The world’s smallest apple at last nearly marketed…
Not having put out a blogletter 18 for a while has been eating at my conscience, so with another season underway, I thought I would try and get the conversations going again. This will be a short letter, with the aim of eliciting your comments and stories, which is what most participants value.
I find every season is a one-off, and leaves you quite unprepared for the next one. Early spring for us was beautifully dry and that showed in very low incidence of brown apical necrosis (BAN) and bacterial blight in spite of not spraying (reasons later)…
When early summer turned to custard with persistent drizzle, bacterial blight really set in; black nuts everywhere. Some varieties were hit particularly hard. Serr and Meyric were among the worst. Fortunately normal summer weather resumed and gave us a half-crop.
How has this season gone for you? Think about it; your experience could help us all.
How different varieties respond to the climate and to your region is collective knowledge to build on. Did some varieties have a year off, or maybe conversely, crop better than usual?
As the harvesting season unfolded with a near perfect procession of storms to bring the nuts down and dry weather to pick them up, further light was shed on the earlier growing season. Normally a nut infected with blight will be a write-off. This year the blighted nuts were largely O.K. It was a pain getting them out of their husks, but the kernels inside were beautiful; white and very tasty. Hardly any nuts were infected with BAN. Those that were, had rotten kernels as usual. So the interesting thing for me to observe was the different effects of these two diseases, and that will be a consideration in any future disease control.
It looks to me that BAN can only do serious damage to the really small nutlets; at the stage you would normally spray at the “praying hands” stage. Bacterial blight seems to be able to infect nuts throughout the growing season, but once the shell has formed, for us in Bay of Plenty at the end of December, the kernel is safe. These are the observations of a simple grower of course and are completely unscientific.
One further development this season has me wary. In one block, about one nut per bucketful had an insect exit hole. Would this be codlin moth? We have never had insect damage before, and it is strange that it coincides with our free range chickens, or should I say feral chooks, being wiped out by some stray hunting doges. I hear that a parasite/predator for codlin moth has been released in the Hawkes Bay apple orchards. Does anyone know how to get hold of it?
Walnut with exit hole. This often occurred on the suture line, but not always.
The decision not to spray was based on economics rather than biology. We sprayed the previous season, the weather was perfect, and the crop double this year’s, and still the return did not cover the cost of spraying, There are two reasons for this. Firstly our spraying costs are high. We have big trees on steep land, so have to use a helicopter. But the main reason is that our yields are too low. That is a result of using unselected seedlings in our oldest block. But most other older grafted varieties would not be much better, with the possible exceptions of Shannon or Roadside 12.
We can all learn from stories of dealing with different seasons in different locations. Did your preparations work? We added a dryer. Mark II of our dehumidifier based design, and now wonder how we managed without it. Did you try new systems or new machinery? If you dry your own nuts, can we focus on that in the next blogletter, with pictures and descriptions of how your machine works?
Quite often I get asked, “What walnut variety should I plant?”, and my answer usually is, “It depends.” Not very helpful, I know, so perhaps we can collectively explore this subject in greater detail.
NZ Tree Crops Assn has published results from two different trails, (discussed in detail in the Tree Cropper) one comparing blight in the Waikato, and one looking at yields in the Manawatu. Since the 1970’s, focus for the industry has changed from being solely interested in nut quality, to consideration of different aspects of nut quality, yield in different locations, consistency of cropping, disease resistance, time taken to cropping, seasonal leafing-out-time and even the effect of rootstocks. One initial concern was pollination, but this has turned out not to be a problem with walnuts here, except that seedlings take ages to produce any male catkins.
WIG are doing two series of comparative variety trials. It will be several years before any results emerge from these, but they are important because new varieties are being tested, including 3 U.S. selections imported from Australia. There are two NZ Tree Crops Assn trials on my place as well, looking at new varieties, and also having another look at some of the older varieties like Wilson Wonder.
So, of the currently available cultivars, what do we know? The strong favourite at the moment is Vern Harrison’s selection, Shannon.
Shannon was the most blight resistant tree in the Waikato blight trial. It was the heaviest, and most consistent cropper in the Manawatu trial. From what I hear it is also performing well throughout New Zealand.
Rex is the most widely planted variety. As a young tree it was the heaviest cropper in the Manawatu trial, but as the trees developed it was overhauled by Shannon. Perhaps this early cropping ability has been an important reason for convincing growers to plant it.
