At the top of the list are the PGS Mixt A & B custom soilless blends. Some of the most experienced master gardeners in Sonoma County swear by these blends. If they work for the pros, they can definitely work for you! Come on down and check them out.

We also have the following soils in stock:

Sunshine #2, Sunshine #4, B’cuzz, Light Warrior, Happy Frog, Ocean Forest, Roots Organic Soil, Roots Organic Soilless, Black Gold Cocoblend, Black Gold Organic, Readigrow Aeration, Power Flower, MJR Blend and Humisoil.

If you use a product that we don’t currently have in stock, we would be happy to special order it for you.

As always, our horticulture experts are on hand to help guide you to the right medium.

Whether its one bag or a whole pallet, we have what you need at a great price! Give us a call at 1-866-PGS-GROW.

Hey guys, its been a cold winter, and it looks like spring has come a little early. It feels so good too! It also feels great to let everyone know that our end of year inventory is over and we are again fully stocked with all the essentials you need for your grow room. We are also gearing up for what is anticipated as the biggest grow season ever. Viva 2010, with outdoor and indoor projects being taken on in extremely aggressive levels, its super exciting for us to be able to provide for all the Sonoma County growers and beyond who are getting involved. We have -

• Traditional soils, organic blends, soilless blends, rockwool, and coco pots ready to go.
• Grow lights, electronic ballasts, magnetic ballasts, reflectors, high output fluorescent systems, LED Grow lights, replacement bulbs.
• Hydro trays, containers, smart pots, complete hydro setups.
• Complete organic and hydroponic nutrient lines – General Hydroponics, General Organics, House and Garden, Cutting Edge, Technaflora and tons of grow and bloom enhancers and accelerators.
• Carbon filters of every size and shape
• Wall, pedestal and exhaust fans and blowers of every shape and size
• Ducting, clamps, foil tape, flanges, reducers, extenders, splitters, splicers
• Co2 generators, controllers and parts
• Organic and chemical pest control products
• Master light controllers, Environmental controllers, High temp. shut off devices
• Water purification systems, accessories and replacement filters
• Ready to grow, self contained Darkrooms
• Valves, elbows, tees, custom hydro fittings, replacement sprayers and misters
• Full service repair dept. complete with loaner ballasts
• Full time accredited botanist

We love to serve and provide the best advice and products available in the indoor/hydroponic/organic gardening industry, give our friendly grow experts a call today and let us know how we can help you. 1-866-PGS-GROW

Rhizoctonia root rot (Rhizoctonia solani) is a fungal disease which causes damping-off of seedlings and foot rot of cuttings.  Infection occurs in warm to hot temperatures and moderate moisture levels.  The fungi is found in all natural soils and can survive indefinitely.  Infected plants often have slightly sunken lesions on the stem at or below the soil line.  Transfer of the fungi to the germination room or greenhouse is easily accomplished by using outdoor gardening tools inside or vice versa.  The germination room should not be used for mixing potting soils or transplanting seedlings as a general rule.

Pythium Root Rot (Pythium spp.) is similar to Rhizoctonia in that it causes damping-off of seedlings and foot rot of cuttings.  However, infection occurs in cool, wet, poorly-drained soils, and by overwatering.  Infection results in wet odorless rots.  When severe, the lower portion of the stem can become slimy and black.  Usually, the soft to slimy rotted outer portion of the root can be easily separated from the inner core.  Species of Pythium can survive for several years in soil and plant refuse.

Phytophthora root rot (Phytophthora spp.) are usually associated with root rots of established plants but are also involved in damping-off.  These species enter the root tips and cause a water-soaked brown to black rot similar to Pythium. These fungi survive indefinitely in soil and plant debris.

Black root rot (Thielaviopsis basicola) is a problem of established plants.  It does not occur in strongly acid soils with a pH of 4.5 to 5.5.  It usually infects the lateral roots where they just emerge from the taproot.  The diseased area turns dark brown, and is quite dry.  The fungi survive for 10 years or more in soil.

