New Findings Further the Study of Dynamic Accumulators

Comfrey is a dynamic accumulator of potassium and silicon — nutrients that both happen to play key roles in stomata regulation in leaves.

There is growing interest in “dynamic accumulator” plants and their potential as nutrient catch crops, “chop and drop” mulches and fodder for home-brew liquid fertilizers. Dynamic accumulators are seen as a promising closed-loop nutrient management solution that converts common weeds into valuable nutrient sources while reducing the need for purchased fertilizers and soil amendments.

However, the term “dynamic accumulator” has largely existed in the realm of informal research and in books on gardening and permaculture. This has led many to believe that dynamic accumulation is unproven pseudo-science, even though the accumulation of beneficial nutrients in the context of cover cropping has been extensively researched and accepted as fact. Likewise, the related field of “hyperaccumulator” plants has enjoyed over 40 years of enthusiastic research and discussion in peer-reviewed journals.

Unadilla Community Farm in central New York State recently completed a two-year SARE-funded study to define what exactly qualifies as dynamic accumulation and to investigate potential applications for these plants. Here are the key findings:

Plant-tissue nutrient concentrations are tied to soil nutrient concentrations. Dynamic accumulators are well-suited to extract specific nutrients from fertile soil, but they aren’t going to create nutrition that isn’t there. Therefore, dynamic accumulators should be regarded as one useful part of a larger nutrient management plan.
That said, even when grown in poor, unamended soil, lambsquarters surpassed the dynamic accumulator threshold for potassium, and comfrey surpassed the threshold for both potassium and silicon. This is particularly exciting because, while there has been ample research on comfrey’s potassium concentrations, there has been little discussion of its silicon concentrations.
Previous studies have shown stinging nettle to accumulate calcium at concentrations above dynamic accumulator thresholds. Our findings show that not only does stinging nettle accumulate a lot of calcium, but it also has a high nutrient carryover rate, resulting in calcium-rich liquid fertilizer and mulches.

The research team’s calculation of dynamic accumulator thresholds resulted in the creation of a new dynamic accumulator online tool, which is available, along with the complete report and other materials, at https://unadillacommunityfarm.org/dynamicaccumulators/.

Evolution of Waterhemp Has Intensified Since 1960s

Waterhemp — here growing in a field of soybeans — has evolved to become resistant to many common herbicides.

New research in Science is showing how the rise of modern agriculture has turned a North American native plant, common waterhemp, into a problematic agricultural weed.

An international team led by researchers at the University of British Columbia (UBC) compared 187 waterhemp samples from modern farms and neighboring wetlands with more than 100 historical samples dating as far back as 1820 that had been stored in museums across North America. Much as the sequencing of ancient human and neanderthal remains has resolved key mysteries about human history, studying the plant’s genetic makeup over the last two centuries allowed the researchers to watch evolution in action across changing environments.

“The genetic variants that help the plant do well in modern agricultural settings have risen to high frequencies remarkably quickly since agricultural intensification in the 1960s,” said first author Dr. Julia Kreiner, a postdoctoral researcher in UBC’s Department of Botany.

The researchers discovered hundreds of genes across the weed’s genome that aid its success on farms, with mutations in genes related to drought tolerance, rapid growth and resistance to herbicides appearing frequently. “The types of changes we’re imposing in agricultural environments are so strong that they have consequences in neighboring habitats that we’d usually think were natural,” said Dr. Kreiner.

The findings could inform conservation efforts to preserve natural areas in landscapes dominated by agriculture. Reducing gene flow out of agricultural sites and choosing more isolated natural populations for protection could help limit the evolutionary influence of farms.

Common waterhemp is native to North America and was not always a problematic plant. Yet in recent years, the weed has become nearly impossible to eradicate from farms thanks to genetic adaptations, including herbicide resistance.

