Information

Can electricity be harvested from the soil around plants?

Can electricity be harvested from the soil around plants?



We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

This is a rehash of a question I originally wrote on Skeptics which got moved to Physics, but I'm really after an answer from a biological perspective.

A device called the E-Kaia is making news by claiming to harvest enough electricity from the soil of a pot plant to charge a phone. They claim they can draw 600mA from the soil, which actually wouldn't charge most smartphones in the 1.5 hours they claim in the article (thanks Physics.SE!).

Is there really electricity in the soil around a plant? I can't imagine there being 600mA there for the taking in the soil of a huge tree let alone a pot plant. Maybe it isn't electricity in the soil but some other kind of energy or chemical that can be extracted to generate electricity - it sounds like the lemon battery experiment, which relies on a chemical reaction.

And surely, even if there was electricity there, extracting all of it would damage the plant?


Electricity may be indirectly generated from plants through the use of a microbial fuel cell, in which biologically-catalyzed chemical reactions are used to drive an electrochemical cell.

A non-technical description of the technology can be found here. The basic idea is that plants produce organic compounds, which are broken down by soil microorganisms to produce carbon dioxide, electrons, and hydrogen ions. Ordinarily the hydrogen ions and electrons combine with oxygen to form water, but there are various ways to divert the electrons to travel through an electrical circuit before the oxidation reaction takes place. This flow of electrons (electricity) can be used as a power source.

This technology is still in its early stages but the process has been demonstrated in some laboratory proof-of-concepts:

  • Strik, David P. B. T. B.; Hamelers (Bert), H. V. M.; Snel, Jan F. H.; Buisman, Cees J. N. (2008). "Green electricity production with living plants and bacteria in a fuel cell". International Journal of Energy Research 32: 870-876. doi:10.1002/er.1397.

  • De Schamphelaire, Liesje; Van den Bossche, Leen; Dang, Hai Son; Höfte, Monica; Boon, Nico; Rabaey, Korneel; Verstraete, Willy (2008). "Microbial fuel cells generating electricity from rhizodeposits of rice plants". Environmental Science and Technology 42 (8): 3053-3058. doi:10.1021/es071938w.

The E-Kaia company has not released enough information to say whether their product is in fact a plant microbial fuel cell, a simple earth battery, or a mere scam.


A Beginner’s Guide to Transplanting Plants

Bethany is a suburban homesteader who grows over 30 types of vegetables in her garden every year to provide the vegetables needed to feed her family of six for the entire year. She practices organic gardening without the use of any pesticide and chemical.

After you start your seeds and sprout your seedlings, the next hurdle that you need to conquer is transplanting your plants into your garden.

Transplanting the wrong way could kill your plants, and that’s the last thing you want to do! That’s why this common process can feel a bit scary you don’t want to do it wrong, but how hard can it really be if everyone does it all the time?

With the right knowledge, it’s not hard at all. Here’s what you need to know.


Calamint Care

Calamint is a relatively low-maintenance little flower that can tolerate a variety of soil types, lighting, and temperatures. These small, bushy, aromatic perennials are known for being so versatile that it makes a popular choice for even the most novice gardeners.

Calamint tea is known for being fresh, fragrant, and sweet, and is also known to help aid in healthy digestion. You can harvest the leaves from your calamint plants at any point through their growing season, though picking the leaves at the start of the season and first thing in the morning is recommended for the fullest flavors.

Light

Plant your calamint in a spot that boasts full sunlight for at least six to eight hours a day. That being said, calamint can also tolerate partial shade, especially during the hot summer months. If your plant is located somewhere that receives afternoon shade, it will likely be just fine.

Known for being able to adapt to pretty much any soil type, calamint can grow in infertile, gravelly, loamy, and sandy varieties without issue. The only truly important factor is that the soil it's planted in boasts good drainage to prevent root rot and other diseases.

Water

Calamint likes to be kept consistently moist, but it copes surprisingly well through periods of drought. To prevent stress in prolonged drought conditions, you should still lightly water your calamint after the top inch of soil has dried out. Overwatering, however, is a bigger problem. Calamint roots don't like to be sitting in standing water and can easily develop root rot if kept moist for too long without being allowed to dry out.