Miscellaneous fungi causing similar symptoms include Sclerotinia (white mold), Sclerotium rolfsii, Macrophomina phaseoli, some species of Botrytis (gray mold), Aphonomyces, Fusarium, Cylindrocladium, and others.  Hence the need for the collective term known as damping-off.

Symptoms of Damping-off:

Seeds may be infected as soon as moisture penetrates the seed coat or a bit later as the radicle begins to extend, all of which rot immediately under the soil surface (pre-emergence damping-off). This condition results in a poor, uneven stand of seedlings, often confused with low seed viability. Cotyledons may break the soil surface only to whither and die or healthy looking seedlings may suddenly fall over (post-emergence damping-off).  Infection results in lesions at or below the soil line. The seedling will discolor or wilt suddenly, or simply collapse and die.  Weak seedlings are especially susceptible to attack by one or more fungi when growing conditions are only slightly unfavorable. Damping-off is easily confused with plant injury caused by insect feeding, excessive fertilization, high levels of soluble salts, excessive heat or cold, excessive or insufficient soil moisture, or chemical toxicity in air or soil.

Above ground symptoms of root rot include stunting, low vigor, or wilting on a warm day. Foliage of such plants may yellow and fall prematurely starting with the oldest leaves.  The roots of a diseased plant will have some shade of brown or black and evidence of water-soaking.  Healthy roots are fibrous appearing and are usually white or tan in color. These symptoms are easily confused with severe mite, aphid, scale infestations, or root-feeding by nematodes or insect larvae. Environmental factors such as accumulated salts in the soil, insufficient light or nitrogen, potbound roots, cold drafts, etc. can be eliminated only by examination of the roots.

Damping-off diseases can be prevented:

• Purchase disease free plants and seeds.  Know your supplier.  Do not be afraid of fungicidal coatings on seeds which will be direct sown out doors in cold soils, such as corn and peas. Seed borne disease can also be avoided by soaking the seeds for 15 minutes in a bleach soak (one teaspoon per quart of water) prior to sowing.
• Use sterile well drained soil mediums. See article on soil mixes. Try to maintain a soil mix pH at the low end of the average scale, i.e. 6.4 pH is less susceptible to root rot than a pH of 7.5.  Commercially prepared germination mixes usually have a pH around 5.5.  As you water the seed pots and your seedlings with tap water (which in many municipalities is quite alkaline), the pH in your pots gradually increases as does the susceptibility to damping-off diseases.  Know the pH of your tap water, and condition it if necessary to maintain a lower pH while the plants are still in the germination room.  I prefer the use of vinegar at the rate of one tablespoon per gallon of water.
• Plants must not have their crowns below the soil line.  Seeds must not be covered more than 4 times the thickness of the seed.
• Use plant containers with drainage holes, water from the bottom only, and avoid excess watering. Do not allow pots to stand in water as excess water cannot drain and the roots will be starved for oxygen bringing all growth to a halt.
• Avoid overcrowding  and overfeeding of plants.  It is important to maintain constant levels of growth through proper lighting and complete control of the growing environment.
• Avoid working with plants (taking cuttings or transplanting) when the soil is wet. Do not use water from ditches or drainage ponds or rain barrels in the germination room.
• Avoid spreading soil from infested areas or tools which have been used out of doors. Disinfect tools and containers with one part bleach in four parts water or with 70 percent rubbing alcohol (isopropyl).
• In the germination room,  sow all your seeds on the surface of the media, then cover the seeds to necessary depth with a material which is less likely to harbor fungi than the media itself.  Use one or more of the following seed toppings instead of soil mix:
  • milled sphagnum moss
  • chick grit
  • course sand or fine aquarium gravel
  • composted hardwood bark (steamed)
• In the germination room, mist seedlings in communal pots or flats once or twice per day with water containing a known anti-fungal agent such as:
  • Captan (or other approved fungicide) especially if walls or floors are damp, or
  • Cheshunt compound, a copper/aluminum formulation, or
  • chamomile tea, or
  • clove tea, or
  • a  one-time light dusting of powdered cinnamon on the soil surface, or
  • a one-time light dusting of powdered charcoal on the soil surface, or
  • if stinging nettle is endemic in your area, make a fermented infusion to use like clove tea.           These last five actions are suggested by sufficient anecdotal evidence to prove  the existence of a low level of fungicidal activity.  I would not hesitate to use them in germination environments which have no history of damping-off diseases.
• Rotate plantings on a 2 to 3 year schedule using plants from different families in order to starve out existing pathogens.
• Provide constant air movement not tied in with the light timer.  Air should move freely 24 hours per day, but not directly aimed at the plants.  This helps the seedlings to aspirate, and excess soil moisture to wick. If you do everything else right but do not provide plenty of air movement, you will still get damping-off.

