text: Higher densities trial
  Research aim: To assess the impact of dwarfing rootstocks and planting density on the establishment of new almond varieties in a 2-dimensional tree shape/fruiting space and the distribution of fruiting sites.
  On this page:
  - Higher density plantings
  - Density and light interception
  - Irrigation management
  - Introduction to the research (2018)
  Higher density tree plantings
  2023 UPDATE - Dr Zel Coetzee, senior research scientist at Agriculture Victoria, discusses the almond tree high density trials at the Mildura SmartFarm.
  Video transcript - Almond SmartFarm higher density planting
  We're currently in the higher density planting. This planting was established to address future planting systems as laid out in the Almond Board of Australia's strategic investment plan for the next five years. The planting is 6.7 hectares in total. It's got almost 7,000 trees. We are evaluating desirable traits across three varieties. Australian bred varieties that are also self fertile, planted on four root stocks, and at three planting distances, increasing the trees from 500 to a thousand, and also 2000 trees per hectare. We are evaluating these different combinations for future planting systems when industry needs to move towards shake and catch harvesting . To enable us to fit a tree into an overhead harvester, which will potentially be the future shake and catch harvesting concept that they will develop, we need to keep the trees quite small, and for that reason, we hedge it. So, you will see we have a quite a tight hedge to keep the interow spacing open. It also limits the fruiting space that we will have, and as soon as you hedge the trees, you'll have vegetative growth. And we are evaluating all these traits of the different combinations to see how they react towards hedging, but also towards tree spacing. So we selected three Australian varieties. Each of its, its own growth habit. Some of them are weeping, some of them are very upright and some of them are very modular. We are evaluating four different root stocks, two who are dwarfing, and two that is generally used in the almond industry.
  Because of the topography of the orchard, it's planted over a dune into a swale, which has very different readily available waters and also water holding capacity after irrigation. Each research plot is individually valved, to not over or underwater any of the research plots, which would be an additional factor to be taken into consideration for yield prediction, et cetera, and for the how the tree is responding to the tree treatments.
  Dr Zel Coetzee, senior research scientist at Agriculture Victoria, discusses the almond plant density and light interception research at the Mildura SmartFarm.
  Video transcript - Almond plant density and light interception research
  So one of the aspects that we're evaluating in the high density plantings, in order to keep the trees small so that we can fit an overhead harvesting shake and catch harvesting system over them, we actually hedge the trees, quite harshly compared to what they would do in industry where they only hedged to increase light interception in their inter-row space, or to open up the inter-row space for access.
  Closest to me, behind me is a dwarfing root stock. You can see the canopy's less dense. It's also much smaller compared to the next research panel, little experimental panel that we have, which have a very high vigour root stock, and you can see it grows very high. There's a lot of lateral growth. We are interested in seeing how these different root stocks react to hedging because, for instance, the higher density root stock, as soon as you hedge, on the ends of the branches that you hedge, they will throw multiple lateral shoots, which in the long term will have implications for light interception into the canopy. Light interception is related to floral bud initiation, so that will basically have implications on your yield, because without floral buds, you won't have fruit.
  Behind us there's a lot of light interception in the canopy. But on the other hand, there's also not a lot of new spurs, so you won't have a massive increase in yield, but there's a higher chance of the, the spurs that are there that they will carry fruit. But in addition to that, there's competition and there's, not enough nutrients and water, and it might be that they're not able to, to ripen the fruit properly because they have such a small canopy compared to the other higher vigour root stock. So, there's always a give and take, and you always have to look at both, both sides.
  Dr Zel Coetzee, senior research scientist at Agriculture Victoria, discusses the almond tree irrigation management and research at the Mildura SmartFarm.
  Video transcript - Almond irrigation management in the higher density trails
  Because of the topography of the higher density orchard, it’s going over a dune into a swale and back into a dune, the readily available water differs greatly from the top where we have 65 millimetres of available water to the plant, into the swale where we have only around 25 minimum millimetres of water available to the plant. For this reason and to avoid overall under watering the treatments, having the capability that every little experimental plot is individually valved so that we can control the irrigation to each plot, we have 72 of these soil moisture sensors installed across the orchard. And randomly distributed to incorporate all the different soil types, all the different treatments, and the topography as well. We use these to manipulate our irrigation. In addition to using it to apply our irrigation, these soil moisture sensors, you can actually put thresholds on them and they can autonomously open and close the valves to only irrigate the plots that we select in that group when it needs water and for the amount that it actually needs. So that will avoid over watering certain parts of the orchard or a lower vigour type. For instance, a lower vigour plot.
  What makes it different than the traditional point soil moisture sensor that most farmers are familiar with? These are three metre strips that are buried along the tree at 40 centimetres, which we have from previous research shown is where the majority of the roots are. So instead of only measuring one point of soil and the soil moisture in that one point, it actually measures a volume of soil across that three meters and gives us an average of what's going on in the soil. So for us, it's a better indication of what's actually happening, especially with the different treatments that we have and the different tree densities.
