Biomass Nut Production in Black Walnut

Well, the book is finally out:
Biomass Nut Production in Black Walnut: Exploring Management
and can be reviewed on and obtained from Lulu

Nuts aweigh

Six months without a word. I should apologize. 2009 went down in the yearbooks as nutless, so I hibernated. Things have not been static, however. The continuous-flow walnut washer joined the suite of black walnut technologies on the farm, and through the efforts of my good friend Rod enough walnuts found their way to the farm back in November for the washer to be given a trial run. Rod also asked me some penetrating questions, so rather than repeating everything here, follow this link to Rod’s blog and photos of the washer in action.

http://rodcroskery.wordpress.com/2009/11/09/a-visit-to-lostwithiel-farm/

Those good seed trees

Rod Croskery (he of the only site currently on my blogroll) wrote to me recently posing a question that I suspect many would like to ask:

[About the tree in Westport] planted in 1937 by Dr. Ford Goodfellow, the parent tree has very little trunk but an enormous canopy. [The owner] assures me that it has borne heavily every year for the last twenty. If the nuts are well-filled, the parent might meet your criteria for a good orchard tree.

This is a bit of a challenge, because it is growing in a site distinct from the farm. I responded to Rod that currently I was only interested in selecting from the population that I had on the farm. Many rural Ontario communities have populations of black walnut trees, many of which (I am separately informed) would be descendents of the original parent stock brought up by United Empire Loyalists a couple of hundred years ago. This ignores the other common knowledge that First Nations’ peoples also spread the black walnut eastwards from southern Ontario.

These populations I have observed to be regularly productive, so here is my suspicion: that the environment in many of these communities reduces the risk of early spring frost damage to the trees’ flowering, mainly, I believe, through low-level mixing of exhaust gases from heating systems. Most of these trees are within or just moderately above the mean roof line of the community, where such effects could be expected.

How could we test this? If you have a potential seed tree in such a community that you are interested in, I suggest you hang a max-min thermometer on the trunk at breast height (1.35m) on the north side, inside some sort of shield to protect it from the elements, and compare the readings with Environment Canada’s values at the nearest observation site on those nights when spring frosts occur. Do the readings match or not? Remember to reset the thermometer daily.

Because my fields are frost prone, I believe my good seed trees must be relatively later flowering than the rest of the on-farm population. Alternatively, my non-seed bearers are too early for my site, something I must quantify this coming spring. More on this later.

2008 harvest report

Well, over 2 tonnes of fruit were harvested over about five weeks from about 10th October. This includes on- (75%) and off-farm (25%) sources. On-farm, harvesting of ‘3’ trees was independent of ‘1’ and ‘2’ trees (see earlier post on range scores). All nuts from fruiting trees were counted, though 1 and 2 trees were counted at time of pick up (three different sweeps of the fields), and the fruit pooled by field during each sweep. Fruit from each 3 tree was kept separate in plastic lugs in the field, and totals counted when there were no further nuts to fall.

All pooled fruit was processed first – weighed, hulled, then washed and dried. Fruit from 3 trees was weighed, hulled, washed, then sampled and dried. Three-nut samples of 3 fruit were retained for drying, then subsequent cracking and separating. This analysis will be reported under the 2008 Nut Report.

Within the global number reported above, there was much hidden. The two main experimental populations (Fields 1 & 3) are reported below (you can click on the image to open it in a larger format).

Firstly, the nut range scoring system was successful in separating trees by eventual yield (at harvest). In each of the two fields, there are in excess of 500 trees. In each field, more than half of the population did not fruit. The number of trees fruiting (total n) was 187 (F1) and 254 (F3). The average number of nuts per tree was 20 (R1), 94 (R2) and 299 (R3). The biggest contrast between fields was for R3, where F1 gave 448 nuts per tree and F3 gave 151 nuts per tree. Correction of these totals by cross-sectional area (CSA) at DBH (diameter at breast height; multiplied by 100 in the above graph to be able to use the same vertical axis) almost completely reduced this variability to 5.09 nuts per sq cm of CSA (F1) compared to 5.53 (F3). I have termed this value Nut Yield (NY), which you can see was, on average, >1 for R1 and between 2-3 for R2 (remember the 100 factor in the graph above). Groups of bars for same range score number are from fields 1 and 3, reading from the left.

