Leading farming systems researcher Dr. Nigel Wilhelm from SARDI recently presented to western Victorian farmers on trouble shooting crop nutrition, in particular the management of trace elements.
Dr. Wilhelm provided advice on how to inspect crops throughout the growing season for trace element deficiencies, test for accurate diagnosis and treatment strategies.
“Zinc deficiency produces a very unique symptom in the cereals; in wheat it manifests itself as two pale strips down the young leaves. In barley, the same symptoms can be seen, but it isn’t as clear and may also show up as spots,” he said.
In oats, however, the old leaves will turn purple.
Copper definciency can be very hard to detect. It can be localised and seasonally dependent, showing up more in a dry spring. Plants with a copper deficiency can show tips withered, curled/twisted and dead. However in the field it is more likely to look like frost damage, but not in the areas of the crop where it would be expected for frost.
Manganese deficiency can make the crop ‘flop’ like it has been through a drought, even though the soil can be quite wet. Manganese can also produce pale green/yellow leaves and soil compaction can relieve the symptoms a little.
Iron deficiency is the opposite. Soil compaction exacerbates the problem, and crops will have canary yellow leaves.
The best method for detecting trace element deficiencies is tissue testing of plant leaves, generally at early growth stages.
The advantage of most trace elements is they can stay in the soil for a long time. A soil application of zinc could last between five and seven years while copper could last up to ten years depending on soil type. One exception is iron.
If it is applied to the soil, it can get tied up within weeks accelerated by calcareous soils.
For maintaining soil zinc levels, Dr Wilhelm suggested applying approximately 0.5kg/ha every year or a bigger application of approximately one kg/ha every five years.
