1. Introduction
Organic foods have become an important component of the US food market, with sales reaching nearly
$61.9 billion in 2020 [
1]. Driven by demand from organic livestock and dairy farms, land planted for organic corn in the US grew over 55% from 2011 to 2016 (from 68,350 to 105,626 hectares), increasing more than other organic commodity grains [
2,
3,
4,
5]. In the U.S., almost all corn is feed grain used for livestock or processed for food and industrial products [
6]. Farmers in the Midwestern Corn Belt and Northeast have been important to this expansion [
4,
7].
While land under organic management is growing rapidly, there has been growing debate over the environmental and economic sustainability of organic production systems [
8,
9,
10]. Many of the sustainability advantages of organic production systems have been linked to the use of practices that promote soil health and support agroecosystem processes to help meet crop nutrient requirements and manage weeds [
11]. Organic farmers are generally assumed to rely on the use of livestock manure, legume forages/cover crops, and diverse crop rotations (including perennials), to meet the nutrient needs of crops and improve soil physical properties [
12,
13,
14]. Conversely, organic farmers tend to use more intensive forms of tillage due to limited options to manage weeds without synthetic chemicals, and that tillage can mitigate many of the soil health benefits of other organic management practices [
9,
15].
In addition, organic conferences and/or trade shows often feature a myriad of soil amendment products designed for organic crop production, and little is known about their agronomic, environmental, and economic benefits. These amendments can be highly variable in terms of nutrient content and cost [
12] and can be a significant driver of organic farm profitability [
16,
17] and environmental footprint [
10,
18]. Foreman (2014) and McBride et al. (2015) estimate that commercial fertilizers, soil conditioners, and manure comprised roughly a third of all operating cash costs for organic corn production, but they did not disaggregate specific types of soil amendments [
7,
19].
Although the scientific literature on the sustainability performance of organic production systems is rapidly growing, much of it is based on comparisons of a package of organic production methods with conventional methods under controlled experimental conditions. How well these representations of organic farming methods reflect reality is not clear. Organic farms can be organized and operated in many different ways. Some have argued that organic agriculture is “conventionalizing” by taking on more and more characteristics of mainstream industrial agriculture [
20]. Research on “conventionalization” has explored whether the organic sector in many countries is “bifurcating” between (a) smaller-scale diversified operations that use the full range of soil health-building management practices and eschewing purchased external inputs, and (b) a commercial organic sector comprised of large-scale specialized farms that meet the minimum requirements of national organic certification programs regarding the use of some synthetic inputs but that are less likely to rely on extended crop rotations, cover crops, and other agroecological methods [
20,
21].
Whereas a number of studies have explored the farm structural attributes and sustainability motivations and orientations of organic farmers [
20,
22], there is surprisingly little information available about the range of management practices used by representative samples of working organic farms, and how this varies based on farm characteristics. Using 2010 data from a sample of 243 organic corn farms across 14 Midwestern states, McBride et al. (2015) found that organic growers managed fewer hectares, relied more on mechanical weed control, and utilized more diverse crop rotations than conventional corn farmers [
7]. Compared to cultural management practices, there is even less published data on how frequently organic farmers use purchased soil amendments [
23].
The present study was conducted to address gaps in our knowledge of organic corn production practices used by farmers in our study region, particularly around soil health management and the use of soil amendments. We implemented a mail survey to (i) describe organic grain farmers’ soil management practices and strategies, (ii) compare the use of different practices by farm characteristics, and (iii) assess the overall economic performance of organic corn enterprises.
4. Discussion
This study is one of the most in-depth and comprehensive efforts to document the complex and diverse agronomic and soil management practices utilized by the rapidly growing organic corn farm sector, which have implications for sustainability. Little research documenting on-farm practices of organic farmers has been published [
7], and much of the agronomic and soils-related organic research has been based on experimental trials conducted on university research stations [
26]. Contrary to the expectations of “conventionalization” scholars, the vast majority of organic corn growers in this region operate at a scale, level of diversification, and manner of utilizing agroecological practices that run counter to trends toward consolidation and specialization in organic systems found elsewhere [
7,
20,
27].