Manawatu variety trial results in 2013
|Variety||Total kg nuts/tree
yr 2008 to 2013
|Between tree R2||On Off Ratio|
The correlation coefficient (R2) of 0.84 for Shannon shows there was not much variation in cropping between individual trees in the trial. The OnOff ratio is a measure of the crop in an off year compared with the on years either side, i.e. a measure of biennial bearing. The higher the value, the better.
Shannon scores highly on both measures, as do Roadside 6 and 12. Dublin’s Glory behaves quite consistently one tree against the next, but are badly affected by biennial bearing. Meyric has a big difference between good and bad trees and terrible biennial bearing. Rex is quite consistent one season to the next, but cropping for individual trees are all over the place.
Nut yield is an important consideration. Nut quality is another factor.
|* new varieties in the WIG trials.|
Those are the numbers, but grower perception, mine included, can be quite different. So I repeat these comments from a previous blogletter.
Comments on individual cultivars by Jeffrey Feint in 2011
– Meyric are by far our best nut but the shells we produce in Wanaka seem incredibly fragile, and I have almost reached the stage of abandoning any sort of machine harvesting because I estimate we lose up to 20 % of nuts due to breakage of the shells even when something as light as a quad bike with wide wheels runs over them.
– Rex is not my favourite nut and frequently very small and difficult to handle falling through the spaces in our walnut washer, but was our first nut to start falling in early April
– Franquette are often large and thick shelled, sometimes they look externally to be a good nut but on cracking them they have poorly developed kernels, especially if the nut looks “ moist” externally. They are also incredibly hard to dry and several years ago I lost several hundred kgs when although I thought that they were well dried they developed a grey mould both inside and outside the shell whilst in onion bags!
I think that one also has to realize that one does not have a single run with a harvester or whatever one uses for harvesting, but that during a harvest one has to make several runs with the harvester, even if a tree shaker is used.
Our nut yields seem to have plateaued at a little over 3 tonnes with our 450 or so trees being between 13 – 17 years old, but I calculate that we should be closer to 10 tonnes or more – I am really at some loss to work out how to increase this yield and would welcome help.
– Stan (Blenheim 300) – a good nut which are easier to process because they are round and do not jam so easily in equipment. Quite a nice nut to taste, relatively early fruiting.
– Wild Nuts – we originally planted about 80 wild trees which I regret because some produce quite good nuts but others are small and do not taste very good.
A typical Franquette nut with poorly formed shell and rotten kernel that I am putting down to Boron deficiency. The shell is ultra thin along the pale lines.
Franquette is a very late leafing variety, and is planted in the South to avoid out of season frosts. I have also found Franquette to be particularly prone to Boron deficiency, so much so that they never cropped at all for years. The comments Jeffrey makes about drying them applies to all the larger nuts. Drying takes much longer and needs to be very thorough. On the other hand we have found that a big nut is much quicker and easier to pick up.
The closer you get to Auckland, the more likely you are to try and grow a big table nut. We have bred Roadside 6 and 12 as an alternative to Wilson Wonder. In the Bay of Plenty we find Roadside 12 out performs Wilson Wonder most seasons, but it has a problem with some kernels not being filled out. Roadside 6 seems to avoid that problem, but the nut quality is not quite as good. Every variety has its good and bad points!
The interaction of variety with site is critical. I have yet to find a way to make Meyric crop here, but we have no problem with out of season frost on any variety. On the other hand a good hard winter seems to increase our crops through initiation of flowering. It is this site interaction that I am hoping will trigger your feedback. Send me your stories about what varieties you like, and where things have turned out different from expected.
I sent a draft of this blogletter to Jeffrey Feint, and got this reply….
Great to hear from you again . We are in the middle of our harvest which is far too late since the leaves have well and truly fallen and for the last 4 days we have had almost constant heavy rain , which has effectively stopped any nut harvesting . On top of that we have had machinery breakdowns – the main motor to our washer , and the hydraulics on our harvester . All in all this tends to make it “ a harvest from hell “ , although after 2 years of very low yields we have a good crop which should come in around 5 tons.
Most of the comments I made in an earlier blog are still pertinent to me – our Meyrics remain our best nut but they are so fragile , and after drying and whilst bagging the shells literally seem to fall apart ,and I think that we must lose 20 % or more in fractured shells which are discarded .It has been pointed out to me that if we hand rolled them all then we wouldn’t have all these breakages but hand rolling over a ton takes quite a bit of time and personnel which we don’t really have . Valda Muller points out to me that Meyrics are also very hard to crack mechanically since the bits stick inside the shells , but I don’t really have any other nuts in comparison .
