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soil science

Soil Health & Cover Crops

in 2019/Climate Change/Crop Production/Current Issue/Grow Organic/Land Stewardship/Seeds/Soil/Spring 2019

A Recipe for Success in Achieving Long Term Soil Conservation

Saikat Kumar Basu

Why Care for our Soils?

Soil is an important constituent of both agriculture and forestry; unfortunately, it is taken for granted most of the time. It is a cheap, easily accessible or available global resource for which we have often forgotten to take the necessary care. We have used it non-judiciously without proper planning and vision for the future.

The concept of soil health has always been there since the dawn of human civilization—but only quite recently have we started to better understand, appreciate, and care for our soils as part of sustainable agriculture. We as humans have possibly matured over time and realized that our exploitative and non-judicious use of our soil resources can limit our long-term agricultural productivity and jeopardize successful crop production.

Unless we are serious enough to take good care of one of our most abundant yet highly sensitive natural resources of this planet, the soils, we ourselves will be solely to blame for the degradation of our soils—thanks to the self-destructive approaches we’ve used to achieve very short-term objectives of making easy profits without thinking deeply about the long-term consequences.

Soil health today has emerged as an important aspect of proper soil management as a component of sustainable agriculture to help in quality crop production without depleting or damaging soil quality and helping in proper soil conservation at the same time (Fig. 1).

What Impacts Soil Health?

Several factors impact soil health, among the most important being over application of fertilizers and pesticides. The soil represents a dynamic ecosystem and an intricate playground of delicate physics, chemistry, geology, and biology. Any chemical application on the soil therefore has some positive or negative impact on the soil quality by interfering with the physicochemical and biogeological processes associated with soil formation. These changes include shifting the soil pH due to various anthropogenic activities that slowly impact the soil quality. Drastic reduction in pH makes soil acidic, while rapid increase in pH leads to alkalinity or salinity; both conditions make the soil unsuitable for a long time for quality crop production. Furthermore, increased emphasis on monoculture associated with our modern industrial agriculture year after year depletes the soil of essential macro and micro nutrients necessary for maintaining optimal soil health (Fig. 2).

Fig 2. Increased emphasis on crop monoculture is detrimental to long term soil health.

Over application of synthetic chemical fertilizers and various pesticides to secure crop production adds too much pressure on our soil, impacting not only the physicochemical and geological processes active in the soil, but also negatively impacting the soil macro and micro flora and fauna devastatingly over a long period of time. Several beneficial microbes like soil bacteria, Cyanobacteria, soil fungi, soil borne insects, spring tails (Collembola), earthworms, and other critters essential for maintaining soil health suffer population collapse due to non-judicious over application of synthetic fertilizers and pesticides.

Many such chemical residues remain in the soil for prolonged period and often percolate deep into the soil, reaching the groundwater table or adjacent surface fresh water resources via surface run off, with long term negative impacts on both soil and water. Often the beneficial soil macro and micro flora and fauna are altered or replaced by harmful species that prove detrimental to soil health and significantly impact crop production and forest ecology. Random unplanned crop rotations and fallow harm our soil more than we actually realize; making them susceptible to weed and pest infestations (Fig. 3), loss of precious top soil and lower crop production due to poor soil health.

Fig 3. Untended soil is subjected to weed infestation that interferes with quality crop production.

Best Management Practices (BMPs) for Promoting Sustainable Soil Health

To maintain optimal soil health for long term success in achieving quality crop production we need to take necessary steps and plan carefully. This takes needs patience, and deeper understanding, as well as painstaking observations to implement good soil health practices on cropland.

Regular soil tests are important to ensure that we are aware of the excesses as well as depletion of necessary macro and micro nutrients in the soil. We also need to look into the topography of the crop field, the low and high spots in the field, the areas impacted by acidification and salinity issues, detailed history of fertilizer and pesticide applications over the years and the successive crops grown. Any past issues associated with the soil should be recorded for future reference. The nature of pest and weed infestations should be recorded to identify any specific patterns with respect to local pest and weed populations. Such detailed record keeping together with advanced GPS- and GIS-generated high-quality images of the field over the years will provide a farmer or crop producer or a professional agronomist ample reference to make judicious decisions to secure comprehensive soil health strategy and crop management for the future.

Based on the above information, we need to adopt a specific crop rotation plan to ensure that the soil is not exhausted of essential soil nutrients. Application of fertilizers and pesticides should follow manufacturer’s guidelines stringently to avoid over application (Fig 4).

Fig 4. It is important to keep track of weed and pest species impacting crop production in a particular field for making judicious decisions regarding appropriate chemical applications at the appropriate stage and dosage following manufacturer’s instructions.

