I'll Take Biochar Dressing on the Side

In addition to top-dressing, side-dressing with biochar looks like a labor-saving method of application. Not only is it easier, but the resulting black mulch will enhance the appearance of gardens like mine. I've been using free shredded wood mulch on the paths between my garden beds. With cardboard underneath, a thick mulch layer helps keep weeds to a minimum and feeds the underlying soil as it breaks down. The same can be said of biochar, but there are several additional advantages. (1) Biochar will last much longer than decayed wood chips. (2) Walking paths suffer from compaction, making them less hospitable to roots. Walking on the biochar grinds it down. Biochar particles contain pore space that will compensate for compaction, aerating the soil as they are leached in over time. Paths that are less compacted (containing more air) are more inviting to roots and mycelia. If the roots don't reach that far, mycorrhizae can perform their horizontal drilling trick, expanding the resources available to the plants. (3) Charred wood spread all over is more reminiscent of a forest fire, which is a kick-starter for new growth. (4) More carbon sequestration. (5) It looks more attractive and doesn't fade out the way wood chips do. (6) It's a provocative way to make neighboring gardeners interested in biochar.

The beginning of my biochar mulched paths project. 

This method will have me applying biochar to paths at a greater rate than most of my garden beds, but they will eventually catch up, due to repeated dosing with biochar-infused compost. Biochar application rates over 150 t/ha have been shown to be excessive. For 10 cm of soil, that comes out to almost 50% biochar, which I take to be the target for my gardens. Most gardeners and farmers won't shoot that high, because diminishing returns come into play around 10 t/ha, but I should be able to make this much biochar, and diminishing returns or not, I hope to see some marginal improvement for 10 successive years all the way up to 50% concentration by using biochar on both my beds and paths. Once applications are maxed out, the infiltration of biochar on the paths will continue to promise some improvement for years afterward.

Sunshine Insurance

Composting biochar and digging it into the soil before planting is a best practice that needn't be followed in all situations. When mulch is needed, especially for warmth-loving plants, biochar could be a better choice than straw or other common dressings. As I pointed out in my previous post, this mimicking of a natural fire's residue gives the biochar an opportunity to become somewhat charged and inoculated while holding moisture in the ground.

My pepper plants basking in the heat from a top-dressing of biochar and black plastic

Plants need three things to exist: Nutrients, Water, and a suitable atmosphere that contains Light. Charging biochar with nutrients and getting it wet make it an excellent buffer for the first two needs. For the sake of completeness, I've been trying to imagine how biochar could also buffer a plant's need for light, allowing it to make sugar without total reliance on photosynthesis. If it does this, it would be by use of an alternative energy source, e.g. electric current.

The discharge of electrical currents around plants is touted by some to aid plants in many ways, including improvement of their capacity for photosynthesis. Or perhaps, rather than using light in conjunction with chlorophyll, plants can use electricity through their roots to power the transformation of CO2 and water into sugar.

Biochar has a quasi-graphene micro-crystalline structure that could make it able to generate photoelectrons by sunlight impingement, which it might then store capacitively until its conductivity is raised by filling with rainwater, allowing the electrons to discharge into the ground. Alternatively, rain could deposit cations on the graphene-like micro-crystals to trigger current. In these ways, biochar top-dressings might act as a photosynthesis buffer on rainy days when sunlight is lacking.

These conjectures enable me to maintain the notion that biochar can provide assurance of plants' three essential inputs. If biochar provides sufficient assurance, then maybe the government will see fit someday to subsidize farmers with biochar instead of crop insurance.

Now, (speaking of assurance) I doubt that exposure to the elements is going to fully prepare biochar for incorporation into the soil over a single season. Using a 50-50 mix of compost and biochar as a top-dressing, however, might be just the ticket.

Making Biochar, Rain or Shine

My small scale biochar production cycle is weather-driven. When rain is infrequent, I make char while the sun shines and pour out the new biochar into a framed area dubbed my "biochar patch." Quite a bit can accumulate before rain comes to rinse the biochar and fill up its macropores, making it ready for the next step. I like to allow no more than a day to pass after a good rain before I crush the moistened biochar with a tamper and screen it through a salvaged patio tabletop into a bin. Dry biochar makes too much hazardous dust when crushing and sifting, so rain is welcome, though a couple of dry days are then needed for my feedstock to dry again. This gives me time to split more wood in preparation for the next round. 