In our Central Otago environment Rex seem to be frequently hit by late frosts and this could be due to the fact that they don’t have big leaves like the Meyrics to protect the buds . A problem which I have always found troubling is that we struggle with very small nuts on Rex’s and Blenheims – to make a double entendre no man likes to be told that he has “ small nuts “ , but I have tried extra watering , fertiliser, ‘poisoning’ the trees with boron all to no avail – is this peculiar to the Central Otago environment, the cultivar [ New Zealand cultivars tend to be small when compared with North American cultivars ] , or whatever – can anyone offer any advice on this problem .Some years ago I visited a walnut processing factory in Victoria and I remember the guy showing me some nuts and saying “ These nuts are so small that we just discard them because nobody would eat them “ , sadly they were a lot larger than most of our bigger nuts !. I note that the Rex’s that are mentioned in your blog from Manawatu are not noticeably any smaller than other cultivars .
Over the last 4 years or so I have not been spraying for blight , but this year I did spray at budburst and later , and I must say that subjectively I don’t think that there was a huge difference between the two periods
My ideas of field grafting my “ wild trees “ is still in my head since I found it difficult to find suitable scion wood from my Meyrics , but I shall keep trying. So keep up the good work with your Blog. Very best wishes. Jeffrey
Thanks for your prompt reply Jeffrey.
Sorry to hear of your difficult season. Being mechanically challenged, I avoid machines as much as possible. So I use gravity for my harvesting, a hand-held hose over wire racks for my washing, and the only moving parts in my whole system is a domestic dehumidifier and fan in each drier. Of course it helps when my wife does even more than I do.
I don’t know why Rex came out so well in my crackout score, but that was the measure I got. Last year I tried hand cracking a sack of Rex nuts and found them much more difficult to get out of their shells than my seedling nuts. I am full of admiration for Jenny Lawrence making a living out of cracking those things. My Meyrics have never produced enough to give me a sack full to try cracking on their own. I also discard a fair proportion of the Rex’s I pick up because they are too small to handle.
Thanks. It is great to hear from someone like you who is pushing the boundaries.
Looking forward to hearing from you.
nick nelson parker
Reproductions. If you would like to reproduce any of nick’s blogletters, you must include the source of your quote and the URL of this web page which is:
Back copies can be viewed on the NZ Tree Crops website:
We follow up with another blogletter 19 so soon because Valda Muller informs me that their operation is about to air on Country Calendar sometime in June, probably the 21st. And I know you don’t want to miss that. Her letter below…
This letter also includes snippets of conversations, edited for brevity, that I have not had room to include before.
Thank you again – it is always good to hear that things have gone well for one when for us it has been a very difficult season – there is still hope there at the end of the tunnel!
All the best to you Nick
We were frosted again this season – after a 4.6 degree average increase in July temperatures and warm spring the trees were all set for an early start to the season when hit by severe frosts during the last week of Oct/first week of Nov – diary notes from last year confirmed that the trees were at exactly the same stage of leaf burst and male tassel exposure as when we were hit in 2013 ….. With exactly the same results! Grrr! After 25 years of getting trees to this stage it would be nice to get the crop!
(To compound our woes our cash crops grown to support the nut habit also struggled – a virus into the garlic caused stunning bulbs to collapse 4 weeks after harvest and December and January were so cold that the hothouse was kept closed almost the entire month and at one stage I thought our heritage tomatoes MIGHT be ripe by Christmas 2014 and most plants still have significant crop yet to ripen (??!!) – all in all a season to forget.)
At least we learnt a little from last years experience and I was out with compost tea sprays each morning to the walnut trees post the frosts and we managed to maintain the trees in a much better state of health and have foliage return much earlier than the previous year – so hopefully …….
Recommendations out of all of this would be for our area to select cultivars which are very late leafing out – we have found that our G26 and Franquette cultivars were not affected this year and cropped well. We have also found that choosing a good cultivar for root stock and ensuring it is really vigorous is of utmost importance. Good cultivar trees on poor root stock will not “recover” and make up growth …….like us you could be pulling them out as hopeless 15-20 years later!!!!