So, what do I do?  Answer:  all of the above, all of the time.

Damping-off diseases can be controlled:

Fungicides may be applied as a soil drench after planting.  They may be incorporated into the soil before planting as a dust. They can be sprayed in mist form on all seedlings as a precaution until they have been transplanted into individual pots. Once transplanted, only those seedlings known to be especially sensitive to damping-off need be misted with fungicide daily until the first or second seed leaves have emerged.  The following chemicals are not recommended for use by the average recreational gardener, but may still be available for use (if not yet banned), providing  the manufacturer’s instructions are followed to the letter.

Captan (sold as Captan) controls most pathogens, but not Rhizoctonia.

Metalaxyl (sold as Subdue or Apron) controls Pythium, Phytophthora,  and Aphanomyces.

Iprodione (sold as Chipco) controls most pathogens, but not Pythium, Phytophthora, or Aphanomyces.

Etridiazole and Thiophanate-methyl (sold as Banrot) controls most all pathogens.

PCNB-etridiazole (sold as SA-Terraclor or Super-X) good general purpose fungicide.

PCNB-quintozene (sold as Terraclor, Fungi-clor, or PCNB) controls Rhizoctonia and Sclerotinia species.

Fosetyl-A1 (sold as Aliette) controls Pythium, Phytophthora, & Aphanomyces.

Well, you get the idea.  There are too many to list, and they go on and off the market very quickly (mostly because they are very dangerous when used improperly, and some are too dangerous to have been put on the market at all.)

So, what do I use?  Answer: Just enough Captan as needed.

The Future of Damping Off Control: 

Biocontrol with microbial fungicides is being investigated in several academic labs.  Typical targets are those plants being mass-produced in nearby commercial greenhouses.  Early results indicate damping-off prevention comparable to that achieved with the use of standard fungicidal drenches like those mentioned above.   However, there remain some notable drawbacks in biocontrol of damping-off.

First, microbial fungicides act against only one species of root or stem rot, and must be applied in advance.  So, in order to prevent damping-off, you must know in advance which species of Pythium or Rhizoctonia or other fungi is likely to attack your crop.  That limits their use to large production facilities.

Second, some formulations of microbial fungicides have been shown to produce substances that are phytotoxic to certain crops.

Finally, small changes in environmental conditions during test periods seem to cause significant differences in test results.

There is much work to be done in this area of biocontrol, not to mention the ultimate necessity of EPA approval.  Use of biocontrol agents for prevention of damping off by home gardeners may well be decades away.  For a list of those biocontrol products which have approval for controlling plant diseases, go to the USDA ARS Biocontrol Plant Diseases Laboratory at    http://www.barc.usda.gov/psi/bpdl/bpdl.html

Thanks to Tom Clothier for the article, original page here

Happy Aloha Friday PGS Blog Readers.

Rice Today’s July-September 2009 edition features the development of drought-tolerant rice and other research the International Rice Research Institute (IRRI) and its collaborators are doing to curb the devastating effects of drought.

With some degree of water shortages predicted to affect 15-20 million hectares of irrigated rice within 25 years, smart crop management and even genetically modified rice may also play a role in helping farmers cope with the crisis.

Rice Today also reports that in Uganda rice production has increased 2.5 times from 2004 to 2008 through government initiatives, private investment, and farmer support.

Across the other side of the planet rice production, consumption, and prospects in Latin America are being explored. Rice is being promoted to consumers in Mexico and Central America and in Brazil production is improving.

