Acotanc: Alley-Farming Tree Crops in Semi-Arid Environments

Alley-Farming Tree Crops in Semi-Arid Environments


Dan Wildy
E-mail: [email protected]

Organization (2004):
Dan Wildy, Research Scientist
Albany Forestry Research Centre
Forestry Research Institute
Oji Paper Co., Ltd
Loc 5762 Albany Hwy, Albany, Western Australia, 6330
PO Box 1891, Albany, Western Australia, 6331
Phone (08) 9845 3160
Fax (08) 9845 3158
Mobile 0429 116 325

Some factors to consider about planting oil mallees.

I am a forester and I am doing a Ph.D. at UWA. When I was doing Forestry, I did a bit of work experience with oil mallees. I cooked up the first oil. I am working out how to grow them so they don’t die, and how much water they use.

I'm going to talk about some of the lessons we have learnt in the development of the oil mallee industry. It is relevant because there are lots of new ventures being thought of at this conference. These are things we have learned on the way to getting a new venture up and running, and pitfalls that you come across. Then I will talk just a little bit about alley farming.

A brief overview: the thing that we are working with; the wheatbelt; and the need for commercial tree crops. These are some of the things you need to think about if you are developing a new industry in the arid lands, and how oil mallees seem to fit in well, so far, with those issues.

This is a quick picture of the wheatbelt, just to set the scene; the native, tall, woody trees, the crops, 16 million hectares or thereabouts. This shows the industrial nature of the farming system. You have to think of crops that can go into an industrial system like that, if you want to get a lot of people to do it, soon.

Salinity is a consequence of all dryland agriculture, but it is particularly bad in WA because of the low transmissivity of the soils and the high storage of salt in the soil, and the fact that it is a very flat landscape that doesn't drain away. In fifty years they predict that 30% of the landscape will be salt-affected, which is a loss of productivity, which leads to a loss of infrastructure in terms of roads, damaged buildings, loss of biodiversity, rivers and remnant bits of bush. One of the beauties of salinity, in a way, is that it is very visible. Everyone can see it and it is big news and everyone is trying to fix it up. It is not something that you can't comprehend. There is a lot of effort going into it and a lot of money being spent so far, and a lot of money to be spent in the future. I believe that one of the ways to solve the problem is to treat the cause of the problem rather than the effects. If it is possible, the most sensible way is to develop tree crops that are compatible with the farming system so that there is green plants growing through the summer, using water and keeping the water tables at bay, and at the same time making money so that it is readily adopted.

With alley farming, there are benefits and disadvantages. Weeds get harboured right next to the trees, because they don't want to spray the trees if they can help it. Alleys are normally a multiple of the width of the biggest machinery, anywhere from 40 metres to 100 metres. Once you get out to 100 m, you have to have a pretty thick belt of trees to balance, to get the ratio right. But then you lose the productivity in the middle of the tree belt, which is like being in the middle of a plantation, and they grow at a quarter of the rate of those at the edge.

If you have a coppiced tree crop, the roots never have to get really big. There is always a ratio of shoots to roots. It is bad management to have a huge root system. The act of coppicing also reduces light competition for the crop. Oil mallees are very deep-rooted. When the shallow roots are ripped, they break up and make an allelopathic effect. Chemicals naturally within them slow the growth of the wheat. It is one of those weighing-up things: you get a smaller mallee crop but more wheat growth. At a study site I have at Killany, there is a hardpan, a silcrete layer between one and eight metres below the surface. You can dig down where it is not too deep and you can see how the roots go down, hit the hardpan, run along until they find a crack, and then they disappear. You can never dig through that, so you never find out for sure. But the fact that the roots are still pretty fat means they are going through and not stopping at the hardpan layer. When you cut the trees down regularly, you will get rid of most of the problems such as shading and big roots going out. They can grow back quickly.

There are species that will grow on salt-affected land, but that is not really the place to put them. They will probably die eventually because the salt builds up underneath them. They draw out the fresh water, the salt accumulates. The growth rate is really slow. If you are going to spend, say, $10,000, you would be much better off putting them in a spot where they will grow well. That is not always where the wheat grows best, either. The trees grow best in the yellow sand because they can get their roots through it easily. I think you have to grow tagasaste in white sand. Most tree crops do like the lighter country, and that is where a lot of the recharge is happening.

In the low-rainfall wheatbelt where salinity is predicted to be just as bad as everywhere else and there is not a lot of trees you can grow because of the low rainfall. Perhaps jujube, prosopis, and that sort of thing. You have to be able to get a profit. So if you are thinking about finding trees you can use, there are a number of issues and requirements you have to meet. You have to have a tree species that has a large market, the market has to be readily available and large, as there is 16 million hectares worth of paddocks growing stuff and you don't want to flood the market. The plants have to be able to survive all the extremes of the climates and soils, which includes occasional frosts, occasional droughts. Transport costs need to be considered; you either need to be producing high-value products or if you have more bulky things they need to be processed in the region. One of the big things for getting people to take up commercial tree crops is the rotation length; you have to wait a long time, so it is hard to convince people to do it. If it is a 30-year rotation, you could put some in every 5 years, but you still have to wait for 30 years before the money starts flowing. It has to be compatible with existing land uses. All of these add up to adoptability.

