Countering Herbicide Resistance (minus tillage)

Herbicide Resistance Basics

The principles of herbicide resistance are straightforward – as the same herbicides are used year after year, there is intense selection pressure in weed populations for resistance traits. Once these traits are developed, they can be passed freely amongst weed populations of the same species. It is well understood that resistance traits can rapidly spread through nearby geographic areas through pollination or natural or human driven seed diffusion. The same principle applies to human health and the development antimicrobial resistance which has rendered antibiotics, antimalarials, and HIV antiretroviral drugs ineffective in contexts where they are relied upon as the sole means of control for various disease-causing pathogens.    

Since the mid-1990s, widespread use of herbicide-tolerant corn, soy, canola, and cotton varieties have led to the development herbicide resistant weed populations in areas across North America where these crops are grown. The highly effective in-season weed control that herbicide-tolerant crop varieties offer, coupled with tight crop rotations have led to the development of resistance to commonly used herbicides such as Round-Up, Liberty, and Xtend. It is possible for weed species populations to develop resistance to multiple herbicides. Once resistance traits are widespread, some herbicides (or combinations of herbicides) can be rendered partially or wholly ineffective. Once herbicide-resistant traits are developed, it is almost impossible to eliminate them.

Non-herbicide weed control strategies (minus tillage)

Fortunately, herbicide resistance can be countered with a wide range of measures. While not all measures discussed in this post are universally practical, any one of them can help to counter herbicide resistance if implemented as part of cash crop production systems. Importantly, these measures do not rely upon tillage. While tillage is a highly effective non-herbicide based weed control measure, the costs of relying upon regular tillage practices are too high (both in monetary cost and soil function).

a) Crop diversification:

Diverse cash crop rotations allow for the use of a wide range herbicide chemistries. This makes it less likely that resistance to a single herbicide can develop since this helps to reduce repeated weed population exposure to the same herbicides.

Multiple cover crops grown over the course of spring, summer, and fall seasons can help to suppress weed populations by outcompeting weed species. Common and fast-growing cover crops include winter rye and buckwheat. Growers would be forced to give up one growing season in order to take full advantage of cover crop weed suppression. However, cover crops can be harvested for seed or grazed in order to partially offset the costs of a lost cash cropping season. An added benefit of skipping a cash cropping year is the ability to break cash crop insect pest and disease cycles.

b) Equipment-based weed control:

A number of recently developed equipment-based weed control methods are available now or are nearly ready for wider adoption. Some many consider the costs of these equipment-based methods to be too high – but there is no doubting their effectiveness.

Flame weeding: This practice is growing in popularity amongst organic row crop farmers and flame weeding could have a place in non-organic row crop production – especially in areas with significant populations of herbicide resistant weeds. Electrical weeding: Electrical weeding has the potential to be a more common practice within the next 3-4 years. Large manufacturers such as Case IH now have electrical weeders on the market.

Weed seed mills: Not commonly used, but weed seed mills have shown promise with initial testing and adoption in Canada, US, and Australia. They are attached below the straw handling systems of a combine in order to not interfere with normal straw distribution. Various tests have demonstrated that weed seed mills can destroy between 90 and 98% of weed seeds sent through a combine.

Controlled traffic farming and chaff lining: In scenarios where controlled traffic farming is used, combine straw handling systems can be set to leave straw (and accompanying weed seeds) in tramlines. This significantly reduces the chances of weed seed germination.

Hybrid Versus Open-pollinated Corn Varieties

Hybrid Corn Varieties
Hybrid corn varieties were widely adopted across North America during the 1950s thanks to the higher yields they offered in comparison to open-pollinated varieties. By the 1970s, high-yielding hybrids led to corn becoming the dominant grain crop in regions with adequate precipitation (or irrigation) and longer growing seasons. By the early 2000s, the development of hybrids that consistently produce well in low soil moisture conditions allowed corn production to expand into dryland grain areas across the Southern and Central High Plains.

A number of biotechnology innovations have permitted corn yields to rise consistently year after year. These innovations include triple-stacked hybridization and GM traits (notably Bt and herbicide resistance). A number of other innovations during the past two decades have also contributed to yield increases, including precision agriculture technology and more precise N fertilizer applications throughout the growing season.

