2022 Iowa Academy of Science symposium

Iowa Can Be: a water cleansing, soil building, flood mitigating sponge, habitat enhancing, human recreating state with a healthy agriculture growing crops and animals in sustainable and non-polluting ways for both people food and manufacturing goods.

2022 IAS Symposium title: Iowa can transition to a healthy agriculture now.

Abstract: Historically Iowa was a water cleansing sponge and soil building land. Because all the agricultural crops and cropping systems discussed in this transition symposium exist today, the symposium will stipulate that the transition to a healthy agriculture has already been completed. The presenters will then be asked to tell how that transition was accomplished from their perspective, and/or, what Iowa is like now that we have transitioned to a healthy and soil rejuvenating agriculture. It is important to let people know that this future can exist today, show them what it would be like, and let them know that we do not need to continue with this inherently polluting industrial model of agriculture to feed ourselves. 


            Industrial agriculture’s inherent pollution is existential for humans in terms of climate change, water – air – and soil – pollution, soil loss, ecosystem pollution, and human health-harming pollution.

            It has been reported that it will take decades to attain just a 45% reduction of this industrial agriculture pollution based on the pace that is actually being done by farmers through the voluntary Iowa Nutrient Reduction Strategy. Do we have that long to wait? Why wait when we can start this transition to a healthy agriculture today?

            What follows is “what we can do.” The “how we can do it” is the discussion that will be difficult because of entrenched forces, and entrenched visions of the future. This transition assumes that mindsets must change, that the Farm Bill must change, and that the government must be involved to achieve the changes envisioned to attain this transition to a “healthy agriculture” and a “livable world” going forward.

Housekeeping before we go to the future: We have been cautioned on two items that have been central to many of us working on these issues, carbon sequestration and STRIPS. We will discuss those cautions here in the present before we go to the future. (Cautions are at the end of this outline.)

Carbon sequestration and Iowa soils – Matt Liebman – Bob Watson.

STRIPS – Bob Watson – Matt Liebman – Chris Jones.

            Transition to a healthy agriculture:

1. Long crop rotations discussion – Matt Liebman.

Enhancing Biodiversity to Improve Environmental Quality and Crop Production:

            Recent meta-analyses of experiments conducted around the world indicate that enhancing biodiversity in cropping systems can promote multiple ecosystem services and environmental benefits without compromising yield. Over the past two decades the effects of different rotation systems comprising different levels of crop diversity have been investigated in a 9-hectare (22-acre) field experiment at Iowa State University’s Marsden Farm in Boone Co., IA. Results indicate that adding oat, red clover, and alfalfa to a conventionally managed 2-year corn-soybean rotation to form 3-year and 4-year rotations had positive effects on a wide range of environmental indicators and crop performance. Compared with the simpler rotation system, the more diverse rotations had higher corn and soybean yields, enhanced soil quality, equivalent profitability, and lower herbicide-related aquatic toxicity, fossil energy consumption, greenhouse gas emissions, and damage to human health due to fine particulate matter. Crop diversification also reduced discharge of soil sediment, nitrogen, and phosphorus. Transitions to more diverse, more sustainable cropping systems can be promoted by at least four factors: state and national policies, including regulations and incentive payments; new marketing opportunities due to changes in consumer preferences and the activities of food processors and distributors; farmer-to-farmer education and outreach; and technical innovations, including those derived from plant breeding. Substantial improvements in the environmental sustainability of Iowa’s agriculture are achievable now, without sacrificing food security or farmer livelihoods.

2. Laura Jackson – how we used Prairie as a model and benchmark for designing our agroecosystems, including features such as perennial grain crops, long crop rotations with ruminant herbivores, rotational grazing, and prairie plantings for biomass energy – thermal heat.

3. Chris Jones – Making choices: Designing a production system around human nutrition, environmental outcomes, and farmer prosperity.

            Nearly all of Iowa’s landscape is highly disturbed, but some areas are much more disturbed than others. Going forward, it makes little sense to continue shoehorning the corn-soybean-ethanol-CAFO model into every possible acre while at the same time wasting taxpayer resources trying to overcome its fundamental flaws. How can we design a production system focused on human nutrition, environmental outcomes, and prosperity? This presentation will look at the varied Iowa landscapes and what they might look like in a transformed system.

4. Bob Watson – The US is one of the world’s largest importers of hemp products. Hemp would be similar to prairie in that it is a cover crop with deep roots, and can seed itself in some applications. Hemp can be used for thousands of products, both food and manufacturing. Hemp can replace many petro-chemical products. As a bulk commodity, hemp can help revitalize rural Iowa’s small communities since it would be best to process hemp locally. We have had hemp factories in Iowa in the past.

5. Bob Watson – by mandating, where possible, that most Iowa county road ditches and Iowa Drainage District ditches are planted to prairie (Iowa Roadside Management). Prairie as a farm bill crop.

            The world now produces enough food through grains to feed double our current population. By encouraging eating lower on the food chain and raising meat animals on the land, we would no longer need the confinements and feedlots that are polluting Iowa’s air, water, and soils, and negatively affecting human health. Iowan’s health, with a healthy agriculture, would have a better chance at positive outcomes.