  The outcomes sought are rootstock/scion combinations better suited to the 2-dimensional fruiting space concept, and, perhaps more importantly, a clearer understanding of what tree growth habit (i.e. architecture) might be preferable.
  A strategic aim of the industry is to move toward shake-and-catch harvesting, driven by the need to avoid some of the weather-related nut quality issues that have dogged the industry in the past. The shake-and-catch engineering solution will be much simpler if the fruiting space is 2-dimensional (i.e. a more-or-less a thin hedge) as compared to the 3-dimensional fruiting space currently used. The industry standard varieties and the newer varieties being made available to industry, were selected for their suitability for the current way orchards are planted (i.e. “H1”). The vigour and growth habit that made them suitable for H1 planting densities do not necessarily make them suitable for a production system geared toward shake-and-catch harvesting. These varieties differ marginally in their growth habit, and it is possible that one or more of these varieties will be more suited to a closer spaced hedged row production system than other varieties.
  Video: Dr Michael Treeby - Introduction to research looking at High density nut trees
  Video transcript - Introduction to research looking at High density nut trees
  The next planting is where we start pushing those trees in closer together and there we're looking for more root stocks that are better suited to producing trees that are smaller, more compact if you like, and then also looking at scions which are stemming from the current Australian Almond Improvement Breeding Program for their suitability for those kind of plantings. So that really is a bit of a look for the orchards that will be established probably 10 years from now. The trial after that is slightly more radical. That's where we've really pushing things closer together and we're trying to, we're looking at all sorts of fairly radical tree training ideas and that's a trial that is very much you know right out on the fringe, if you like. Remember that the orchard of the future may well be a two dimensional fruiting space. By that we mean probably more or less like a grape vine is at the moment. This really just height and length and at the moment almond orchards are more or less a three dimensional fruiting space. They've got height certainly but I've got width and length as well and add some depth if you if you like. So, we're moving away from that in order ultimately to shake and catch. The industry wants to move away from shake onto the ground, which is an uncontrolled space that potentially produces some results and some issues for them, to a situation where they shake and catch the fruit. So, it doesn't go onto the ground, it removes that problem. So we'll be looking at a row crop very much a row crop, but with the dimensions or the layout of the orchard, is the bit we don't know, and the light experiment if you like, trial, is trying to provide the design specifications in one of another term.
  2019 - Almond research update
  Video: introduction and progress of orchard development for the high intensity plantings
  Dr Michael Treeby, Senior Research Scientist from Agriculture Victoria, introduces the research on intensifying almond orchards, with a look at the progress of the orchard in December 2019, at the Nut research orchard in Irymple, Victoria.
  Transcript - Research into intensifying almond plantings with Dr Michael Treeby
  This trial has been established to try and answer some questions around the intensification process for almond production. Most people's initial response to trying to intensify almond production is to just plant more trees together, closer together. And in a sense, we don't really know what's going to happen when we do that.
  We know that they will probably fill out the space between the trees more or less sooner or later, depending on how many trees we have. We don't know what's going to happen as far as tree structure goes. So, in a sense, we don't know what sort of tree structure we need for that intensification or that more intensive production system.
  What we've planted here is a fairly extensive trial, about six hectares. It's three or four rootstocks, which will impart varying degrees of vigour to different scions and the different scions are all the new University of Adelaide varieties that have been recently released and are being adopted by industry. They're all self-fertile as well.
  They all have different tree structures. Some branch more, some weep, and we don't know what that might mean with the different rootstock underneath it, in terms of what sort of structure will be suitable in the future for intensive production systems. That's exactly what this whole thing is about.
  Filling out the space, what happens to that tree structure has a function of that spacing and then of the rootstock underneath, which may well change the tree architecture in ways we don't quite know yet. So, the difference in vigour is obvious now and will become really obvious in those more intensively planted, those trees that are planted closer together. They will fill out the space quicker. We don't know whether that has a negative effect or not. We know that they will get pretty crowded, and probably start to look pretty ugly, but we don't know whether that really matters. That’s more or less the guts of it.
  The vigour will be affected by the rootstock and the scions to some degree, but mainly the rootstock, and as we plant them closer together, does that mean that they would just simply start going expanding outwards? We simply don't know. In some senses the treatments, the extreme treatments are extremes to try and prove the point, to push the point, and to accelerate the trial, if you like, the progress in the trial.
  Almond research at the Mildura SmartFarm
  The research platform was established by the Victorian Government as part of ST16001 – Advanced production systems for
  temperate nuts with co-investment from DAFF (previously known as DAWE) through the Rural Research Development for Profit Program. The project was administered by Horticulture Innovation Australia.
  Additional investment was provided by the Agriculture Infrastructure and Jobs Fund, Agriculture Victoria’s SmartFarm Initiative,
  Victoria’s On-Farm Internet of Things Trial and Agriculture Victoria’s Smart Traceability Design and Innovation program.