While these innovations have led to unprecedented yields, hybrid varieties can have drawbacks when it comes to production and harvest costs. Hybrid corn varieties have significant input costs including large N fertilizer requirements and high seed costs, for example. Additionally, the high yields of contemporary hybrids can often lead to increased harvesting, shipping, and storage costs.

Open-pollinated corn varieties

Thanks to the yield advantages of hybrid varieties, it would seem that open-pollinated corn would no longer have a place in commercial production systems. Yields of open-pollinated corn can never match contemporary hybrids. However, there has been a revival of interest in open-pollinated corn varieties for some use cases thanks to some advantages they offer. These advantages include potentially lower seed costs, lower N requirements, and superior qualities for human consumption.  

Seed Cost and Variety Selection

Most open-pollinated varieties are produced at very small scales, leading to high seed costs that are hardly competitive with hybrids. However, one commercial corn breeder in Michigan is currently producing open-pollinated seed corn that is cost competitive with hybrids.

Another advantage of open-pollinated corn is that even though initial seed costs may be high, it is possible for a farm to meet its seed corn needs through the selection of desirable traits on farm and then scaling seed production up over several years. While producing seed corn for on-farm use is time and labor-intensive, the longer-term cost savings and the development of unique traits may be worth the additional effort.

Lower N requirements
Due to lower yields, open-pollinated corn has significantly lower N requirements. However, another factor may be at play – recent research has demonstrated that newer crop varieties tend to have poor root development because robust root development is not prioritized by commercial grain breeders. This poor root development in turn leads to poor N uptake. It is unknown if this principle applies to corn. However, it may be a factor to consider if reducing N application rates is a priority.

Superior Qualities
Outside of potentially lower production costs, open pollinated varieties have superior food qualities when compared to hybrids. For specialty markets where grain qualities for human consumption are prioritized, open-pollinated varieties have a clear advantage over hybrids. Whether corn will be milled into cornmeal or nixtamalized for hominy or masa, taste, texture, scent, and color are the most important factors for food processors and manufacturers.
There is a growing demand amongst distillers for specialty corn. Small-scale distilleries are increasingly seeking out open-pollinated corn varieties for the terroir that they can lend to various types of corn-based liquors, such as whiskey and bourbon. This is akin to wine makers using grape varieties produced under specific soil and climate conditions to create unique and high-value finished products. If a farm business is interested in producing open-pollinated corn for high-value food or alcohol products, there is a significant amount of profit potential for cleaning and bagging grain on farm. This would allow for the sale of a relatively unique and high-quality product that could be milled, nixtamalized, or fermented immediately upon delivery to buyers.

Diversity and Flexibility for Winter Cash Crops

The majority of annual grain, oilseeds, and pulses grown in Canada and the United States are planted in spring ahead of the summer season or from early to mid-summer in order to ensure sufficient crop maturity ahead of the first frost. However, a small number of annual cash crops can be seeded in fall and then harvested the following spring or summer. There are significant advantages to overwintered cash crops such as helping to distribute seeding and harvesting work more evenly throughout the year and making soil health Principle 4 (Continual Live Plant/Root) possible without using a cover crop.

New crop variety development
Winter rye, winter wheat, and triticale have long been the pillars of overwintered cash crops. In locations north of the 43rd parallel, winter canola and winter camelina varieties are now widely available and they provide some much-needed diversity to traditional winter small grains. Locations south of 43rd parallel may not have much success with winter canola and winter camelina due to milder winters, but new varieties of winter barley, winter-tolerant oats, and winter forage peas are all good choices for producers looking to diversify beyond winter rye, winter wheat, and triticale.

Double Cropping
Overwintered annual cash crops can present an opportunity for double cropping in locations south of the 43rd parallel. Provided that significant soil moisture is available, a second cash crop can be sown or planted immediately after harvest. Second cash crops could include short day corn, short day sunflowers, foxtail millet, or even buckwheat.

Mixed Grain Intercropping
Mixed grain intercropping is on its way to becoming a commercially significant practice in Canada and the United States. But it is typically done using spring-seeded cash crops. Overwintered annual cash crops could lead to some interesting mixed grain intercrop combinations, such as winter tolerant oats-winter forage pea or winter canola-winter forage pea. These combinations could provide the advantages of both an overwintered cash crop and a mixed grain intercrop.

