Using Nitrogen Fixing Plants

Using Nitrogen Fixing Plants

The use of Nitrogen fixing plants in your garden is widely known to be beneficial to your annual crops.

This is because the Nitrogen made available in the soil by these plants becomes available to the food crops.

The same concept applies in food forests where Nitrogen fixing trees and shrubs are used in place of cover crops.

What tends to be glossed over, or overlooked entirely is information on how to release this Nitrogen in a form that is available to other plants. 

Often, the reader is left to assume that the hard work performed by the bacteria, and the plant that they live in symbiosis with just give it away freely, and this is not the case.

Nitrogen compounds and sugars are exchanged between bacteria, and the root system of a Nitrogen fixing plant. This Nitrogen is stored within the roots of the plant until it is needed.

Some of this Nitrogen goes toward the production of foliage, but by far the most is used for the construction of seeds, and seed pods.

The only way that this Nitrogen can be made available to other plants is to prune the Nirtogen fixing plant.

Turning in a cover crop is pruning in its simplest form where the entire plant is killed, and its decomposition releases the desired nutrients.

Pruning a tree or shrub for the purpose of mulching is a more sophisticated process because it is desirable that the plant survive and grow back so that the process can be repeated many times.

When any plant is pruned above ground, there is an equivalent self-pruning done by the plant in the root network.

This means that Nitrogen is introduced through the decomposition of the foliage as well as the unseen decomposition of roots.

Actually, a plant will self prune it's root system in dry times as well, which means you can fertilise your garden simply by not watering your Nitrogen fixing plants.

Knowing that a plant self prunes its root system is useful because it is a highly efficient means for fertilising the soil. The roots decompose, leaving nutrient rich compost in a fine web through the soil without any need for digging or turning in. This compost not only provides nutrients, but also a network of corridors through which water can permeate.

With many nitrogen fixing plants, deciding when to prune is important from a Nitrogen release perspective.

For example, if you desire that most of the Nitrogen is to be within the soil, then the optimum time to prune is when Nitrogen is concentrated within the root system. This is just before the plant sets seed.

If you desire most of the Nitrogen is to be on top of the soil (as mulch or compost) then the optimum time to prune is when Nitrogen is concentrated in the foliage. This is when the seeds are approaching maturity.

These aspects of pruning and timing form the basis of chop n drop mulching practices in a food forest.

These techniques can be applied to a garden bed without having to till the soil. 

For example, bush beans are known to continue bearing beans so long as you pick them.

This means that the Nitrogen stored in their roots is not exhausted after the first flush.

There is little Nitrogen left anywhere in the plant once it finally dies after you pick all the beans, but if it is cut off at the soil level after its first flush, then the following results:

• A bean crop can be obtained
• A large portion of Nitrogen released to the soil without the need for tilling
• Nitrogen rich foliage useful for composting
• Space and time in the garden for a second crop 

Plant of the Weekish - Autumn Olive

Autumn Olive

Autumn olive is a close cousin to Russian Olive, and American Silverberry.

This large shrub grows to about 15 ft tall whose fragrant flowers produce a rich nectar and valuable bee fodder because they're one of the first trees to bloom in the springtime.

The resulting honey is light, mild, and with a floral aroma.

The dense, thorny foliage provides a wonderful protective environment for wildlife, an effect animal barrier, and useful windbreak.

The beautiful, abundant, edible, and highly nutritious fruit are prized by birds, and many people enjoy its tartness straight from the bush, or made into preserves to be served with cold cut meats or cheese.

Did I mention that it fruits abundantly? A mature bush can produce 650 Kg of fruit in a season. Yes, that is Kg, over half a ton. 

This shrub is a Nitrogen fixing plant, and can be coppiced for firewood, or chop n drop mulching. 

Interestingly, Autumn Olive doesn't produce suckers, but because birds just love the fruit, the seeds will be dispersed widely, resulting in its classification in many places as an invasive alien.

Now, when faced with an invasive alien, we need some way to control and manage it effectively.

Will Smith seems to be a little preoccupied at the moment with his own invasive aliens, and so we will have to make do with the next best thing:

Yes, it turns out that goats absolutely love eating Autumn olive. If you're blessed with acres and acres of Autumn Olive then it's time to get into the goat cheese business.

