Walnut Blogletter 6

This blogletter will focus on systems and techniques to make harvesting more efficient. Again I am not purporting to define how it is to be done, but I am hoping to be a little provocative, so that some of you cannot resist telling me how it REALLY should be done. I had hoped to cover machinery that I know many of you are developing, but that will have to wait for another time. But, first let’s cover some interesting responses to the last blogletter.

Hi Nick & Pauline,
Thanks for Blogletter 5; interesting and informative again!

Re. Ground clearing. I keep a Roundup-sprayed patch clear around all walnut trees
on the flat part of the grove throughout the year. This helps during harvest but some
nuts do fall onto the grass which we mow shorter than usual about when the first nut falls.

On the slopes we spray fully twice a year. As you have found the trees pretty much stabilise the banks. Our trees are a mix of nigra and regia and we, to date, have ignored the product from the black walnut trees.

This is our first year with a decent crop from J. regia [ trees now 10-12 years old ].
The following sample data may be of interest: Sample: 1kg whole nuts taken at random as collected. Av. Weight: 6.85grams per nut. Recovery (crackout): 53.33% from sample minus defective nuts.
Regards, Tony Walker

This is quite an impressive crackout from what Tony presumes are seedling trees…

And another comment about keeping the ground clear for harvest with sprays.

Don’t think spraying, long term you will bugger up the soil profile. [I] once sprayed some gorse with roundup. Where there was a gap in the gorse the spray landed on the ground, you could tell where as no water was getting into the ground there, by experience this lasts about 3 months, no Monsanto will not tell you this. Try harvesting with bare feet, you should find the nuts in the grass. Have any members had sulphur-crested cockatoos? They love walnuts.

Thanks Hew, for your input. Australian walnut growers I have talked to, rate Sulphur-crested cockatoos as their no1 enemy. I have often wondered how a trap with a resident tame bird calling in the wild ones would work.

Valda Muller sent this comment;

Otto injured his hand just before harvest so I had a busy time with him in hospital in Dunedin and nuts to harvest in Cromwell ……… just proves I will be able to cope with next years harvest if it is bigger and better than this years! Pleased with both nut quality and quantity – now is the time we get the benefit of the good planning and preparation we have done over the years. Otto’s hand progresses well and he is now at the rehabilitation stage.

And when I asked for more detail she added:

general comments – they would be very much in line with other growers ie the things that I find helped were:

1.  A range of cultivars so that the harvest season is spread – having all nuts ready at the same time would make it very difficult for me to get around all of the trees everyday.

2.  Facilities, which enabled harvested nuts to be dehulled, washed and dried in a single layer of racks with minimal transfer of nuts between tasks.

3.  Good systems around date of harvest, drying sequence and nut packaging

4.  Ensuring all market labels and packaging are ready prior to the start of the season

5.  Nut grading, shelling and shell separation processes which are efficient and effective. This year almost all nuts were first grade nuts, which greatly reduces handling time in the factory.

6.  Established market

7.  Stamina  !!!!!

Best wishes, Valda and Otto

I thought this would be a good outline to discuss general orchard systems, as they have obviously put a lot of thought into it. When I worked as a forest planner for a big company, I learnt that you get nowhere until you describe the whole system first in general terms. Then you fill in the details later. Each one of Valda’s points raises a number of issues and decisions that would be better made as part of an overall plan rather than by default as the orchard develops.

Length of harvest season

Starting with the idea of length of harvest season, it would be interesting to hear other people’s experiences. Those of you who have only planted Meyeric and Rex; how long a season do you get? Has anyone else deliberately planted a mix of varieties to extend the season? We have a huge range of varieties, since most of them are seedlings. Our nutfall went from 5th March to 5th May this year. (Some nuts did fall after that, but we did not pick them up.) So the differences in harvest time does take the pressure off a little, but all the varieties dump their nuts on the couple of nights when they are really falling heavily. To completely separate the harvest times, we would need just to plant Serr (very early) and Franquette (very late).

Valda and Otto use a harvesting machine and tree shaker which would make a difference, as they can collect the nuts when the tree is ready rather that when the weather knocks them down. Is anyone else using a tree shaker? I used to view tree shakers as unnecessary hassle, but I am changing my mind. They are generally credited with giving paler kernels, as well as giving greater control of the harvest. It would be interesting to hear someone else’s experience.

By the way, many people worry about drying their nuts in the sun, because it results in darker kernels. But I did a trial one year, drying some batches in the sun, and getting others straight into the drier without lying in the sun. There was no difference. The reason is that the damage happens from the time the husk starts to split and the nut is exposed to the weather still on the tree. That is why tree shakers give paler kernels. It eliminates the time nuts are exposed to the weather in split husks up on the tree.

Facilities and systems.

I would have lumped Valda’s points 2 to 4 as one, so that would indicate that I have not really grasped what is involved. How have people managed to minimise handling of the crop from paddock to customer?

It also sounds like most people have young trees and are mechanising step by step. And again some people decide not to overcapitalise, making do with homemade equipment until there is enough crop to give the returns, while others want to do it properly right from the start. If you go with tree shakers you need a dehuller. However you harvest walnuts, they need washing and drying. Depending on who your customer is, they probably need grading at some stage too. Last, but not least is storage. You need a dry, rat-proof place to store your crop, even if it is for a few days. We can all save a lot of mistakes and money if share what we are doing; both equipment we are using, and managing the changing needs caused by older trees and increasing crops. email me your story.