A general comment re the use of compost teas – I have observed significant increase in foliage size and depth of colour following the use of the teas and we also had an increase in weight of nut yield/tree (2012) with a larger proportion of nuts being in the bigger size gradings ……. Of course it would have been nice to have verified this through crops in the last two years! There is always more than one variable in farm management so I cannot yet say it is the compost teas that has led to this change.
We still have a very low technology approach to nut drying – with a household log burner in a concrete bunker with fans and an expelair to remove moist air – the nuts are placed in a single layer suing stacks of bread crates. A bit of handling but it is all “woman’s sized” and manageable – and surprisingly efficient in terms of throughput and rotation. I will shift the nut grader into this area so that I have the larger nuts on their own trays and can leave them the extra couple of days to finish off the drying.
Otto’s harvester works well – but we planted with this form of mechanical harvesting in mind. (It really needs level ground, appropriate spacing and pruning). He is keen now to have a business develop the prototype and make it available commercially as this is beyond our current resources. Interested parties can contact Otto. The beauty of the harvester is that ripe nuts are collected direct to bins – so there is no washing required and not the daily collection of nuts from the ground is largely avoided.
I am hesitant to mention this (as I will probably be hiding over the Nevis on the day!) ….. But if any walnut growers out there are interested in our harvest and shelling processes the Country Calendar team visited at this stage. I have been told the programme will probably go to air on the 21st of June. They were a great team and I am sure they will make the most of it – had thought the focus was going to be more on Otto and his mechanical inventions ….. But the timing was not good as he went off to the Treecrops Conference and came back to the second day of filming pretty tired to two very cold days! There may be something there of interest to some growers.
Yields per hectare
I got your email from the report on the Walnut trial in The Tree Cropper journal. I am looking for yields of nut crops in NZ per hectare (and overseas yield data also) to compare nut cropping with other farming systems.
I am making a case for tree based land use as a sustainable shift in NZ agriculture.
I sent him the trial results in a bit more detail. The trees were planted at 10 metre spacings. At this age they would have yielded the same per tree if they had been planted at 5 metre spacings or closer. So for Shannon with 13.6 kg of nuts per tree in 2013 at age 15 would have equated to 1.36 t/ha at 10 metre spacing, and 5.4 t/ha at 5 metre spacing. Rex at 8.6 kg per tree would equate to 860 kg/ha at 10 metre spacings, and 3.4 t/ha at 5 metres.
You are right to concentrate on yields per hectare. It is the single most important factor holding back walnut cropping in NZ. Our mature stand of unselected seedlings is only giving 1200kg/ha, while our best crop has been 2.5 t/ha for 16 year old ‘Roadside 12’ trees.
Australian research (can be viewed on rirdc.infoservices.com.au/items/00-100 ) in an article titled “High yields and early bearing for WALNUTS” starts with the sentence, “The aims of the project were to raise the yield of quality walnuts from 1.5 to 4t/ha…”
Figures from the Sun Diamond Grower News ( no longer available online without a password.) for Summer 2008 talked about average crops for newer plantings of 5, 000lb per acre. (5.6 tonne/ha) Older orchards were said to be yielding 1,500lbs /acre. (1.68t/ha). The summer 2010 Grower News quotes per-acre yields for China of 500 pounds.(0.56 t/ha) But I have heard of a Chinese research block claiming to get 6 tons/acre (14.5t/ha). [I think that must have been 6t/ha actually.]
How do you fare on this scale? Email me with your successes and frustrations……
Spotted; this advert in Papers Past: Waikato Times, 23 July 1892, p. 3
Large French Variety.
A limited number of Well-grown Three-year-old Walnut Trees of the above variety for sale. Apply to C. H., c/- Waikato Times Office, Hamilton.
Wonder if they were Franquette?
Cheers Kathryn M
Many thanks for latest blogletter (16). So interesting to hear about walnut growing in China and Jeffreys account of his visit there.
Let’s hope that some of the disease problems that they face don’t find their way here too quickly!
On a personal note, we have about a dozen trees ( mostly grafted varieties) ,planted over the last 30 years, and for home nut consumption. However, as furniture maker, I’m keen to know a bit more about pruning for timber. If there is anyone who can offer advice ( about when best, painting cuts, avoiding bleeding etc. )I would be very grateful. Also I’ve used walnut timber from a number of different walnut trees in our locality (Wairarapa), and the colour of the wood varies
Following on about the variety of timber colours in locally grown trees, I was wondering about the cause. The heartwood in them seems to vary from very dark, almost black, grain through to really pale. Different soil with the different locations? They all looked like Regia, but different varieties? I’ve had a Black walnut tree too ( Nigra) and that had the usual purpley / brown heartwood, similar to the imported stuff from the USA.