It is also important to note if soil compaction is causing a problem for the field. If this is an issue, then highly mechanized farming activities and movements of heavy vehicles need to be restricted to a specific easily accessible area to reduce negative impacts of soil compaction on the field.

Intercropping could be practised depending upon the farming need and also to use the soil resources judiciously. This can enhance crop production and add crop diversity to the field important for maintaining soil health.

Role of Cover Crops in Promoting Long-Term Soil Health and Soil Conservation

Cover crops are an important aspect for maintaining general soil health if used with scientific outlook and proper planning. Several cover crops choices are available. Annual and perennial legumes, various clovers and sweet clovers, bird’s-foot trefoil, hairy vetch, common vetch, cicer milkvetch, sainfoin (Fig. 5), fenugreek, fava beans, soybeans, field pea or forage pea, cowpea, chickpea, green pea, black pea, different species of beans, oil crops such as annual and perennial sunflower, safflower, flax, forage canola, different mustard species (Fig. 6), brassicas such as forage rape, turnips, collards, radish, forage crops such as tef grass, Sudan grass, sorghum, sorghum x Sudan grass hybrids, corn, cereals such as winter rye, wheat and triticale, different millets, such as Proso millet, Japanese millet, German millet, red millet, special or novelty crops such as hemp (Fig 7) , chicory, plantain, phacelia, buckwheat, and quinoa are only a handful of choices to mention from a big basket of abundant crop species currently available across Canada.

Fig 5. Mustard cover crop in full bloom.
Fig 6. Perennial forage legume sainfoin is an excellent cover crop that can be successfully used in crop rotation cycles. Sainfoin is also exceptional for pollinators, attracting bees and other insects in large numbers.
Fig 7. Hemp is a new speciality crop for Canada and has been generating serious interest among farmers for agronomic productions. Hemp has been found to attract diverse species of insect pollinators too.

Several grass species such as orchard grass, tall fescue, short fescue, meadow fescue, creeping fescue, chewing fescue, festulolium, timothy, annual and perennial rye grass, Italian rye grass, and various other forage and native species are being used in specific legume-grass mix, in highly planned and organized crop rotations or in soil reclamation and pollinator mixes for attracting insect pollinators to the crop fields and in checking soil erosion effectively.

Cover crops should be selected based on the agro-climatic zone and soil zones of the region and used in planned rotations. Species or different appropriate cover crop mixes are to be selected based on the long-term objective of the crop production. For example, cover crop mixes used as pollinator mixes could not only be planted in the field during a fallow; but can also be used in agronomically unsuitable areas, along field perimeter, under the centre pivot stand, hard to access areas of the farm, shelter belts or adjacent to water bodies or low spots in the field too.

Forage cover crops could be used where the field is partly subjected to animal foraging or grazing or ranching. Similarly, oil crops, pharmaceutical or neutraceutical crops, or specialty or novelty cover crops could be used in crop rotations with major food or industrial crops grown in the particular field in a specific agro-climatic region.

Fig 8 Cover crops rotations can be an effective long term solution for managing optimal soil health with long term positive impacts on soil quality and soil conservation.

Cover crops not only play an important role in crop rotation cycle; but, also help in retaining soil temperature and moisture as well as protect top soil from erosive forces like wind and water. The presence of live roots in the soil and a rich diversity of crops stimulate the growth and population dynamics of important soil mega and micro fauna and flora for sustaining long term soil health, soil quality and soil conservation. Cover crops help in balancing the use of essential soil macro and micro nutrients in the soil, as well as promoting better aeration, hydration, nitrogen fixation, and recycling of essential crop minerals, assisting bumper production of food or cash crops due to improvement in soil quality for successive high-quality crop production.

It is important for all of us to understand and appreciate that soil is a non-renewable resource and needs special care and attention. Unless we are careful to use this special resource so deeply associated with our agricultural and forestry operations judiciously, we may be slowly jeopardizing crop productivity—and our common future—in the not so distant future.

Proper planning and scientific soil management practices can play a vital role in keeping our soil productive as well as healthy. Use of crop rotations and cover crops are some of the important approaches towards long-term soil health, soil conservation, and crop productivity. We need to learn more about our local soil resources for our future food security and incorporate more soil friendly practices to prolong the life and quality of our soil.


