Micronutrient Field Evaluations

A summary of six experiments on field responses to micronutrients in western Victoria.


22 Jan 2013

Project Description

Objective – to compare delivery strategies for Zinc and/or Copper and/or Manganese in wheat under field conditions.
Site selection: Any nutrient response experiment depends on selecting sites where there is a good probability of response. For Zinc and Manganese the most likely situations are alkaline sandy soils. A high P content will reduce Zinc and drought will also reduce the availability of both. Copper deficiency is most common on acidic sandy soils with a high organic matter content.
Pre-sowing Soil test: Send top 10 cm soil samples off for analysis, and the usual extractant is DTPA and critical ranges for these nutrients are Zn (0.8-5.0 mg/kg), Cu (0.3-5 mg/kg) and Mn (2-25 mg/kg) which indicates the difficulty is identifying potential responses/deficiencies with soil tests. However, having a soil test will give a clear indication of where deficiencies are NOT likely rather than anything else.
Crop: Wheat, whatever is the best local cultivar. Differences in seed micronutrient content can make a big difference, and the ideal situation would be to use the same seed at each site – but the logistics of this make it difficult.
Treatments and Replicates: Four replicates.
    · Base treatments - Nil fertilizer, Base fertilizer alone, Nutrient at sowing (on fertilizer – full rate), Nutrient applied at start of stem elongation (foliar – full rate), Nutrient applied at booting (foliar – full rate). = 5 treatments per nutrient
    · Additional Treatments – Nutrients half and half (on fertilizer at half rate, plus half foliar rate). Nutrient half at sowing plus half at stem elongation, Nutrient half at sowing plus half at booting. = 3 more treatments per nutrient.
    · Additional – use chelated or oxide forms of the nutrients rather than the more soluble sulphate forms suggested. Could add in a chelate or oxide form at the same addition rate in either of the foliar applications. = 2 or 4 more treatments per nutrient.
    · To do the three nutrients with base treatments, require 60 plots (20 per nutrient). If the other additions are considered, this could double the size of the experiment to 40 plots per nutrient.
Rates and forms to apply – suggestions only at this time
Full rate fertilizer treatments
    · Zinc – 5 kg Zn /ha as zinc sulphate added to MAP/DAP is full rate (get half rate by mixing untreated with treated fertilizer). Foliar use Zinc sulphate at 1 kg/ha as 1% solution.
    · Copper – 1 kg Cu /ha as copper sulphate added to MAP/DAP is the full rate. Foliar use copper sulphate at 250 g/ha in a 0.5% solution.
    · Manganese – 10 kg Mn /ha as the sulphate form added to MAP/DAP is the full rate. Foliar use manganese sulphate to apply 0.7 kg /ha in a 2% solution.
I will look to get these MAP micronutrient mixes made up by Incitec Pivot and can send them out to you – I will need to know the plot sizes so that I can get enough made up.

Sample Randomization:
BorderNilTE Foliar 1TE Foliar 2Base FertTE on fertBorder
BorderTE on fertBase FertNilTE Foliar 2TE Foliar 1Border
BorderTE Foliar 2TE Foliar 1TE on fertNilBase FertBorder
BorderBase FertNilTE Foliar 1TE on fertTE Foliar 2Border

Plot Size:
Matched to sowing and spraying equipment. We would usually use 20 m plots by the number of rows on the seeder.
    · Before the first spray of micronutrient, take whole plant samples (20 per plot) and microwave. Also take 20 youngest mature leaf blades per plot and microwave – keep separate from whole plant sample. Dispatch to me for analysis.
    · At maturity, take 10 g per plot of clean grain, Dispatch to me for analysis.
    · If possible, take a stubble sample and dispatch to me for analysis.
    · Take grain yield and if possible biomass at maturity (to calculate harvest index). Hand harvest may be best.
What analyses will be done?
Tissue, grain and whole plants will be analysed for the target nutrients (Cu, Zn or Mn). These values will be interpreted in terms of uptake and also grain nutrient density.