The Tatura Hedgerow System for Walnut Trees
Mobile: 0407-335 231
Organization:DNRE: Department Natural Resources and Environment
Private mailbag 1, Ferguson Road
Tatura Vic 3616
Phone: +61 3-58335231
A comprehensive research project about soil management and growing walnut trees in Victoria, and exciting new developments for the industry in Australia.
I thought I would spend a bit of time talking about the history of the work I have been doing in the walnut industry. I come from a place called Tatura. For those who don’t know, it is a tiny place you can hardly find on the map, about two hours north of Melbourne. It is an irrigation area and there is a lot of dairying and a large stone and pome fruit industry. I have spent some 30 years in the stone and pome fruit industry and quite a lot of time developing soil management systems for various crops, including fruit trees, vines, nuts and so on.
When we think about irrigated crops, we are very fortunate in horticulture. There are a lot of things we can do with this crop that we can't do, say, in dryland farming. We have a high-value crop so we can pay for things. We have a perennial crop, and usually, we have a permanent irrigation system, so we can use water efficiently. When you roll all this together, it means that you can have a very successful, sustainable industry. Over the years, we have developed our orchards into hedgerows, so now, instead of having orchards with widely spaced trees the trend is toward hedgerows. We are farming a lot of trees, close together, so that we get high, early yields and we get small trees which are easier to manage. If it a fruit tree and the tree is short, it is easy to pick. If it is a nut tree, perhaps we don't have to worry about picking the nuts because they fall to the ground, the tree is easier to manage because we can get sprays, for instance, into the canopy if the tree is short. Ultimately, it is more efficient.
Also, Tatura is famous for the Tatura trellis, which is the Y-shaped trellis that was developed there back in the '70s. I had involvement in that project. That Tatura trellis is now being used throughout the world in various fruit-growing areas.
So, let's talk about nuts. This is a 70-year-old black walnut tree that was washed out of a river bank in the Ovens Valley. I was pleased to hear another speaker saying that these trees are very valuable. Black walnut trees like this are sometimes sold back to the United States for making veneered dashboards. Even the Toyota motor company are getting into this act, but they will only buy plantation trees, they won't buy self-seeded trees. The point I wanted to make here is, when you look at the root system of a 70-year-old tree, the bulk of the fibrous roots, the small roots that do a lot of the work in supporting that tree, are quite close to the trunk, in fact, within a metre of the trunk. Yet when we look at the literature, when we talk about growing many crops including nut trees, they all say we need a deep, well-drained soil....and so on. Uniform texture. And yet, why is it the text books also say that 70% of the root system might be in the top two feet? So, in fact, our philosophy ascribes to the fact that most of the useful roots are very close to the tree trunk, and we take advantage of that.
I wanted to show you a profile of the red-brown earth. At Tatura we have good quality water, we have a distribution system from rivers and reservoirs, and we have a good, Mediterranean climate, low rainfall, low humidity, low risk of fungal diseases. But, in fact, we farm some of the worst soils in the world. The top soil, for instance, is only 20 cm deep in many of our red-brown earths. Underneath is a mass of clay which is poorly drained, poorly structured, lacks a lot of nutrients, it disperses, slakes, does all the wrong things. We very easily get water tables perched on this clay layer and it caused many problems in the early days of fruit growing. Back in the '50s and '60s we lost entire orchards through waterlogged trees. For about 50 years we have been developing a soil management system to cope with this, and we found that there were a lot of advantages. In fact, by dealing with this soil problem, we actually discovered something about soil management and managing orchards.
What we have done in terms of soil science is that we worked out a number of standards for the soil, a number of physical properties. We like to have the ideal soil in the orchard. We called them 'specifications which are not non-limiting to tree roots.' I won't go through all of them except to say, in things like water management, if we can keep the soil wetted to within that range of 10 to 40 kilopascals of suction, we will find that water is not limiting the growth of the tree. If we keep the soil wetted to just the right amount so it is not too wet to cut off oxygen supply, and is not too dry to limit tree growth. In terms of root growth, to just pick out a couple: Air fill porosity--if we can keep it around 10%, we will have enough oxygen getting into the roots again, so it is not limiting tree growth, and so on.
Penetrometer resistance is another one. Sometimes soils can be wet enough but simply too hard for roots to grow into them. The roots can't extend. So, even if you have plenty of water, the roots aren't really moving and aren't extending so they are not able to develop, extend and pick up water and nutrients. We need to keep the soil soft, and so on.
Soil stability–even if we set up a brand new orchard, we cultivate the soil, set up the aggregates beautifully, nice and loose, aerated, wet, etc., that soil, if it is unstable, could very well collapse. After the first irrigation, the whole lot turns into mud, sets hard, dries, cuts off oxygen supply, becomes too hard for roots, and so on. So, once we have set up an ideal soil, we need to make it stable so it stays that way for a long time. We do this by adding organic matter, watering carefully, keeping the tractors off it so it doesn’t get compacted.
We have worked out these standards, some from the literature, some from work we have done ourselves, and we target these specifications. We try and get the soil there in the first place and then try and keep it there. If we have a problem in an orchard, we can go out and take some measurements, just like a doctor taking your blood pressure, finding out whether they are within the standards. And if they are not, we can identify the problem of why that orchard isn't performing.
