Analysis of freshly harvested grain can:
- – show if that crop had a hidden hunger that may have limited yield
- – document the degree of a known deficiency
- – confirm its suitability to use as seed
- – inform future crop nutrition strategy for the paddock.
Tissue testing of grain is valuable for assessing trace element availability in a paddock – noteably copper (Cu), zinc (Zn), manganese (Mn) and molybdenum (Mo). It can supplement a soil test when there’s concern about the uptake of micronutrients from plant roots and/or the translocation of micronutrients to grain later in the season.
Results also provide feedback on the nitrogen (N) (although protein content and grade also inform N review) and sulphur (S) status of the crop just grown. Higher phosphorus (P) and zinc (Zn) levels may highlight a better seed source for future crops. On the other hand, grain testing is of no value for assessing potassium (K) because grain concentrations do not reflect crop status.
The quantity of nitrogen and other nutrients that are exported in grain can be used to develop a crop nutrient replacement strategy, rather than relying on frequent soil testing. Keeping a record of nutrient export over successive crops will fine-tune understanding of the paddock’s nutrient status.
Successive testing in specific paddocks is valuable in interpreting grain analysis, as grain concentration can vary, both within and between regions, around the concentrations used as ‘rules of thumb’. The variance can’t yet be attributed to yield, genotype, or soil attributes.
Any crop can be sampled, but wheat is the most tested, and therefore the crop with the most data to support interpretation of results. Ideally, grain should be collected from clearly identified parts of the paddock so that any variation within the paddock can be better understood by relating that information back to soil test data, fertiliser inputs and management practices.
Dr Kaara Klepper, QDAFF, plans to investigate further in a proposed study. She says that at less than $50 for a grain nutrient concentration test, grain testing represents good value for money if it becomes a reliable predictor of yield.
You can read more detail in Plant tissue testing – an underutilized tool for diagnosing hidden hunger in crops by David Lester & Mike Bell, 2010.
Technical input from Kaara Klepper, QDAFF, James Easton, CSBP & Liam Ryan, DAFWA.
Photograph GRDC library