Temperature and Humidity

If you experience chilly winters, calamint could be suited to your garden. They're relatively cold hardy and can survive even when temperatures reach below freezing. However, this isn't a plant that appreciates extreme heat or humidity—those conditions may necessitate a slight change in your care routines, such as more shade or more frequent watering.

Fertilizer

Unless planted in highly infertile soil, your calamint won't need any fertilization. If your soil is particularly deficient in nutrients, applying a balanced fertilizer just once at the start of the spring could help to increase the plant's vigor.


Turn soggy spots into wetlands

Since nitrous oxide emissions come mainly from wet zones, letting these areas remain as wetlands is another climate-smart strategy. Soggy areas tend to yield poorly in most years, and farmers rarely recoup their investment in cropping them. However, wetlands can be troublesome to farm around, which is why many farmers try to drain and farm through them.

But healthy wetlands also provide benefits: They sequester carbon, store and filter water and provide crucial habitat for mammals, birds, frogs and other organisms. The Agriculture Department’s new Climate-Smart Practice Incentive will support wetland restoration on agricultural lands.

Another USDA initiative, the Farmable Wetland Program, pays farmers to take previously farmed wetlands and buffer areas out of production for 10 or more years. Enrollment is currently capped at 1 million acres. A climate-smart agricultural policy could expand the program by removing the acreage cap and boosting incentive payments.

A prairie wetland in Minnesota, formerly part of a crop field (left) and restored to provide habitat for water birds (right). Shawn Papon/USFWS, CC BY


How Healthy Is The Soil On Your Farm? 'Soil Your Undies' To Find Out

In Australia, farmers are burying underwear to gauge soil health.

Question - for the sake of the environment, are you willing to soil your undies? Before you lunge for the radio dial in disgust, I should explain we're talking about burying cotton underwear as a way to test the health of your garden's topsoil. In Australia, dozens of farmers have taken the Soil Your Undies Challenge. Oliver Knox helped organize the effort. He's a senior lecturer at the School of Environmental and Rural Science at the University of New England in New South Wales.

OLIVER KNOX: So these farmers take their pairs of pants out into their field and dig a shallow hole - literally, 5 centimeters deep, so the - you know, the depth of their fingers. And they lay the pants down flat, cover them up. And then they go back eight weeks later. They dig them up, and they're looking for degradation of the cotton, the breakdown of the pant. So in a nice, healthy soil where the soil biology is both diverse and active, all they'll get back will be the elastic waistband and the poly cotton stitching because the bacteria and the fungi in the soil have really gotten to work on that cotton fiber and broken it down into the sugar that it's made of and consumed them.

GARCIA-NAVARRO: The tasty cotton underwear was actually supplied by Knox and CottonInfo, an Australian industry group. Eight weeks after sending 50 pairs of undies to 50 farmers, the results came in.

KNOX: Fifty of these little Ziploc bags came back with soiled underpants, and it became a real competition between the farmers. You know, my soil's better than your soil because my pants are more degraded. And it was just wonderful to see them sort of create that competition between themselves but also just to start that conversation around soil biology and their soil health.

GARCIA-NAVARRO: The Soil Your Undies Challenge began in the United States and Canada a few years ago. But when Knox and his colleague Sally Dickinson brought the project to their own country, they encountered an especially Australian problem.

KNOX: The protocol basically said bury the underpants and leave the waistband above the surface so you can go back and exhume them really easily. So the first pair we tried, we did that. And we went back, oh, within a few weeks, and the pants had gone, but there was lots of kangaroo paw prints around the hole. So somewhere, Skippy's out there running around the outback with a pair of tighty-whities, as they like to call them here. So after that, complete burial and a flag, so we knew where they were.

GARCIA-NAVARRO: Jokes about kangaroos aside, the Soil Your Undies Challenge is a low-tech, accessible way to gauge soil health and draw attention to the shrinking supply of the world's topsoil.