Saikat Kumar Basu has a Masters in Plant Sciences and Agricultural Studies. He loves writing, traveling, and photography during his leisure and is passionate about nature and conservation
Acknowledgement: Performance Seed, Lethbridge, AB

Featured Image: Fig 1. Scientific management of soil health contributes towards long term high quality crop production as well as soil conservation. Image Credit: All photos by Saikat Kumar Basu

Ask an Expert: Soil Testing

in 2019/Ask an Expert/Crop Production/Current Issue/Grow Organic/Land Stewardship/Soil/Spring 2019

Tools for your Nutrient Management Toolkit

Amy Norgaard, Dru Yates, & Emma Holmes

Every year farmers align countless variables to produce healthy crops that make it to market. Crop planning. Bed prep. Transplanting. Irrigation. Weed management. Pest management. Harvest. Storage and transport. Typically, there is a sweet spot in terms of either quantity or timing for each of these, and there are indicators or measures to stay in that ideal range. For example, the weather forecast and local temperatures highlight best times for transplanting, thermometers track temperatures in storage facilities, and in-field insect traps help monitor pest pressures. Nutrient management is another one of these farm management components that we can stack in our favour—and soil sampling is an essential tool to make informed decisions in this area.

The main reason for soil sampling in agriculture is to assess soil fertility and related properties like pH and texture. Results not only inform management practices for the current season but can also act as a report card for past decisions. Just like we can feel or measure the soil to make irrigation decisions, we can use soil tests to provide us with a snapshot of fertility status and amend accordingly. Being able to apply the right nutrients in the right quantities is just another opportunity to add another piece to the puzzle on the way to our yield, quality, and/or productivity goals.

Best Practices for Taking a Soil Sample

When collecting soil for analysis, the goal is to obtain a sample that is representative of the area you are interested in. Since soil properties vary across fields, there are several steps to ensuring the most reasonable average possible.

1. Take several sub-samples from your area of interest and mix them together to get a composite sample:

  • If your garden plot is small (100 – 200 sq. ft), take 4 – 5 samples.
  • If your garden is larger (500 – 10,000 sq. ft.), take 9 – ­ 10 samples.
  • If you are measuring a larger area (i.e. 1 – 25 acres) and that area is relatively uniform in cropping and management history, take about 15 – 30 samples to make your composite sample.
  • If your sample area is larger than 25 acres, try to arrange your sampling areas so that a single composite sample does not represent more than 25 acres.

2. Avoid spots that look different from the rest, or that have been managed differently. For example:

  • Wet spots in an otherwise well drained field.
  • Areas where plants are growing exceptionally well, or exceptionally poorly compared to the rest of the field.
  • Greenhouses that are left covered over winter.
  • If you are curious about an area that is different from the rest, sample it separately.

3. Make sure each sub-sample is the same volume and is taken to the same rooting depth (usually 6 inches for most nutrient tests).

4. Collect samples randomly from the entire field area. A soil probe is the ideal tool as it is fast and ensures consistency among depth and volume of samples, but if you don’t have one readily available, a trowel or garden spade works well. You will also need a bucket and plastic bags. It helps to pre-label the bags with the sample name using a sharpie so that samples don’t get mixed up! Clean any equipment that comes into contact with the sample (eg. shovel and bucket) with clean potable water and dilute soap.

5. Start collecting samples from the sampling area and add into the bucket. Remove any bits of vegetation, pebbles, or fauna with a gloved hand. Once you have all your sub-samples for your area in a bucket, mix them together and take a ½ cup of soil and put into the prelabeled ziplock bag.

6. Repeat for other samples, making sure to clean your tools between sites.

For more details on taking a soil sample, please refer to this factsheet, which can be accessed by searching for ‘Soil Sampling for Nutrient Management’ on the BC Ministry of Agriculture website

Due to inherent variability in analytical methods, two labs can provide different values for the same nutrient of interest because labs use different extraction methods and equipment. Even when using the same method there is lab to lab variability. Therefore, it is important to use the same lab consistently to monitor trends over time. It is also important to take into consideration the methods used when analyzing the results.

On Testing Compost and Amendments (It’s a Good Idea)

Composts are commonly used in organic agriculture as a source of organic matter and plant nutrients. However, these amendments vary widely in their composition depending on many factors, such as feed-stock, composting process, and storage conditions. These not only affect the initial nutrient content, but also influence nutrient loss prior to spreading, as well as the soil nutrient dynamics (release and availability to crops) when the amendment is spread in the field. Therefore, testing a compost pile shortly before spreading gives us the best snapshot of its composition and represents another tool in our toolkit when making site-specific nutrient management decisions in systems using these products.

Composts can be tested for a variety of properties, including both macro- and micro-nutrient content, carbon to nitrogen ratio (C:N), pH, electrical conductivity (EC), organic matter content, etc. Together, these provide an overall picture of compost quality and can help predict the subsequent effects on soil quality and nutrient supply to crops. The specific parameters to test for depend on the goals for using the product, and any specific concerns or goals. For example, farms that already have salinity issues may want to test potential soil amendment sources for EC as an indicator of salt content to avoid exacerbating this pre-existing situation.