We believe that oil mallee does meet some of these needs. It is a native species, there are 3 or 4 species that grow naturally in the wheatbelt that have high oil content. They will grow in the landscape and, most importantly, have a high water use throughout the summer. Initially, the idea was for a tree that you could harvest oil out of and sell as an industrial solvent, and there is also a small market for eucalyptus oil in the pharmaceutical area. Nowadays, it has gone towards bioenergy production similar to the prosopis in India. CSIRO has developed a system where the biomass is harvested from the trees, oil is cooked off as a sort of by-product, and the rest of the material is gasified and used to drive electricity turbines, and ash used for activated carbon for use in the mining industry.

There is a plant being built at Narrogin in a year's time, a quarter-sized plant. Woodside has committed money to build one at Esperance, as well. The idea is that the trees are cut down every couple of years, and they shoot back from their lignotubers or mallee roots. Over east, they are cut down every year, and they have been doing it for a century in naturally occurring woodlands of various species. At the moment there are 900 farmers involved in planting oil mallees, and 20 million trees in the ground. That is pretty good, considering the fact that no money is being made yet.

There are also some guys at Killany who have just brought some stuff over from the melaleuca industry over east. They have a still and a harvester, and they are just going to make oil on a trial basis, just to see how the trees respond, etc.

On the question of plant robustness and the selection of the plants...being a native plant, you don't have that weed problem, which is a big problem when you are thinking about other crops such asprosopis. Whether you believe it or not, if the government is not going to let you bring them in, it is going to be hard to get an industry based on it soon, which is what needs to happen for the salinity. They are also able to slot into the ecology of the area so that you would never see real hard insect damage or disease. There is always a little bit of insect attack going on, but there are all the spiders and birds, so it should be pretty safe from that sort of thing. They are the dominant species in the bush.

I will just speak of the process of getting a new venture going. Once it is going, there are seeds being collected, seedlings produced, sites selected, plants are growing, harvested, made into products and sold. This is just a guess at the number of people who are heavily involved in the different processes to show you that it is a lot of work going into it. All the southwest nurseries are growing seedlings. In terms of a chain and weak links, we have found it is hard to just grow these seedlings in the nursery. A lot of farmers never get as many as they ought to. Another hard thing is to build a harvester that can chop down trees at the rate of one a second, no matter how big they are. All these things are being worked on. They are not going to break the chain, just make it a bit slower. This is a list of some of the people involved in it, also to show the amount of effort that goes into developing a new industry.

Just quickly, I will run through some of the lessons that we have learned other than the technical lessons, in terms of how to make the seeds germinate and how to cut down trees. One is that native plants can make good crops. They grow particularly fast when they are coming into agricultural landscapes because of all the extra water and nutrients. They will not become weeds, hopefully. The worst that oil mallees would do in that sense would be to mix their genes which have mainly been collected in the southern wheatbelt with northern plants, which mucks up the local genetics. But that is not too much of a worry in the grand scheme of things.

Another thing we have found is that the large production bases necessary for the ball to start rolling, you have got to sort of make promises and predictions about how you think things are going to go, and try to get people to believe you. We have found that there was a bit of debate earlier about whether to cut the trees early and just go into the pharmaceutical market, or whether to hold out for the IWP process, bioenergy plant, which would need a very large base for continuous supply. That is the chicken-and-egg sort of scenario.

A lot of capital is required to start up new ventures. So far, in the case of oil mallees, it is about $20 million, mainly from farmers themselves. In the blue gum industry, it costs about $1 to plant a tree, and there are 20 million trees, so that is not too bad, considering a big industry could get up off the ground, as well. Longer rotations rapidly decrease the attractiveness. The main point to make is that even though there has been good uptake of oil mallees to date, and no money made, economics is the main factor that influences people's decisions about whether it is a good thing or not. Things have got to make money to be acceptable on a large scale. A large scale is what it is all about. A little here and there is going to be swamped by the majority. We have marketed oil mallees as landcare that pays for itself, or that may pay for itself. At least, it is landcare.

These are all serious things: don't make promises, no matter how enthusiastic you are with developing new things. With oil mallees, it has always seemed to be able to say, next year there will be a harvester and a still is always a lot harder than you think. People get disillusioned by all the promises that got made, even though they were genuine.

In summary, there has been a pretty good uptake of oil mallees so far. It is mainly a reflection of the fact that there is a very big problem in the wheatbelt. People are actively looking for trees that make money. It is looking good, even though that is not a promise. If it does work, it would make a big difference. That is why we are trying so hard.

Author comment: I feel that this is now (2004) a bit outdated and weak. I would also like to add a reference to a new paper, particularly the free online publication
Dan Wildy