The first thing we need to do is to optimise our precious resource, and that is our soil. I mentioned earlier we only have 20 cm of topsoil. What we do is move our best soil on to the tree line with a road grader. It is efficient, doesn't handle the soil too many times, it is cheap and it does a pretty good job. So we are simply moving that top soil into the bank where we need it most, that is where most of the tree roots will be, and this area then becomes the traffic line. In depth, the bank is usually about half a metre, depending on the depth of the top soil. In our part of the world, we are limited by the shallowness of the clay layer. So, once we strike the clay, we stop. Ideally, we get those banks as high as we can, and push that top soil that is in such short supply into the tree line bank.
I want to make a point here, that in the beginning we did a lot of this simply to improve drainage. We thought that if we created banks, the water runs off. Since that time, we find that we only have floods every 20 years. It is insurance against flooding. In the early days we used tile drains which are expensive and difficult to put in. Nowadays, we don't use tile drainage; we simply short-circuit the heavy rainfall and take it away with surface drains. But we discovered that trees did better on the banks even when we had a drought. So why was it those trees were doing better on a raised bank? We have given away the flat earth theory and almost none of our orchards now grow on the flat; they are all on banks. Orchardists in Victoria wouldn't dream of planting trees on flat country--they are all on raised banks.
The other thing we do...I mentioned earlier about making soil stable. We need to correct any deficiencies in the soil in the beginning. Our soils tend to disperse, they are unstable and contain dispersing clays with a high percentage of sodium, so we add gypsum to that soil to reduce the shrinking and swelling of the clay. We apply heavy doses of gypsum. We have created the bank, and we apply the gypsum to just a narrow strip, about 2 metres wide in this case because we are planting walnuts. With crops like vines we sometimes treat a one-metre strip.
So we only put our inputs on that tree line. The rest of the soil is left untouched. It is cheaper, and there is no point in improving the infiltration of the traffic line, the inter-row space, because we are simply using it as a road to run tractors on. We want that hard and able to shed water. So we have two different zones: a permeable zone where the roots will grow, and a roadway for the middle where the equipment runs. So we are sacrificing part of our land surface, but in fact, we find this is the best way. There are other inputs too: lime, etc. You will see later that we put organic matter there, too.
On some soils, we need to perform subsoil tillage. It is not necessary with all soils, but we find sometimes where we have impermeable layers, clay pans, we need to till the soil at depth, or subsoil. We do not use an ordinary ripper. In the '70s we just hired a bulldozer with big heavy tines, put the tines down to a metre or so and ripped through and thought we were doing a wonderful job. In fact, sometimes we were doing more harm than good, because we would end up with clods as big as footballs and a lot of dust in between, and not many useful aggregates of soil. You certainly couldn't use it as a seedbed. Some of these big lumps of clay that would come up would persist for years, rolling around like footballs.
We decided we had to put some science into this. We went back to our standards and worked out a system of using a winged tine. A lot of the work on the design of the tine was done by Professor Gordon Sp...(?), who worked out how to shear soil and create a nice aggregate using this winged tine. Like using a winged keel on Australia II. At the bottom of the tines, which were about a metre long, are these wings. They actually shear the soil and create a nice tilth down below ground level. We did it at three different depths. If you go too deep, you will heave up great lumps of soil. We measured the effects and found that yes, indeed, we were producing this ideal tilth. You note we are only treating the tree line. No point in ripping up our roadway.
The other thing we did was, we knew that once we tilled the soil, it was like an opened wound. If we should get rain on it, the soil could collapse. The orchard was already sown to rye grass to stabilise the soil, and as soon as the ripping is done, we sow it to rye grass. There is a whole technique involved there which I won't go into now, as it is soil science, and we are supposed to be talking about walnuts. Rest assured, there is a complete recipe there on how to get the soil right long before you get a tree anywhere near it. It sounds complicated, but it all happens in a few months. We can prepare the soil in the autumn and winter, and have it ready for planting in late winter or spring. Many of us are anxious to get trees into the ground, so what do we do? We order trees first before we have prepared the land. We rush out, plant them, no irrigation, no soil preparation--the trees fall over. I do urge you to get the soil right; get the foundation right just as you would do with a building. You don't put up the walls until you have the foundation down.
We looked at the effect of deep ripping on the Tatura soil, we looked at the effect of deep ripping and gypsum which go together, on the vigour of the trees. We measured the vigour of the trees simply by measuring the butt circumference. We put a tape measure around the tree and measure its growth. After about six years of doing this with walnuts and peaches, we found that the soil management had little effect on the tree vigour. We changed the soil properties, we made that soil safer so that in the event of a heavy rain or watering, there was drainage. But we couldn't show an effect of the tillage, and we wondered why. Walnuts are supposed to be deep-rooted. Again, we harked back to the idea that a lot of the roots are quite close to the surface, close to the tree trunk. So, in fact, it wasn't having a great impact on our tree growth. It is not to say on some other soils deep ripping may have an effect. These are irrigated soils and we provide irrigation on demand. If you are relying on rainfall, you may get a totally different picture. Under irrigation where we can turn the water on and off at will, we showed no effect.