From a broad nutrient management perspective, testing for C:N, nitrogen (N), and phosphorous (P) are valuable first steps in balancing these nutrients, as compost products are often used to supply all or at least part of the N and P needs in organic farming systems. Additionally, these nutrients are important to consider because they are not only needed in significant quantities, but are also environmentally damaging when lost to surrounding ecosystems. In general, applying compost to target crop N requirements results in the over-application of P, and over time we see excess P levels in soils where this management practice is common (Sullivan & Poon, 2012). This highlights the advantage of implementing soil and compost testing, where we can not only monitor our soil P levels over time, but also be aware of the quantity we are applying by testing our amendments.

Finally, while N and P are two important plant macronutrients, compost provides a variety of other plant nutrients that can be important considerations, depending on the crop we are amending, soil test values, and any other farm-specific considerations. Implementing compost testing as a tool to be more informed about the properties of these amendments allows for more specific, targeted use and more efficient, environmentally-friendly farming systems overall.

How to Calculate Amendment Needs

While compost and soil tests answer the question “What’s there?”, there are still a few steps to go from these values to a target amendment application rate in the field. This can often be the most intimidating element and involves a few calculations. However, there are several online or downloadable calculators and resources for this process. The two nutrient calculators listed below are good starting points, and are accompanied by several resource pages and/or documents to get oriented to how they work. The BC Ministry of Agriculture’s Nutrient Management Calculator allows you to pick your lab when inputting your values, and will assist you in choosing the right rate and nutrient source for your crops.

Amendment Calculators:
Organic Cover Crop and Fertilizer Calculator (OSU Extension)
BC Ministry of Agriculture Nutrient Management Calculator

Additional Nutrient Management Resources:
Fertilizing with Manure and Other Organic Amendments (PNW)
Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon (OSU)

Soil Fertility in Organic Systems – A guide for gardeners and small acreage farmers (PNW)

Post-harvest Nitrate Testing

The post-harvest nitrate test (PHNT) is a soil test performed in the late-summer to early-fall to evaluate nitrogen (N) management, and is another soil test to add to your nutrient management toolkit. This test measures the amount of nitrate-N remaining in the soil following harvest, and represents the plant-available N that was not used by the crop during the growing season.

Nitrate is highly mobile within the soil system and so is highly susceptible to leaching during winter months. For example, in coastal BC, effectively all soil nitrate is assumed to be lost from the root zone (in absence of an established cover crop) due to high winter rainfall. As such, it is:
1. common for spring nitrate-N soil test values to be minimally informative, and
2. important to manage soil N in ways that keep PHNT values low.

The PHNT is often referred to as a “report card” assessment of N management as it is used in retrospect—an evaluation of the impacts of nutrient management decisions that were made for the previous season. It provides a way for growers to assess and adjust their N management, to both get the most effective use out of the fertilizer inputs they are paying for, and to reduce environmental impacts of excess nitrates entering waterways.

Rating General Interpretation PHNT (kg/ha)

0-30 cm

Low Continue present N management < 50
Medium Adjust N management to improve plant uptake efficiency 50-99
High Reduce N inputs, implement strategy to reduce N leaching (e.g. cover crop) 100-199
Very High >200

Table 1. Post-Harvest Nitrate Test (PHNT) ratings developed for corn and grass in the B.C. Lower Mainland (taken from Kowalenko et al. 2007).

To take a sample for PHNT, follow the general instructions for a taking a soil sample (see above in ‘Best Practices for Taking a Soil Sample’), plus the following modifications. Note that PHNT sampling protocols are somewhat crop and region specific. The following are generalized tips:

Timing: the general guideline is to sample after harvest, and before cover crop seeding, soil amending, and significant rainfall. For example, sampling before 125mm cumulative rainfall in south coastal BC on fine to medium textured soils is ideal.

Depth: sample to a minimum of 30cm. This is deeper than standard nutrient sampling recommendations.

Adjust for volume: take the nitrate-N value that you get from the soil lab and multiply by depth (0.3m), multiply by the bulk density of the soil (kg/m^3), and divide by 100 to get PHNT value in kg/ha. Soil bulk density will vary by soil type, and farm-specific values can be attained by paying for a bulk density test at a soil lab. The finer the texture, the denser the soil – many commonly used book-values fall between 1150 to 1300 kg/m^3.

For certain forage crops in coastal BC, such as silage corn and grass, target PHNT values have been developed to indicate whether N inputs should be managed differently in the following season. Under these rating systems (Table 1), higher ratings mean lower N-use efficiency and greater risk for leaching loss of nitrate-N.