Relay Cropping
Relay cropping is becoming more well-known south of the 43rd parallel. The winter wheat-soy combination is the most popular winter small grain-spring pulse relay combination at this time. However, combinations of winter wheat-dry bean or winter wheat-lentil offer similar agronomic advantages and there is no good reason why these combinations couldn’t work as effectively as the winter wheat-soy relay combination. Relay cropping is a practice that is typically not used in areas north of the 43rd parallel thanks to a shorter growing season. However, a winter small grain-spring small grain relay crop could be viable if the spring small grain was seeded relatively late and the winter small grain was cut for green feed before the spring small grain reached the reproductive stage.

Cover Crops: Frost Termination

Frost termination can be a viable (and cost-free) method of cover crop termination provided it does not interfere with cash crop production during the primary growing season and sufficient soil moisture is available following harvest. Ideally, a cover crop planted for frost termination in the Fall would be able to produce significant biomass growth and it would be killed by below freezing temperatures prior to seed set. Due to these requirements, frost termination of cover crops works best in continental (inland) climates between 35 and 50° N. However, in locales with the potential for mild winters, a backup plan for termination should be in place in the event of the cover crop surviving the winter.

Frost-terminated cover crops would be viable following an over-wintered small grain harvested in late June or early July, or after a pulse crop harvested between August and mid-September. If a cash crop is harvested in mid-summer, warm season annuals such as millet, sorghum, buckwheat, and sunflowers will produce a significant amount of biomass ahead of the cooler temperatures and shorter days leading up to the first frost. If a cash crop is harvested in August or September, cool season species like mustard, daikon radish, oats, and white clover would be more suitable.

Overwintered or spring planted cover crops should produce a significant amount of biomass prior to termination. In cooler climates or years with cooler springs, there may be very little cover crop growth until mid-May and this growth delay can have significant impacts on cash crop planting dates. This is not an issue with frost terminated cover crops because they produce biomass during the late summer and early Fall and in turn, this dead cover crop biomass can be direct seeded into the following spring during optimal planting windows. Therefore, frost-terminated cover crops might be a viable option in drier and colder commodity producing areas of Canada and the U.S.

Some dryland/livestock mixed farm operations on the U.S. central High Plains have had good success with planting warm-season forage mixes in late Spring, grazing at various points during the summer, relying on frost to terminate the warm-season forage mix in the Fall, and then direct seeding a cash crop the subsequent spring. The only disadvantage to this use of frost-terminated cover crops is that one season of cash cropping is missed. However, the residue and added fertility from ruminants can contribute to higher yields and lower synthetic fertilizer requirements in cash crops the following growing season.

The major issue with the frost termination method is that it violates Principle 4 of soil health practices (Continual Live Plant/Root). This means that no biomass or root exudates will be generated between cover crop termination in the Fall and cash crop planting the following Spring. However, the diversity added to the cropping systems, potential for grazing, heavy residue, and the flexibility in cash crop planting dates in the following Spring will override any disadvantage to not having live continual live plant/roots in place during Winter and early Spring.

Tracking Soil Health With Practical and Cost-effective Soil Testing

Farm operations implementing soil health practices can readily observe improvements to soil structure, water infiltration rates, and water-holding capacity. However, farms wishing to closely monitor changes to the physical, chemical, or biological characteristics of their soils as a result of soil health practices should ensure that soil testing remains simple, practical, and cost-effective. The first step in soil sampling is selecting a sampling methodology and sampling intervals.

After a sampling methodology and sampling intervals have been selected, soil tests should be chosen that can provide practical information on soil characteristics. Some basic tests like soil texture (% of sand, silt, and clay), pH, soil organic matter (SOM), and bulk density can be done using a lab analysis after samples have been collected. Soil health practices will not change soil texture, but they can help to bring pH closer to neutral, increase SOM, and lower bulk density. These basic tests are relatively low cost and can even be done on-farm with the bare minimum of soils lab equipment. Furthermore, soil samples for this set of tests can be collected at any time of year when the soil is not frozen.