I'm going to take a bit of a quantum leap. Graham introduced the subject of the cost of walnut trees. They are expensive. You can pay $30 a tree for a walnut tree. They are difficult to graft. If you wanted a large quantity of trees, it is difficult to find them because we simply don't have the nurseries producing them. I visited the Californian industry twice and took great interest on the work done over there on direct seeding of nut trees. It still goes on; it was done at the turn of the century and beyond and still continues today as a cheap alternative to establishing walnut orchards. Rather than rushing off and buying walnut trees from a nursery, you grow your own. The idea here is that you direct-seed a rootstock, allow it to grow for a year or two, graft it in the field and presto, you have a tree. In fact, some research suggests that you get a better tree, because the tree is never moved. You plant two or three seeds at the planting site, and the tree grows from there.
The seed is primed. We store the seed in wet sand, it gets its chilling requirement, it imbibes water, starts to swell. In fact, sometimes it starts to germinate before we get it to this stage. Essentially, it is just placing a primed seed in a hole, ready to go, and in spring up comes a rootstock. The reason we plant two or three seeds at a site is because we get seedling variation, plus some seeds simply don't germinate for a whole host of reasons, or seedlings may get damaged. Because we are dealing with delicate seeds or seedlings, we don't want any spaces left in the orchard. The seed is cheap, a few cents per seed. We choose the most vigourous one, keep that one, cut out the others, or transplant them. So we end up doing a bit of seedling selection for vigour.
Then we can go along and graft that tree, or patch bud it, T bud it. This seedling was sown in early spring. By mid-summer it has two buds on it. Once those buds have calloused, you have a grafted tree. They can be cut back four weeks after budding. Shoots will grow, or they can be simply left as dormant buds until the following spring. We have teams doing this in Victoria on quite large properties, some would be twenty, thirty hectares or more. Teams of about six people come through and can do a thousand trees a day. They often put two buds in just to double the chances of take.
If that bud is left over winter as a dormant bud and the stock is cut off just above the bud, and the bud is forced away, you can get this sort of growth, three metres or more. It shows you the sort of vigour you can get. That is two season's growth. It is possible for those trees to grow two and a half centimetres a day. If that tree is managed properly, you get into production cheaply. Even if you get contract people in to do the budding, the cost of the trees is reduced to about $3. If you do it yourself, it doesn't cost you anything but a lot of hard work.
Our soils, many Australian soils, lack organic matter because of the arid climate, shallow soils and the way the soils are managed. Typically, our soils have less than 2% organic carbon, very, very low on the world scale. We need to increase organic matter levels to improve the stability of the soil, to make it more porous and stable. In an orchard we can afford to do things you can't do in other industries. We can import straw and apply it to the tree line, using machinery. Thirty years ago we used to spread straw using square bars and a pitchfork; very effective but terribly expensive and slow. In those days, we used to farm the whole orchard, use enormous amounts of straw. You would have this huge fire risk with piles of straw over the entire orchard. In the new system, we only spread the straw on the tree line in a strip about two metres wide, and we adopted machinery from the grazing industries such as a round bale hay feeder. You simply drive along the row, the straw bale unravels and drops the straw on the tree line, and hey, presto, the job is done. In fact, now there are contractors going out and doing that. We first introduced it to the viticultural industries about 25 years ago. It wasn't adopted very widely at that time. Just late last year I was in the Clea (?) Valley in South Australia and I saw they have rediscovered this straw mulching, and it is everywhere. And they are saying, "Hey, this really works!" I guess it had to go through this incubation period before it was adopted.
One of the reasons we set up the trial at Tatura, which is now about 8 years old is we wanted to be sure we could grow walnuts on these shallow soils. Was it really going to happen, or would the whole system fall over? Did we really need deep soils to manage a supposedly deep-rooted crop like walnut trees? We had to prove to ourselves. Again, we tried to show that deep ripping the soil, or a deep soil, was a benefit. We couldn't show this. Of course, we were managing our soils quite differently to the way they were managed in the past. This is mean root length, and we have two treatments. G&R refer to gypsum and ripping. No G&R is the control. We found there was no significant difference between the trees in rooting depths, whether we ripped the soil or not. There were some subtle changes in soil properties that would affect drainage, but not on root growth.
The other thing we discovered was that root densities close to the surface, right up under the straw, were extremely high. We were getting a network of very fine roots, growing right up under the straw. You only had to scrape the straw away and you could see the walnut roots growing right at the surface. And why wouldn't they? Right at the surface we have plenty of water, plenty of aeration, the soil is soft with plenty of biological activity. In fact, when you scrape the soil away, dozens of earthworms jump up and greet you. Biologically, the soil is very active and you can actually see the earthworm tunnels and the casts, so the soil is very porous. The most useful worm to us are the European ones that were introduced in the early days of settlement from soil that came as ballast in the holds of ships. We don't add the worms; if you provide the food, the straw and keep the soil moist, the earthworms will multiply very quickly. We did a survey of district orchards which, at that time were cultivated with no straw mulch. We were lucky to find, on average, fifty earthworms per square metre. In our system, we find up to two thousand per square metre. Normally they stick close to the surface near the food supply unless the surface dries out, then they are forced down deeper and tend to go into hibernation.