Now before everyone panics because they don't like goat cheese, I can tell you that this shrub doesn't tolerate shade well, and will die off when your primary trees mature. They won't  "choke" out trees like commonly thought, but they will smother weeds, grass, and wild flowers.

The reason it does this is because its primary role in the ecosystem is to pioneer the regeneration of the forest. And it does this very well.
It also happens to be one of the few shrubs that can tolerate growing next to black walnut, which has the potential to bear fruit in Thunder Bay provided that the correct micro climate is established.

What To Do With Swampy Land?

What To Do With Swampy Land?

The Thunder Bay region is an area dotted with small lakes and extensive wetlands. 

The natural inclination when faced with this type of terrain has historically been to simply drain it with a series of ditches.

Much of the land has been treated this way, and whole residential subdivisions are slowly sinking into the muskeg, due to the falling water table. Flood events are becoming more frequent due to the accelerated rate of water run-off because water regulating land features, such as wetlands, are being destroyed.

This mindset is so entrenched in the wider population, that many believe the only alternative to managing wetlands is to simply leave it to the mosquitoes and leeches.

This is not necessarily a bad thing. Wildlife needs their natural environments intact so that they can survive and thrive.

But is there another way? A way that creates an industrial scale food producing system, while at the same time benefit the natural ecology, maybe even enhancing the wetland diversity? Is it possible?

It turns out the answer to that question is yes.

Chinampas

Tenochtitlan was an ancient Aztec city located in what is now Mexico city. 

The area was originally a swamp (and today Mexico city, just like parts of Thunder Bay, is slowly sinking), and yet the city is believed to have supported a population of around 350,000 people.

A study of Tenochtitlan's agricultural systems reveals that they had one of the most efficient models of food production and distribution ever employed by humanity.

This model of food production is based on things called "Chinampas". A chinampa is basically a finger of artificially created solid ground separated by shallow canals.

A chinampa is constructed by driving stakes, or piles, into the wetland/ lake bed, and building a fence between them by weaving branches, reeds, etc to form something like a giant basket 30 meters long by 2.5 meters wide.

Mud is then excavated from the swamp / lake bed and placed inside these "baskets" until an area of dry land has been formed, and canals between them exist as a result of the excavation.

Once the land has been constructed, water loving trees, typically willows, are then planted along the banks to reinforce the fences, and annual crops planted in the isles.

Irrigation of the plants in such a system is extremely efficient, and works through the capillary action of water infiltrating the growing beds from the canals, and driven by the evaporative action of the plants themselves.  The more water they need, the more water is supplied without any external input required by the farmer.

In increase the productivity of the system further, trellis arches are constructed over the canals, unto which vining crops like cucumbers and melons are grown. 

These have the added benefit of providing shade over the water, and creating a suitable environment for raising fish.

Aquatic fowl, like ducks and geese are then added into the system and feed of aquatic plants and insects that live within this diverse ecosystem.

The fish and fowl defecate in the water, and the subsequent nutrients are taken up by the crops as part of the previously described irrigation mechanism. 

By all accounts, this system takes aquaponics, and applies it on an industrial scale that is simply not economically feasible using our modern technological  approach.

The elimination of the need to fertilise and irrigate crops means that the energy required to maintain such a system is considerably reduced, and human effort can be focussed on the task of harvesting and distributing the harvest.

Harvesting

History has proven that by far the most efficient way to transport goods is via boat. The same principle applies to harvesting and transporting produce.

The reason for this is that the carrying capacity of a boat is very high in comparison to the energy required to move it.

The canals within a chinampa system adhere to the permaculture principle of stacking as many functions as possible within a component of a design system.

In this case, the canal serves as:

• Irrigation
• Nutrient Transport
• Food Growing Medium (Fish etc)
• Harvesting Conduits

Cold Climate Adaptation

The traditional climate for this agricultural system is sub tropical wetland, so there as some factors that need to me taken into account when applying it to a zone 3 environment as we have here in Thunder Bay.

The most obvious factor is the effect of winter ice and snow on the system, and how this influences suitable plant and animal species.

