Managing for growth

In a previous post (A bit more about cultivars, Feb 3) I promised to come back to the topic of managing for growth. All that I’ve seen in our plantations suggests that rapid seedling growth (increasing height, expanding DBH) leads to more rapid physiological maturity, and that this in its turn is displayed as fruit setting (nutting). At the core of management for early growth will be weed control, and if you plant, as I did, in old pastures or hay fields, this means grass control. Grasses are particularly pernicious, if you’ll forgive the alliteration. A little while ago I gave a talk to a local woodlot association, where I was tackled about my use of glyphosate. “Why” I was asked “didn’t I mulch my trees?” Laziness, I suppose, though economists would probably interpret that as awareness of an infinitely low return to labour were I to do so, because I am not inherently lazy. The difficulty lies in the number of trees we have – we would have to mechanize the mulching process if we wanted not to have to work around the clock. Let me first, though, defend myself to the purists. In the early years, I did work around the clock, using a Honduran sickle (don’t ask right now) to control grass and weed growth manually. The trees didn’t grow. I also used plastic brush mats (inorganic mulch, if you like). The trees didn’t grow. So I bought myself a backpack sprayer, having seen the local CN maintenance crews spot-spraying for brush control along the local railroad track. I even bought the same model. The trees began to grow. By this time I had 1,500 trees, and found that I could spot-spray the lot in one good day’s hard work. Much better than bending over for several days with my old Honduran friend in hand, without result. The trick was to lower a piece of old 15cm stovepipe over each tree, for protection, while whipping the spray-wand around it. That tells you how undeveloped they were, because even a 50cm seedling can develop enough branches that you’d need a 50cm diameter stovepipe if you were to lower it over the tree quickly.

So the trees grew, and outgrew my technology. Then I picked up an old orchard sprayer from my local machinery dealer, and gravitated to band spraying (switching a tractor-mounted sprayer off between trees requires more dexterity, accuracy, and even controls, than I had, and doesn’t do the machinery much good). Though by this time the trees were getting to the point where a continuously clear band was only going to be good for expanding root growth, so I didn’t begrudge them that extra bit of herbicide. They grew wonderfully. So the lesson in this is that herbicides can be very useful and, if the sums were done, probably far more economical (let alone effective) than mulching. And in case you believe ‘herbicide’ and ‘conservation’ shouldn’t be mentioned in the same breath, or the same sentence, just try g**gling them together, e.g. http://www.appliedeco.org/conservation-research/prairie-restoration-research, or http://www.ecologyandsociety.org/vol7/iss1/art6/
So, let me finish this post off with a couple of photos. The first is courtesy of the Ontario Ministry of Natural Resources and dates from the early 1980s when a lot of work on hardwoods, especially black walnut, was being done. The photo shows the contrast in tree growth between herbicide (background) and no herbicide (foreground). When I find the booklet (it’s lost in my files somewhere) I will confirm the herbicide (simazine, I think) and the agency involved (Canadian Forest Service, I think). Fred Van Althen was the principal researcher. I think the photo speaks for itself about grass effects on black walnut.

The second is from our farm, and dates from 2004. Two years before, these trees were very much like the trees in the foreground of the previous photo. Glyphosate sprayed at the recommended level of active ingredient per hectare gave the grass control you can see here. Some of these trees nutted in 2004, which does not speak to an immediate herbicide effect but rather that the previous spot-spraying was itself effective. Now, I only spray seedling trees under establishment (mainly the selection blocks). My current weapon of choice (not used in this photo) is an ATV-mounted Enviromist Sprayer, with a 60cm spraydome. I can now do hectares of plantation per hour.

Let me mention some of the other consequences of vegetation, mainly grass, control with herbicide. As I generally spray only once, in the spring, there has been an interesting proliferation of broad-leaved species, with an accompanying increase in insect and bird diversity. Note that I say broad-leaved ‘species’, rather than ‘weeds’. The definition of a weed is ‘any plant growing where you do not want it to grow’. While I was quite surprised by the influx of milkweed, and of some other species, it is only ragweed that I truly dislike. Ragweed, apart from its noxious asthmatic-inducing pollen, is a plant with no redeeming features, and can be as oppressive to young black walnut as grass can be. So a second application may be called for. The remaining vegetational diversity I value, as it co-exists with the trees without direct competition. As the trees grow they quickly shade the other species, and I am now mowing beneath them as some grass has returned. There seems to be no juglone intolerance in these broad-leaved species, as I see no major species-difference where they grow between fields with trees or without.

As I walk the walnuts - 5

As I walk the walnuts, either measuring pole or diameter calipers in hand, as it is measuring season, there are things that I notice. It is spring here, though the trees are one of the last to emerge from their winter solitude. When I am measuring height, I often look beyond the tip of the tree to a solitary bird well up in the sky making use of the currents that there must be at that altitude. Not geese, for they announce their passing well in advance, and clear the sky by force. No, these are occasional hawks or gulls that catch my eye and make me pause and wish that I had their talents for silent passage. Where are they going, and who awaits them?