In-situ tests, like water infiltration, can be challenging because they must undertaken at a time of year when soil conditions reflect growing season conditions and a series of water infiltration tests across a sampling grid or field zones can quickly add up in terms of time and labor. Other tests, such as respiration can give a good indication of soil biological activity. However, the labor necessary to conduct respiration tests makes them a questionable measure for large numbers of soil samples. Tests for N are of limited utility thanks to the dynamic state of plant-available nitrogen throughout the year and monitoring above ground cash crop biomass (using a methodology like N-Rich) would be a more effective way of monitoring N levels throughout the growing season. Tests for P can be effective, however testing methods must be chosen carefully based on specific soil chemical properties.

In summary, tracking soil health can be done in a cost-effective manner. But sampling methodologies as well as particular soil tests chosen must be simple, practical, easily repeatable, and have low overhead costs.

Tracking Soil Health With Precise and Consistent Soil Sampling

Tracking changes to soil characteristics over time can be labor intensive and expensive. However, soil health practitioners often find soil testing to be worth the investment because it provides a systematic way of evaluating the impact of soil health practices. Basic soil measurements like pH, organic matter, and water infiltration rates can help to quantify and track the impacts of soil health management practices over time. Regardless of which soil tests are used, a sampling methodology should be chosen and used consistently over several sampling intervals to make the time and money invested into sampling and testing cost-effective. Ideally, sampling intervals should range between 1 and 3 years.

Currently, there are four primary sampling methodologies in use: bulk, grid, zone, and sensor. Bulk and grid sampling require the use of basic GPS equipment to ensure samples are taken from the same location at each sampling interval. Zone and sensor testing only make financial sense if a farm operation already uses variable rate technology. However, if variable rate technology is already in use, zone and sensor testing are much better values than bulk or grid sampling.

Bulk sampling:

Bulk soil sampling entails gathering a number of soil samples which best represent a field’s overall soil characteristics. Samples are then well-mixed prior to running soil tests. Bulk sampling can provide an understanding of overall soil characteristics in a field. But it gives no indication of soil variability across a field’s surface. Additionally, bulk sampling may not be able to provide any reliable indication of how soil characteristics are changing over time, unless samples are taken from the same sampling sites for each sampling interval. The primary advantage of bulk sampling is that it can be a relatively inexpensive way of understanding soil properties of a particular field since only 1 series of laboratory tests are required.

Grid sampling:

Grid sampling involves setting up a grid of a predetermined size and sampling once within each grid square. Grid sampling provides a good indication of soil characteristics across the surface of the field. Grid sampling may be suitable for fields with relatively uniform soil characteristics. However, in fields with highly variable soil conditions, grid sampling cannot represent soil characteristics in an accurate manner because grid squares will match up poorly with topography and landscape features.

Zone Sampling:

Zone sampling requires the use of already established variable rate zones. Variable rate technology has been used to increase the accuracy of fertilizer applications for almost two decades and variable rate seeding or planting based on similar technology has become more popular within the past five years. Variable rate zones are established based on a number of different variables such as topography, landscape features, and soil characteristics. The number of variable rate zones is highly context dependent. However, the common features of each zone means that only one soil sample from each zone is necessary. This can greatly simplify sampling and reduce costs.

Sensor Sampling:  

A number of different companies have developed digital soil mapping systems based on custom-developed sensors mounted to an ATV or truck. It is a form of predictive mapping that can infer a range of soil characteristics, such as texture or organic matter. These systems can provide hundreds of sampling points per acre and often produce data in a format that can be used by variable rate systems. However, sensor sampling is limited some ways because it cannot measure important physical measurements of soil health such as bulk density or water infiltration rates.

In conclusion, all four sampling methodologies have their advantages and disadvantages. But regardless of which sampling methodology is used, precise and consistent soil sampling should play a key role tracking the impact of soil health practices in a cost-effective manner.

Cover Crops and Carbon Cycling

Cover crops have a long history of use in annual cropping systems worldwide thanks to benefits they can provide (such as reducing soil erosion, improving soil function, suppressing weed growth, breaking pest and disease cycles, and providing livestock fodder). Despite these benefits, cover crops fell out of favor amongst non-organic grain/oilseed/pulse commodity growers in North America following the Second World War. During the past decade a small but growing movement of commodity growers in Canada and the U.S. have found ways integrate cover crops back into their commodity production systems and cover crops are again becoming an important tool in profitable commodity production systems.