So what? (you might say). Well, it confirmed that it is not just tree size (measured here as DBH) which accounts for NY. There are other factors which make some trees more productive than others. It also suggests that you could forget about harvesting R1 trees and still collect just about the same total weight of fruit, or, put another way, R1 trees contribute very little, individually, to the total harvest, though they make some of this up by sheer numbers. As we are embarked on an inter-generational venture, as long as NY is the main contributor to total kernel yield (KY) per tree, it is only from R3 trees from which we should wish to select. We would want to analyze this characteristic only within the population of R3 trees. It also offers the means (i.e. a sufficient number of very uniform nuts) to set a cracking machine to crack optimally for a given set of nut characteristics, which is some of the rationale underlying US selection of black walnut ‘cultivars’ based on kernel percentage (K%; sometimes measured in efficiency terms as ‘crack out’), though high K% is the other aspect.

In my top-yielding F1 tree, nut number was >1700, with a NY of 7.88. However the top NY (16.15) was from the top F3 tree which gave only 343 nuts. Correction for size is thus immensely important to understanding productivity within a relatively uniform environment, and were both trees to show the same K%, the first would be of greater economic importance to me at this point in time. The former had a 2007 K% of 26% in a nut weight of 15g, which suggests a total KY of 6.4kg from this tree this year. Not insignificant.

Why do I think so many trees are not producing? Probably because they are too early for my site. I shall test this next spring, comparing a random sample with the ‘3’ trees.

Finally, you probably think I’m crazy to do so much counting. Learn to do it, for it will tell you a lot. Use range scoring first, though, so you only count nuts from the ‘3’ trees.

Interim 2008 harvest report

More than a ton of fruit harvested to date, with the scoring system providing essential insight to the trees upon which to concentrate. All category 3 tree fruit is still in the field, awaiting the final nuts to fall before the nut count is done. Fruit from all scored trees has been counted, with category 1 trees averaging about 20 nuts per tree and category 2 about 70 nuts per tree. Category 3 trees are well up into the hundreds of nuts.

Some modifications to the wet processing area were undertaken, with significant improvement in effectiveness and efficiency.

The full report will follow once harvest is complete.

Join our regional germplasm screening study

The trees I shall discuss here are those considered in the post 2007 Nut Report.

How will this work? We will have seed available this fall from these ~25 source trees showing superiority in several variables (e.g. kernel yield per tree, leaf spotting disease resistance).

Firstly, you should be sure that you have a good site – reasonably deep clay loams are best; heavy undrained clays, or very sandy soils will not work.

When you know your site, measure it, and see how many rows of trees you think you can plant. We use rows 6m (20’) apart and plant our trees 6m apart within the rows, but you could use a different between-row spacing if you choose (best not less than this within the row). One field of ours has 12m between rows. You could go higher, especially if you want to continue farming between the rows.

To ensure comparability between all sites, we propose to provide a planting plan according to the number of trees you are interested in. We will request that you plant according to the plan we provide, otherwise we cannot guarantee that we will be able to compare your data to others’.

When you know the size and shape of your site, and have determined the numbers of trees and spacing, divide your site into two components:

a. a rectangular centre section which will be the section we will provide you nuts for, your experimental block; and

b. the outside rows (sides and ends), which you will find your own local seed for ( these are the ones the squirrels will find first, if you have a squirrel problem).

We will divide all available screened seed into packages. The numbers of nuts in a package will correspond to the numbers of rows you have identified in your centre section/experimental block (x 2, as you will plant two nuts per tree location). We will send you the number of packages that correspond to the number of trees in the rows. So you are going to tell us that your centre section is 20 x 8, for example, equivalent to 20 trees per row in 8 rows. The planting plan will provide you the randomly selected positions of each tree in each row, so that you would plant each of the mother-tree selections 8 times across the rows. We suggest that you limit the size of this experimental block to 20 x 8 or less, because you would require 320 (40 x 8) nuts for it, which will be a large drain on our seed resources if many people are interested, and will be the basis on which we calculate cost (cost per nut, including the planting plan, and our email support/quantitative analysis for as long as you send complete annual data sets will be about $1.00).

We would suggest this anyway, because you could always expand in a subsequent year, and you are better off starting with a small block and working out what seems to be working and what doesn’t. We suggest the minimum number of rows to be 4-5, and block size 4 x 4 or 4 x 5. We will suggest how to plant the seed in a later post, but it may be that not every nut germinates, and you will want to replace some ungerminated nuts with nuts from the same mother tree a year later. We typically do this, so factor it in as quite probable.