Many thanks, Jeremy B
As you may know, my whole project is about growing J.regia for timber (+the nuts). You are asking the same questions I am.
Firstly, about the heartwood. I wish I knew what caused the colour. We thin to waste regularly, and I have yet to find a tree with any coloured heartwood. I am hoping that that is just an age thing. A couple of months ago we cut 2 trees up for sawntimber. I wasn’t surprised that there was no dark heartwood, though the trees were 35 years old with a dbh of about 35cms. If you are using walnut timber from different sources, maybe you are in quite a good position to take note of the environment of the tree and compare it to the colour?
Pruning is quite simple. Trees bleed from early June to mid December here (BOP). It will not be that different down your way. The bleeding looks terrible, but I don’t think it does too much damage to the tree. U.S. reports on pruning black walnuts say you must make sure no branches reach 2 inches diameter. With European walnut grown in NZ that is impossible. I have come to the conclusion after many years of trial and error that it is better to cut off a big branch than leave it because a big branch deforms the whole stem, and the most important consideration for a sawmiller is a straight stem. My current approach is prune twice a year. I do a whip around in early January to nip any problems in the bud; – branch getting too big, leader lost its way, that sort of thing. Then I do a more aggressive prune after harvest in May. Diana Loader’s rule of thumb is quite useful, “Take at least one branch off every tree.”
The other problem with pruning walnut trees is that they tear badly. So I do a 2-cut approach if the branch is more than a couple of centimetres thick.
The article at the Walnut Symposium about growing walnuts for timber in Spain will be interesting. You should be able to read it on the net before long, as that is what happened to previous symposia.
Good to get your feedback
Thanks for your advice and comments. Much appreciated. I will try and take more note of tree environment in relation to it’s timber colour. However, I have to say, that from one avenue of walnut trees near here, that were quite old and decrepit, there was a big variety of colour difference, and yet the trees looked similar.
I agree you get very little heartwood showing in young trees. Even a 50 year old tree I had some years ago was only about 100mm heartwood.
I fear I’ve missed the boat with pruning this year, and will remember to do it in the autumn. There are one or two I’d like to try and train for a future timber tree . Most, I don’t mind branching out and producing nuts!
Will look forward to the report on the Spanish experience on timber production.
Walnuts Australia cracks the domestic market
Australia’s only large-scale commercial supplier of walnuts has ended nut processing in Vietnam.
All of the nuts grown by Walnuts Australia at Tabbita and Leeton in southern NSW and at Swansea on Tasmania’s East Coast are being shelled, graded and packaged in the Riverina.
Operations manager Derek Goullet say its new $11 million processing plant at Leeton is designed to mimic a hand-cracked product.
“A lot of our customers are accustomed to hand-cracked kernel from our Vietnam process that we utilised. We need to make sure that we’re meeting those customers expectations on what they see, so the kernel they get is unscuffed and as many large halves as we can, to make sure our margins are as high as we can make them.”
The company is now supplying walnuts to Woolworths for its Select brand and expects to pick up new export markets for its Australian processed product.
“There are a lot of export customers that do want kernel, that currently don’t buy our in-shell nuts. Asian markets, such as Japan, is one of those potential markets that we don’t currently supply that we’re looking more and more into.”
The new cracking plant is also expected to reduce the cost of production and limit exposure to foreign exchange rates.
Food Storage moths
Following on from the mention of codlin moth last time, it has been brought to my attention that some people may be confusing it with the food storage moth. They are quite different insects. The food storage moth, also called the pantry moth, is called the Indianmeal moth in America because it was a major problem for the American Indians’ corn storage.
It can be quite a problem for walnut growers, possibly worse than rats. Processors have to be vigilant, and growers who only sell nuts in shell can get caught out as well. And it is sometimes hard to tell if a nut has been infested until you open it.
Eggs: Eggs of the Indianmeal moth appear grayish white and range in length from 0.3 to 0.5 mm. Eggs are oviposited singly or in clusters, and are generally laid directly on the larval food source.
