Tag: weed ecology

Collaborative paper published on winter wheat, farming practices, and climate!

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The second paper from Tindall’s master’s work at Montana State University in the Menalled Lab has been accepted for publication! Tindall defended her master’s in August 2021, and has been working at a plant production company in Bozeman since then.

Ouverson, T., Boss, D., Eberly, J., Seipel, T.,  Menalled, F.D., Ishaq, S.L. 2022. Soil  bacterial community response to cover crops, cover crop termination, and predicted climate conditions in a dryland cropping system. Frontiers in Sustainable Food Systems.

Abstract

Soil microbial communities are integral to highly complex soil environments, responding to changes in aboveground plant biodiversity, influencing physical soil structure, driving nutrient cycling, and promoting both plant growth and disease suppression. Cover crops can improve soil health, but little is known about their effects on soil microbial community composition in semiarid cropping systems, which are rapidly becoming warmer and drier due to climate change. This study focused on a wheat-cover crop rotation near Havre, Montana that tested two cover crop mixtures (five species planted early season and seven species planted mid-season) with three different termination methods (chemical, grazed, or hayed and baled) against a fallow control under ambient or induced warmer/drier conditions. Soil samples from the 2018 and 2019 cover crop/fallow phases were collected for bacterial community 16S rRNA gene sequencing. The presence and composition of cover crops affected evenness and community composition. Bacterial communities in the 2018 ambient mid-season cover crops, warmer/drier mid-season cover crops, and ambient early season cover crops had greater richness and diversity than those in the warmer/drier early season cover crops. Soil microbial communities from mid-season cover crops were distinct from the early season cover crops and fallow. No treatments affected bacterial alpha or beta diversity in 2019, which could be attributed to high rainfall. Results indicate that cover crop mixtures including species tolerant to warmer and drier conditions can foster diverse soil bacterial communities compared to fallow soils.

Figure 1, showing a schematic of the fields and experimental design.

Related works from that research group include:

Collaborative paper accepted on winter wheat, weeds, and climate.

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The last paper to be generated from the large-scale, multi-year, collaborative research I participated in as a postdoc at Montana State University in the Menalled Lab in 2016 has finally been accepted for publication! At the time, I was working on the soil bacteria associated with winter wheat crops under different simulated climate change scenarios, and with added stressors like weed competition and different farming strategies. I was part of a large team of researchers looking at various aspects of agricultural stressors on long-term food production, including several agroecologists who led the development of this paper.

Weed communities in winter wheat: responses to cropping systems and predicted warmer and drier climate conditions.

Tim Seipel, Suzanne L. Ishaq, Christian Larson, Fabian D. Menalled. Sustainability 2022, 14(11), 6880; https://doi.org/10.3390/su14116880. Special Issue “Sustainable Weed Control in the Agroecosystems“

Abstract

Understanding the impact of biological and environmental stressors on cropping systems is essential to secure the long-term sustainability of agricultural production in the face of unprecedented climatic conditions. This study evaluated the effect of increased soil temperature and reduced moisture across three contrasting cropping systems: a no-till chemically managed system, a tilled organic system, and an organic system that used grazing to reduce tillage intensity. Results showed that while cropping system characteristics represent a major driver in structuring weed communities, the short-term impact of changes in temperature and moisture conditions appear to be more subtle. Weed community responses to temperature and moisture manipulations differed across variables: while biomass, species richness, and Simpson’s diversity estimates were not affected by temperature and moisture conditions, we observed a minor but significant shift in weed community composition. Higher weed biomass was recorded in the grazed/reduced-till organic system compared with the tilled-organic and no-till chemically managed systems. Weed communities in the two organic systems were more diverse than in the no-till conventional system, but an increased abundance in perennial species such as Cirsium arvense and Taraxacum officinale in the grazed/reduced-till organic system could hinder the adoption of integrated crop-livestock production tactics. Species composition of the no-till conventional weed communities showed low species richness and diversity, and was encompassed in the grazed/reduced-till organic communities. The weed communities of the no-till conventional and grazed/reduced-till organic systems were distinct from the tilled organic community, underscoring the effect that tillage has on the assembly of weed communities. Results highlight the importance of understanding the ecological mechanisms structuring weed communities, and integrating multiple tactics to reduce off-farm inputs while managing weeds.

The related works from that project include:

Similar work has been done by that group, including:

Wrapping up summer projects

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After a hot, dry summer growing season in Montana, the samples have all been collected and the crop harvested for my project investigating wheat production under farming system (organic vs. conventional), climate change (hot or hot and dry), disease (wheat streak virus), and weed competition (cheatgrass) conditions.  We collected wheat and weed biomass from every subplot, totaling 108 bags of wheat and an estimated 500 bags of weeds!  This will be weighed to determine production, and diversity (number of different weed species) will be assessed.

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The biomass bags were temporarily stored in my office until we could find enough shelf space in the lab.

At the end of July, we also collected our final soil samples, which required over 500 grams of aseptically collected of soil in each subplot.  With the extremely dry, clay-containing soil on the farm, this was no quick undertaking, and it took 6-7 lab members a total of 9 hours to collect all 108 samples!  Those soil samples will be used for DNA sequencing to determine what microorganisms are present, and compared to other time points to see how they changed over the summer in response to our treatment conditions.  The soil will also be measured for essential nutrients, such as nitrogen and carbon content, and saved to be used in a greenhouse experiment to look at the legacy effects of microbial change.