KNOX: Our biggest risk is probably erosion. And then as climate change gives us more severe and more unpredictable rain events, we always run the risk of erosion. Our topsoil is so important. You know, it's where a lot of our nutrition and our mineral turnover occurs, which is what our plants rely to grow on. So, yes, we've got a lot of fragility there - the risk from pollution. And I always throw into that mix as well, particularly in urban areas, you know, that risk from sealing of our soils - concrete, tarmac, the things - the houses, our infrastructure that we build on it. You know, we've sealed it up. We can't grow on that anymore.

GARCIA-NAVARRO: School teachers in Australia are also drawn to Knox's project, though COVID lockdowns have affected his work.

KNOX: Not being able to go out to school groups and do our usual extension, we decided we'd open up this Soil Your Undies as a citizen science and particularly, a school-based challenge. So last year, we basically got 207 pairs of pants out to community groups, 161 of which were schools. And they soiled their undies, and we exhumed them, and they sent them back to the University of New England and put images up on social media. And we just got a really nice feel for, basically, the state of our soils right across Australia. To get, I think, school kids engaged in thinking about what goes on in these soils - I think if we can stimulate an interest in them at that young age and encourage that, then I think, hopefully, we can see changes in the way that maybe we behave towards our soils and our landscapes and make our future more sustainable through them.

GARCIA-NAVARRO: That's Oliver Knox from the University of New England in New South Wales.

Copyright © 2021 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR&rsquos programming is the audio record.


How to Grow Brussels Sprouts

Time planting so that Brussels do not grow in periods of extended warm weather much above 70°.

Brussels sprouts are a slow-growing but very bountiful crop. Planting Brussels sprouts from seed outdoors requires a very long, cool growing season. Timing is important when growing Brussels sprouts.

  • In most regions, it is best to plant Brussels sprouts so that they come to harvest in autumn.
  • Start seeds indoors 12 to 14 weeks before the first frost in autumn for harvest after the first frost.
  • In mild-winter regions plant Brussels sprouts in late summer or autumn for winter or cool spring harvest.
  • Brussels sprouts reach maturity 80 to 90 days after transplanting and 100 to 110 days after sowing seed depending on the variety.
  • Time planting so that Brussels do not grow in periods of extended warm weather much above 70°.

Where to Plant Brussels Sprouts

  • Brussels sprouts grow best in fertile compost-rich, well-drained soil. Add 6 or more inches (15cm) of aged compost or commercial organic planting mix to planting beds before planting then turn the soil to 12 inches (30cm) deep.
  • A heavy soil, not a light sandy soil, is best for growing Brussels sprouts.
  • Brussels sprouts prefer a soil pH between 6.0 and 6.8. If clubroot disease has been a problem in the past, add lime to adjust the soil to 7.0 or slightly higher.
  • Avoid planting Brussels sprouts in the same location two years in a row. Crop rotation is important to prevent soil nutrient depletion and soilborne diseases.

Start seeds indoors about 5 to 6 weeks before you want to set transplants in the garden.

Brussels Sprouts Planting Time

  • Plant Brussels sprouts so that they come to harvest in cool weather the ideal time to harvest Brussels sprouts is in autumn after the first fall frost.
  • To determine the best time to plant Brussels sprouts, estimate the date of the first fall frost then count back the number of days to maturity for the variety you are growing that is the date to set Brussels sprouts transplants in the garden.
  • Sow seed directly in the garden 10 to 12 weeks before the first average frost date.
  • Time the planting so that harvest comes about 2 weeks after the first frost.
  • The best average temperature range for Brussels sprouts growth is 60° to 65°F (15-18°C). Temperatures much above 70°F (21°C) can cause Brussels sprouts to bolt and go to seed.
  • Brussels sprouts will reach maturity 80 to 90 days after transplanting and 100 to 110 days after seeds are sown.
  • Mature Brussels sprouts plants are not suited for temperatures greater than 80°F (26°C) sustained warm temperatures will leave Brussels sprouts bitter tasting and may cause their tight cabbage-like heads to open.

Space or thin plants 24 to 30 inches apart in the garden.

