Plant tissue testing helps ensure fertiliser responses are not compromised by factors we can control.
How effective was the fertiliser applied?
Tissue testing tells a lot about the effectiveness of different fertiliser treatments. The effectiveness of one product compared to another, or one strategy versus another is ultimately determined by the amount of fertiliser nutrients that make their way into the plant for an economic response. Plant tests from canola trials have given us the confidence in some trials to withhold topdressed nitrogen and sulphur fertiliser inputs and still grow crops of 2.5 – 3 t/ha.
How nutrient interactions may be affecting plants
Potassium deficiencies identified by plant testing can explain poor responses to nitrogen. Copper and sulphur deficiencies can be induced by high nitrogen inputs where soil copper levels are marginal. Tissue testing can reveal issues in nutrient uptake that may affect grain yield before these are severe enough to cause visual symptoms – hidden hunger.
About the effects of soil amelioration practices
Applying lime, claying, mouldboarding and spading feature in many trials because these practices affect nutrient availability and therefore fertiliser requirements. Plant test results can help explain the responses we see… or don’t see.
Prepared by James Easton, CSBP, with technical input from Graeme Schwenke, NSW DPI.
Photo shows a lime * spading * potash trial at Marchagee, WA, that produced a 0.3 t/ha response to potash last year but plant tests showed that potassium was still deficient. There was a 0.15 t/ha response to spading and no response to lime. This trial is being continued this year.
Diagram from David Lester’s article PLANT TISSUE TESTING – AN UNDER UTILISED TOOL FOR DIAGNOSING HIDDEN HUNGER IN CROPS on the GRDC website.