My biochar patch with screening tools

Screened biochar

The admittedly tedious process of sifting biochar by hand has the advantage that any remaining torrefied pieces can be culled and sent back for more charring. Torrefied wood, i.e. pieces not charred completely through, inhibits plant growth, and does not belong in the final product. A less laborious (but more polluting) method of granulation is pouring damp biochar into a chipper/shredder. Occassionaly, I do this and then purge the machine by shredding leaves or sticks to prevent the residual biochar from corroding the metal and to avoid having a black dust cloud emerge when the machine is started up the next time. I've seen others use gas powered portable blower vacs to grind up biochar. (My electric blower may do the trick with dry biochar - something to try out.) The output from my shredder is a gelatinous concentration of biochar particles that needs to be mixed well with the soil or compost so that it becomes aerobic once again.

My biochar patch serves as a unique area of water retention for the garden that I am working to turn into something of a tropical paradise. Aside from getting free water to rinse and moisten the biochar, staying in rhythm with nature this way includes the benefit of a nitrogen charge whenever a new storm comes through. During lightning storms, some of the diatomic nitrogen (N2) that predominates in the atmosphere is ionized. These nitrogen-rich ions become entrained by raindrops that deposit it on the soil where it is mineralized into a form that plants can use and biochar can store as a slow-release fertilizer. If enough rain falls on biochar, I suppose it accumulates a sufficient charge of nitrogen to make it garden-ready.

Particles needn't be so fine as from a shredder when biochar is added to the soil. It helps earthworms to ingest them, but the larger (< 2 cm) particles that drop through the expanded metal screen used in a manual approach will break down from freeze-thaw cycles over time and the larger size doesn't reduce biochar's effectiveness in the meanwhile. Some situations are well suited to top-dressing with raw biochar in bulk form. Weathering eventually breaks up these unground particles, so they leach into the soil beneath. In the interim, they acquire nitrogen from above and pioneering microbes from below that make this labor-saving method of biochar application most economical. In my next post, I want to talk about one more reason top-dressing could be preferable to burying biochar.

Making Ponds out of Parking Lots

In the Chesapeake Bay watershed, climate change will make cleanup efforts more challenging because, aside from the storm surges and shoreline damage from the rising sea level, runoff will increase with the greater amount of precipitation predicted in the cooler half of the year. Rain barrels can help only so much, due to their limited volume, but a pond could capture much more water, depending on how it is fed and drained.

Most garden ponds aren't designed with stormwater management in mind, but by allowing water to be partially drained in dry spells and filled up by storms, the pond would function much as a rain barrel does in supplying water to other parts of the landscape and saving on the water bill.

I hate to see all the extra free water from above wasted, so I am considering converting part of our overly large, increasingly obsolete driveway to a segmented pond that would provide a cool and sedate point of entry to our home.  It could be fed by rain barrel overflow, a shed roof, and the adjacent sidewalk. Since it is the high point on our property, it could also be used to water other garden areas. A nitrogen-fixing bacteria filter would be a good place to incorporate biochar, as would containerized submerged planting media. It could be integrated with an aquaponics system in the future.

Photo by Bernie Pallek

Geoengineering Your Garden

Photo by YoungToymaker

When life gives you liminality, make lemons or some other subtropical (or even tropical) fruit. For us here in hardiness zone 7, climate change will probably have us in zone 8 in a decade. My palm trees and peaches will feel right at home. To grow citrus or bananas, however, a little geoengineering will be needed by way of tweaking areas of our property where the microclimate can be pushed a bit further in the warm and humid direction. In Paradise Lot, +Eric Toensmeier and +Jonathan Bates offer many suggestions on expanding your hardiness zone.

Raingardens, ponds, and swales all contribute to higher ground-level humidity. Our future hops vines, growing at a angle to a height of 35 feet should also create a quasi-greenhouse beneath, especially with the compost pit dug into the ground near their base. We also want to leverage warm, sunny spots created by South-facing walls as good areas to tropicalize.

And for that, we have a secret ingredient. Biochar, with its low reflectivity, is a great infrared energy absorber, warming the soil. It also holds about 3x its weight in water. The elevated temperature and moisture create a high humidity zone in the immediate airspace above high biochar concentrations.