Planting and Spacing Brussels Sprouts

  • Sow Brussels sprouts seeds ¼ to ½ inch (6-12mm)deep.
  • In flats or containers, sow seed 2 inches (5cm) apart when plants are 5 to 7 inches (12-17cm) tall they can be transplanted into the garden.
  • Space or thin plants 24 to 30 inches (61-76cm) apart in the garden. Space rows 30 to 36 inches (76-91cm) apart.
  • Leggy transplants or transplants with crooked stems can be planted up to their first leaves so they won’t grow top-heavy.
  • Be sure to firm the soil around Brussels sprouts transplants so that they are well-rooted and anchored as they mature.
  • Plant 1 to 2 plants per person in the household

Container Growing Brussels Sprouts

  • Grow a single plant in a container 12 inches (30cm) wide and deep or larger.
  • In larger containers, allow 24 to 30 inches (61-76cm) between plants.
  • Keep the soil evenly moist.
  • Feed plants compost tea or diluted fish emulsion solution every three weeks.

Watering Brussels Sprouts

  • Keep the soil around Brussels sprouts evenly moist water at the base of plants.
  • Brussels sprouts require 1 inch (16 gallons/60.5 liters) of water each week or more.
  • Mulch around plants during the summer to slow soil moisture evaporation and to keep the soil cool.
  • Give plants shade if the weather warms much above 70°F (21°C).
  • Reduce watering as Brussels sprouts approach maturity.

Feeding Brussels Sprouts

  • Fertilize before planting and again at midseason side-dress plants with well-aged compost or feed with an even organic fertilizer such as 5-5-5 or 10-10-10.
  • In regions with heavy rains or sandy soil, supplement the soil with a nitrogen-rich fertilizer.
  • If Brussels sprouts develop hollow stems or small buds, the soil may need the plant nutrient boron. You can add boron to the soil by dissolving 1 tablespoon of borax in 5 quarts (4.7 liters) of water and sprinkling it evenly over the planting bed (this will cover 50 square feet/4.6 square meters).

Companion Plants for Brussels Sprouts

  • Plant Brussels sprouts with beets, celery, herbs, onions, potatoes avoid pole beans, strawberries, tomatoes.

Set a stake in place soon after planting or transplanting mature plants will be top-heavy with sprouts and can lean or fall. At stake is necessary wherever it is windy.

Caring for Brussels Sprouts

  • Place cutworm collars around young seedlings.
  • Set a stake in place soon after planting or transplanting mature plants will be top-heavy with sprouts and can lean or fall. At stake is necessary wherever it is windy.
  • Keep planting beds free of weeds. Cultivate shallowly or weed by hand to avoid disturbing roots Brussels sprouts are shallow-rooted.
  • To encourage all of the sprouts on a plant to come to harvest at the same time, pinch off the top terminal bud when the plant is 15 to 20 inches (38-50cm) tall or 4 weeks before harvest time.
  • Remove lower leaves from the sides of stalks as sprouts develop and are harvested leave top leaves intact.

Brussels Sprouts Pests

  • Brussels sprouts can be attacked by cutworms, aphids, cabbage loopers (preceded by small yellow and white moths), and imported cabbage worms.
  • Aphids can be knocked off of plants with a strong blast of water.
  • Cabbage loopers and cabbage worms can be handpicked off of plants and destroyed or spray with Bacillus thuringiensis.
  • Place cutworm collars around young plants early in the season.

Brussels Sprouts Diseases

  • Brussels sprouts are susceptible to yellows, clubroot, and downy mildew.
  • Cabbage yellows are a fungal disease lower leaves turn dull green then yellow and then the disease spreads upward the stem and vascular system become brown and rot. Control yellows by applying compost tea to roots bacteria in compost tea can suppress fungal spores. Plant resistant varieties.
  • Clubroot is also a fungal disease. It causes roots to swell plants become weak, yellow, and wilt. Control clubroot by maintaining a soil pH of 7.0 and add calcium and magnesium to the soil. Rotate Brussels sprouts and other cabbage-family members out of infected beds for 7 years.
  • Planting disease-resistant varieties.
  • Keep the garden clean of debris to reduce the possibility of disease. Remove and destroy diseased plants immediately.
  • Rotate crops each year.