The typical, potential reasons for inefficient N-uptake are:

  • N applications were in excess of total crop needs;
  • N was not applied at the optimal time(s) for crop uptake; or,
  • N was not applied where it was accessible to plant roots, or that other growing conditions (e.g. moisture, temperature, other nutrients) were limiting to crop uptake of N.

Relative differences in PHNT values are a useful tool in N management decisions, regardless of crop-specific target PHNT values. If you can identify a field or crop with high PHNT relative to your other fields, this is something to note, adjust nutrient management, and evaluate how that impacts your PHNT values the following season. This PHNT approach to N testing will provide much more insight into your N management than the N values you will receive from your spring soil tests. To address the need for more PHNT information in other field vegetable crops besides silage corn and grass, work is ongoing in BC to better understand PHNT testing and its implications.

Further detail on taking samples and interpreting PHNT values is available through the OSU Extension Catalog, search ‘Post-Harvest Soil Nitrate Testing’.

Assistance can also be found by contacting your Organics Specialist, Emma Holmes (Emma.Holmes@gov.bc.ca) at the BC Ministry of Agriculture.

Soil Labs 

AGAT Laboratories
120 – 8600 Glenlyon Parkway, Burnaby, BC V5J 0B6
Phone: (778) 452-4000

Exova (formerly Bodycote/Norwest)
#104, 19575 – 55A Avenue, Surrey, BC V3S 8P8
Phone: (604) 514-3322 Fax: (604) 514-3323
Toll free: (800) 889-1433

Maxxam Analytics (formerly Cantest Ltd.)
4606 Canada Way, Burnaby BC V5G 1K5
Phone: 604-734-7276 Toll-free: 1 (800) 665-8566
Email : info@maxxamanalytics.com

Ministry of Environment Analytical Laboratory
4300 North Road
PO BOX 9536 Stn Prov Govt Victoria, BC
Phone: 250-952-4134
Email: NRlab@gov.bc.ca

MB Laboratories Ltd.
By Courier: 4 – 2062 West Henry Ave, Sidney BC V8L 5Y1
By Mail: PO Box 2103, Sidney BC V8L 3S6
Phone: (250) 656-1334
Email: mblabs@pacificcoast.net

Pacific Soil Analysis Inc.
5 – 11720 Voyageur Way, Richmond BC V6X 3G9
Phone: (604) 273-8226
Email: cedora19@telus.net

Plant Science Lab (affiliated with TerraLink Horticulture Inc.)
464 Riverside Road, Abbotsford, BC V2S 7M1
Phone: (604) 864-9044 x1602
Email: pwarren@terralink-horticulture.com


Amy Norgaard: Amy has a BSc in Agroecology and is now working on a MSc in Soil Science in the Sustainable Agricultural Landscapes lab at UBC. She has worked on several small-scale organic farms and is an Articling Agrologist with the BCIA. Her research is focused on nutrient management on organic vegetable farms. She can be reached at: amynorgaard@alumni.ubc.ca

Dru Yates: Dru has a M.Sc. in Soil Science from UBC, is an Articling Agrologist with the BCIA, and currently works as a consultant with E.S. Cropconsult Ltd. Her work includes providing integrated pest management (IPM) services to vegetable and blueberry growers throughout the Fraser Valley, as well as performing sampling and local research trials related to nutrient management. She can be reached at: dru@escrop.com

Emma Holmes: Emma Holmes has a B.Sc. in Sustainable Agriculture and a M.Sc. in Soil Science, both from UBC. She farmed on Orcas Island and Salt Spring Island and is now the Organics Industry Specialist at the BC Ministry of Agriculture. She can be reached at: Emma.Holmes@gov.bc.ca

References

Kowalenko, C.G., Schmidt, O., and Hughes-Games, G. (2007). Fraser Valley Soil Nutrient Study 2005. A Survey Of The Nitrogen, Phosphorus And Potassium Contents Of Lower Fraser Valley Agricultural Soils In Relation To Environmental And Agronomic Concerns.

Sullivan, C. S., & Poon, D. (2012). Fraser Valley Soil Nutrient Survey 2012.

Feature Image: Amy Norgaard sampling soil. Credit: Teresa Porter

Footnotes from the Field: Intergenerational Soil Stewardship

in Fall 2018/Footnotes from the Field/Grow Organic/Land Stewardship/Organic Standards/Tools & Techniques
Onions by Moss Dance at Birds and Beans

Intergenerational Soil Stewardship: Our Only Hope?

Marjorie Harris BSc, IOIA V.O. P.Ag

Soil, specifically topsoil, is the foundation of life on this earth. Earth is the only planet with healthy fertile soil on it that we know of yet, in the whole of the universe. Fertile soil is a little-understood mixture of biology and geology whose potential only exists in the topsoil layer. The topsoil layer is composed of the topsoil itself and organic matter in various stages of mineralization and humus production. Degradation and erosion of the topsoil depletes soil fertility, restricting plant growth, vitality, and micronutrient content. Hence, it becomes imperative for one to reach out to a website, and take aid of professionals in combating the problem of soil erosion.