An advantage of a winter freeze on a chinampa system is the ability to access the growing areas using land based machinery via a way of miniature "ice roads" formed by the frozen canals. 

The seasonal glaciation events within the growing areas caused by frost heave introduce an additional mechanism that aids in soil aeration. This action has not been observed in a working chinampa system, and so further research on it's effects could lead to some very interesting findings.

Suitable perennial species of trees and shrubs needs to be identified. The traditional willow that is utilised to reinforce the banks can still be used if a cold hardy species is selected. However, a permaculturist is looking to stack functions...

For bank stabilisation and fruit production, pears seem to be an appropriate alternative due to their moisture loving roots and inclination to grow well on river banks. They're also suited to our climate. Although they produce an edible crop, pears do not float, which means that any fruit that falls into the canal will be recycled back into the system as nutrients.

Apples are another option for over story food production and bank stabilisation provided that the correct variety is selected for moisture tolerance. Apples also float, and the trees can be trained to form living trellises (see espalier) over the canals onto which vining crops, like cranberry, hops, grapes, and melons can then be grown.

Cranberries will grow in this climate, and its vining habit means that it can be trained onto trellises over the canals.

This makes the additional task of harvesting simple because the fruit floats, and can be simply knocked off the vines into the canal.

Something to take note of is that hazelnuts also float, and the shrub grows well on canal banks. It is also an excellent coppicing wood and provider of spring bee forage.

Appropriate Nitrogen fixing support species suitable for stabilising the canal banks include seabuckthorn, which produce an edible crop amongst many other functional attributes.

Blue False Indigo is a perennial under-story Nitrogen fixer suited to river bank environments which is loved by bees and can be heavily and repeatedly chopped and dropped.

Lupines are an annual under-story Nitrogen fixing plant also loved by bees, although it doesn't seem to tolerate shade as well as blue false indigo.

Bees love blue false indigo

Cold Climate Examples

There is unfortunately very little information available regarding cold climate chinampa implementations in cold climates.

Rick Larson has a working demonstration in Wisconsin where he is growing wild rice and blueberries. 

This video below is in a zone 5 climate, located in Montana:

Rick had some neat videos of his chanampa project but have since been pulled from Youtube. Maybe he will put them up again one day...

Final Thoughts

Traditional chinampa involve the creation of annual crop growing beds separated by canals whose banks are stabilised with willow trees. 

A modern, cold climate permaculture implementation involves the use of food producing and Nitrogen fixing trees for bank stabilisation and wind breaks. The incorporation of aquaculture, animal systems, and vertical stacking boost the productive capacity of traditional annual crops.

Something to consider with regards to the annual crops is the incorporation of Hugelkultur as a way to increase productivity, diversity, and edge zones to the system. 

Thunder Bay has an abundance of windfall trees thanks to the abundant, fast growing, shallow rooted, and short lived black spruce, which makes for great hugelkultur building material.

Raising crops up off the water table in this way also provides an opportunity to grow plants that prefer dryer conditions than would otherwise prevail.

Additionally, the physical barrier to the effects of wind would create warm, humid micro-climates, and offer the potential to extend the growing season.

The soggy back forty on many Thunder Bay farms has the very real potential to produce food in both diversity and scale, that far exceeds the capacity of what is commonly considered prime acreage.

Furthermore, the water holding and run-off regulating characteristics are preserved.

Once these areas are developed, they provide a sophisticated wetland ecosystem incorporating far more species of wildlife than the previous environment was capable of doing.

Plant of the Weekish - Russian Olive

Russian Olive

Russian olive is another important support species tree for an extremely cold climate food forest.

It grows to about 20 ft high and is used for its high rating as a Nitrogen fixer.

The tree produces edible fruit, which hangs on the tree through the winter months, providing food for birds and other wildlife.

The fruit has a mealy texture and is used primarily in soups, while the leaves are a desirable fodder for browsing animals such as sheep and goats (and probably deer).

Russian Olive flowers in the spring with clusters of heavily scented blooms that attract bees and other pollinating insects.

The tree will coppice, making it a suitable chop n drop species as well as a source of fuel for rocket mass heaters. 