Harvest buds when they are small and tight, about 1 to 1½ inch in diameter.

Harvesting Brussels Sprouts

  • Sprouts begin to form in lower leaf axils first and then continue to develop and mature upward. When sprouts mature, nearby leaves turn yellow.
  • Harvest buds when they are small and tight, about 1 to 1½ inch in diameter.
  • Break or cut off yellow leaves above developing buds as you harvest upwards. Remove leaves just above buds a few days before harvest leaving about 2 inches of leaf stem on the stalk as you remove each leaf. This will give developing buds room to grow round.
  • The harvest of buds from one plant can last as long as 6 to 8 weeks.
  • One plant can produce as many as 100 sprouts.
  • If you want to harvest all of the sprouts on a plant at once, pinch out the growing tip—the top set of leaves𔃂 weeks in advance of harvest. All of the sprouts on the stem will come to harvest at once.
  • Tendergreen leaves can be eaten as greens or cooked like collards.
  • Cool temperatures and frost will sweeten the flavor of buds coming to maturity.
  • Warm temperatures will cause sprouts to be loose-leaved and strong flavored.
  • If a severe, hard freeze is forecast before the end of harvest, lift the whole plant root and all and put in a cold frame or unheated shed you can complete the harvest there. Pack earth around the roots so that the plant does not dry out.
  • The first sprouts harvested will not be as flavorful as the last.

Storing and Preserving Brussels Sprouts

  • Brussels sprouts buds will keep in the refrigerator unwashed for 3 to 4 weeks keep them in a plastic bag or air-tight container.
  • Sprouts can be frozen for up to 4 months after blanching.
  • Stems loaded with buds in late fall can be harvested and kept in a cool (30° to 40°F), dry place for several weeks.
  • Remove loose or discolored outer leaves from stems before storing them.
  • Do not wash buds until you are ready to use them.

Brussels Sprouts Varieties to Grow

Bubbles (110 days) Catskill Early Half Tall (90 days) Jade Cross (90 days) Long Island Improved (95 days) Oliver (90 days) Prince Marvel (90 days) Royal Marvel (85 days) Rubine Red (105 days) Seven Hills (95 days) Tasty Nuggets Valiant (110 days).


Harvest Carbon From the Air

Carbon is as precious as gold to plants. Working with water and sunlight, carbon makes plants grow. Plants assimilate carbon in the form of carbon dioxide, extracting it from the air to make roots, shoots, and leaves. With the help of soil microbes, the plants then transfer the carbon to the soil through roots and decomposing residue.

The stable storage of this carbon below ground not only builds soil organic matter and improves future crops but also, like a pressure valve, relieves the atmospheric carbon buildup.

Carbon benefits

The benefits of this plant-driven harvesting of carbon from the air extend far beyond the farm and ranch gate.

“If we were able to increase the carbon in the soils of the world by sequestering 3.6 gigaton of carbon per year [1 gigaton equals 1 billion tons], we could offset or negate the additional effects of climate change that will be caused by future increases in carbon dioxide released by the fossil fuel use of a growing world population,” says Rattan Lal. Lal directs the Carbon Management and Sequestration Center at Ohio State University.

“It is this assumption that was the basis of the 4 per Thousand program initiated at the Climate Summit in Paris in December 2015,” he says. “The strategy of this program is to sequester carbon in soils of the world at the rate of 0.4% per year in the top 16 inches of soil. Implementing such a program would require appropriate policies to encourage farmers to adopt the recommended management practices.

“Globally, the release of carbon into the atmosphere from fossil fuel use is 10 gigaton, and it goes up annually,” says Lal. “The U.S. accounts for about 18% to 20% of that amount. In the U.S., the per-capita rate of release of carbon into the atmosphere is going down but rising globally. Global warming has resulted from the increasing levels of carbon in the atmosphere. This is causing an increased frequency and intensity of extreme weather events such as floods, droughts, and hurricanes.