The theme for this month’s BC Organic Grower is: “Bioregionalism: building place based economies.” Agricultural philosopher Wendell Berry suggests that an agrarian economy is based on local adaptation of economic activity to the capacity of the land to sustain such activity.

This is a challenging idea because history shows us that farming as practised in the past and the present always causes topsoil degradation. Through the ages, soil degradation, or erosion, has steered the fate and course of human civilizations and ultimately caused the demise of those civilizations. This story has repeated itself throughout the world and in the history of every type of farming. In the words of Sir Winston Churchill, “Those who fail to learn from history are doomed to repeat it.” No greater historical comment can be made for agriculture: learn or be doomed. All farming societies exhausted their topsoils within 800 to 1700 years.

The Canadian Organic Standards speak to soil conservation and soil fertility specifically in the following sections:
The general principles of organic production in Annex 1:
1. Protect the environment, minimize soil degradation and erosion, decrease pollution, optimize biological productivity, and promote a sound state of health.
2. Maintain long-term soil fertility by optimizing conditions for biological activity within the soil.

Clause 5.4.3 Tillage and cultivation practices shall maintain or improve the physical, chemical and biological condition of soil, and minimize damage to the structure and tilth of soil, and soil erosion.

Principle of Health

Organic agriculture should sustain and enhance the health of soil, plants, animals, humans and the planet as one and indivisible.

We have run out of new lands to discover on planet Earth. In 1995, Dr. David Pimental of Cornell University calculated that we had already lost 30% of the arable land we were farming to soil erosion. With the advent of chemical and mechanical agriculture the soil erosion problem has increased a hundred-fold in areas. As an example, in the past 150 years, one-half the fertile topsoil of Iowa has been lost to erosion.

Topsoil is a strategic and underappreciated resource. Soil can be conserved, made, and lost and it is the balance of these factors that determines the soils fertility. How we manage the soil resource in our generation will affect generations to come. As long as soil erosion continues to exceed soil production, it is only a matter of time before agriculture fails to support Earths humanity.

What Can We Learn from the Trials and Errors of Our Ancestors?

Çatalhöyük, Anatolia (modern Turkey) was home to a Neolithic farming civilization that lasted around a thousand years starting about 7500 BC. Scientists have studied skeletal remains which have provided a highly informative record of human health. From the skeletal health record they have been able to divide this civilization into three distinct health time periods: Early, Middle and Late. During the Middle period the civilization reached its peak in population and health, and then as soil fertility was depleted the human skeletal health parameters demonstrated decline. By the end of the Late period 52% of human births resulted in infant mortality before the age of two months. Similar skeletal health studies have been conducted on the remains of other farming civilizations globally with outcome of human health declining in parallel with topsoil and soil fertility depletion, supporting the assumption that human health is interdependent on topsoil retention and soil fertility.

Dr. David R. Montgomery succinctly identifies the problem and a potential solution in his book Dirt: The Erosion of Civilizations: “Sustaining our collective well being requires prioritizing society’s long term interest in soil stewardship; it is an issue of fundamental importance to our civilization. We simply cannot afford to view agriculture as just another business because the economic benefits of soil conservation can be harvested only after decades of stewardship, and the cost of soil abuse is borne by all.”

What Does a New Sustainable Agriculture Ethic Require from Us?

In Dr. David Montgomery’s more recent publication “Growing a Revolution: Bringing Our Soil Back to Life,” he outlines solutions to soil conservation and topsoil rebuilding techniques he has witnessed applied in the field around the world. He identifies the main culprit of soil erosion in agriculture as the invention of the plow. The plow breaks the soil structure and exposes the underground community of biota to the surface. “The plow is the villain that set the seeds for soil degradation. Only deserts have bare earth and Nature tends to clothe herself in plants.”

Another challenge is that during one generation a farmer can seldom see the effects of topsoil erosion unless a dramatic natural weather event sweeps the soil away. During day to day farming it is difficult to ascertain the minimal yet additive effects of traditional tillage techniques. Fallow land tillage is a traditional technique that leads to desertification and needs to be abandoned and replaced with topsoil preserving methods. Topsoil conservation and rebuilding requires the focused consciousness of Intergenerational Soil Stewardship to guide agricultural sustainability.

Soil is in a Symbiotic Living Relationship with Plants

When plants are actively photosynthesizing they release 30% to 40% of the sugars, carbon compounds, and proteins they manufacture through their roots into the root rhizosphere. The root exudes these nutrients to feed the underground community of fungi and microbes in exchange for micronutrients from fungi and microbial metabolites that act as growth stimulators and plant health promoters.

