Chop and Drop of Trees and Biomass Plants

The building of fungal rich soils is most often the goal of Permaculture systems and this hinges on returning organic material back to the soil, above and below for decomposition. Chop and drop accelerates soil succession thus facilitating a plentiful soil food web full of complexity and diversity. The interactions between the diverse microbes subsequently advances nutrient cycling bringing cascading affects of resilience into the landscape. However, unfortunately in modern day as we grow gardens, enrich pastures, and plant for yields from tree crops, more often than not we are dealing with poor or depleted soils. From a soil succession perspective they are bacterial

permaculture guild

driven and are in fluctuation with what they can produce. Weeds are rampant, pests and disease reek havoc and extra work is created by this imbalance in the soil. Thus to stabilize the overall ecology we aim to develop biomass producing guilds and other systems of integrated cultivation so that the material needed on a site can enrich soils in relative location. Consequently this produces functional interconnections and ecosystem health as we orchestrate the principle of acceleration of succession and evolution. Often in early stages of a Permaculture, we happily cycle outside sources of carbon material that are seen foolishly in society as waste like woodchips and cardboard and not cycled appropriately. Understandably we play the role of cyclers through composting and mulching but ultimately these outside inputs should be waned over the years. Instead our creative human interaction with nature through design and years of management allow us to procure these soil generating materials on site.

With that we generally cycle carbon in the following ways on site:

• Lopping of branches from trees and shrubs with a focus on nitrogen fixers and high biomass producers
• Cutting of herbaceous layers including grasses and forbs found in grasslands and guilds
• Letting animals chop the green and woody material passing through their gut and dropping as wastes.

In this article we will focus on the design and strategies and techniques within management of the first two and articles on animal systems will specifically address that facet.

Chop and drop of branches from trees with a focus on nitrogen fixers and high biomass producers

When developing integrated systems like food forests or windbreaks or even in the tropics with crop production, branches of trees and shrubs (woody material with leaves) are utilized for soil regeneration. Some utilizable species maybe present already on a site in your outer zones especially those with invasive tendencies. Often they are nitrogen fixers but like in Northern Kentucky, USA (zone 5-6, humid temperate climate) where I

coppice honeysuckle regrowing after chop and drop

manage the family land project, we have Bush Honeysuckle which is extremely prolific and its growth rates are astounding despite not being a nitrogen fixer. I am not sure its exact role in the ecosystem yet, but as we have chopped the forest so much into fragmented bits we have created heaps of edge. This habitat fragmentation allows bush honeysuckle’s niche to proliferate and the forest succession level to coincide for what some call a plague like infestation. Chemicals are used to control it often but I prefer hand powered saws and loppers to cut buck its rampant growth. I lay this material around other native forest tree crops there like spicebush and paw paw but also move it around the site to my cultivated tree crops. These truthfully are not in relative location and demand the pickup truck but further planting out of biomass species in relative location has begun.

One that I have chosen to plant next to tree crops is Siberian Pea Shrub, a nitrogen fixing, fast growing temperate legume. It forms one layer of support and there are options below and above that. Black locust and silk tree both are taller species that can be coppiced easily and the material used as mulch. The finer you cut it the faster it will break down as edge is increased. While chipping wood is a fantastic way to create more edge and speed this breakdown up, in some ways a slower

Black Locust in Flower

breakdown process might be in order. I saw this at my work at Edible Tree Crop farm in Nelson New Zealend (2005-06) where we chipped mostly Tagasaste, a wonderful Mediterranean climate nitrogen fixing small tree, to feed the tree crops. Unfortunately the chips broke down very quickly and a scramble to mulch them further again ensued. Furthermore, when building a food forest, all layers that we normally think of should also contain support species. Whether it’s the vining Wysteria or bramble layer like broom plant, or the tall mulberry or willow, we have a choice of nitrogen fixers and non to fill each level. Thus our human role is to overplant in the support species and over time role this excess vegetation back to our hungry food

From left to right- felling ax, machete, pruners, rice knife, brush clearing ax: tools for chop and drop

producing tree crops. Walking through with a machete, secateurs, loppers, or pruning saws, allows us to balance shade and soil cover depending on the time of year. In general material is cut in wetter parts of the year in those climates that have pronounced wet/dry seasons. Fungus is more active at this time and the sun and wind not such a limiting factor in terms of dehydrating the landscape. Thus the canopy of say a gliricidia tree in the tropics is reduced by 1/3-1/2 and the material fed to surrounding tree crops. If planted in relative location to a cashew tree, the nitrogen-fixing plant like gliricidia will also slump off roots and feed the tree below the ground. However if the rainy season has subsided you are better off having shade and wind protection so time your cutting so that your trees are fully mulched in rainy parts and when things start to dry out you are not scrambling to mulch then. It’s not just nitrogen fixers either, but trees that grow rapidly like mulberry can even be used.