“Estimates of the total potential of carbon sequestration in world soils vary widely, and this potential is finite in capacity and time,” says Lal. “Nonetheless, soil carbon sequestration buys us time over the next 20 to 50 years until the low-carbon or no-carbon alternatives to fossil fuel take effect.”

The capacity for soil to sequester carbon is finite, because it’s limited to the soil’s original capacity to store carbon. Agricultural use over time has caused soil to lose carbon. Restoring soils to their original states accounts for the global potential for carbon sequestration.

“The potential soil carbon sink capacity of managed ecosystems approximately equals the cumulative historic carbon loss estimated at 55 to 78 gigaton,” says Lal. “Some recent estimates indicate the historic loss as high as 130 gigaton. Restoring carbon stock in world soils by 130 gigaton would be equivalent to a drawdown of atmospheric carbon dioxide by about 65 parts per million. Such an achievement could happen in 50 to 100 years.”

Lost carbon

For some U.S. croplands, the historic carbon loss translates into a loss of more than half of soil’s original carbon content.

“Within the Great Plains, a historical evaluation from Texas to Montana found relative soil organic carbon losses to range from 39% to 59%,” says Mark Liebig, soil scientist at the USDA-ARS Northern Great Plains Research Laboratory at Mandan, North Dakota. “Losses of soil organic carbon were due to cropping practices that relied on the use of intensive tillage and fallow for the production of corn and small grains.”

Restoring carbon in the soil results from a matrix of management practices that reduce soil disturbance, conserve root and plant residues, improve soil structure, and enhance soil biology and nutrient cycling growing diverse crop rotations including cover crops and perennials. These processes tend to increase populations of fungi, microbes, and other beneficial soil life critical to restoring soil health and sequestering soil carbon.

Carbon Sequestration Responses

Measured carbon sequestration responses to specific practices include the following.

  • Spring wheat grown by conventional tillage. A study at the Northern Great Plains Research Laboratory showed how differences in cropping systems affect soil structure and, ultimately, soil carbon. In the conventionally tilled spring wheat, the soil had 14% water-stable aggregates, and the carbon in the top 3 inches of soil measured 6.6 tons per acre.
  • No-till continuous cropping of spring wheat/winter wheat/sunflowers. The same study found no-till soil had 47% water-stable aggregates, and the carbon measured 9.6 tons per acre.
  • Pasture managed under moderate but continuous grazing. In this third treatment of the study, the soil had 93% water-stable aggregates, and the carbon measured 12.8 tons per acre.
  • Switchgrass production. A five-year on-farm study by the Agricultural Research Service evaluated switchgrass for ethanol production. The study encompassed 10 on-farm fields in Nebraska, South Dakota, and North Dakota. The fields were located in marginal land areas that would have qualified for the CRP.

“Within the top 12 inches of soil, soil organic carbon increased across all sites at a rate of 980 pounds per acre per year,” says Liebig. “In Nebraska, where four sites were sampled to a depth of 48 inches, carbon increased at an average rate of 2,590 pounds per acre per year.”

The changes in soil organic carbon were variable among sites, ranging from a decrease of 540 pounds per acre per year to an increase of more than 3,800 pounds per acre per year.

The study underscores the potential of perennial grasses to sequester significant amounts of carbon in the soil. These deep-rooted perennials are more effective than the more shallow-rooted annual crops at storing carbon at depths where it’s less likely to be released back into the atmosphere due to possible soil disturbance.

Yet the study also shows the variability in carbon-accrual rates of a single practice played out in different settings. Geography, climate, production practices, and other variables play a role in accrual rates.

A process for measuring the rate at which carbon accrues in soils is presently not readily available to farmers and ranchers.

However, rough estimates of carbon pools in soil may be drawn from levels of soil organic matter.

“Organic matter is about 50% carbon,” says Lal. “If organic matter is increasing over time – such as by no-till farming with a cover crop – it is possible to increase soil carbon stock at a rate of 500 to 2,000 pounds per acre per year. By the use of petroleum-based production inputs – such as fertilizers, herbicides, and farm operations – some carbon is also being used in order to sequester carbon. So there’s a gross carbon-accrual rate and a net rate.”