“While waterhemp typically grows near lakes and streams, the genetic shifts that we’re seeing allow the plant to survive on drier land and to grow quickly to outcompete crops,” said co-author Dr. Sarah Otto, Killam University Professor at the University of British Columbia. “Waterhemp has basically evolved to become more of a weed given how strongly it’s been selected to thrive alongside human agricultural activities.”

Notably, five out of seven herbicide-resistant mutations found in current samples were absent from the historical samples. “Modern farms impose a strong filter determining which plant species and mutations can persist through time,” said Dr. Kreiner. “Sequencing the plant’s genes, herbicides stood out as one of the strongest agricultural filters determining which plants survive and which die.”

Waterhemp carrying any of the seven herbicide-resistant mutations have produced an average of 1.2 times as many surviving offspring per year since 1960 compared to plants that don’t have the mutations.

Herbicide-resistant mutations were also discovered in natural habitats, albeit at a lower frequency, which raises questions about the costs of these adaptations for plant life in non-agricultural settings. “In the absence of herbicide applications, being resistant can actually be costly to a plant, so the changes happening on the farms are impacting the fitness of the plant in the wild,” said Dr. Kreiner.

Agricultural practices have also reshaped where particular genetic variants are found across the landscape. Over the last 60 years, a weedy southwestern variety has made an increasing progression eastward across North America, spreading their genes into local populations as a result of their competitive edge in agricultural contexts.

Meat Substitutes May Contain Low Nutritional Quality

The availability of foods based on plant proteins to substitute for meat has increased dramatically as more people choose a plant-based diet. At the same time, there are many challenges regarding the nutritional value of these products. A study from Chalmers University of Technology in Sweden now shows that many of the meat substitutes sold in Sweden claim a high content of iron — but in a form that cannot be absorbed by the body.

The study analyzed 44 different meat substitutes sold in Sweden. The products are mainly manufactured from soy and pea protein, but also include the fermented soy product tempeh and mycoproteins — that is, proteins from fungi.

“Among these products, we saw a wide variation in nutritional content and how sustainable they can be from a health perspective. In general, the estimated absorption of iron and zinc from the products was extremely low. This is because these meat substitutes contained high levels of phytates — antinutrients that inhibit the absorption of minerals in the body,” said Cecilia Mayer Labba, the study’s lead author.

Phytates are found naturally in beans and cereals and accumulate when proteins are extracted for use in meat substitutes. In the gastrointestinal tract, where mineral absorption takes place, phytates form insoluble compounds with essential dietary minerals, especially non-heme iron (iron found in plant foods) and zinc, which means that they cannot be absorbed in the intestine.

Plant Roots Change Shape and Branch Out for Water

Plant scientists from the University of Nottingham have discovered a novel water-sensing mechanism that they have called “hydro signaling,” which shows how hormone movement is linked with water fluxes. The findings have been published in Science.

Water is the rate-limiting molecule for life on earth. Roots play a critical role to reduce the impact of water stress on plants by adapting their shape (such as branching or growing deeper) to secure more water. Discovering how plant roots sense and adapt to water stress is of vital importance for helping “future-proof” crops to enhance their climate resilience.

Using X-ray micro-CT imaging, researchers were able to reveal that roots alter their shape in response to external moisture availability by linking the movement of water with plant hormone signals that control root branching.

The study provides critical information about the key genes and processes controlling root branching in response to limited water availability, helping scientists design novel approaches to manipulate root architecture to enhance water capture and yield in crops.

Dr. Poonam Mehra, one of the lead authors, explained that “when roots are in contact with moisture, a key hormone signal (auxin) moves inwards with water, triggering new root branches. However, when roots lose contact with moisture, they rely on internal water sources that mobilize another hormone signal (ABA) outwards, which acts to block the inwards movement of the branching signal. This simple, yet elegant, mechanism enables plant roots to fine tune their shape to local conditions and optimize foraging.”

Increasing Crop Yields by Breeding Plants to Cooperate

A simple breeding experiment, combined with genetic analysis, can rapidly uncover genes that promote cooperation and higher yields of plant populations, according to a new study publishing in the open access journal PLOS Biology. The results have the potential to quickly increase crop productivity through conventional breeding methods.