That is what is happening: we have moved the root system, shifted it up close to the surface, where we can control it. As soon as we apply irrigation, or it rains, the roots very quickly pick up the water and any nutrients we apply, and away it goes. So the roots are growing very close to the surface, encouraged by the protection offered by the straw mulch.
The straw mulch does several things. It slows the evaporation rate so the soil stays moist and lets the roots grow there. It reduces soil temperature, it provides food for earthworms. The earthworms actually ingest the straw and drag it down the tunnels and incorporate the organic matter in the soil. It raises the level of organic carbon. We are also encouraging other microbial activity in the soil by the breakdown of that organic matter. And we are protecting the soil surface from heavy rain, so we don't get crusting of the soil. If you get heavy rain on bare soil, it tends to slake and set a firm crust, and then it is difficult for water to penetrate that crust. We have never had a problem with the straw and fire hazard, or collar rot or insects in the thirty years we have been using the straw. The straw is very fluffy when it goes on, but after a few irrigations, it pack down. By the end of the growing season, most of the straw has decomposed and there is hardly any left. We have had no problem with the straw blowing in the wind or the air-blast sprayers. We usually renew the straw every year. Sometimes it will last two years, but our aim is never to let the soil become uncovered. As soon as that happens, the porosity disappears, the soil crusts, and so on. I might add, if there is a risk of frost, which we get in certain areas, we delay the application of straw until the risk of frost has passed, because it may interfere with air flows.
We have tried other mulches: rice hulls, lucerne hay makes a wonderful mulch but is expensive. We did try sawdust in the early days, but that can introduce other problems. We have tried chipped tree foliage, but you need to be careful about which species you use so as not to introduce problems. We don't like to use hay because you can introduce weed pests. The straw is clean and cheap. At the moment, we buy in straw at $10 per roll. It is pretty hard to beat. A company in South Australia is now taking household waste like tree prunings, shredding them, composting them and applying it to vineyards, but it is quite expensive. The dominating factor is the cost: any organic matter is better than none, as long as you are not introducing another problem.
Talking about roots...again with the two treatments...the bulk of roots are down to about 45 cm. So there is a huge mat of roots up in the shallow layer, nothing much down below.
We proved to ourselves that, yes, we can grow walnut trees on the shallow soils. Although deep soils may be a useful buffer against things going wrong, they are not essential to produce healthy trees. This opened up a whole new challenge for us. Perhaps we can grow these tree crops on marginal soils. It would be wonderful to have Californian soils with 30 feet of topsoil, uniform texture, beautifully drained, structured and everything else. But we simply don't have them.
I wanted to talk a little bit about yields. We set ourselves a target of producing 4 to 5 tonnes per hectare at maturity. These are some of the yield figures from our trial. The trees started producing commercial yields of nuts in Year 4. The district average of walnuts, even from 50-year-old trees in Victoria, has been around a tonne to a tonne and a half per hectare. There aren't many orchards producing more than that. There is a new generation of orchards coming along which will. Yet in Year 4, our first crop, we were getting 0.2 to 0.3 tonnes per hectare. By Year 5 we had pretty well caught up to the district average, and by Year 6 we were getting close to 2 tonnes per hectare. Again, you will note that there was no difference whether we ripped or did not rip. So we have discounted ripping for these soils.
This is what we have come up with: the Tatura hedgerow system for walnuts. The trees are planted at 6 by 3 metres. In fact, we are toying with the idea of going even closer. These are the same species of trees, 6 by 3 m spacing is used in California, too. It is about the closest I have seen of commercial plantings of walnuts. The orchard takes on a completely different appearance. It starts to look like an apple or pear orchard. Nothing like those wonderful old plantings where you see widely-spaced, huge walnut trees, cattle grazing underneath. A wonderful sight, but it is simply not economic.
These little trees are only going to grow to 5 or 6 metres tall (tape ends and is turned over)
...a mini-flood at the dripper. What we are looking for here is not only to supply the tree in terms of water, we want to wet the soil evenly, slowly so it doesn't collapse. Because if you saturate a soil, it can slake and slump, and we want to avoid that because we have gone to an awful lot of trouble to set up this ideal structure, and so we water very carefully with microjet sprinklers. The microjets, of course, can apply just a few millimetres of water. The distribution is reasonably uniform, and we are working on better microjets. It is much easier to spread water in air than it is in soil. If you apply it at a point source, you have to move the water from the saturated zone out through the soil. You get a gradient of wetness in the soil. What we want is uniform wetting so we can irrigate when we like. We can press a button, set the time clock, or whatever, and apply just enough water to keep the soil wetted between 10 and 50 kilopascals of suction, and the roots are happy and get enough aeration.
These white tubes are potentiometers in this trial plot, where we monitor the soil water at four different depths. You wouldn't need to do that on a commercial orchard. We wanted to keep a close handle on things in this trial.
These are just a few Chandler walnuts. They are one of the most popular cultivars in the world, developed at UC Davis. They are a dry climate walnut, one of the lateral bearers. Nuts are borne in clusters on just about every lateral on the tree, as opposed to the earlier French varieties like Franquette that tend to produce nuts only on the tips of major shoots. They are also a very high quality nut. The ratio of shell to kernel is around 50%, so it is quite high. The nuts tend to be a mid-season nut so they are not flowering too early, which avoids some of the risk of walnut blight, caused by spring rains. They are a heavy bearer. Our trial was largely based on those. In this country we have a number of these lateral-bearing types, mostly from California, so we are fortunate that they were introduced some years ago.
