More Profit from Crop Nutrition: Micronutrient Survey

Project methodology and sites used

The assessment will aim to identify areas where wheat and canola are at most risk from micronutrient deficiency (B, Cu, Mn and Zn). The following evidence about these nutrients will be considered and intergrated into a georeferenced database, linked through soil types within each agroecological zone (except the Burdikin, Tasmania and the Ord zones):
Part 1: Regional Soil characteristics (pH, texture, type, %OC – primary drivers)
It is proposed that micronutrient availability is largely controlled by the primary properties of soil pH, soil texture and soil organic matter content, as well as underlying geology. Therefore, reference to existing soil database information should provide prima facea evidence about the risk of micronutrient availability. Table 2 below is a summary of the properties that would be appropriate relative to each of the micronutrients under consideration.
Table 2: A summary of soil and climatic factors affecting micronutrient availability. + indicates increased availability, - indicates reduced availability.

	Cu	Mn	Zn	B	Mo
pH > 7.0	---	--	---	**	++
pH < 5.5	++	+++	+	--	--
water-logged soil	+	+	+
drought	---	---	-	---	--
high organic C content	---	++	++	++	-
high P-content	-	-	---	-	+++
sand	---	--	---	--	-
compaction	+	+	+	+	+

Existing soil information, such as from the Australian Soil Resource Information System (ASRIS), will be used to assess the risk within each agroecological zone. Using digitised soil maps from the Atlas of Australian Soils, each soil type within each agroecological zone will be assessed on the criteria in Table 2 for the risk of micronutrient deficiency, and while it is accepted that this is an imperfect assessment it should give a first approximation of the risk based on pH, texture and organic matter.
The output from this part of the project will be a GIS map for each AEZ showing soil types and their risk of micronutrient deficiency. A table of potential areas at risk will also be produced. These data would also be made available through the MPCN website once it becomes active.
Part 2: Soil Test Information
Even though soil tests for micronutrients are not strong indicators of responses to added fertilizer, existing data on soil test levels will be incorporated against the soil type information collected in part 1 of the project. Standard soil tests for Cu, Zn and Mn (0-10 cm as DTPA extracted) and B (0-60 cm or 10-60 cm as either Hot water or hot CaCl₂ extracted) would be requested from the NVT collaborators. Some sites will not have the deep B tests although samples of mineral N are taken and these could be retested for B. Historic data from around 1000 site/soil tests will also be collected from the NVT database where appropriate micronutrient analyses have been undertaken.
Other data sources could be soil test data from the two major commercial laboratories CSBP and IPL, although at present no negotiation has been undertaken to access these data. This added information would improve the confidence of the assessments made in part 1.
Part 3 Grain nutrient concentrations
Grain from the wheat and canola NVT series would be collected and analysed for nutrient content using ICP-OES. Analytes reported from this analysis are Al, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Ti and Zn. As mentioned earlier, Co and Mo contents in grain are generally below the analytical limits for this technique, and Cr and Ti are reported as indicators of soil contamination. Barley grain could also be analysed from the NVT series, but 85% of the wheat and barley trials are co-located so the testing of barley would largely be covered by the wheat site evaluations.
In 2009 around half the NVT sites in the southern region had Zn supplements added, and it would be requested that – if possible – no supplement be used in this year. Otherwise, normal fertilizer practice would be followed.
Because of cultivar differences in Zn uptake recognised for wheat in particular (e.g. Cakmak et al, 1998), it is proposed to collect samples from common cultivars across each site. Unfortunately, there are no common cultivars across all NVT sites, but Yitpi, Spitfire and Elmore CL are common across the western and southern regions, and Elmore CL and Gasgoyne are in the northern region but also represented at some sites in the southern and western. In the 2009 survey, Gladius and Yipti were assessed, so the inclusion of Yitpi here will extend that dataset. So, a combination of these four should give coverage across the whole series of wheat trials and with around 200 sites each contributing two (and for cross correlation three) cultivars. There are around 170 canola sites and a similar process will be followed to select appropriate cultivars for testing. It is estimated that around 900 grain analyses will be required to complete the dataset.
Relationships between the soil properties and grain contents will be tested to evaluate the hypothesis about the link between the two proposed in part 1 of this project.
Part 4 Collation of field experimental data on micronutrient responses
Literature from refereed and other sources will be collected and collated for presentation in a web-based map similar to the current Better Fertilizer Decisions for Crops database map or through Google Maps where good georeferencing is available. It is proposed that this be available through a MPCN website and the final achievement of this milestone will depend on the progress of that project towards establishing the overall website.