Organic corn farms in this sample operated relatively modest acreages, which likely reflects the fact that most respondents were integrated crop-livestock operations (mainly dairies). While this sample was representative of this region in terms of farm size, organic farms in this region tend to be smaller on average than the national average [
7]. Within this sample, cash grain operators farmed significantly more organic cropland than farmers who raised corn as part of a livestock operation. The high level of land ownership found among organic corn farms in our sample may also reflect the high investments and commitment involved with the 3-year transition required for organic certification [
28] and the land tenure security required to run an integrated crop-livestock operation [
29]. Most organic corn was harvested as field corn to be fed to on-farm livestock as grain or silage. The presence of livestock on most farms in this study enabled them to utilize more perennials and diverse crop rotations and maximize the use of farm-produced manure as a critical nutrient and soil amendment.
The smaller farm sizes found in our study also reflect the fact that horses were used for field operations by nearly two-thirds of our respondents, most of whom we presume were members of Old Order Amish communities. Their reliance on horses and desire to live in close proximity to each other may encourage Old Order Amish farms to be smaller than non-Amish farms that rely on tractors for fieldwork [
30]. As other dairy farmers exit, the percentage of Amish-owned farms has increased in states with heavy Amish populations [
30]. Given that the Amish population doubles every 20 years, and they primarily reside in rural areas, this trend may continue [
31]. Contrary to popular conceptions, most Amish farmers do not sell certified organic products. However, there is a strong organic movement among a subset of the Amish who view organic farming as a good way to remain economically viable and stay consistent with their values of family farming and stewardship of the earth [
32].
Our analysis of economic costs and returns suggests that most organic corn grain growers in our sample had positive returns to labor and management in 2017, a result consistent with several recent studies of profitability in organic agriculture [
7,
8]. The majority had positive net returns (97%), and 82 percent had net returns over
$1000 ha
−1. Positive net returns are a function of higher commodity prices, because U.S. prices for conventional corn in 2017 were
$127 Mg
−1, over 65% lower than prices received for organic corn [
33]. Some have argued that organic farmers have lower production costs [
16]. However, based on our survey results, organic corn enterprise variable costs (seeds, soil amendments) appear to be similar to those incurred by conventional corn growers in this region in 2017 [
34].
Overall, the heavy use of diverse crop rotations and reliance on cover crops is consistent with previous studies of organic farmers and in striking contrast to the management practices used by conventional corn growers, who rely principally on alternating corn with soybeans or growing corn for several years in a row [
7].
Cover crops are increasingly recommended as a way to improve soil physical properties, increase soil organic matter and biological activity, prevent loss of soil and nutrients, and control weeds [
35,
36]; perenniality can also provide some of those same benefits [
37]. Nearly half of our respondents also reported the use of cover crops in the winter prior to planting corn, significantly higher than adoption rates reported by conventional grain growers [
38,
39]. There was a definite difference in forage and cover crop use by farm type. Organic corn growers with livestock were much more likely to incorporate perennial forages into their crop rotation, and as a result, were less likely to use cover crops. By contrast, growers who did not raise livestock had less diverse crop rotations and fewer perennials in rotation but were more likely to use annual cover crops. Both approaches offer potential soil health benefits, but livestock producers can utilize perennial hay crops as a feed source.
Tillage is a primary means of weed control for organic grain farmers compared to the current widespread use of no-till planting methods, a trend that has been facilitated by the use of genetically engineered corn varieties that are resistant to glyphosate herbicide, an option not available to organic farmers [
40,
41]. Not surprisingly, no-till and conservation tillage approaches were used by only a tiny fraction of our respondents, which is consistent with a 2015 national study of organic field corn growers that found 65% of the growers used a moldboard plow and only 5% used a no-till planter [
7].
Farmers expressed soil management philosophies that reflect greater reliance on agroecological processes to manage weed, pest, and crop fertility challenges. Nearly a third of farmers relied on manure as their only amendment on fields being planted to corn. Our findings are broadly consistent with the results of one recent national study [
7], which found that 75% of U.S. organic corn growers used some kind of manure (compared to 90% in our sample), and roughly half used commercial certified organic fertilizers (compared to 42% in our sample). Meanwhile, significant numbers of organic producers reported use of purchased soil amendments that are often recommended by proponents of biological or regenerative agriculture [
42,
43,
44], which some may characterize as an “input substitution” approach that has been linked to conventionalization in the organic sector (e.g., [
20,
22]). Among our respondents, between 20–25% reported use of micronutrients or microbial stimulants/inoculants, and 10–14% applied foliar products, fish fertilizers, sulfur, or boron on their corn fields.