Participants will purchase the number of packets of seed that correspond to their plan, one per mother tree, up to the total number of trees in their rows. We will generate and post a selected list. Seed packets will be distributed (first-come, first-served) in the order of the trees on the list until that particular tree is sold out (different trees will produce different numbers of nuts; we will retain and plant a seed packet of each source tree to ensure we have trees with which to compare yours). The selected list will rank trees in accordance with the data that we currently have, using the kernel yield per tree for 2007 as the primary indicator. Every other indicator that we use (e.g. leaf disease expression) will be successively discounted by approximately 50%, so that what we know to be economically important receives the greatest weight in our selection. We will post our development of this ranking procedure.

We expect the select list to change in size each year, as we add trees to it (while we like the current 25, we do not guarantee them yet to be the best in our plantation; the current 25 will be kept on to provide replacement seed, and to act as the reference trees in our analyses). If you plant future blocks, planting plans can account for the mother trees already represented in your present block.

If you plant, we hope that you will commit to collecting data on these trees, and sharing it with us. In fact, what we are proposing is really a regional information network, to form the basis of an emerging nut industry. This requires multiple sites.

We commit to maintaining, for as long as we are able, all data on your growing trees, and providing you with annual performance charts concomitant with the number of seed trees represented in your planting. As suggested above, you may wish to undertake something like this iteratively, planting in successive years. We will accommodate your iterative program.

Why do this? We believe black walnut provides the only opportunity for nut production at a commercial scale in much of eastern Canada. It has been our observation that there is no structured program of support for landowners interested in diversifying into nutculture. A simple, practical program, based on a network of interested growers, offers the best opportunity of extending basic knowledge and skills suited to a new tree-based livelihood. It is our interest to foster region-wide adoption of black walnut. Welcome to our network!

I am sorry, but we will not be able to ship seed to the US. All other international destinations will be at your risk.

More than just seed sales

Among our thousands of trees are some which show valuable characteristics: precocity, high tolerance or resistance to leaf-spotting diseases, and high kernel yield. While black walnut is open-pollinated, and there is no complete guarantee that natural offspring will be as disease resistant or productive as the tree from which the seed is harvested, there is a greater probability that these traits will be evident in such trees than those established from non-select trees of unknown origin (e.g. common black walnut purchased from forest nurseries, or grown from seed collected).

We believe that the establishment of semi-improved biomass stands, from seed from trees screened in the way we are screening ours, is less expensive and reasonably predictable compared to other options. It allows you to test many genotypes to find those best suited to your site. Our confidence in this approach can be seen in our own development strategy: expanding our own plantations in exactly this way – select and plant. We offer you the opportunity to do exactly the same. It goes almost without saying that you must have a long-term vision of nutculture on your property to make this worthwhile, as you may have to wait for your first nutcrop for up to 7-10 years from planting. In the meantime you can compare your tree growth with sister trees grown here at Lostwithiel Farm and on other collaborators’ sites.

I will start to post individual tree data soon. You will be able to see the trees we have selected and are on-planting (i.e. the trees the nuts are coming from).

If you are interested in seed this year, I suggest you send me an email. Firm commitments with payment should be made by Oct 15th.

Wet processing

It has been my intention for some time now to post the developing layout for a continuous-flow wet processing area. Until now, all my processing has been on a batch basis, which is very limiting and time consuming. It is my intention to get to the point where my system will contemplate tonnes of product with relative complacency.

My wet processing is done under a steel-roofed addition to my barn. This offers ample opportunity to collect adequate rainfall for storage in two elevated cisterns (8). The area measures about 30' x 15'.

Nuts (more accurately, the fruit) will be received on a conveyor (1), lifted (2) and dumped into a geared-down forage blower (3). This will pre-split the hulls and physically propel them to the hulling machine (4). Hull material will exit the area on another conveyor (5) and the cleaned nut will enter the continuous-flow washer (6) before dropping into the dryer(7). Most transfers depend on gravity, so steps 2 and 3 are intended to lift the incoming material to adequate working height.

The continuous flow washer is this year's collaborative project with Algonquin College, and the initial design is already being critiqued. I hope we will have a proof-of-concept ready for this fall's harvest.

If you click on the above diagram it will open at larger scale in another window.

Tree scoring

Once again, I am indebted to the Ontario Stewardship Rangers (this year aka Josh Bowes, Stefanie McCann, Jessica Rothwell and Eric Dopson), from the Lanark County Stewardship Council for spending a day at the farm and scoring my two main stands of trees for nut load (>1000 trees). This is the third year the OSR has done this, and each year I introduce changes to the system. The 2007 crew had the hardest job.