Larvae: There are five to seven larval instars. Their color is usually off-white, but has been observed to be pink, brown or almost greenish, depending on the food source. The mature larvae are about 1/2 inch in length. They have five pairs of well developed prolegs that help them move considerable distances to pupate.
Pupae: The larvae pupate either in a silken cocoon or unprotected. The pupae are 1/4 to 2/5 inch long (6 to 11 mm) and are pale brown in color. Pupation takes place away from the infested material. In fact, the late instar larvae can travel such distances that they are often mistaken for clothing pests. Within the pantry the small larvae often climb to other shelves before pupating. This misleads people trying to find the source of the infestation.
The above comments and pictures are off the ‘net from the University of Florida. But this is my approach to control…
I have found that good hygiene is paramount. The pupae shown in the picture seem to last quite a long time in unobtrusive places only to re-emerge and infect the new crop.
Our aim is to make sure there are no in-shell nuts in any buildings by the end of January. Our personal supplies, to last us over till the next crop, are all cracked and put in the deep freeze. We even do a complete clean out to make sure there are no nuts or broken pieces in corners or behind the driers. I read somewhere that all stages of this insect including the eggs are killed if deep frozen for 4 days. That was put to the test one day when they got out of control at my mum’s place. So we disposed of the obviously infested products, threw all her flour, seeds, spices and other dry goods into the deep freeze, and wiped down all the walls, shelves etc. to get rid of the pupae. It worked a treat.
There does seem to be difference between varieties as to how susceptible they are to infestation. Tight sealed nuts are moderately impervious. Wilson Wonder can have a weak spot at the stalk end, and the new variety Gaudion seems to have a problem too.
Now let us hear how you deal with this troublesome pest.
Enjoy the Muller’s Country Calendar programme,
nick nelson parker
Get in touch with editor Nick by contact form – click here…
Reproductions. If you would like to reproduce any of nick’s blogletters, you must include the source of your quote and the URL of this web page which is:
Back copies can be viewed on the NZ Tree Crops website:
- The Walnut Industry – viable!
- Nut crops summary – Walnut, Chestnut and others.
- Walnut Blogletter launched in 2010 by Nick Nelson Parker
- Index to all Walnut Blogletters
RESEARCH DISCUSSION PAPER
The Management committee has asked me to look into the need to promote the research side of the organisation. The research fund has not been widely used over the past few years and funds are available to branches for their use. Is it due to a shortage of ideas, an uncertainty as to whether a topic or project is worthy of the name research, a lack of knowledge of how to apply for funding, lack of members with time or expertise to carry out research, or all of the above?
Past funding has been given to studies on the compounds in apples, a search for pheromones for the Guava Moth and its distribution, and research into the flowering of Hazels. Is it time some basic research was done on crops relevant to the local situation and of direct benefit to that branch, or perhaps nationwide projects whereby individual members can participate by making local field observations?
Some suggestions for research projects:
- A North Island Survey to determine the current spread of the Guava Moth.
- National Survey of a specific crop and varieties to determine bud burst, flowering and fruit maturity dates to ascertain the suitability of crops for regions in N.Z.
- Study of a crop’s phenology for a particular area (stages in growth and fruit production cycles). This can be applied to determining the best time and type of fertiliser application.
- Local compilation of crops suitable for year round fruit and nut production.
- Pruning methods and their effect on yield, any crop.
- Any other suggestions
On an organisational level do we need to have a more centrally driven direction for research or leave it up to branches as at present with the research committee just giving guidance so that research results are reliable?
Does the funding criteria and procedure for application need clarification or advertising?
Where should the research findings be held and how accessible are they to members?
This is a “Starters” paper to stimulate your thoughts and bring ideas out of the woodwork. Your ideas and comments would be most welcome.
20th September, 2013
Wellington Horowhenua Branch NZTCA Branch Representatives
Dear Jean and Robyn,
At our last Management Committee meeting we unanimously voted to accept your Branch’s application for funds of $834 from the Branch Innovations Fund.
Your project “Almond Cultivar & Management Trial” with the objective of optimising almond production is a very worthwhile one.
When this money is spent, please send copies of the invoices to our Treasurer, enabling him to claim back the GST portion.
Your successful application will be notified on the Association’s website and in the relevant edition of the Tree Cropper.
We request that you report to your branch members and to Management Committee on progress with the project, including how project money has been spent; and provide material for publication in the Tree Cropper and/or on NZTCA’s web-site by the end of the first year of the project.