The hard wood is fine grained and suitable for woodworking. 

In fact, its wood has a very interesting character, and makes for some very beautiful pieces, such as the one pictured on the left that was made by the Canadian artist Hermann de Vries.

Plant of the Weekish - Siberian Peashrub

Siberian Peashrub

This extremely fast growing shrub gets to about 12 ft high when fully mature and is often used as an ornamental tree for its pretty yellow flowers.

To a permaculturist who is interested in stacking functions, this shrub has great potential in our climate.

So let us explore the many ways Siberian Peashrub can benefit an extremely cold climate ecology...

Hopefully the reader has guessed from the photo that this shrub provides lots of food for bees. 

The reader may also have guessed from the name that it might produce some sort of edible pea, and again they would be correct. The fruit pods produced by this shrub are edible by humans and animals, while the leaves make good fodder for browsing animals like sheep, and certain breeds of cattle. Chickens make short work of the pods and the protein rich seeds they contain (12.4% oil and up to 36% protein).

It's also a leguminous plant that fixes nitrogen in the soil. It grows back vigorously when heavily pruned (coppicing), which means that it's an excellent under-story support species candidate for a food forest where chop n drop mulching is practised.

Siberian peashrub has a dense thorny foliage, that provides excellent nesting habitat for songbirds, as well as medium sized windbreaks, animal barriers, and fedges.

Oh, did I mention it's regarded as as invasive weed in many places? Hard working immigrants just can't get a break can they...

Neonicotinoids and Bees

Neonicotinoids and Bees

Neonicotinoids are a class of pesticides that have recently been linked to widespread bee deaths.

Cities all over North America are now moving to ban the use of this chemical as a result.

Interestingly, the concentration of this ingredient is highest in retail products that are sold to the home gardener.

These products are currently on sale in garden centres and big box stores (like Home Depot and Walmart) around the city, but I wouldn't be too confident that your average staff member would be able to help you identify them.

From a permaculture perspective, all pesticides, and herbicides for that matter, are counter-productive and should be avoided. Even the "organic" chemicals destabilise the ecosystems we work had to establish and they have no place in a permaculturists toolbox.

That said, as a public service, I thought it would be valuable to publish this post identifying the Neonicotinoid containing products so that the consumer can make a more informed decision when waging chemical warfare on nature.  

The list is obtained from the following source.

Bayer, that friendly old German company who moved on from gassing Jews at the end of WWII to gassing bugs in your back yard has the following arsenal on offer:

	12 Month Tree and Shrub
	12 Month Insect Control plus Fertilizer
	2-in-1 Rose and Flower Care
	Insect, Disease & Mite Control
	All-In-One Rose and Flower Care
	Complete Insect Killer
	Criterion Insecticide
	Dual Action Rose and Flower Insect Killer
	Fruit, Citrus & Vegetable Insect Control
	Merit Insecticide
	Season Long Grub Control
	Termite Killer

Then there is the Scotts company, famous for its Round-up herbicide product:

	Green Light Grub Control
	Green Light Tree & Shrub
	Ortho Bug B Gon
	Ortho Flower, Fruit & Vegetable
	Ortho Max Tree & Shrub
	Ortho Rose & Flower Insect Killer

And finally, the miscellaneous brands:

	ALOFT Insecticide  (Arysta)
	Arena Insecticide  (Valent USA)
	DIY Tree Care Products Multi-Insect Killer (ArborSystems)
	Ferti-Lome 2-in-1 Systemic (Voluntary Purchasing Groups, Inc)
	Hi-Yield Systemic Insect Spray (Voluntary Purchasing Groups, Inc)
	Knockout Grub Killer (Gro Tec, Inc)
	Maxide Dual Action Insect Killer (Gulfstream Home and Garden)
	Monterey Once a Year Insect Control (Lawn and Garden Products, Inc)
	Safari Insecticide (Valent U.S.A)
	Xytect Insecticide (Rainbow Treecare Scientific Advancements)
	Xytect Infusible (Rainbow Treecare Scientific Advancements)
	Zylam Systemic Turf Insecticide (PBI/Gordon Corporation)