The purpose of scoring is to identify superior trees ahead of harvest. Different-coloured flagging tapes are tied to the tree in accordance with the assigned score. The superior trees are the ones I am most interested in selecting nuts from for on-planting, and for cracking analysis. We are a season away from mechanical harvesting, so all nuts from superior trees would be hand-harvested and counted before the mechanical harvester was passed through to pick up everything else. The following table indicates the scoring ranges used in the past three years:

2006	2007	2008
None	None	None
1-5	1-5	Few
6-20	6-20	Medium
21-80	21-80	High density
>80	80-320
	>320

The simplification of 2008 stemmed from the realization that counting the nuts on the tree was very difficult and often inaccurate at best (at the high end). Nuts are counted anyway at pickup time, so no more is needed than an estimate of ‘nut density in the canopy’. Thirty-eight trees in total fell into the high category in 2008, about 50% more than 2007.

Prior to harvest the trees will also be scored for other features, and expression of leaf-spotting diseases is one of these. The pairing of low disease expression with medium nut density in the canopy would boost a tree into the ‘of interest’ grouping, such that it would also be selected for on-planting and cracking analysis.

If one embarks on biomass nut production, as we have, where extensive plantations of non-select trees are used, it is important to find management tools which simplify and streamline management for production. Tree scoring is one of these, allowing one to focus on the trees that will eventually add more to the bottom line than others.

Thanks again to the Ontario Stewardship Rangers for their help for the day!

Those spring frosts

The bane of any tender fruit producer’s existence is a spring frost, occurring at bud emergence, and which, depending on severity, can play havoc with the rest of the year. I have noticed that at Lostwithiel Farm the critical period is the first week of May, and that if we can get through it with nothing less than 2^oC our course should set fair. What is the likelihood of this happening?

Environment Canada has just made it easy to search historic weather data for just such trends. I have deliberately chosen a dataset for a location slightly colder than ours (100km to the NE) as being more representative than data collected near Lake Ontario. I have graphed both date and temperature of the latest event in May of equal to or less than 2^oC over the nine-year period for which data is available at this station:

What we immediately see is a high probability of a damaging event occurring at least mid-month or later, and that we should not be surprised by any late spring frost. The 2002 event, a negative reading on the May 25^th, would have tested anyone’s resolve.

However, another factor to consider here is tree size. I collected nuts widely throughout our region in 2002, in fact, it seemed to be a bumper crop, for I have not seen the like since. Frosts generally occur as a result of a temperature inversion, and my hypothesis is that a tall tree has most of its canopy above the freezing zone. What I hope eventually to see, as our trees grow taller, is a declining effect of spring frosts on our own nut production. It is possible that many of the trees out in the landscape have been naturally selected for late flowering, though I don’t place much confidence in this. As far as I know, our first-planted trees are derived from nuts collected in our own seed zone. I actually believe lateness in bud emergence (and thus flowering) runs counter to the natural trend, and that earliness is of evolutionary advantage, but this is nothing we shall prove at the farm. What we will test is the heritability of date of bud break in the 25 lines selected this year, and see whether there is any consistent lateness between maternal and F1 lines.

2007 Nut Report

This week I completed the analysis of the nut samples from the trees selected for on-planting in 2007: I had collected all the nuts from these trees, cleaned and dried them in the usual way, then selected three nuts at random per tree for later cracking. These three-nut samples were then forced-air dried in paper bags at outdoor ambient temperatures for about six weeks before being transferred indoors, and left to stabilize in a warm, low-humidity environment for another six weeks. All nuts were cracked with a Master nutcracker. Nuts were cracked as replicates, i.e. one nut per tree was cracked until all trees were assessed, then the second nut in the same way, and finally the third nut from each tree. The order of cracking within each replicate was random.

Before presenting the results, it is important to note the characteristics of the 2007 harvest. A very late spring frost (May 19^th) caused widespread damage to emerging flowers. Nutting was considerably reduced when compared to 2006. Selection of trees was made initially on low expressed leaf-disease scores, then adjusted in total number for the number of trees that actually gave a sample big enough to ensure sufficient nuts for on-planting. The area selected for planting of this F1 material was big enough for a randomized complete block study of 25 lines replicated 11 times. The planted sample (two nuts per location) thus consisted of nuts from the 25 maternal trees with characteristics (traits) considered most interesting (low disease scores, high nut number in a low nut number year, precocious trees – nutting at a small size/young age, range in nut sizes, etc). As no cracking analysis had been done to date on-farm, there was no prior knowledge of kernel weights or percentages.