In classic evolutionary theory, individuals compete, and those with the most competitively advantageous genes create more offspring that bear the same winning genes. This poses a challenge for plant breeders, who are often want to select plants that cooperate rather than compete. In a dense monoculture stand of corn or wheat, for example, overall yield may be improved if individuals avoid growing too tall or spreading their leaves too wide.

Discovering the alleles (versions of genes that differ between individuals) that may promote cooperation is challenging, but the authors designed a system to reveal them. In alignment with game theory, the authors reasoned that the most cooperative genotype will perform best with similarly cooperative neighbors, but will do poorly when facing selfish, highly competitive neighbors. They used the model plant Arabidopsis to compare the performance of a given plant when grown with another genetically similar individual (modeling a monoculture) to its performance when grown with a set of “tester” genotypes that varied in their growth strategies.

By determining both the overall vigor of each plant (as measured by above-ground biomass) and the difference between its growth in the two situations, they could see which plants maximized both the ability to grow rapidly and the ability to cooperate with genetically similar individuals so that their neighbors also grew well.

With that data in hand, they used published genome-wide polymorphism data to find the genes associated with the cooperative trait. They found it was most strongly associated with a small group of linked polymorphisms, and in particular a minor allele at one gene. When plants carrying that minor allele were grown in close proximity, they collectively produced 15 percent more biomass when grown at high density than plants carrying the major allele at the same locus. The cooperative effect was accompanied by reduced root competition — adjacent plants may have spent less energy invading their neighbors’ root zones for nutrients.

The same comparative strategy could be used for discovering cooperative alleles for any measurable characteristic, Wuest said. “Such variation, once identified in a crop, could rapidly be leveraged in modern breeding programs and provide efficient routes to increase yields.”

Wuest added, “The ideas that inspired this work are not new; many have in fact been formulated decades ago. And yet, the thought that we humans, one of the most cooperative species, can profit from making our crops more cooperative, too, still intrigues us today.”

Mad Capital Raises $4 Million to Finance Regenerative Agriculture

Mad Capital, an impact-focused lender that offers equitable, flexible funding for organic and transitioning farmers, have raised $4 million in a seed round of investing.

“Regenerative agriculture aspires to work with nature, rather than against it,” said Phil Taylor, co-founder of Mad Capital. “Mad Capital is a bold reimagination of financing in nature’s image, empowering farmers to create farm ecosystems that are good for the Earth and good for humanity.”

“Our goal is to finance 10 million acres of farmland by 2032. We are thrilled to have expanded our investor community and now have the resources to continue backing farmers who are transitioning more land to regenerative organic production,” added co-founder Brandon Welch.

Many farmers struggle to convert to regenerative organic because traditional banks are largely unwilling to supply transition financing. “In the coming year, we’ll turn our focus to building out our network of mission-aligned capital partners and launching our second Perennial Fund, with a goal of financing an additional 100,000 acres of farmland in 2023,” commented Welch.

Mad Capital manages innovative pools of capital that offer farmers flexible and customized financing to help them thrive during the organic transition period. Their inaugural fund, the Perennial Fund, blends debt funds with traditional financing to create one-of-a-kind capital stacks for their farmers to accelerate their transition. Without this custom working capital, farmers often take a financial hit during the standard three-year period it takes farms to regenerate their ability to produce a consistent crop yield.

Mark Lewis of Trailhead Capital, an investment firm focused on regenerative agriculture, said, “Mad Capital is working to determine how do we optimally reward the stewards that are doing the most noble and regenerative work? That is the question we aim to address and innovate on.”

Mad Capital is working to prove the viability of regenerative organic agriculture as an asset class that can provide consistent yield in the face of an uncertain macroeconomic environment. Over time, Mad Capital plans to securitize their regenerative organic farm loans to scale the growing industry while helping capital partners meet their climate and sustainability goals.