Diverting Rainwater to a Filtration System

In certain areas, and for certain uses, it can be a good idea to think about diverting rainwater through a filtration system. Simple filters of straw/charcoal, sand, and gravel can remove particulates prior to use. Reed beds or other phytoremediation areas can use plants and micro-organisms to filter further impurities out of the water before it is used.

Should you wish to do so, it is also possible to use more sophisticated modern filtration systems to turn rainwater into water that will be suitable for use inside your home. This can be a useful option to consider in off-grid situations. To harvest rainwater for drinking, consulting a professional for guidance can help ensure you set up a safe system.


7. Broadleaf Mustard

Broadleaf mustard (Brassica juncea) is a cool-season autumn cover crop planted to boost nutrients (and repel pests) for the following growing season. As a green manure, these plants work to pull nutrients from deep below the soil surface, making them available for next year&rsquos veggies. Broadleaf mustard also keeps weeds down, repels garden pests, and holds soil in place to protect against erosion from winter precipitation.

Plant broadleaf mustard in late summer as the first of the warm-season veggies finish harvest. Broadleaf mustard will produce leafy greens for a month or two, followed by little yellow flowers. It generally takes about 3 months for mustard to produce seeds. When growing it for green manure, make sure to cut down the crop before the seeds are produced. After trimming, work the organic matter into the soil as green manure.


Silicon, Nitrogen, and the Soil Food Web

The previous subheading on soil testing indicates optimum levels of minerals for plant efficiency and nitrogen fixation. Though these guidelines are generally higher than those considered adequate in chemical agriculture, these levels are desirable for efficient photosynthesis, especially at lower temperatures. This is particularly true for silicon, which is almost always deficient in conventionally-farmed soils. Silicon, and its co-factor, boron, are the principal keys to transport speed, which is the key to abundant photosynthesis in plants. Energy must be transferred from the chloroplasts in the leaf panel to the leaf ribs where sugars are made. Silicon is basic to fluid transport, and this transport determines how fast sunlight is converted into sugar.

Nitrates, nitrites, and other nonorganic forms of nitrogen impair the silicon chemistry of the plant as well as the symbiosis between plants and their microbial partners in the soil — unlike amino acid nitrogen, . Raw manures and poorly composted manures, especially raw poultry manure, are extremely detrimental because of the nitrate burden they impose on the soil biology. Nitrates flush silicon out of both plants and soils. How well a plant picks up silicon from the soil depends, at least in part, on the level of actinomycete activity at its roots. This in turn depends on the extent to which the soil opens up and is aerated, which in turn depends on sulfur levels and soil microbes such as Archaea that digest siliceous rocks. The sensitive biochemistry of these activities, in both soils and plants, is impaired by high levels of nitrates.

Animal activity in the soil around plant roots provides freshly digested amino acid nitrogen, which encourages the release of silicon from the surfaces of soil particles. Living in partnership with plant roots, actinomycetes form fine fuzz along the root exudate zone of young roots, and nitrogen-fixing microbes make this their home. In the process, the actinomycetes utilize the silicon and boron in forming their fine, fuzzy hairs. As roots age and mature, these microbes are consumed by soil animals ranging from single-celled protozoa upward. The nutrients they excrete are taken up as nourishment by plants, often providing a high proportion of amino acid nitrogen and amorphous fluid silicon.

Soil microbial life can only access silicon at the surfaces of soil particles where moisture, air, and warmth interact. The rest is locked up. Nitrogen fertilizers, particularly nitrates, suppress actinomycete development and the nitrogen-fixing microbial activity they host. On the other hand, if actinomycete activity is robust, the soil food web freely provides a luxury supply of both amino acids and amorphous fluid silicon.

Biodynamic practices promote this activity as a way to achieve quality production that sustainably and efficiently rivals the yields of chemical agriculture. The bonus comes when environmental conditions are less than ideal. Biodynamic production can then easily surpass chemical yields.