This is a commercial orchard, seedling trees direct seeded in that paddock. We sometimes put the sprinkler quite close to the tree in the first year, particularly with a seedling because it is a very tiny plant, and very dependent on the sprinkler. Ultimately, we prefer to move the sprinkler out to the space midway between the trees, because we have a problem in this country with phytophthora root rot. Phytophthora is a water mould that develops in saturated soils and multiplies very quickly. There is an inherent problem with putting a sprinkler close to a tree or tree guard. When the sprinkler strikes any obstacle like the tree stem, the guard or a stake, you get a high concentration of water at that point, you get flooding, and that can encourage root disease. Once the seedling tree has developed its root system, we move the sprinkler out and try and arrange the sprinkler so the wetting pattern stops short of the tree trunk so we don't encourage root rot.
Water management is one of the most powerful tools you can use in the orchard. Of course, with irrigation, we are getting better at it. Try to keep the soil wetted in the ideal range so water is not limiting to the plant. If we take saturation as zero...when the soil has drained under gravity, there is a certain amount of air space in the soil, yet it is as wet as we would like it to be, we tend to call that field capacity. It is around 8 or 10 kilopascals. We find that water is readily available up to about 40 kilopascals of suction, or tension. As the soil dries out, we get to a point like 1500 kilopascals where the plant wilt and dies. We don't want to get up to that range. By turning the sprinklers off and arranging our irrigation timing, we can try and keep the soil wetted in the best range. The soil goes through wetting and drying patterns, it is not a straight line. The trick, as managers, is to be clever and never let the soil get too wet, which cuts off oxygen supply to the roots and root disease develops, and yet we don't want it to get too dry, because the tree has to work too hard to pull the water out of the soil. It is using a lot of energy and its growth rate slows down.
So we use tensiometers. There are lots of other instruments you can use but tensiometers are cheap, simple and quick. Here we have a keen scientist just measuring in the walnut orchard. There is a little vacuum gauge measuring the vacuum in those tubes. That gives us a direct reading of how tightly the water is being held in the soil. We do this before each irrigation. We can adjust our irrigation and so we can try to apply just enough water to wet that soil up again.
The traditional way of producing trees is to produce them in a field nursery. This is a shot of a nursery in Tasmania managed by Webster Walnuts. We visited there last year. There are some 120,000 rootstocks there, of which about 60,000 have been grafted. They are using these trees largely to plant up their own orchards. They have some joint venture schemes going. So this is the traditional way: you grow the rootstocks, you dig them up, take them into a room, you whip-and-tongue graft them, get them to callous, then you plant them out in the orchard. Beautiful trees, very good quality, but of course, expensive. They are barely supplying their own needs. There aren't enough left over to supply the industry. That is certainly the biggest walnut nursery in Australia.
If you want to use grafted trees, there is another way. That is to do some micrografting. This is a seedling tree that has grown...the rootstock has grown in a little gro-tube. Seed is imported from the United States. The stem on this tree is only about 4 or 5 mm in diameter. It is micrografted, a whip-and-tongue graft with a bit of scion material on the top. Technically, the whole lot, once it is calloused, could be planted out in the orchard or grown on in a pot.
The small scion wood is collected sometimes by hard-pruning the trees and getting them to send out a lot of fine shoots, and you take these tiny tips and micrograft them. The whole lot is done virtually within just the space of a few months. In this technique, the idea is to develop a fibrous root system so the tree transplants well, and discourages the tendency of the tree to produce a strong tap root. Bearing in mind that pot is only about 5 cm in diameter, the name says it all: micrograft. It can be risky. We haven't done it ourselves, but one nursery has had some disasters with that type of propagation.
At the moment we are going through a rapid expansion in the walnut industry. There is an enormous amount of interest; people want trees, there are a lot of requests for planting stock. So we went back to the direct seeding method. It is cheap, it is simple, it is very forgiving. Almost anyone can put a seed in the ground and have a tree growing. Also, it allows you to grow this rootstock...as I said earlier you have this wonderful black walnut timber. In fact, what some people are doing is letting the rootstock grow for two or three years so it is several metres high, then you can actually put a bud in at two metres height, grow your timber tree and the top produces nuts for thirty years. Then you saw it down and use Jaguar dashboards. It works quite well. You have time to get the orchard established, you don't have high costs, and any trees that don't get grafted turn into timber trees.
We thought that that needs revisiting. But we found that to do the job well and make it economic, that ideally, the trees should be grown from a seed and grafted in that one year. Now, some people didn't make it; the trees weren't quite big enough to graft or patch bud, so they had to wait two years. We want to improve on that.