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The samples might be collected, but we aren’t done yet.  This was year one of a two-year project, and as winter wheat and cheatgrass need to be sown soon, before it gets cold, we have a lot of prep work to do.  This includes resetting our data collection tools, including gypsum blocks for soil moisture and ibuttons for soil temperature.  We will also need to set up our climate chamber equipment in all new subplots, since we are interested in third-year winter wheat that is part of a five-year crop rotation.  We also plan to start a greenhouse experiment looking at the legacy effects of our soil this fall.  Not to mention all of data to analyze over the winter months!

What I do for a living Part 3: Soil Ecology and Weed Management

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In May, 2016, I started a post doctoral position in a laboratory that focuses on weed management in agricultural systems, especially organic farms which don’t use chemical fertilizer or herbicide. My role is to integrate microbial ecology. For example, is the soil microorganism diversity different in fields that compete better against weeds than in fields that can’t? Are there certain microorganisms that make it easier for weeds to grow, and how do they do that? Can we suppress weeds by manipulating bacteria or fungi in the soil?

So far, I’ve been doing field work for my project, as well as assisting other lab members in their own projects, as many large scale greenhouse or field experiments require large groups of helpers to accomplish certain tasks. I’m also new to weed ecology, and I wanted to learn as much as possible. Thus, I put on some sunscreen and one of those vendor t-shirts you get when you order a certain dollar amount, and got to work.

Some of our projects investigate the link between crop health and climate change.  To simulate climate change, we create rain-out shelters to mimic dry conditions, and plastic shielding to mimic hotter conditions.

Making climate change simulators.
The gypsum block will absorb soil moisture, and we can measure conductivity off of that.
This one is very dry.

One of the treatments is to infect crops with wheat streak mosaic virus, to determine whether climate change will affect the plant’s ability to fight infection, and whether it will change soil microbiota. To do this, we needed to infect our crops, which meant growing infected plants in the laboratory and selectively spreading them in the field as a slurry.

Blended wheat.
We need to filter out the particles or they will clog the sprayer. Also pictured: Dr. Fabian Menalled.

 

A similar project is using mites as a virus transmission vector, so we attached mite-infected wheat to healthy wheat.

Kyla and I are attaching wheat to other wheat with paperclips.
We hope the wheat mite get infected.

Another project is collecting data about ground beetle diversity in organic versus conventionally farmed soil. For this, we planted pitfalls traps in fields to collect and identify beetles.

Throughout many of the ongoing lab projects, I’ll be investigating the effect of treatments on soil health and diversity.

The core sampler is used to collect soil from certain depths.
The soil is then put in sterile containers until analysis.

My project is part of a larger experiment, which also involves assessing crop and weed communities.  For this, we need to randomly sample plants in the field and collect all above-ground plant material (to measure biomass as weight), as well as the biomass of each individual weed species to measure diversity (number of different weed species) and density (how large the plants are actually growing).

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And, of course, there is plenty of weed species identification!

Field bindweed study sampling

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Field bindweed (Convolvulus arvensis) is an invasive plant related to morning glories.  Their winding vines grow into a tangled mass which can strangle other plants, and a single plant can produce hundreds of seeds.  The plants can also store nutrients in the roots which allow them to regrow from fragments, thus it can be very difficult to get rid of field bindweed.  It will return even after chemical or physical control (tilling or livestock grazing), but it does not tolerate shade very well.  Thus, a more competitive crop, such as a taller wheat which will shade out nearby shorter plants, reduce the viability of bindweed.

Bindweed wraps around other plants.
This patch goes all the way to Lazarro.

First seen in the US in 1739, Field bindweed is native to the Mediterranean. By 1891, it had made its way west and was identified in Missoula, Montana.  As of 2016, it has been reported from all but two counties in Montana, where it has been deemed “noxious” by the state department (meaning that it has been designated as harmful to agriculture (or public health, wildlife, property).  In the field, this can be visually striking, as pictured below.  In the foreground, MSU graduate student Tessa Scott (lead researcher on this project) is standing in a patch of wheat infested with bindweed. Just seven feet away in the background, undergraduate Lazarro Vinola is standing in non-infested wheat, with soil core samplers used for height reference.

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In agricultural fields, bindweed infestations severely inhibit crop growth and health.

 

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Last week, Tessa, Lazarro, and I went to several farms in and around Big Sandy and Lewistown, Montana in order to sample fields battling field bindweed. To do so, we harvested wheat, field bindweed, and other weed biomass by cutting all above-ground plant material inside a harvesting frame.  These will be dried and weighed, to measure infestation load and the effect on wheat production.

The sampling locations are consistent with previous years to track how different farm management practices influence infestations.  This means using GPS coordinates to hike out to spots in the middle of large fields.

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It also means getting very dirty driving and walking through dusty fields!

Thalspi, or pennycress, which is dropping seeds even in my shoes!
The van did very well on rocky, uneven field roads!