Our National Treasurer, Andrew Hutson, will send your Branch Treasurer a cheque for $834. We wish you great success in this venture.
National Committee Members
Colleen Brown – National Secretary
Trials for tree croppers
Pushing the boundaries and answering the unanswered is what NZTCA is all about. There are thousands of questions, each with different answers for different climates.
Which is the best cultivar?
Do organic practices produce more or less fruit than conventional?
Which produce the most wholesome fruit, seedling or grafted trees?
The questions are endless and the answers aren’t found in the lab, but by NZTCA members planting and observing nature.
Anyone can plant a trial — Heather North outlines the considerations you need to take into account.
Why do we set up trials?
We set up trials to compare the performance of several different plant cultivars or species, or several different rootstocks.
Usually we have questions like:
- Which cultivar will perform best in my climate/soil?
- Which rootstock is most disease-resistant?
- Which cultivar has the highest crop yield?
We aim to get quantitative data on these questions so we can draw well backed-up conclusions. It’s a bit more formal that just making a few observations on a couple of trees every now and again — though these observations can be useful too.
It is a good idea to talk through your trial plans with the NZTCA Research Co-ordinator, but the following notes will give an idea of the issues you need to consider.
Two important considerations in trial design.
“Replicate” each cultivar in the trial — we know that plants can vary a great deal in yield, vigour, disease resistance and so on, even within a single cultivar.
If you observe just a single specimen of that cultivar, you have no way of knowing whether its performance is average for its type, or whether it’s extreme (eg unusually vigourous, or unusually disease-prone, for its type).
And if you compare just single specimens of two cultivars, you could draw the wrong conclusion about which is better, if one performs unusually well and the other unusually badly in your trial.
The answer is “replicates” — you should have more than one specimen of each cultivar in your trial so that you can see what is average and what is extreme for each.
You can then compare the average performance of several cultivars with each other. How to decide how many replicates is enough is discussed in detail below.
“All other things being equal” — In a cultivar trial, you want to observe only the differences in performance that are due to cultivar, not those due to any other factor.
Ideally, all the cultivars in your trial would be grafted by the same person, grown in the same soil type (though see comments on block design below), irrigated the same amount, pruned in the same way, etc., so that you can be sure any differences in performance are not due to these extraneous variables, but only to cultivar.
In practice, of course, it is hard to achieve this. Ways of dealing with this — particularly randomisation and block design — are discussed in detail below.
Trials across several sites
In practice, we often want to plant out the same trial (same set of cultivars) at multiple sites — where each site may have its own soil type, climate, and management.
There are a number of reasons for this, including:
- If the same cultivar shows up as performing best across several different climates/soils, then we can make a very robust recommendation for that cultivar, which will hold true across a wide variety of environmental conditions, OR
- We may want to know which cultivar performs best in each of a number of climates (and they may not be the same).
- We may not have enough space for all the replicates of all the cultivars at a single site, so we must spread it across several.
You still need randomisation (within each site) and replication (in fact you will need a few extra replicates).
How many replicates are enough?
This is the most common question asked, and the answer is not straightforward. It’s a good idea to consult your NZTCA research co-ordinator (or another scientist) for your specific trial. The required number of replicates depends on two things:
- How variable is the characteristic you are trying to measure (for example, yield)? If it is highly variable, you will need a large number of replicates to get a precise average.
- How precisely do you need to know the measurement? If you only want to detect gross differences between cultivars, then you don’t need many replicates, but to detect ﬁne differences, you need a lot.
In practice, a lot of tree crops trials around the country (including the walnut, chestnut and hazelnut blocks at Lincoln University) have around five to six of each cultivar.
The following is a very rough example of what you can do with this trial design.
Say you want to compare the average crop yield between two cultivars, and, from this result, conclude which cultivar is better.
With five replicates, you should be able to detect differences of 2kg in crop yield between cultivars1, but probably not differences of lkg.
1 Assuming a standard deviation in crop yield from a single cultivar to be lkg.
That is to say, if the difference in average crop yield between two cultivars is only lkg, you will not be able to conclude that one cultivar is better than the other (the evidence is not strong enough).
But if the difference is 2kg, then you will be able to draw this conclusion.
This may well be sufficient for your needs.
However, planting ﬁve to six replicates of each cultivar at each of three to four sites will give you a stronger trial, and allow you to detect ﬁner differences in performance.
It will also enable you to check whether your conclusions hold over a range of different climatic and management conditions.