In light of further boosting production, IRRI takes a look at some practical solutions to help reduce grain losses and improve grain quality during postharvest. Between 15-20% of rice grains are often lost at this stage because of unsuitable drying techniques, pests, and other factors.

Original Page Here

By Mike Amaranthus Ph.D and Tim Eagan

The more we learn about life on Earth, the more we learn about the mechanics of superior plant performance. We now realize that in natural systems, organisms work not independently but interdependently.  There is no doubt that nature is less a battleground and more a marketplace. Symbiotic organisms that exchange materials and services in a mutually advantageous living arrangement can be the key to successful planting and growing. Hydroponic growers are gaining increased appreciation of the living soil and more frequently incorporating soil biology and mycorrhizal products into their practices.

Fig. 1 – Picture of a mycorrhizal colonized root. Mycorrhizal fungal filaments radiate into the soil from the mycorrhiza root tip.

What are mycorrhizae?

More than 90 percent of plant species form a symbiotic arrangement with beneficial soil fungi called mycorrhizal fungi. The roots are colonized by the soil fungus, which attaches to the roots and whose threads or “hyphae” extend  far into the surrounding soil environment (figure 1). The colonized root is called a mycorrhiza. Mycorrhizal fungi are the dominant microbes in undisturbed soils accounting for 60 percent to 80 percent of the microbial biomass. Mycorrhizae are fundamental for superior growth, supplying the water and nutrients needed for good growth, flowering and fruiting and, in exchange, receiving essential sugars and other compounds supplied by the plant.

Fig. 2 - The white threads on this seedling grown in a glass box are mycorrhizal hyphae.

What do they do for plants?

These mycorrhizal fungi increase the surface absorbing area of roots 10 to 1,000 times, thereby greatly improving the ability of the plants to use the nutrients and water (figure 2). Estimates of amounts of mycorrhizal filaments present in soil associated with plants are astonishing. Several miles of fungal filaments can be present in less than a thimbleful of soil. But mycorrhizal fungi increase nutrient uptake not only by increasing the surface absorbing area of roots. Mycorrhizal fungi release powerful chemicals into the surrounding environment that capture nitrogen, phosphorous, magnesium, iron and other plant nutrients. This extraction process is particularly important in plant nutrition, flowering and fruiting and explains why mycorrhizal inoculations have been so successful in hydroponic operations.

What other functions do mycorrhizal fungi perform?

Suppression of diseases and pathogens are additional benefits for a mycorrhizal plant. Mycorrhizal fungi attack pathogen or disease organisms entering the root zone. For example, excretions of specific antibiotics produced by mycorrhizal fungi can immobilize and kill disease organisms. Many practical benefits can be expected from using mycorrhizal fungi in common practices. These include improved rooting (figure 3), flowering and fruiting (figure 4), and protection against diseases.

Where’s the beef?

The plant-mycorrhizal fungi relationship is the best understood in the field of soil biology. There are more than 60,000 studies in literature on the subject. But there is more important proof. The mycorrhizal relationship with plants is one of nature’s longest and most successful experiments. The earliest fossil record of the roots of land plants contain mycorrhizae almost identical to what is found today. Most scientists today believe the plant-mycorrhiza relationship allowed aquatic plants to make the transition to the relatively harsh terrestrial environment some 460 million years ago. In nature, mycorrhizae make plant growth possible, linking the roots of plants to the surrounding soil. In nature, neither can survive or grow without the other. Now hydroponic growers can benefit from this essential relationship.

How do I use mycorrhizal products most effectively?

High-quality commercial mycorrhizal inoculum is now available from a variety of sources. Inoculums containing mixtures of species of mycorrhizal fungi often give the best response. Mycorrhizal inoculum comes in granular, powder, liquid and tablet forms. The most important factor is to get the mycorrhizal propagules near the root systems of target plants. Most mycorrhizal propagules will stay dormant and until root activity begins. The chemicals pumped into the soil by active roots cause mycorrhizal propagules to become active and grow. Inoculum can be injected into the rooting zone of hydroponic systems, watered into porous soil-less mixes, mixed in granular form into soilless mixes or directly dipped on root systems using gels during transplanting. The form and application of the mycorrhizal inoculum depends upon the needs of the applicator. What is clear is that mycorrhizal  inoculation is highly effective.