The other problem that most everyone had was the fact that they couldn't control the weeds, because you have a little seedling tree coming up, you are feeding it water and nutrients and the weeds are taking all that stuff on board. So there is strong competition. We don't have a herbicide selected enough to protect the tree yet control the weeds. We decided we needed tree guards. We utilised the technique used in the viticultural industry. This just shows a row of trees. We tried some very tall tree guards, some were about 90 cm tall. Now we have gone down to 500 mm tall. This shot was taken in mid-summer, the hindsii black walnut seedlings planted in a nursery row. In the foreground the weeds have been controlled with glyphosate so we are able to weed-spray those trees. In fact, it can be done with a tractor, you don't have to hand-weed. The tree is protected in the tube. On the other side, it is covered in weeds. It illustrates the point.
The other thing we are doing is protecting the little seedling tree from wind, from rabbits and hares. We are providing a microclimate inside the bag. One of the fears we had was, will the little seedling tree get too hot enclosed in a little plastic tube. We found that if the tree was well-watered, even tiny seedlings survived quite well. I don't know what the temperature was getting to in those bags, but most of the trees had their tops out of the bag before summer temperatures set in.
The other thing we do in the field is use steel rod as stakes. We take an 8 mm high-tensile steel rod, poke it in the bag. This rod is about two and a half metres high. We found we had a nice, flexible tree stake, quite cheap compared to timber. It is recyclable, you can reuse it. We believe the flexing is useful in helping the tree develop its strength. It is something you can tie the tree to easily--we used taping machines. It is easy to get a small tie around it, unlike a wooden stake.
The process has been that we take seed, put it in coarse sand to prime the seed, the seed takes up water, goes through stratification, its chilling requirement. Then we transplant it into the field. Now, what we are doing is getting rather lazy: we take one of these tubes, put a staple in the bottom, put a handful of sand in, two or three seeds, another handful of sand, stack them in boxes. The seed gets stratified, starts to germinate, we sort through them and take all the best seedlings. We take them out to the field and in one fell swoop we auger a little 10 cm diameter hole, pull the staple out or slice the bag, drop the whole lot in and put a stake in. We have stratified seed, germinated it, and staked it and put the tree guard around. That's what we are playing with. It is early days yet. For the commercial growers who have taken it on, it has saved them an enormous amount of work.
We are also looking at in vitro propagation. It is something we are not doing in this country. There is a commercial company in Spain that has successfully mastered this technique. It is both tissue culture and in vitro propagation. Tissue culture is where you are dealing with a handful of cells. It is a very delicate technique in a sterile laboratory. They are also producing little plants from tiny little cuttings, little nodal cuttings. The whole lot is done in a test tube or a glass jar in a very sterile, controlled temperature environment. You produce little plantlets that can be multiplied up quickly, grown on an agar substrate.
The other technique is that you take a piece of walnut stem, chop it up with one bud. Then that stem and bud is placed in a test tube with agar. The little plant grows. Then the little plantlets can be potted up in these gro-tubes. The advantage of this system is that you can clone everything. You can clone the rootstock; at the moment the industry is based on seedling rootstocks, which can vary enormously. This way, you can select the best rootstocks, resistant to root diseases, vigourous, whatever. You can grow the rootstock, then graft it over to the best cultivars, so you have the best of both worlds. It also allows you to multiply up large quantities of trees from a small amount of material. We have some people now who are planting very large orchards, say a quarter of a million trees. You simply won't get them in the country, so we need to go with these techniques.
Sometimes the trees are grown on their own roots, not actually grafted. You just take something like a Chandler bud, it grows its own roots, grows its own top. These trees have proven to be extremely vigourous. They grow very fast. We used to do the same thing with peach trees, growing them from little cuttings like this, because the plumbing is not interrupted as it would be with a graft. But you don't have the resistance to root diseases that you might have with some rootstocks.
We operate in groups, so we have a group of farmers in central Victoria. We meet once a month. These people run mixed farms of grazing, cropping and other things. They are looking at diversifying into tree crops such as walnuts.
Q. I was impressed with your soil specification analysis. Is there anything there that doesn't apply to other tree crops?
A. No, the specification should be applied to all soils, even the best soils, but in fact, some of those specifications are already met. For instance, in some of the krasnozem soils, very well structured, you don't need to do some of those things. We have noticed over the years that even the best soils will suffer under bad management. Compaction will occur, but it takes longer. With ours soils, it happens within twelve months. In these other soils it might take 50 years, but you still need to be careful.
Q. We have a lot of sloping land in WA, can you apply the same principles along the contour?
A. Yes, one of the things I mentioned about sowing it down to a cover crop...we use rye grass, pasture if you like. The idea of leaving raw soil around is very bad for the structure and collapse can erode. What we do...get all the engineering done first, roughing out, and sow it down immediately. If it is done in autumn, autumn rains will stabilise that bit before the winter rains set in. If you do any cultivation, make sure it is stabilised again.
Graham Fellows: We have found cover crops very important over here. This year we are going along a project with Irwin Hunter. They developed over the years a cover crop which is based on growth of rye grass because it is the deepest growing root structure of all rye grasses. They have blended this with various clovers to introduce into the orchard the good wasps, etc. We are introducing this on three properties this year on a trial. We are going one step further, and it is a mixture of two or three rye grasses. This is a system Harold has developed where we get these roots dying away very quickly, forming airways and waterways. We are also getting a good, dense cover on the surface, and we are introducing things like crimson clover to attract in the good bugs, the good wasps. Of course, all these things have to relate to soil types. I started following Harold's work, the Victorian work, to the letter, and I fell foul. For one thing, gypsum was a problem here with our soils. I actually got the soil into the worst condition by using the gypsum that we used. The gypsum used in Victoria is a by-product of the fertiliser industry, ours is mined out of Lake Grace, absolutely full of salt and totally useless for what we wanted. And, our soils are so different. In Victoria you are working on mostly alkaline soils, we have acid soils. You have to bear this in mind. It is a bit horses for courses.