Furthermore,  in managing my broad acre native food forest in Kentucky, I use the native species of Box Elder as it is a rapid grower and coppices readily.  Also when felling trees like black locust for posts, the tree tops are cycled through by chopping the branches fine with a machete and ax.  I lay those around the paw paw patches along with other raked forest detritus as we clean up after the light logging.  This forms a long-term mulch source that feeds the fungus and slows waters descent through the system. I focus on plants that coppice well knowing that plenitude of biomass will come again and again.

Wildlife brush pile

paw paws mulched from invasive clearing and tree harvesting

new sprouts growing on the coppiced black locust

paw paw in fruit

Chopping waste palm fronds

placing chopped palm fronds on a papaya circle

mulched plant from the chopping and dropping of palms in Dominican Republic

Chop and drop of herbaceous layers including grasses and forbs

Not only can woody material be cycled to enrich soils, but also the herbaceous layer which contains no woody stem can be cut back and fed to plantings. The classic example within organic gardening is using comfrey as its high biomass producing quality is easily exploited. It can be cut five times a year and its leaves contain the minerals that it mines as it is a deep taprooter. Other weeds like dock are helpful as well as Jerusalem Artichoke with its pithy stem that can be used in the fall time. Even banana in the tropics I have used before as mulch for other tree crops as it is easily chopped finely with a sharpened machete.

Before chop and drop of diverse mix of guild plants

After chop and drop of diverse mix of guild plants

Also grass clippings can be used in thin layers if you are cutting with mechanical power, yet it is still chop and drop. I have used this in my orchard in Kentucky and let the grass grow for a year around the trees and cut it the next year shooting the grass towards the planting thus mulching with the fresh green spring growth and the dried material from the year before. Otherwise a scythe can mow down heaps of material quickly in longer grasses and forbs. Having wild patches along the edge are great for this as you can procure lots of material easily from these transition zones as well as other ecosystem services such as Integrated Pest Management. Again the finer you cut them, the quicker their breakdown.  They feed more of the bacteria part of the soil food web except when the perennial vegetation is left to complete its yearly cycle and the stalks become dry and much more of a concentrated carbon resource.  In this time the plant material is a nice transition between the green herbaceous layer and the more branchy material outlined above. It helps to build towards the fungal rich soils that will rapidly breakdown the higher concentration of carbon material in branches and helps to spur a more complex and complete soil food web.

Jerusalem artichokes stalks and tuber being harvested in the fall

Jerusalem artichokes stalks

Jerusalem artichokes stalks showing the pithy center

mulching paw paws with Jerusalem artichokes stalks in the fall after chop and drop

Plant Propagation for eventual chop and drop

Furthermore, don’t forget to set up your own nursery or learn skills of plant propagation as building these diverse plantings can get expensive if done only through nurseries.  From a phases of implementation perspective you may even want to grow these support species out for a couple of years before planting your main crops.  It is very important to plan ahead providing multiple elements for the important function of chopping and dropping. This will reduce stress on the system and build abundance more quickly.  Collect seed and plant material where you can which includes roadsides and neighbors lands.  I often due this when in a new context and even botanical gardens can be a great resource. The pic below shows seeds collected from crotolaria, a nitrogen fixing herbaceous tropical plant.  I found these seeds roadside and collected heaps of nitrogen fixing seeds along the road and botanical gardens which we propagated with the local kids. It was a great exercise on community involvement and recognizing the patterns on nitrogen fixers for plant identification is extremely important.  

Conclusion

So get to know your materials, the timing around the cutting and design in wild patches and coppicing trees along the way.  Integrate heaps of other trees and herbs into your agroforestry areas as to provide material on site for energy efficient carbon cycling. Don’t forget to turn the problem into the solution and those “nasty invasives” might indeed become your new best friend.  Advance your soil food web, protect it well, and abundance is sure to be procured as systems stabilize from years of neglect or system setup disturbance.

Written by Doug Crouch

Header art by Sien Verpoest