Don’t Forget the Farmers

“Even though comprehensive soil quality tests can be commercially ordered for less than $10 per acre … few appraisers, lenders, and investors request them,” Vivian Zhong and Clay Mitchell point out in “For Better Soil, Get Better Data” (Issues, Summer 2025). But what about farmers? They are the ones cultivating the soil, and the question is, do they see a benefit from modernized soil tests?

Based on my work with many farmers, often in second- or third-generation farming families, I’ve come to appreciate how their experience shapes their decisions. Following seasons of trial and error, farmers decide on cropping and cultivation patterns that work best for their soil and terrain, rainfall levels, and growing period. Often this assessment does not include soil tests as farmers have already determined their cropping patterns and nutrient applications, aided by knowing where their profit point is on a cost-per-acre basis. This approach, however, does not account for loss of topsoil, which occurs often due to on-farm actions such as cultivation.

One approach to minimizing soil loss is to use alternative tillage methods that reduce soil disturbance and to add cover crops, silage, or organic material. But it may take farmers not already using such practices a few years to implement them. It is during this “transitionary” time that soil testing can be particularly useful to gauge whether the alternatives are proving efficacious.

In discussing soil loss, a common value has been the “tolerable soil loss rate,” or T Value, which is calculated as the maximum amount of soil lost without significantly impacting long-term crop productivity. Depending on soil type, a generally “safe” T Value is estimated to be from two to five tons of soil lost per acre per year, balancing soil loss with natural soil formation.

Early on, when the importance of soil loss on farms became apparent, the federal government saw that some form of stimulus would be needed to promote improved T Values and accept good cultivation practices. In response, the US Department of Agriculture implemented the Conservation Compliance Incentives—and they did have some measure of success.

But more is needed. The integration of modern data gathering (as presented in the authors’ examples), conventional soil testing, advisement on soil conservation plans, and an effective incentive structure would do much to ensure that all avenues of soil improvement are working together for better soil fertility and tillage practices on the nation’s farms. Such an approach, presented in a manner that addresses a farmer’s challenges with a comprehensible plan, would help boost the interest of farmers in soil fertility and utility of modernized soil testing.

Joel I. Cohen

We applaud Vivian Zhong and Clay Mitchell for strongly recommending more “boots on the ground,” rigorous studies of soil variability and change, especially in intensely cropped fields. And we appreciate their citing work at Iowa State University as an example of what is possible with modern soil mapping.

Of course, other researchers worldwide are also leveraging these technologies to create the geospatially explicit soil maps desperately needed. We will continue to debate the optimal methods for predicting unsampled locations and how to measure uncertainty in those predictions. However, all our spatial models are underpinned by data from field sampling. What we cannot do is improve soil maps where no original data are available. Ergo, we need to be continuously collecting data to have a basis for comparison.

Researchers often use broad-stroke statistics when talking about how much soil is lost from fields, but those numbers are generally intangible for landowners. Zhong and Mitchell, for example, state that 50 tons of soil per hectare erode from fields annually, which we calculate amounts to an average of 3.5 millimeters per year. But studies, including several by one of us (Burras) and Jessica J. Veenstra, have found that topsoil depth often rapidly rebounds. As a result, within the scientific and farming communities, we often argue among ourselves about whether erosion rates of topsoil are sustainable.

This misses crucial points that soil maps must record. The entire soil profile is changed through erosion due to loss of rooting depth and the soil’s ability to retain water. Additionally, most eroded soil doesn’t leave the field, but is deposited downslope, burying the natural soil with sediments, which lack the structure that supports the soil’s water-holding capacity and maximizes seedling emergence. Many other changes also occur in the soil profile, each of which must be measured and included in modern soil maps in such a way that clear predictive trajectories are available to landowners, so they will know what they are buying today and what it is likely to be tomorrow.

We also appreciate Zhong and Mitchell mentioning soil productivity indices. Our only comment is that land taxation needs to be separated from market value. There must never be a tax incentive to degrade soil, just as there should never be a regressive tax for landowners who improve their soil. Reflecting this, for example, two important indices in our region—Iowa’s Corn Suitability Rating index and Illinois’s Soil Productivity Index—rigorously compare inherent soil productivity while not taking into account the typical impacts of day-to-day field management. This is increasingly difficult given the magnitude of soil changes across fields, but the topic merits additional attention.

We end with a major question: Should soil mapping be a public or private endeavor? For the past 100 years, the National Cooperative Soil Survey’s public approach has yielded arguably the best soil map in the world. Here again, the authors have forcefully brought forward the fundamental discussion of who should have access to what soil information, and in what format and time frame it should be available.

Bradley Miller

Lee Burras

Vivian Zhong and Clay Mitchell make a compelling case that soil, specifically the health of an agricultural field’s topsoil, is undermeasured and undervalued. With modern technology, the costs of measuring soil health are low, and effective techniques to mitigate soil loss are known. So why are farmers not embracing this technology?

First, as the authors point out, massive amounts of topsoil have eroded over the past five decades. A forward-thinking farmer who adopts healthy soil-building techniques may be interested in an accurate accounting after mitigation strategies are implemented, but the assessment may well show that the field in question still has less topsoil or poorer soil health than what is currently referenced in the US Department of Agriculture’s out-of-date Soil Survey Geographic Database (SSURGO), resulting in the perverse effect of lowering the value of that land. In other words, there is little incentive for individual farmers to allow more accurate and modern accounting of soil health in many cases.

Also, agricultural land is expensive. Many new and beginning farmers are entirely priced out. Zhong and Mitchell argue that the lack of data distorts land value, but fixing the distortion is arguably more beneficial to land buyers than sellers, to the party that already has the upper hand. To incentivize the disclosure of accurate data in a land sale, the data would need to improve the selling value of the land in most cases. Even if soil health mitigation strategies were adopted by current landowners, as many of them have done, those who disclose their soil health data are at a disadvantage to those who do not.

The only way to advantage those good actors who already adopt soil health strategies is if all soil data were collected with similar techniques and were equally available. This is not to say the data from private farmlands would be publicly available—the data can be collected through a publicly funded effort, but access could be restricted to landowners. The important point is that a buyer would know that such data exists, that it was collected by an impartial third party, and that it can be requested.

As the authors point out, data collection efforts at USDA, in addition to the databases themselves where the data is stored, are notoriously underfunded. The National Agricultural Library, for example, receives only about 6% of the funding provided to the National Library of Medicine to accomplish the same tasks, including housing data. Moreover, agricultural data, because it is associated with so much geographic and conditional metadata, is at least, if not more complex than medical data. For soil health mitigation strategies to become commonplace, the United States must invest not only in the collection of soil data from every US field, but also in the unexciting yet crucial task of building secure storge databases so every farmer has private access. Perhaps then landowners would all be equally incentivized to improve the health of their soil by adopting the beneficial strategies the authors describe.

Elizabeth Stulberg