My tomatoes and peppers grow prolifically, in part, due to top-dressing with biochar. Where I have cut holes in the black plastic, I mulched with biochar to prevent weeds, capture moisture, discourage pests, and further decrease albedo. I add extra organic fertilizer when it's time to feed the plants, in order to adjust for the nutrient sink created by the biochar. Next season, the biochar will be already charged and populated with soil microbes so that it can be dug in and do long-lasting service in the ground. I prefer this technique over composting of biochar, as it saves time and effort (though compost plus biochar is a superior soil amendment).

Maximizing the biochar concentration in garden beds (up to 50% of soil volume) will produce similar results. The terra preta effect will move your garden to more equatorial climes. We have a lime tree that's been container-grown for 12 years, but one day it might find its place in the sun where the snow never sticks.

Your Own Little Rainforests

Lawns do a fair job of capturing runoff, but just putting an average-sized house on a lot can double the amount of runoff from that property. Much of that increase is channeled to gutters and then downspouts, at which point an owner can take a number of further measures to reduce problems downstream. Outlets from downspouts, be they splash blocks or French drains will often evince erosion where the water is let loose to run freely on the soil. This is the place to intervene with a rain barrel and/or a swale. These may still lead to erosion wherever the water discharges, so a garden can be added to infiltrate the excess.

By concentrating the captured runoff, areas of Maryland properties typically receiving 44 inches of rainfall per year can easily get double that amount, making them like miniature rainforests.  Forest gardens are very good absorbers of groundwater, as are rain gardens.

Photo by Dion Gillard

One of my rain barrels discharges through a 25 foot garden hose into a French drain which discharges to a rock filled swale that empties into a rain garden 80 feet from the house. That easily meets the minimum distance requirement of 15 feet from the foundation and is also at a low point on the corner of my property. The rain garden contains a good deal of biochar and compost and I am planning to fill the cracks between the swale rocks with biochar once I obtain plants that grow well in rock gardens. I also have rain barrels for the other three downspouts on my home, two of which are for keeping mushroom logs watered and one for watering the five terraced garden beds in the backyard.

For water coming off an impervious surface such as a patio onto a lawn, a swale or series of them can be added that run on contour. These are interspersed with raised bed gardens that use the water captured by the swales. Yards with slopes up to 33% can use this device, so where such slopes themselves are the source of runoff, these would also be very helpful. The key to making all these alterations efficacious is gardening. To some that may create the impression of unending toil, but it needn't since the gardens will be watered by the rain flowing to them and can be kept moist and fed with the help of biochar.

Char Your Lawn

Of the nutrients that pollute the Chesapeake Bay lately, phosphorus has been the worst. "Why, of course, with all those chicken factory farms on the eastern shore," might be one's reaction to this statement. In fact, the major phosphorus inputs are coming from tributaries on the western shore of the Chesapeake. The cause has not been identified, but it could well be leaching from residential yards. Maryland soils are generally high in phosphorus, so soil disturbances by developers could also play a role.

In 2012, Maryland passed a law that prohibits the use of phosphorus on lawns except for one-time applications in cases of repairing patches, establishing a new lawn, renovating an entire lawn, or if a soil test shows a deficiency. As the phosphorus gets used up over the years, lawns will then suffer, more soil testing will be needed, and more phosphorus. Biochar can help here. Along with its many other soil enhancing benefits, biochar is very good at adsorbing phosphorus and feeding it to plants, including turfgrass. Most biochars, e.g. those made from wood, also produce a temporary liming effect in the soil, raising high acid soils' pH to one more suitable for turf (6.0 to 6.8). By applying biochar to turf, you can avoid frequent repeat applications of phosphorus and help to reduce pollution of your watershed.

Photo by Mr Thinktank (CC BY 2.0)

The steps to take when renovating a lawn include dethatching with a thatch rake or machine, and then using an aerating machine to remove small plugs throughout. After aeration, apply fertilizer-charged biochar with particle sizes small enough to drop into the newly created holes. (If phosphorus is adequate per soil test results, fertilizing with biochar will still help preserve other nutrients added, as well as the extant soil phosphorus). Spray with water to wash the char into (but not off) the lawn, then seed and water again. The biochar will also help keep the lawn moist while the seed germinates. Check the pH semi-annually to see if lime is needed and don't mow it less than 3 inches.

Permasoil

Weeds like cypress spurge can establish themselves where nutrients are scarce, but most horticultural plants require more care and feeding in order to grow to their full potential. Nitrogen is the macronutrient in highest demand by vegetables, requiring most gardeners to supplement their soils with fertilizer at certain times in a plant's lifecycle. Farmers typically use aged manure as a nitrogen source, which may put their customers at slight risk of pathogens in their produce. Synthetic fertilizers are used by most non-organic farmers and gardeners, leaving a large carbon footprint and upsetting soil microbial communities. Compost adds some nutrients, but the nitrogen is typically consumed within six weeks.