When plants are fed synthetic N, P, K they grow big on top of the ground but do not invest in growing a big root system and do not deliver as much nutritious root exudates to feed the underground microbial and fungi communities. As a result the plant does not reap the benefits of vitality factors and micronutrients. The plants overall health is less and the plant tissue has demonstratively less micronutrient content to pass on up the food chain. Micronutrient studies demonstrate that under conventional agriculture the plants have lost between 25% to 50% of their micronutrient content in the past 50 years.

The solution to successful topsoil building Dr. Montgomery observed while touring farms around the world required three things to happen at once: no till planting techniques, cover cropping, and adding organic matter to the soil. Dr. Montgomery has coined the method Conservation Agriculture and the methods can be applied in both conventional and organic farms—because when it comes to soil conservation and restoration, everybody needs to get on board.

Principles of Conservation Agriculture:

1. Minimal or no disturbance/direct planting of seeds (e.g., no till)
2. Permanent ground cover: retain crop residues and include cover crop in rotations
3. Diverse crop rotations: to maintain soil fertility and break up pathogen carryover
4. Livestock assisting in topsoil building: mimic bison grazing, move cattle in a tight herd to intensive graze (high disturbance), and move frequently to produce low frequency grazing.

Benefits of Conservation Agriculture, after a short transition period of 2 to 3 years to allow soil organic matter to build fertility:

1. Comparable or increased yields
2. Greatly reduced fossil fuel and pesticide use
3. Increased soil carbon and crop resilience
4. Higher farmer profits

“This is not a question of low tech organic versus GMO & agro-tech….this is about ‘how to apply an understanding of soil ecology to the applied problem of increasing and sustaining crop yields in a post-oil environment’.”

“Agriculture has experienced several revolutions in historical times: the yeoman’s revolution based on relearning Roman soil husbandry and the agrochemical and green revolutions based on fertilizer and agrotechnology. Today, the growing adoption of no-till and organic methods is fostering a modern agrarian revolution based on soil conservation. Whereas past agricultural revolutions focused on increasing crop yields, the ongoing one needs to sustain them to ensure the continuity of our modern global civilization. The philosophical basis of the new agriculture lies in treating soil as a locally adapted biological system rather than a chemical system.”

Intergenerational Soil Stewardship: Society on a global scale based on an agrarian economy adapted to its bioregion dedicated to topsoil conservation and restoration and the development of soil fertility.


Marjorie Harris is an organophyte, agrologist, consultant, and verification officer in BC. She offers organic nutrient consulting and verification services supporting natural systems.

References:
1. Montgomery, D. (2007). Dirt: The Erosion of Civilizations. University of California Press. Montgomery, D. (2017). Growing a Revolution: Bringing Our Soil Back to Life. W. W. Norton & Company.
3. Pimental, D., Burgess, M. (2013). Soil Erosion Threatens Food Production. Agriculture, 3(3), 443-463; doi: 10.3390/agriculture3030443
4. Montgomery, D. (2014). Soil erosion and agricultural sustainability. PNAS. 104 (33) 13268-13272; https://doi.org/10.1073/pnas.0611508104

Ask an Expert: Fostering Resilient Soil Ecosystems

in 2018/Ask an Expert/Crop Production/Spring 2018

Emma Holmes, Organics Specialist, BC Ministry of Agriculture

Studies examining soil microbes are showing huge potential to improve growing practices. A number of soil microorganisms have abilities to increase soil fertility, aid in nutrient and water uptake by the root system, and protect crops against pests and disease.

Soil Bio-fertilizers

If you grow legumes, you are likely already familiar with Rhizobia, the family of soil bacteria that form symbiotic relationships with legumes to convert atmospheric nitrogen to a form of nitrogen that is plant available. Producers have been inoculating their legume seeds with rhizobium since the ‘50s and it is estimated that 70 million tonnes of N are fixed annually by Rhizobia (Zahran, 1999). There are significant potential gains to be had from reducing dependence on nitrogenous fertilizers by increasing biological nitrogen fixation including reduced input costs, pollution prevention, and improved yield and crop quantity (Kelly et al., 2016).

But it is not just legume crops that see big returns in partnering with soil organisms. Farmers around the world are using bio-fertilizers to cut back on expensive fertilizers, build their soil quality, and better protect their waterways and aquifers.

There are six main types of biofertilizers:

Symbiotic Nitrogen Fixers (e.g. Rhizobium) form nodules on the roots of legumes and can fix 50-200 kgs N/ha in one crop season.

