are well above critical then urea, if you are looking to maintain soil sulphur level or the existing level is below critical, then GoldN.

If the paddock is being sown to a pulse next season and you are in the habit of planting pulses with high analysis fertilizers that contain very little sulphur, then any residual sulphur from the GoldN application may be of benefit to the pulse crop.