Micro reality

Growing plants hydroponically requires an understanding of the many processes important in facilitating uptake, storage and cycling of nutrients and water by the target plant species. In nature, these activities are largely performed by the “tiny little secrets,” working hard below in the root zone of plants. Hydroponic growers can now make a  “Declaration of Interdependence” and incorporate mycorrhizal fungi into their programs

Dr. Mike Amaranthus spent 20 years with Oregon State University and the U.S. Department of Agriculture Forest Service, and has written more than 60 research papers on mycorrhizae. He is the recipient of the USDA Highest Honors for scientific achievement and has been featured on several major national and international television programs. Tim Eagan is an expert in the practical application of mycorrhizal fungal inoculums and is Vice President of Plant Revolution Inc.  located on the web at www.plantrevolution.com.  All photographs accompanying this article are courtesy of Mycorrhizal Applications Inc.

* 7 species Endomycorrhizae & 11 species Ectomycorrhizae * 67,000 Endo & 1.5 billion Ecto Propagules per lb. * 19 species Bacteria/ 2 species Trichoderma/ Biostimulant Package/ Vitamin Package

Hey guys, I love this product. It’s a little more expensive then some of the other Mycorrhizae products available, but it is well worth the price! I also like that you use it with water instead of pouring it into your medium. It is very obvious that this stuff is a completely different product then all other Mycorrhizae inoculants. It’s moist and rich texture has a pungent smell and is not dusty freeze dried spores, but soft, ready to be diluted in water Mycorrhizae, Trichoderma and more… Using it is easy and almost impossible to over use. You WILL see dramatic results from this product! They suggest using it once every few waterings, but using it for every watering seemed to produce the most visible and dramatic results!

Great White Mycorrhizae is a plant root inoculant.  It contains a combination of Mycorrhizae, beneficial bacteria, trichoderma, and plant vitamins. This enables plants to break down and absorb nutrients efficiently and effectively,  increase water uptake and the overall absorption area of the root system. Great White Mycorrhizae can be used in hydroponics as well as soil.  I recently got a chance to try Great White Mycorrhizae.

It is easy to mix up for application.  One scoop that comes in the little blue tub makes 2 gallons of inoculant as a root drench or as a nutrient solution.  I used distilled water, to prevent chlorine from killing any of the beneficial bacteria.  I tested it with a couple of snow peas in coco coir.

The plant on the left got the Great White Mycorrhizae.  I didn’t think the results would be dramatic after just 2 weeks, but the foliage is fuller on the inoculated plant and is more than a leaf set ahead in growth.

Just to make sure that it was not a fluke,  I tested it on a couple of Miracle Fruit trees in soil.  The manufacturer recommends re-inoculating every two weeks, but I did every watering.  They are typically slow growers, but there was a “pop” in growth after application.  The plant on the left using Great White speaks for itself.

The results were quick and dramatic.  I plan on using Great White in my entire garden.  Plant Revolution’s Great White Mycorrhizae is a great supplement that gives visible results in the garden.

Thanks to Red-Icculus – Original Page Here

Plant Success Recommended Feed Schedule

Galaxy Electronic HID Ballast

Lets start with the foundation of any indoor garden, lighting…First thing is first, electronic ballast, or magnetic ballast. We have both types stocked in 600 and 1000 watt varieties.

Harvest Pro Magnetic HID Ballast

Next thing to consider….Light Reflector. We carry a HUGE line of options, priced competitively. We can help you determine the optimal reflector for your situation based on 20+ years of experience.

HID Reflectors Stocked and Ready

Moving on to…. grow method. If your a die hard organic soil or soil-less fanatic, or a hydroponic scientist, we have a complete stock of containers, hydroponic mediums, and complete systems to meet anyone’s needs.

Next Step… Ventilation.
Anyone serious about growing indoors knows that ventilation is one of the most important things to take seriously. PGS has got you covered. Dampers, Filters, Extenders, Fans, Clamps, Reducers, Controllers and more….