Asymbiotic Free Nitrogen Fixers (e.g. Azobacter) live in the soil and fix significant levels of nitrogen without the direct interaction of other organisms.

Associative Symbiotic Nitrogen Fixers (e.g. Azospirillum) form close relationships with grasses and can fix 20-40 kgs N/ha.

Phosphate solubilizing bacteria (e.g. Fusarium) convert non available inorganic phosphorus into a plant available form.

Algae biofertilizers (e.g. Cyanobacteria) can provide plants with growth promoting substances (ex. Vitamin B 12) and fix 20-30 Kgs N/ha.

Mycorrhizal fungi refers to the symbiotic association between plant roots and soil fungus that enhances plant soil and nutrient uptake.

Growers in the Fraser Valley have reported that using a bio-fertilizer has allowed them to reduce their N fertilizer application by as much as 30-40% while seeing similar yields and higher product quality. The bio-fertilizer is called TwinN, a freeze dried microbial product that contains a group of asymbiotic free nitrogen fixing bacteria called diazotrophs. Along with N fixation, the diazotophs in TwinN have also been shown to increase root growth and root hair density and decrease root infection. It is thought that the colonization of the plant with beneficial bacteria protects the host plant from harmful bacteria (similar to the use of probiotics to promote human health).

Soil FoodWeb

Dr. Elaine Ingham, a soil microbiologist who previously worked with at Oregon State University and the Rodale Institute, is now the president of Soil FoodWeb. She has dedicated her career to help producers grow crops better by directly observing and promoting life in the soil.

Soil FoodWeb features comprehensive guides and online courses on making compost tea and analyzing soil samples using a microscope. Commercial growers using the Soil FoodWeb management programs report substantial savings in crop production input costs, reduced water usage, and increases in yield and quality.

Korean Natural Farming (KNF)

Koran Natural Farming looks very holistically at the entire farm system, including the people in it, and uses inputs that are generally close at hand and relatively inexpensive. Unlike bio-fertilizers, which involve bringing in microbes from another region or lab, KNF focuses on fostering beneficial Indigenous Micro-Organisms (IMO) within the ecosystem in which the crops are grown.

For more information, check out this link to a video on KNF Indigenous Micro-Organisms: https://vimeo.com/35078856

RootShoot in Vancouver provides 2-day workshops on KNF that includes a detailed explanation of the actual making of inputs including indigenous microorganisms, fermented plant juice, fish amino acid, and lactic acid bacteria.

Measuring Soil Diversity

The Plant Health Laboratory in Abbotsford can conduct a nematode assessment for $16-$32 (depending on turn around time). Nematodes are used as biological indicators of soil health because the number and types present in a soil reflect changes in the microbes they consume, and the soil’s physical and chemical environment.

Independent Soil FoodWeb consultants can analyze bacteria, nematodes, protozoa, and fungi using microscopes.

Managing for Soil Diversity

As the complexity of the food web increases, productivity of the soil tends to increase. Strategies for supporting robust soil biology include:

  • Supply organic matter, which acts as a home and food source for soil microbes. Composts and manures can also provide an input of beneficial soil microbes.
  • Leave crop residue to break down in place. Surface residue encourages decomposers and increases food web complexity.
  • Plant winter cover crops to act as a food source for bacteria in a time when food is otherwise scarce.
  • Create a diverse landscape that supports diverse niches of life.
  • Reduce tillage, which can disrupt sensitive organisms such as fungi. Over the long-term, tillage can deplete soil organic matter and thus reduce soil activity and complexity.
  • Minimize the use of fertilizers and pesticides. Even organic products can reduce the populations of fungi, nematodes, protozoa, and bacteria.
  • Minimize fallow periods, which can result in starvation for many creatures in the soil food web.
  • Minimize compaction and improve drainage to support aerobic microbial populations.
  • Cultivate beneficial indigenous micro-organisms
  • Apply compost teas and/or bio-fertilizers.

Emma Holmes has a B.SC in Sustainable Agriculture and M.Sc in Soil Science, both from UBC. She farmed on Orcas Island and Salt Spring Island and is now the Organics Industry Specialist at the BC Ministry of Agriculture.

Emma.Holmes@gov.bc.ca

References:

Kelly,  et al., (2016). Symbiotic Nitrogen Fixation and the Challenges to its Extension to Nonlegumes. Applied and Environmental Microbiology, 82(13). Retrieved from: http://aem.asm.org/content/82/13/3698.full

Zahran, H.H. (1999). Rhizobium-Legume Symbioses and Nitrogen Fixation under Severe Conditions and in an Arid Climate. Microbiology and Molecular Biology Reviews, 63(4). Retrieved from: https://www.ncbi.nlm.ih.gov/pmc/articles/PMC98982/

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