Randomisation: how to make other things as equal as possible
As mentioned, you usually want to know only about the differences in performance due to the cultivars, species, or rootstocks under trial.
You don’t want your observations to be confused with differences due to other factors.
There are some sources of variability that you can control, and it’s important to do so if possible.
For example, you can:
- Get all specimens from the same propagator.
- Ensure all specimens are on the same rootstock (in a cultivar trial), are of similar
diameter and height, and are all free of disease.
- Ensure all specimens at a single site receive the same management, including irrigation, fertiliser and pruning.
There are other sources of variability that may be hard to control. Even if you try to make conditions in your trial site as uniform as possible, you may still have variations in:
- Soil fertility or drainage
- Amount of wind protection (distance from a shelterbelt)
- Amount of shade
- Irrigation ﬂowrate
The method for dealing with this is to plant your cultivars in a random layout. This is to ensure that each cultivar (assuming there are, say, ﬁve replicates of each) experiences the whole range of variability in each of these factors.
You avoid the situation where, for example, all the replicates of one cultivar are planted in a row along a shelterbelt, so all of them receive more shade, less wind and possibly less water than the neighbouring row of another cultivar.
If you are planning trials that will be planted out in commercial orchards, growers may not like the idea of a random layout (if they need to harvest crop from different cultivars separately), so it is worth mentioning this requirement in advance.
In practice, there can be problems with purely random layout, so generally a modiﬁcation called randomised block layout is actually used.
As mentioned, the purpose of randomising layout is to ensure that each cultivar covers the full range of variability (in soil, shelter, etc.) that exists in the trial site.
In many cases, drawing random numbers to allocate cultivars to locations will provide this, but there is also a chance that it will not. There is a chance that the randomly drawn locations for a single cultivar will all turn out to be in one corner of the trial site, or on a single soil type.
Block design avoids this by ﬁrst splitting the orchard into smaller blocks, and then randomly allocating locations, as shown in the diagram below.
This diagram shows a randomised block design for four replicates of each of six cultivars (numbers one to six).
The trial site has been split into four blocks, and each block contains one replicate of each cultivar.
The cultivars are allocated randomly to locations within each block.
What to measure
The characteristics of the trees and crop that you choose to measure will depend on the purpose of your trial.
However, the following are some useful measurements of vegetative growth and cropping, and also some important environmental factors (which might help you understand any observed differences between sites or between years).
At the start of the trial:
- You may want to do a soil test
Vegetative growth (annual measurements):
- Tree height
- Diameter of trunk at a height of 50cm (use calipers) – or measure trunk girth at 50cm
- Spread of canopy can sometimes be useful
- Current year’s shoot growth
Reproductive growth (annual measurements):
- Flowering dates (start, middle and ﬁnish of ﬂowering period)
- Harvesting dates
- Total weight of crop
- Weight of a sample of 20 nuts/fruits
- Disease incidence (type and timing)
- Annual foliage test for nutrient status
- Records of management operations (eg pruning, fertilisation)
- Frost dates
- Rainfall records
- Put a temperature recorder in the orchard (eg a TinyTag)
Analysing your data
At the simplest, you can calculate averages for each cultivar (eg average crop weight, or average shoot growth), and compare these between cultivars.
It’s useful to display these results on graphs so you can clearly see the comparison.
However, it’s a good idea to get some help from your NZTCA research co- ordinator unless you are used to working with statistics.
That’s because you need to know whether or not any difference observed between cultivars is actually signiﬁcant. A small difference could be just due to chance, rather than a real difference in performance.
All the best as you discover suitable cultivars and rootstocks for your climate and soils!
For details on trials and research projects already underway with NZTCA, see the website archives main index…
TreeCropper Editor’s note:
Of course, information, including that obtained from a trial, is only useful if it is recorded and shared — reports, observations and comments about trials are always welcome in the TreeCropper.
( – on behalf)
MC (Management Committee) is concerned that the NZTCA should be doing more to promote research.
The emphasis I think should be on encouragement of research.
Little can be achieved without the enthusiasm, commitment and knowledge of branch members. [Read more…]
[While we re-think how we re-present this content, this edition makes an interim appearance as one big post. Nick’s hosting is in upright characters; guest contributions and responses in italics – web ed]
Walnut Blogletter 17 August 2013
Obviously people enjoyed Jeffrey Feint’s account of his trip to China. This was a sample response: [Read more…]