Lets continue on to CO2 Enrichment… Tired of small yields and airy product? Increase your yields and overall structure with CO2 enrichment. We carry a large line generators, tanks, regulators, and controllers.

Little things that make the difference between bumper crops and bogus results.

Keep your plants happy and healthy through the entire bloom cycle!

Now lets address Environmental Control….
Now that you have a great room in the making, don’t let the environment go to shit with neglect! Dial in the perfect temperatures, humidity levels and your electricity to run flawlessly at all times. PGS has any kind of controller for your environment you can imagine.

Get Notified While Your Gone If You Have a Fire or a Breakin

Onto… Propagation What good is all of this without clones and cuttings to get your future crops ensured? PGS carries popular aero clone machines, as well as tradition Oasis, and Rockwool cubes, clone solutions, gels, and powders, modern T5 fluorescent systems and more…..

The key to success over a long period of time, is an intelligent, planned out nursery program, that includes all the things you would address in your bloom or vegetative environment. Temperature, co2 levels, relative humidity etc… Your future crops are only as good as the plants your nursery produces! Take the extra time to really create a perfect nursery and you will enjoy years of massive crops and prosperity!

T5 Fluorescent Grow Lights - Perfect For Vegetative Growth and Propagation

Let’s not forget the staple of ALL gardens.. Nutrients

Ah… what to say about nutrients? Take the time to learn what works best for your particular situation. We can help, we have just about every major plant nutrient product that is available today, AND we know how to use them.

Perhaps you want a ready to go Growroom? There are some really great ready to go grow rooms that are easy to assemble, and easy to break down. They make alot of sense for even the most experience growers in some situations. They come in every size for any project… Including massive Mammoth size ones for epic projects.

Don’t let garden pest ruin all your have built!… Pest Management.

After all your doing to build this dream room, don’t let bugs ruin this scenario! PGS has a full arsenal of organic and non-organic forms of pest management.

PGS Pest Managment Station

Did we almost forget Water Quality? Hell NO!

Without healthy, clean water as a basis, you will NEVER have a bumper crop. PGS has simple pacific sands filters, to full on huge RO systems.

Ok, I could go on and on about all the rest of the odds and ends, but the point is WE HAVE IT, from white plastic, Mylar, timers and fittings. Above all we offer a smile, and countless years of combined experience. Call us for prices and tell them Pete from the blog said to give you a deal!!! 1-866-PGS-GROW

]]> http://pgsgrow.com/blog/2009/11/19/custom-build-your-dream-indoor-garden-with-pgs/feed/ 0 http://pgsgrow.com/blog/2009/10/20/an-interesting-approach-to-growing-seed-balls-for-victory/ http://pgsgrow.com/blog/2009/10/20/an-interesting-approach-to-growing-seed-balls-for-victory/#comments Tue, 20 Oct 2009 10:10:34 +0000 Pete http://pgsgrow.com/blog/?p=1140 We recently got a comment concerning an old post I made about seed balls. This concept is so fantastic it deserved a 2nd post! Imagine taking your outdoor, or indoor for that matter, to this level. I this is an amazing way for us to preserve some valuable genetics and possibly increase yields.

Seed balls (土団子,土だんご, Tsuchi Dango Earth Dumpling) consist of mixing one measure of seeds for next season’s crop with 3 measures of compost and 5 measures of red clay, and sometimes manure then formed into small balls. Much less seed is used than in conventional growing, resulting in fewer plants which are smaller but stronger with a higher yield. The technique is useful for seeding thin and compacted soils, and avoiding seed eaters.

It is an ancient technique that was re-introduced by Masanobu Fukuoka, an advocate of “natural farming”.

Soil Chemistry

As plant material dies and decays it adds organic matter in the form of humus to the soil. Humus improves soil moisture retention while affecting soil chemistry. Cations such as calcium, magnesium, sodium, and potassium are attracted and held to humus. These cations are rather weakly held to the humus and can be replaced by metallic ions like iron and aluminum, releasing them into the soil for plants to use. Soils with the ability to absorb and retain exchangeable cations have a high cation-exchange capacity. Soils with a high cation-exchange capacity are more fertile than those with a low exchange capacity.

