After a difficult season for almond production and quality, Anthony Wachtel with the Almond Board of Australia (ABA) says when it comes to tree nutrition, “there is still a lot to learn about what we don’t know yet’’. 
 
Anthony is Orchard Manager at the ABA’s Almond Centre of Excellence property near Loxton, which it manages for a wide range of research with industry departments, tertiary institutions and commercial organisations. 
 
The 60-hectare property, comprising loamy sand soils, was planted in 2017 to several varieties and rootstocks, including some new Australian lines, with the research looking at various issues including tree densities, irrigation, tree structure, soil amelioration and orchard machinery, as well as nutrition. 
 
High quality fertilisers are used in the orchard, including Haifa’s Multi-K potassium nitrate, as well as calcium nitrate, potassium sulphate, phosphorus, liquid fertilisers, UAN and micronutrients including reasonable quantities of iron and magnesium and foliar blends. 
 
“Potassium nitrate was applied in every fertiliser mix last season from August 16 to October 28, including with every nutrient foliar spray,’’ Anthony said. 
 
Fertiliser applications were lower overall due to the very cool and wet conditions and, similar to reports from other areas, the Nonpareil crop was looking light. 
 
“The weather conditions may have affected pollination. Despite bee numbers being at standard stocking rate, early flowering varieties like Nonpareil and Shasta showed more duds, deformed kernel and poor crackout percentages,’’ Anthony said. 
 
However, a switch from using an EDTA iron chelate to an EDDHA iron chelate to better suit the soil pH on the property last season, combined with magnesium and micronutrient blends, resulted in “greener trees’’, and this had since triggered discussion with Haifa Australia Southern Agronomist Sheri Robinson on what this could mean for future crops. 
 
Sheri said she noticed a significant difference in the leaf health at the Almond Centre of Excellence property last season compared with some other orchards that may have been impacted by limiting micronutrient supply and “wet feet’’. 
 
“The site started looking green from the start, which is a good indication of a strong micronutrient program,’’ Sheri said. 
 
She said Haifa now offered an EDDHA iron chelate with the highest ortho-ortho level of 5.2pc, ensuring more efficient use of the nutrient and improved production and quality. 
 
Anthony said in the early part of the season they applied 1.3 kilograms/ha of EDDHA iron with a 3pc ortho-ortho level per week, combined with magnesium and a liquid micronutrient mix. It amounted to a total of 8kg/ha of iron and resulted in healthy green leaves. 
 
“We noticed the difference with the strong micronutrient program and the health dropped away slightly leading in to harvest. The difference this leaf health makes to future crops could be interesting and we will be taking a closer look at it, particularly the benefit over the November to March period.’’ 
 
Anthony also has taken note of the fertiliser input curve presented at the Australian Almond Conference last October by Dr Patrick Brown, which indicated a reduced post-harvest requirement for fertiliser if leaf and tree health is maintained through to harvest. This curve suggests maintenance of small amounts of fertiliser from November to harvest, instead of a significant post-harvest feed, to ensure leaf health and return of nutrition to trees in storage for the post-harvest shut-down period. 
 
“We have traditionally applied fertiliser to mid-November and then post-harvest, but the trees can lose leaves and start to shut down. Last season it was significantly healthier all the way through to harvest.’’ 
 
Sheri said as trees shut down post-harvest, it was known the leaves store carbohydrates back to the trunks and the subsequent tree health could impact the next year’s crop. 
 
In line with Dr Brown’s fertiliser curve, she said instead of growers applying 30pc of the fertiliser post-harvest, there could be a benefit from “teaspoon feeding’’ trees at no extra cost over the four-month November to March period to maintain leaf health. 
 
“The flow-on effect for orchard health from the recent season into the next will be interesting to observe and record on a nutritional performance level to explore these benefits from one year’s tree health into another. This is especially of interest as growers look to reduce costs and, hence, in some cases, fertiliser quality. The question to consider is: What will the impact be to following crops if I adjust my fertiliser program?’’ 
 
“Rather than applying sulphate of potash, UAN and NPK fertiliser post-harvest, some of this larger feed could be applied using Poly-Feed, a complete NPK fertiliser with micronutrients, at the lower requirement period from November to harvest. It could be trickled to the trees with the aim of better leaf health for improved post-harvest health and carbohydrate return.’’ 
 
Sheri is interested in tracking plant nutrition through regular testing in almond orchards with Anthony and the industry, particularly during the November to March period and comparing between different fertiliser programs to explore Dr Brown’s theory. 
 
“There is also opportunity to further investigate nutrient use efficiencies, as well as the use of micronutrients including manganese and silica, as these are known to provide plant resilience to pests and diseases,’’ she said.