            This is Iowa’s choice. Will we continue to be an existential threat to human life on earth through the industrial model of agriculture now prevalent in Iowa, or will we be part of the solution to that threat?

Questions and comments.


STRIPS – because tile lines and groundwater both allow nitrogen ladened water to bypass STRIPS and enter streams and rivers, we caution the expected nitrogen removal from the use of STRIPS where tile lines and groundwater flow exist.

Carbon Sequestration in Iowa soils – Matt Liebman:

Sequestering atmospheric carbon in agricultural soils is being discussed a lot by both farmers and scientists. Most of the people I interact with believe that the potential to draw carbon dioxide out of the air and store large quantities of it in farm soils is being oversold in the northern Corn Belt.

The carbon capture potential of soils is a function of their minerology, organic matter content, and management history. In the SE US, like in Georgia, older highly weathered soils (e.g., Ultisols) can hold quite a bit of carbon if tillage intensity is reduced, and organic matter additions increase. Well managed grazing systems there have demonstrably beneficial effects on soil C levels.

In the north central states, on much younger Mollisols, it is MUCH more difficult to put large amounts of carbon in soils. See, for example: https://www.agupdate.com/agriview/news/business/soil-carbon-tells-grim-story/article_020700ad-7d18-5690-9827-ed4028e4833e.html,  https://mosesorganic.org/publications/broadcaster-newspaper/farms-as-carbon-sinks/?eType=EmailBlastContent&eId=5d9f6a33-7387-42d3-8744-4241346c07fe for summaries of long-term soil assessments in the University of Wisconsin’s Integrated Cropping Systems Trial results. I can share technical results from Iowa that show the same pattern.

Where cropland is placed under continuous cover, e.g. CRP, soil C levels can increase but recovery may be slow. See, for example: “Soil health recovery after grassland reestablishment on cropland: The effects of time and topographic position.” https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/saj2.20007

“Native grasslands had superior soil health compared with cropland and most CRP soils, and even 40 yr since grassland reestablishment was not adequate for full soil health recovery. Patience is needed to observe changes in soil health, even in response to a drastic management change like conversion of cropland to CRP grassland.”

In the croplands of north central Iowa and much of the tile drained areas of the Corn Belt, increased oxygenation of soil that had originally been seasonal wetlands has changed soil C dynamics. Where there is more oxygen in the soil, organic matter decomposes more readily, releasing CO2. Conversely, recreating wetlands can be an important way to increase soil C. You can consider the likelihood of doing that in north central Iowa cropland.

Sampling depth of soil can strongly influence conclusions about soil organic C levels. No-tillers often report dramatic increases in soil C after cessation of tillage, but typically the measurement s are made only on surface soil (e.g. 10-15 cm, 4-6”). Accurate assessment of soil C stocks must include deep soil layers, not just the surface layer. In an experiment conducted in the Central Valley of California, Tautges and colleagues (“Deep soil inventories reveal that impacts of cover crops and compost on soil carbon sequestration differ in surface and subsurface soils,”.

doi:10.1111/gcb.14762) compared soil organic C stocks to a depth of 200 cm over a 19-year period for corn and tomato grown in rotation with and without winter cover crops. For the full 200-cm profile, no net change in SOC was seen for the corn-tomato system without cover crops, whereas soil C stocks decreased by 13.42 metric tons C ha-1 (-0.67 metric tons C ha−1 year‐1) when cover crops were included in the rotation. Importantly, focusing only on the surface layer of soil could have resulted in “grossly overestimating” SOC gains. In the corn-tomato rotation with cover crops, constraining soil C measurements to the top 30 cm would have shown gains of 1.44 metric tons C ha-1, compared to cumulative losses of 14.86 metric tons C ha-1 in the 30�200 cm layer. Inclusion of deep soiil layers in the assessment of SOC stocks was necessary to prevent drawing false conclusions in this experiment.

At least in the north central states, I think it would be much more worthwhile to concentrate on farming techniques that reduce the use of fossil fuels and minimize emissions greenhouse gases (CO2, N2O, CH4) than focus on capturing and storing large amounts of carbon. Our Marsden Farm plots show a 64% reduction in fossil C use and a 64% reduction in GHG emissions in the 4-year rotation (corn-soybean-oat/alfalfa-alfalfa) rotation compared to the 2-year rotation (corn-soybean) (“Fossil Energy Use, Climate Change Impacts, and Air Quality-Related Human Health Damages of Conventional and Diversified Cropping Systems in Iowa, USA,” https://dx.doi.org/10.1021/acs.est.9b06929). There has been no difference in soil carbon levels in those plots (“Whole-profile soil organic matter content, composition, and stability under cropping systems that differ in belowground inputs,” https://doi.org/10.1016/j.agee.2019.106810).

My recommendation is to support increased conservation and enhancement of soil, water, and wildlife through reducing tillage intensity, diversifying rotations with perennial crops like alfalfa and clover, and introducing high-level grazing management. Soil carbon won’t be diminished by those practices but we shouldn’t expect that they will have dramatically positive effects on soil C in many cropland sites Iowa. Where farming practices do have a beneficial effect on whole-profile soil C stocks, changes may be on the order of decades.


Matt Liebman

Professor Emeritus of Agronomy

Iowa State University

[email protected]