The resurgence in cover crop use has been facilitated by improvements in no-till (or direct) seeding and planting equipment, the development of scientifically-based cover crop extension knowledge, and a wealth of farmer-developed knowledge shared via social media. Recently, cover crops have become central in debates around commodity agriculture’s potential to sequester excess atmospheric carbon.
Commodity grain, oilseed, and pulse production is based on annual plant species. In North America, the land clearing and heavy annual tillage that make commodity production possible have made these farming systems significant net atmospheric carbon sources since colonization. Cover crops (combined with no-till, heavy cash crop residue, plant diversity, and ruminant livestock) have the potential to turn North American commodity grain/oilseed/pulse production systems into net atmospheric carbon sinks for the first time. It is due to these changes in soil management practices and their potential to play a partial role in climate change mitigation that has garnered the attention of lawmakers, government agencies, and corporations.  

It is important to point out that the biomass of cash crops and cover crops breaks down too quickly to sequester atmospheric carbon for any significant amounts of time. Instead, root exudates are the primary means by which excess atmospheric carbon can be fixed in the soil for long periods. Root exudates can take a number of different forms, but long chain starches are the most important regarding climate change mitigation. It is estimated that these long chain starches can be stable for up to 500 years. Therefore, if cover crops are fixing carbon in the long periods outside of the main growing season and cash crops are fixing carbon during the main growing season, the potential of annual agriculture systems to sequester excess atmospheric carbon is significant.

In conclusion, cover crops can be useful tool in commodity production systems thanks to the agronomic and soil health benefits they can provide. They also can play a key role in fixing excess atmospheric carbon. However the buzz around cover crops as a climate change mitigation tool should come with the following warnings:

1) The ability of commodity production systems to fix excess atmospheric carbon is highly dependent on local climatic conditions and farming practices
2) Methodologies for monitoring carbon cycling is still in its infancy and scaling these methodologies up to measure carbon cycling across commodity production landscapes is not possible at this time
3) Cover crops are inappropriate for large tracts of dryland commodity production areas in North America thanks to cold and dry climates.

Soil Health Management in Colder and Drier Climates

In Canada and the United States, cover crops are heavily promoted as an essential component of soil health in grain/oilseed/pulse production systems. Ideally, cover crops are grown before or after the main cash cropping season so that a growing season is not devoted solely to cover crops. Under the right conditions, cover crops can help to improve water infiltration and retention, reduce soil erosion, and provide livestock fodder.

However, cover crops are not ideal for all climates outside of the main cash crop season. In areas of Canada and the United States north of the 43rd parallel and west of the 100th meridian, cover crops usually will not work outside of the main summer cropping season due to short growing seasons and/or relatively dry climates. While irrigation is important in some areas (i.e. Central High Plains, South-Central Saskatchewan) dryland acreage of grain/oilseed/pulse cash crops is significantly greater than irrigated acreage across this region. Considering the expense of irrigation infrastructure and the limits of existing water resources, dryland production of grains/oilseeds/pulses north of the 43rd parallel and west of the 100th meridian will remain an important method of commercial production well into the future.

While various forms of wheat-fallow rotation became dominant across the region between the 1920s and 1970s, the financial and environmental viability of wheat fallow-only systems started to be questioned as a result relatively low wheat prices along with severe soil erosion and poor soil function resulting from long periods of soil being left bare. A number of practical innovations have been adopted in these colder and/or drier climates that have allowed for the adoption of continuous cropping systems (with some important exceptions in extremely dry climates of interior Washington State or the Southern High Plains). At present, continuous cropping dryland systems use a number of innovations which allow for soil health practices to be used minus cover crops. They include:

1) Maximizing post-harvest crop residue: This can be achieved using stripper headers (small grains), pan headers (sunflowers), or specially configured conventional corn headers. Another benefit of not processing residue through combines is reduced machine wear and tear and lower fuel consumption.

2) No-till drills or row crop planters configured to handle large amounts of the previous year’s cash crop residue: Newer no-till drills or planters use a significant amount of downforce along with discs to cut through residue, establish good seed/soil contact at optimal planting depths, and minimize hairpinning. While no-till equipment has been widely available since the 1970s, a host of innovations have significantly improved no-till seeding and planting equipment since 2010.