The mean nut weight (NW) was 15g, and the mean kernel weight was 2.5g. By themselves, these values don’t tell much about the sample. The following histogram indicates the distribution of KW. NW ranged from about 7.6g to 18.8g. Kernel weight (KW) similarly ranged from 1.7g to 3.9g (line 1-1-17), though NW and KW are not directly correlated, i.e. lowest NW did not exhibit lowest KW, nor highest NW the highest KW.

But I’ve left the best to last. The sample showed a mean kernel percentage (K%) of 22%, calculated from KW as a percentage of NW. Also shown as a histogram, we can see that almost 25% of the trees showed a very respectable K% of 25% or more. The highest recorded K% was over 28% (line 1-9-23). This was far higher than I expected to find in this sample. I had expected a mean K% of about 20%, with perhaps the top line approaching 24%. These expectations are the results of earlier surveys I’ve done off-farm where I’ve had many more trees in the sample, and mainly where lowest K% was far lower ( ~12%). But it is actually quite exciting to find 28% kernel, because the probability is that we shall eventually find higher values. Again, K% is not correlated with NW or KW. In fact, the highest K% was found in a line with mean NW <10g,>

If we complete the analysis by calculating kernel yield per tree (KY, by multiplying KW by the number of nuts per tree; no of nut data is lacking for two lines), we once again find a re-ordering of lines. Line 1-1-14 yielded 1.34kg of kernel. The tree with highest KW (1-1-17) yielded 0.45kg, and the tree with highest K% (1-9-23) yielded 0.32kg. As economic yield will be more closely related to KY, the other parameters of KW and K% become less critical in our selection focus.

Grafted named selections in the US have yielded K% of up to 39%. Our experience in 2007 indicated the existence on the farm of lines of up to about 75% of this potential K% in common walnut obtained from our own seed zone. Far less has been published on nut yield per tree. We have planted an F1 trial of these 25 lines to examine heritability in K%, and the other traits measured on each tree. Almost all of the 25 lines had good disease expression scores (lower incidence); it will be interesting to observe heritability in this trait.

The premise underlying our biomass approach to nut production is that there will be enough trees in the overall population with traits of sufficient value to exploit multiple income streams. To date we can characterize these streams as kernel, shell, and sequestered carbon. We have no intention of focusing on a single trait in our selection program but have yet to construct the functional model which will guide us in optimizing multiple selection criteria. All in all, our economic yield is likely to be defined by how we market the different carbon streams partitioned by the tree. So this is an interim report.

So, how many generations?

Another doughty question. Generation time in our black walnuts is somewhere from 8-15 years, depending on the individual. This is not necessarily the same as the age at which a tree produces a its first nut. The generation time requires that we, as service managers, have enough time to identify and quantify key abilities. If a tree first fruits at six years of age, it is likely to be year 8 or 9 before we have enough data to decide whether we want to add its offspring to our biomass plantations. The nuts will not germinate before the subsequent year. Some trees are not producing fruit even at 15 years of age. Thus, while they are providing environmental services, unless we can identify an income stream independent of fruit production, these less prolific trees are unlikely to add to the farm's bottom-line. As we use a planting layout which requires that some trees be removed to leave room for others to grow, it is more likely to be these less-prolific trees which pay the ultimate price. The first identification of mother trees for on-planting was made in 2007. Offspring will germinate next year. From here on while those offspring will not be evaluated for several years, we will continue to on-plant from useful mother trees, according to several criteria.

Biomass Nut Production

My definition is nut production based on extensive plantations (multiples of 1000) of non-select trees where the objective is the production of large volumes of low-cost fruit annually. How does this differ from other models? The majority of farm-scale black walnut nut production (in the US, where the main concentration of the species occurs) is focussed on grafted selections; these selections are clones of trees found in the landscape which generally satisfied the discoverer's criteria of high kernel percentage and supposed ease of cracking and separation. These named selections, because they are all nursery stock, are expensive ($20+ per tree). While I have no axe to grind with nursery-people needing to make a living, because my broader purpose is nut production as an outcome of an environmental service, I cannot see myself getting there by putting $20,000 into 1000 trees. I might instead buy 1000 $1 seedlings from a forest nursery and work with a genetically diverse stand more likely to throw out interesting specimens under our present climate change scenario. We have 2,500 trees on the farm.