Hydrogen ion concentration in the soil is measured in terms of the pH scale.  Soil pH ranges from 3 to 10. Pure water has a pH of 7 which is considered neutral, pH values greater than seven are considered basic or alkaline, below seven acidic. Most good agricultural soils have a pH between 5 and 7. Though acidic soils pose a problem for agriculture due to their lack of nutrients, alkaline soils can pose a problem as well. Alkaline soils may contain appreciable amounts of sodium that exceed the tolerances of plants, contribute to high bulk density and poor soil structure. Alkaline soils are common in semiarid regions.

Soil is an essential natural resource, formed spontaneously from rock over an extensive period of time, and made up of soil solids (mineral particles and organic matter) and pore spaces filled with water and air.

Soil profile

Soil is made up of several distinct layers or horizons. These layers form what is known as the soil profile.

The top layer of soil or topsoil is the richest, having the most amount of humus (partially decomposed organic soil material). This phenomenon is largely due to the presence of decomposers (predominantly bacteria, fungi, and earthworms) that recycle dead organic matter (plants and animals) into humus. The subsoil is below the topsoil and is low in humus. However, this is where most soil nutrients are found. Below the subsoil is weathered parent material, which is full of rock particles and minerals with no humus. Parent material is the initial state of soil and can be bedrock, organic material or deposits from water, glaciers, volcanoes, or wind. Physical weathering over millions of years has broken down these materials into fine particles, and soil inherits physical and chemical properties from this parent material. Bedrock sits underneath the weathered parent material and is made up of solid rock. This solid rock will stay hidden and undisturbed until an earthquake or erosion expose it to the surface where some of it will be weathered to make way for the next batch of parent material, which starts the soil forming process all over again. However, soil is not the end product of weathering rock, it is simply a stage in the mineral cycle, and the process by which nutrients such as carbon, nitrogen, and calcium cycle between living things, and the atmosphere and soils.

What is soil structure?

The form that the soil takes based on its physical and chemical properties is termed soil structure. Mineral particles that make up soil ranges in size from fine to coarse and are categorised accordingly as clay, silt, and sand. The amount of clay and organic matter in a soil plays an important role in determining soil structure. Clays carry a negative electric charge and can attract positively charged cations and water molecules, forming small aggregates. Sand and silt do not have any charge, but are combined into these aggregates when their surfaces become coated with clay or organic matter. These small aggregates can then form larger aggregates with the help of fungal hyphae. The structure of the soil depends on the size, shape and arrangement of these aggregates, and on the pores between these aggregates.

Why is structure important in your garden?

A ‘well structured’ soil will hold large amounts of water and dissolved nutrients. The aggregates will withstand cultivation and will not ‘puddle’ when wet or become dusty or set hard when dry. The network of pores will ensure adequate drainage and aeration, which are essential for the health of plant roots. Additionally, good structure will provide an excellent medium from which seedlings can emerge and through which roots can explore for moisture and nutrients.

Grading soil structure in your garden

How to improve soil structure?

The most preferred soil structure for growing crops contains a ratio of 2:2:1 of sand, silt and clay, and is referred to as loam or balanced soil. However, a good soil structure can be obtained by adding organic matter to the soil.

Clay and hardpan type soils can be improved by adding gypsum to the soil. Gypsum tends to improve soil structure by loosening the soil, improving drainage and aeration and reducing crusting. However, you still must add organic material to the soil to add nutrients and assist good soil structure.

Note: Gypsum use on sandy soils can aggressively leach out nutrients.

Functions of organic matter

• Serves as a source of plant nutrients (especially nitrogen and phosphorus)

• Helps the formation of soil aggregates with the help of microorganisms (especially fungi), improving soil structure, aeration and water infiltration and resisting erosion
• Increases buffering of soils
• Provides sources of energy that affect the activities of both macro and microfaunal organisms
• Improves nutrient holding capacity (cation exchange capacity)
• Improves soil colour

From: www.uvm.edu