3) Broad and flexible cash crop rotations: Ideally, 5-6 cash crops are grown in rotation and rotations are set on an annual basis. Cash crops are chosen based on interrupting pest and disease lifecycles, diverse herbicide programs, post-harvest residue maximization, and market demands. Typically, small grains play a key role in these broad rotations because they provide significant post-harvest residue relative to oilseed and pulse crops.

4) Synthetic N fertilizer optimization: Synthetic N rates can often be reduced thanks to improved soil function, broader cash crop rotations, variable rate fertilizer equipment, and monitoring N requirements throughout the growing season.

5) Other synthetic input optimization: Broad cash crop rotations can result in reduced requirements for fungicides, insecticides, and herbicides.

The practices that I describe have become standard approaches for soil health practitioners in drier and/or colder areas of North America. During the past decade a number of other innovations have been added to these standard practices, which include:

1) Mixed grain intercropping: Raising two or more cash crops at the same time and separating after harvest can provide specific agronomic benefits like reduced lodging and reduced fungal pressure.

2) Variable rate seeding: Like variable rate fertilizer, variable rate seeding allows for seed cost savings and in some cases, higher yields.

3) Ruminant livestock integration: The grazing of livestock on early-stage cash crops, cash crop residue, or forage crops are extremely old practices that have been used worldwide. However, there has been a recent resurgence of interest in grazing livestock on dryland cash crop fields after a significant decline in the 1970s.

While cover crops are an important soil health tool in the right contexts, they can be difficult to make work in dryland cash crop systems in drier and/or colder climates in Canada and the United States during the main growing season. Cover crops can certainly be grown during the main summer growing season to improve soil function, but farm operations must be willing to give up a cash crop for one year and ideally a cover crop raised during the growing season would be grazed by ruminant livestock.

Can Anthrosols Inform Soil Health Practices?

Anthrosols are a soil group with properties that have been modified by human agricultural activity. Some anthrosols have been intentionally “engineered” over time to improve their function for agricultural production. Amazonian Dark Earths (ADE) are good examples of anthrosols that have been created by Indigenous peoples to boost agricultural productivity. ADE have significantly different physical, chemical, and biological characteristics when compared to nearby unmodified soils of the same type. While soils across the Amazon basin are incredibly diverse, most soils across this vast area are highly weathered, have high iron and aluminum oxides content, and have high pH levels (with some exceptions such as portions of the Brazilian state of Rondônia). In principle, such soil characteristics should limit agricultural productivity. However, the widespread use of ADE was one factor permitting significant agricultural activity across the Amazon basin prior to colonization (such activity has been maintained at smaller scales up to the present day).

ADE are created through a variety of different methods, but common ADE improvements across the Amazon basin include the addition of biochar, the incorporation of large amounts of organic matter, and the mixing of soil horizons. These amendments lead to improved soil characteristics such as lower bulk density, higher cation exchange capacity, and measurable increases in the types and overall numbers of soil microorganisms. ADE horizons can be up to 1 meter(!) in depth.

The large historical populations of Indigenous peoples across the Amazon basin resulted in between approximately 0.1% to 10% of soils across this vast region being modified into ADE. It is important to point out that it is not one magic ingredient or practice the led to the creation of ADE. They were (and still are) created as part of broader landscape management practices and it takes a significant amount of conscious effort and time to create them. Importantly, anthrosols similar to ADE have been independently developed in other parts of the world, such as West Africa.

Soil health practices have gained traction amongst commercial grain, oilseed, and pulse farmers in Canada and the United States during the past decade. As with ADE, the end goals of soil health practices are to improve the physical, chemical, and biological characteristics of soils with an explicit focus on agricultural production. Soil health principles include no-till, residue maximization, cover cropping, and livestock integration. This is a relatively new perspective in soil management since most academic, government, and farmer-developed approaches to soil management long assumed an irreversible decline in soil function after the conversion of “natural” soils to commercial production.