Q. You mentioned eliminating the previous pasture....
A. The way we see it any plant is better than none. You leave it. So when we say sow ryegrass...ryegrass is a weed in our part of the world, it is cheap, easy to sow, and so on, it does do a good job. The reason we use grasses is because they have a fibrous root system, deep tap root. Weeds then tend to come in, but we don't despair, we just manage the weeds.
Graham Fellows: When we are doing a job, we don't touch the existing land at all, unless there is a problem weed there. If it is just basic pasture that has been well-maintained and is in reasonable condition and there is not any weed burden, we do not touch it until we come to the road grading scheme. Of course, once we come to grade that property, the whole surface is gone. This is usually done as soon as the land starts to get a little bit of moisture on it in the autumn, so you can control the soil, move the soil. But then we still do a certain amount of ripping. We only double deep rip with winged tines on soil similar to what Harold has in Victoria. We just do a single rip. We only use a winged tine if it is necessary, purely and simply to break up any hardpan and to bring the area of the tree line into friable condition without creating that problem of balling up and creating more problems through ripping. We rip selectively where we have light sandy soils, just to open up the soil so we have a good bed for the trees to get established in. Then we go straight into that cover crop to prevent erosion and to start the development of our soil management program using that cover crop.
Q. Would it not be an advantage to have a cover crop that is nitrogenous?
A. It is useful, but our system is a high-input system, and it wouldn't be nearly enough. It is barely enough for the cover crop. Unless you are growing organic produce and getting a premium price it is simply not worth it. We can now efficiently put nitrogen through the irrigation system. Compared to the days when we were flood-irrigating orchards, we are using about one tenth the amount of nitrogen we used to. It is well-targeted, only treating that tree line strip. It is acceptable to have sheep in the orchard, but not desirable.
Graham Fellows: We have a law here--nobody goes over the tree line. Once that ground is prepared, you would get shot with a 12-gauge if you drove a tractor, a ute, a 4-wheel motorbike over. The tree line is purely and simply for growing trees. Harold talked of the 6 x 3 spacing; with our land here being readily available and reasonably cheap, I use and 8 x 4 planting because it cuts down on the amount of pruning later on. It helps with the development of the orchard from a cost point of view, because you are putting in approximately 320 trees per hectare compared to 550. Research coming out of California is showing from Year 10 to 12 there is very little difference in the total tonnage per hectare from an 8 x 4 to a 6 x 3. In my early plantings at 6 x 3, I actually pulled out every second tree.
Q. Harold, would you comment on that?
A. Well, it depends...Graham's right, you may elect to plant on a wider spacing and use fewer trees. The closer you go, the more plumbing you need and the more trees. The more trees you have to manage. If you are pruning a tree every five minutes, it is almost twice the number of trees. If you look at the returns from your investment on the spread sheet, you only need to increase the tree number very slightly, say 10%, and it shows up very favourably on the balance sheet, assuming you have the cash flow and the resources to do that.
There are a lot of other factors too. A lot of our work is involved in controlling tree growth. I was speaking to someone in the macadamia industry; they based their spacing on either 12 or 15 metres. Now, they are looking at new investments where they are going down to 7 m x 3.5 m. As you know, a macadamia tree is a very large tree, it is a tropical tree--deep soils, high rainfall, so there are real problems controlling vigour. We have seen some photos of hazelnut orchards where the trees are shading out, and you start losing production. The aim is never to get to that situation. That is done by clever irrigation, tree training, which means pruning the tree to a specification so that in time you don't set a limit on production: you don't start shading out the bottom of the tree. That takes deliberate effort, intervention. You can't just let the tree do what it likes. But, it pays off. The apple industry has developed into a science where you know where every limb is going to go. You put a ruler against it and say, "I will have a scaffold at this point." I don't think we have come near that with nut trees. In our early orchard, although we are pleased with it, we didn't know pruning. We just grew them the way the industry grew them. We wouldn't do that again. We can do much better.
Q. What is walnut blight?
A. It is a bacterium, endemic throughout the world. The difficulty is that it multiplies so quickly under moisture, rainfall and high temperature. So, unlike a fungus, a few days can mean a lot. Our strategy has been that you will never get rid of it. In the early days we were timing our sprays. We would spray fortnightly, and so on. But nowadays, we tend to treat it as we did blackspot in pears. If rain is forecast, we put on a cover spray. If we get more than 5 mm of rain and more than 20o, within hours of the end of the rain we put on another cover. And then we might not spray for another 2 or 3 weeks if it remains dry. That has proven to be quite effective. Very targeted control measures. If you get one small bit of infection in the top of a tree and it rains, it will very quickly spread through the whole tree, and you can lose half your crop, too.