When I am measuring diameter (I measure height and diameter separately, because I struggle to carry all those bits and pieces at one time) my gaze is closer to the ground. Why, I wonder, is there an apparent association between ants and black walnut trees? In my field where I collect most of this data, there is commonly one ant hill between 50cm to 1m from the base of the tree, in the grass-free band along the rows of trees. I frequently find the ants cruising the tree, though sometimes stationary on the terminal buds, and I can only surmise that they are feeding on the sap I sometimes see escaping from larger wounds. But I am amazed that the rule is one hill per tree, where I find them (not all trees have anthills). If this were not a deliberate association, I would expect to find anthills at random distances between pairs of trees, and perhaps in multiples, but this is not the case. Who passes the message on? This is my tree, mate, go and find your own (actually ‘ours’ given that ants are social insects, but ‘ours’ doesn’t mean ‘yours too’). Perhaps there is a scent trail at the base of the tree which says just that: Trespass at your peril!

Applied Research Day

Yesterday (10 April 2008) was Applied Research Day at Algonquin College, where student teams showed off the technology they worked on during their final year at the college. Front and centre was Black Walnut Team 3, exhibiting the current iterations of the harvester and cracker/separator (shown in the picture), and taking up the largest footprint in the exhibition hall by far. I say Team 3, because this is the third annual iteration of students to work on machinery development. It has been a pleasure to work with each team, each bringing its own assortment of personalities and skills, working towards our goal of cost-effective farm-scale technology for black walnut nut production (I think we’ve been a reasonable partner, because I frequently hear the words ‘patient’ and ‘supportive’ applied in our direction; from our perspective these are just elements of our commitment to the emergence of a regional nut production industry).

This event marks a milestone: the completion at the College of work on the cracker/separator, and the production of an experimental harvester which we can begin to analyze practically, i.e. under field conditions, before embarking on a ‘second generation’ model. Both units will come to the farm over the summer and be exhaustively tested. Only the harvester will feed back into Team 4’s program; the cracker/separator will be taken up by the members of Team 2 who demonstrated the first proof of concept to the NNGA last year. They will work with us at the farm to define efficiency, where cost savings in manufacture can be made, and to complete (by the end of the year) the construction of the first five units which we hope to offer to the market. Bookmark this post!

As I walk the walnuts - 4

As I walk the walnuts, I reflect on the changes in bird life on the farm. Back in the early days, before the trees it was pretty sparse, though there were the annual visits from bobolinks, snow buntings, and red-winged blackbirds. Even the occasional kestrel, though this was a function of the hydro cable crossing the farm, and thus the prior existence of a superb scouting perch.

Those all still come, though in ways they didn’t before. The open areas of standing grass between the trees continue to attract the ground-nesters, and the trees themselves offer nesting sites for birds that wouldn’t have nested before. The red-winged blackbirds like to conduct their mating rituals on the aerial infrastructure the trees provide, making a good racket in the process. The kestrels are as likely to perch on the trees now, and it is wonderful to watch their young in their cart-wheeling antics up and down the rows in fall. This year, the snow-buntings may have had a harder time finding food in the open fields because a flock of a hundred or so took up semi-permanent residence in the few trees just outside the kitchen window, thus close to the bird feeder, and would come swooping in every half-hour or so, like a school of tropical fish flashing over a reef, all taking some sort of signal from one, feeding as a flock and not as individuals, taking flight together when someone called the time out. On those cold winter days these were my family, and I took great care to look out every hour or so, to make sure that there was sufficient seed for them, on the ground as much as on the table, as most would feed from that swept off the table either by their mates or by the blue jays that come in and shovel around, looking for the elusive peanut amongst all that other stuff.

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.

The Triumph of the Tree

John Stewart Collis, in his lyrical prose in the book of the same name, begins: We were nursed into life by trees. It is to trees that we owe the development of a physiology which made Man possible – that is to say, made conceptual thought possible. JSC was a remarkable writer, more a natural philosopher, a conscript to WW II who requested to spend it on the land, and who served in an agricultural brigade as a result (he’d actually served in the conventional sense in WW I, so one cannot question his motive). Out of this came The Worm Forgives The Plough (1973) among others, the first book of his I read. His writing had far more in common with the blogging style of today than with the writing of the time http://transitionculture.org/book-reviews/the-worm-forgives-the-plough-john-stewart-collis/). Again, in The Triumph of the Tree (1950), in fact it is not unlikely that in the course of the next few decades after we have had some really rude shocks – we will gradually return (this time on the plane of consciousness) into the Order of Nature, as one factor of the whole. If this happens, the turning point will undoubtedly have been this century. It seems that he was probably just a decade out, a remarkable insight into the perils facing us at a time when global warming was unknown. He is able to conjure questions enough to make a tree laugh, but in spite of its lyricism this is very somber reading, because, sixty years on, one can really see how much further out we now actually exist on the edge, and all, if we accept JSC’s arguments, because we lost our wonder (perhaps fear) of trees, and fled the Era of Mythology. I would like to think that the Era of Science could restore some of this wonder (perhaps respect).

(There have been various publishers of The Triumph of the Tree, starting with William Sloane Associates, and House of Stratus. Most are now extinct, but I see that the used book is still available through the Internet).

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.