Anthrosol development and soil health practice implementation are highly context specific. Is there a possibility that anthrosols can provide some lessons for soil health practitioners? Biochar shows promise as a soil amendment in the commercial production of grains, oilseeds, and pulses. However, biochar is not the “silver-bullet” that it is often hyped to be. Its success as a key component of ADE hinges on the addition of other soil amendments and the use of other landscape management practices. At the same time, it remains questionable as to whether the manufacture and application of biochar at the scale needed for large grain/oilseed/pulse farms can be made commercially viable.

In conclusion, processes developed to manufacture anthrosols may not directly translate into commercially relevant soil health practices. However, the independent development of methods to improve soil characteristics for agricultural production at various times and places around the world demonstrates that soil management is an essential part of agricultural production, regardless of context.  

Are Perennial Grains, Oilseeds, and Pulses Ready for Production Ag. Systems?

The Land Institute (TLI) is a Salina, Kansas-based not-for-profit organization which is working to develop perennial varieties of grains, oilseeds, and pulses through the domestication of wild perennial species and through the perennialization long-domesticated annual crops like wheat, rice, and sorghum. TLI has the ambitious goal of building grain, oilseed, and pulse production systems around perennial crops. Importantly, TLI is using an open source development model which allows for the organization’s research and crop varieties to remain in the public domain.

Perennial crops have a number of production advantages when compared to annual crops. They include:

-a single seeding pass for multi-year cropping cycles
-zero tillage after establishment
-year-round soil cover without the need for annual cover crops
-extensive root systems, allowing perennial crops to access water and macronutrients deep in the subsoil
-longer windows of cash crop biological activity, allowing for greater amounts of exudates (in principle) when compared to annual crops

While the production advantages of perennial grain, oilseed, and pulse varieties are attractive, there remains some unanswered questions about the practicality of perennial crops in production systems. Diverse and flexible annual cash crop rotations can provide a significant amount protection against weed infestations, insect pests, and fungal infections. These crop protection advantages may be lost with long-lived stands of perennial crops. At the same time, annual cash crop rotations can more easily be adapted to market conditions. It is expected that stands of perennial crops would be productive between 5-10 years, making them less adaptable to shifts in market demand on a year to year basis.

Most of TLI’s perennial crops are still in the development stage, but two have recently been adopted in production systems at small scales. Intermediate wheatgrass (trademarked as Kernza) and a hybrid rice variety. Kernza is now being grown commerically in Canada and the U.S. for baked goods and beer. However, Kernza’s low grain yield, small seed size, limited productivity after 3-4 years, and limited seed availability ensure that it will remain a low-volume specialty crop for the time being. Perennial rice now produces acceptable yields for 3-4 years and has been used for commercial rice production in China since 2018. Breeding work continues on both Kernza and perennial rice to select for higher yields, improved grain characteristics, and longer plant lifespans.

Crops still in the development stage include silphium (a perennial oilseed sunflower species), perennial wheat, and perennial sorghum. State of the art computer-aided genetic sequencing and year-round greenhouse breeding is being used to accelerate the development of these crops. It is expected that it will be another 15-20 years until silphium, perennial wheat, and perennial sorghum are ready for adoption in production systems.

Beyond current perennial crops in development, TLI is working with Missouri Botanical Garden and St. Louis University to identify herbaceous wild perennial species around the world that would make good candidates for domestication in both temperate and tropical climates. These longer-term projects reflect TLI’s long-term mission for perennial crop selection and breeding over the next 50-100 years. TLI has invested significantly in fund-raising capacity and organizational development to ensure that it will survive long enough as an organization to achieve its ambitious goals.  
As more perennial grain, oilseed, and pulse varieties are developed, TLI anticipates that they can be grown as suites of mixed intercrops. Mixed intercropping can provide specific agronomic benefits, including a decreased need for N fertilizer or help to lower susceptibility to insect pests. A great deal of practical work on mixed intercropping seeding, harvesting, and grain separation has already been done in annual cropping systems on the Canadian Prairies and U.S. Northern Plains, demonstrating that mixed intercropping can be profitable and practical in production agriculture systems.

TLI does not expect that their perennialized crop varieties will completely replace annual crop varieties in the long term. However, mixed stands of perennial grains, oilseeds, and pulses which are commercially viable and which complement annual production systems are an exciting prospect we can realistically look forward to in the next 15-20 years.