Organic grain farmers indicated that building soil health and organic matter were their most important soil management considerations. This is consistent with previous research that focused on organic vegetable producers [
45]. Interest in soil health is also becoming more important to conventional farmers [
39]. Previous work has demonstrated that many organic producers have a strong interest in soil health and programs and resources that can help them assess how different soil amendments, crop rotations, and tillage practices interact to impact soil health and agronomic outcomes would likely be welcomed [
26,
45]. At the same time, soil management decisions by organic farmers reflect more than just a focus on soil health. For example, their decisions about tillage are driven more by a desire to control weeds than by impacts on soil quality. Similarly, the choice of crop rotations reflects a mix of goals—including improving soil quality but also breaking pest and disease cycles.
This study has several limitations and a number involve the complications of economic calculations from farm survey data as outlined in our
supplemental materials. First, we did not include several categories of economic costs that might be considered in a traditional profitability analysis (e.g., utility and energy expenses, storage and transport costs, interest expenses, and insurance costs). These unmeasured costs usually account for 25% of typical corn variable costs in Ohio [
34]. Additionally, our results are for a single 2017 cornfield reported by farmers in the survey. Differences in market and weather conditions can affect yields, revenues, and costs over time. For example, organic corn prices dropped by nearly 25% between 2017 and 2020, a reflection of reduced demand from a stagnant organic dairy sector and oversupply from new entrants into the organic feed corn market [
24]. Finally, there are few datasets and published methods for estimating the costs of fieldwork for farms that utilize horses instead of tractors. Given that nearly two-thirds of our sample consisted of these types of farms, conventional assumptions about the economic costs of machinery ownership and use (and relative labor time required per hectare) may not apply. Another limitation was focusing the analysis primarily on corn, as many of the farms in our study were integrated livestock operations so assessing profitability may involve different calculations [
46].
Future research should further explore agronomic, economic, and sustainability issues of organic corn production systems that this study was unable to fully address. For example, analyses of the use of specific inputs are associated with agronomic or economic benefits. Most organic grain farmers still rely heavily on moldboard plowing for tillage, and there is evidence that tillage can undermine the positive benefits of organic management on soil health [
47,
48,
49]. There are significant challenges to managing weeds without synthetic chemicals; possibilities exist for combining cover cropping, mulching, and mechanical methods, but more research is needed in conjunction with farmers to work through unknowns and complications [
15]. Future research on the use of conservation tillage in the context of organic farming could provide important insights for adapting current systems and improving the environmental footprint of organic corn production [
47,
48,
49]. Likewise, producers use a wide range of purchased products on their organic corn fields, many of which have received little attention from the scientific community [
50] and should be further explored in terms of their agronomic and economic benefits for farmers.
Given the significant number of Amish organic corn farmers in these states, organic farming outreach programs should consider ways to adapt content to the unique cultural and religious beliefs of this population, and modes of dissemination should focus on or include printed products and in-person farmer meetings [
51]. While national studies suggest that organic farmers had higher levels of formal education than conventional farmers [
7], Amish producers traditionally prefer experiential and home-based learning, have lower levels of formal schooling, and English is typically their second language [
52]. Therefore, extension and outreach materials should be written at a basic level. It also would be helpful to work with local leaders within the community to help distribute written materials and/or to organize workshops. Additionally, conservation tillage and soil health research and outreach efforts should be adapted to farmers who rely on horse-drawn implements [
51].
Our findings can be used to improve the design of formal scientific research on organic corn production (and for studies of organic cash grain systems more generally) to ensure they are representative of the actual practices used by organic corn producers. Many published studies that assess the performance of organic corn systems have not adequately represented organic systems. To accurately represent the production approaches used by most organic corn growers in our study states, it would make sense for research trials to utilize livestock manure, diverse crop rotations (including perennial forages), and intensive tillage [
53], and to test different organic amendments in combination with organic cultivation practices [
12,
54]. Given that organic corn growers in this region are usually livestock producers, future organic grain research that explores the dynamics of integrated crop-livestock systems would be of value to many producers. In terms of economic research, the integrated nature of many organic corn farming systems should be taken into account so that complementarities are recognized [
46].