Q. Have you been using bacterial control, with BT, for example?
A. No, we only use copper. It can still be done, but you must have this sort of targeted program and respond very quickly. So we make spraying the highest priority. It doesn't matter if you are halfway through slashing or going to town, spraying takes priority. I used to do a lot of this in pear control. We left the spray pump permanently hooked up to the tractor for that reason. It was almost like a fighter force--you did that first thing in the morning before anything else happened. That works quite well. Copper sprays are accepted in some organic circles. As I understand it, copper sulfate is not classed as an agricultural chemical, as such.
Graham Fellows: Getting back to the block...a lot depends on your climatic zone. In Victoria, they get summer rain. In our area, at Deeside, we can almost guarantee we will not have rain between the end of October and March. If you move closer to the coast, I have never seen a walnut blight spot on any of my 800 trees, mainly because all of those trees are late-bearing. They all leaf out after, or as close as after as we can get to the finish of the rains. This again is choosing the right crop for the right place. Where you haven't got the chance to do that, simple copper sprays control that. If you select the right cultivar in the first place.
Harold Adem: We have a distinct advantage with the harvesting of walnuts. It is a large nut, it is well-known, it is round. There are basically two machines. One is the shake, sweep and pick up system that is used in the US. That is certainly efficient and it is fast, but it is expensive. You are looking at hundreds of thousands of dollars if you are thinking of three machines. In Australia we have two manufacturers who produce fingerwheel machines, I call them. The idea was developed in the US and was used for picking up golf balls, I believe. Basically, all they do is roll along the ground and is like a giant hair brush. Nuts are trapped between the plastic fingers and as the roller comes around, another set of fingers combs them out. It just elevates the nuts into a hopper on the conveyor. You push these machines along; they come in all sizes from a little pedestrian machine to one that is about a metre wide that you can pull with a motorbike to much larger machines. They start off at a few hundred dollars. The motorbike version is a couple of thousand dollars, I think. There is a tractor machine for about 6 or 8 thousand dollars. It does offer a cheap alternative for the developing orchard where you have young trees. The nuts are mostly near the tree line. It is also handy for cleaning up the orchard. There are a number of these machines around the industry. They were really developed for the macadamia industry where there are at least 600 machines operating. It is fairly selective, but still picks up sticks and leaves. Unlike a sweeping machine that sweeps up everything, soil included, these tend to be more selective. Ideally, a blower is useful. If the orchard is well-irrigated, we don't get a lot of leaf drop until after harvest. If the orchard is not irrigated, you can have a problem. The machine will actually pick up in grass. We trialed it in grass about 10 cm high. If you are using the fingerwheel machine, you usually wait for the nuts to fall, rather than shaking the trees. You go through once and pick up everything in the orchard. While you are grading that lot, you go back in a week's time and have another go. Do it three times, and you have picked up most of the nuts.
Graham Fellows: With these new varieties, the husk tends to stay on the tree for quite some time after the nut has dropped. Generally, if you go along with an ordinary orchard mower just before nut drop, if you have a blight problem or some other problem that causes early nut drop, you can clean them up readily. You have a good ryegrass base of the cover crop which you mowed nice and short. Then you go along with this machine and it will pick up virtually nothing but nuts and you don't even have to sort the husks out.
Q. What are the chill requirements of the new varieties?
A. (Graham Fellows) Very similar across the board. We do need that climatic zone to grow in. You cannot grow them near Perth. Our two speakers who were not able to get here are actually working at the moment on a project which aims to develop a nut based on neotropica, the tropical walnut. They are trying to breed a commercial walnut which will not require so much chilling. Generally, unless you have a microclimate, you have to go south of Dwellingup to grow commercially. You can grow walnuts, sure, but not commercially. They will have all sorts of problems. You won't get the fruit set. You need to be in this lower southwest area that we talk of because you must have that climatic zone at this stage for the cultivars that are available. The figures are approximately 700 hours below 8 to 10 degrees. But, some of those hours need to be a lot lower than that. You couldn't have 700 hours at 9 degrees, commercially.
Q. What lifetime do you anticipate for these orchards?
A. (Graham Fellows) There is living proof there of 140 years. My philosophy is that I don't intend to leave the same trees in. I am already pulling certain things out. Like the apple industry...where will you find Cox's orange pippen, whatever, these days. They turn over so quickly. These trees are based on Juglans regia, they were bred from the same basic stock that Andrew Muir brought into this country. There is nothing to suggest that they will be different.
Harold Adem: People in California tell me that the economic life of a walnut orchard is thirty-five years. That doesn't mean to say the trees will die. Markets may shift, as they do with other crops. One of the issues is that if you do start getting root diseases moving through the orchard and you are losing trees, you may find that you are farming a large area with only a handful of trees in it, so it isn't very economic.
Q. Is there any information yet on the susceptibility to diseases?
A. (Harold Adem) So much of it is linked to management. One of the things we strive for in an orchard is uniformity. It is not going for the highest yield. I'm sure you could do that, but in doing it that way you may risk the orchard. Consistency of yield is much easier to manage. One of the reasons we found the tree line, having a sprinkler per tree and all that, is to try to get the trees as uniform as possible. Try and use clonal material, because then you can manage it carefully.