Healthy soil has the ability to cycle nitrogen to plants from the activity of microbes with no outside supplementation. Healthy soil requires the presence of live plant roots throughout the year, e.g. cover crops, with no more than three weeks dead space. If one added compost at a high rate every year, the soil could become nutrient sufficient after many decades. In the meantime, a grower needs to fertilize in addition to using compost.

The missing piece from this discussion is biochar. Biochar raises the cation exchange capacity (CEC) of soil better and more permanently than compost, meaning more nutrients will be available to plants for a longer period. If small portions of biochar are added annually to a plot of land, poor soil health can improve to a self-sustaining level in only a decade or two because it harbors a plethora of soil biota. Once soil reaches that state, it becomes a treasured renewable resource rather than a recurring receptacle. Biochar that is pre-charged with nutrients and inoculated with microbes can bring soil to a regenerative state most quickly.

Photo by Willi Heidelbach (CC BY 2.0)

You can be a successful grower by relying on synthetic fertilizers, or you can be even more successful by following organic practices, including natural fertilizers and compost, but unless you grow on prime farmland already, you can only be fully successful in your lifetime if you use biochar. Until your soil gets to that point, keep the fertilizer handy (but please hot compost the manure).

Pretty, Hardy Weed

After considering problems in critical areas, the next logical runoff concern is that from slopes in general - the steeper the slope, the greater the concern. Slopes not only erode easily, but they also often carry water away too quickly for it to infiltrate the soil. A slope of sandy soil can wash out very quickly and sandy soils are the norm here in Calvert County.

Such was the case at my church where a pocket pond filled up with sand that eroded from its banks before vegetation could stabilize the slopes. The county inspectors finally caught up to us and put us on notice to fix it. The repair plan involves filling up woven bags with the sandy deposits and stacking them on the eroded banks. In short order, we need to also establish better vegetation cover to avoid future problems. Here might be a good place to show how biochar and compost can allow things to grow in difficult conditions.

Not many plants want to grow on sandy slopes, but cypress spurge is one that I found recommended for that situation. I will be on the lookout for it on the roadside as I go about in the next few weeks. If it's as invasive as it's reputed to be, the plant should be pretty easy to find. In fact, I believe I noticed some recently, but wasn't in the market for it at the time. Though normally considered invasive, cypress spurge is the only plant for poor soil among ten recommended by the University of Maryland extension for stabilizing slopes.

Clueless Commissioners

Hugelkultur may not be in the Maryland Stormwater Design Manual, but it doesn't matter for the majority of properties. If a development activity doesn't disturb more than 5,000 square feet of land, the Manual isn't applicable. Most developed properties under private ownership are not going to build more large surfaces or structures, they just get landscaped, so we can do lots of things not discussed in the Manual that will contribute to cleaning up the watershed.

Some locations are still subject to local restrictions; critical areas, for instance. There are many homes in Southern Maryland located in critical areas, i.e. within 1,000 feet of a tidal waterbody. They are critical for the obvious reason that their proximity to the water makes them, by far, the major potential contributors to water pollution. Critical area buffers are therefore, the primary element of watershed protection that should be enforced everywhere.

Violators of critical area rules are sometimes fined when they are reported by neighbors or passersby, but there could be reinforcement of the rules by a more systematic monitoring effort to identify those who bypass the permitting process or don't follow requirements when they develop their waterfront properties. One such effort was proposed by our local Watershed Restoration Specialist that would have entailed making observations of properties via boat and reporting concerns to homeowners and authorities, if necessary. The knee-jerk rejection of said proposal by a St. Mary's County commissioner elicited the rejoinder,"Why Mr. Commissioner? What are you doing illegal on your property?"

Clueless in Tarcoles by Carol Blyberg  (CC BY-NC 2.0)

I hope someone does finger that particular politician and that he ends up paying in full for whatever he is trying to hide. Meanwhile, in Calvert County, Evan Slaughenhoupt, has raised the ire of environmentally conscious citizens by his favoring of Dominion with their white elephant LNG plant construction. He also seems to favor opening the gates wider in the county to land development, with all of the lovely environmental consequences, one of which is the failing D grade given to the Patuxent River on the latest Chesapeake Bay Report Card.