I must admit that our systems have only evolved on an “as-needed” basis. Our dedicated nut storage happened in a hurry because we had a dog that peed on a sack of nuts. Then we stuck a dehumidifier into an old caravan as a drier, and our washing facility was an upturned wirewove bed we got from the dump for $2. This has worked so well that we still use three of them. They are mounted in a plastic house, so the light is perfect for checking for dud nuts, which get graded out at this stage. Oh, and the dog is long gone!

Nick washing walnuts


When we decided to take the nut production a bit more seriously, we worked back from the way we sell our in shell nuts, which is in 5kg garlic sacks. We just handle complete bags of nuts right from the washer to point of sale. Each sack is tagged with a number and which stand it came from, and weighed. Our current drier is designed around the dimensions of one of these bags. It is described in the email exchange below with Paul Devine, which I include here as it gives an interesting insight into the process of mechanising.

Hi Nick
Our harvester is a prototype and has had its first run. Modifications now need to be made but then we think it should work well. The next thing we are beginning to think about is a drying system. The wet harvest season we have just been through, also A Cracker of Nut is indicating that they wont be able to offer complementary drying for everyone going into the future, so I would prefer to find an answer now rather when I forced to.

We have also had a walnut washing machine made using water blast technology. It washes the nuts very clean and also quickly. All the things we are having made are with the future harvest in mind. We moved most of our trees after we bought the place even though they were 25 years old and some 10 meters tall. Ross didn’t expect them to come back into full production until 2014 as a result of the heavy pruning and major removal of their root structure. Our crop this year is…

Kind regards Paul

I know nothing about engineering, but I still built my drier myself; with some help from a local electrical shop. That article I sent you shows the size and type of fan for the depth of walnuts you are trying to push air through, and the electrician helped source the right one. An article I read in California Agriculture years ago pointed out that the most efficient way to dry walnuts is a closed system with a dehumidifier. That apparently is more energy efficient than drawing new air in from outside, even in California’s dry climate, and certainly would be so in Bay of Plenty.

My first attempt at drying walnuts was just to put them in a drying room with a dehumidifier. That worked OK but was too slow to cope with my increasing crop. Then Jenny Lawrence told me about forced air dryers. So my current drier is based on the size of the onion sacks I use. I dry batches of 6 or 12 at a time. Each batch goes in for 24 hours and then I finish them off in the drying room with another dehumidifier, but no fan. The way I test whether they are dry is to weigh the sack when I think it is dry, then put it back in the drying room for a couple of days. If the weight does not change over that time I know it is dry. I find that easier than cracking nuts to see if the midrib is snappy. If I had tons going through my drier every day it might be a different story. This year it cost me $90 per tonne for electricity to dry my crop, whereas the drying room with no fan used to cost me $300 per tonne.

The drier I built was very cheap, basically the cost of the fan and the dehumidifier. But I am only trying to dry a couple of tonnes of nuts, which it handles easily. It is 50 x 75 x 120 cm, though you could scale it up quite easily. The big mistake I made was to use an old deep freeze chest. It gets way too hot even with no heater in it, just the dehumidifier. So I have to leave the lid open and cover it with a plastic sheet. That also turned out to be an improvement, as I need a flexible lid to get a better seal around the nuts. And being able to gets the nuts basically dry in only a day was a great boon this wet autumn. Most years the forced air drier removes nearly 80% of the water in one day, but this year with the extra moisture it was only 72%.

I am sure you could build a closed system drier with a dehumidifier for the more conventional bin structure. Diana and Walter Loader have built their own drier too; quite a different design. It dries a constant flow of loose nuts, and I hear they are very happy with it. They live in Wanganui.

If anyone else wants the technical details of the sized fan you need to push air through a heap of walnuts, email me, and I will send it to you.

Anna Brenmuhl sent this very encouraging news clip, which you can use to help sell your nuts.

US: Walnuts have healthiest antioxidants of all nuts, study says

Walnuts are top nut for health, say researchers from the University of Scranton to the American Chemical Society. Walnuts are the nuts to eat for health, a new study presented to the 241st National Meeting & Exposition of the American Chemical Society (ACS) indicated recently. Walnuts, scientists on the study said, contain not only more healthy antioxidants, but also have a higher quality of antioxidants than any other nut. “Walnuts rank above peanuts, almonds, pecans, pistachios and other nuts,” said Joe Vinson, Ph.D. at the University of Scranton, who did the analysis. “A handful of walnuts contains almost twice as much antioxidants as an equivalent amount of any other commonly consumed nut. But unfortunately, people don’t eat a lot of them. This study suggests that consumers should eat more walnuts as part of a healthy diet.”

In the next blogletter we will look at walnut oil. A friend has just made a press for 10% of the cost of a commercial and has sent me the details. And we look at the opposition. Anyone heard of Camelina? Don’t forget to send me your mechanisation stories.

Your engineeringly challenged blogger,
nick nelson parker