Interactive Effects of Cover Crops, Soil Health Practices, and Insect Community Dynamics on Corn Production

Final report for GNC16-227

Project Type: Graduate Student
Funds awarded in 2016: $9,998.00
Projected End Date: 05/10/2017
Grant Recipient: South Dakota State University
Region: North Central
State: South Dakota
Graduate Student:
Faculty Advisor:
Jonathan Lundgren
South Dakota State University
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Project Information

Summary:

Many agricultural landscapes aim to maximize the amount of harvestable acres, which has resulted in most cropland becoming large monocultures whose productivity is maintained through a reliance on tillage, external fertilizers, and pesticides. This model of farm production has resulted in a reduction of biodiversity within the agricultural ecosystem. Despite the current paradigm of corn production, some farmers have developed a regenerative model of profitable farm production that promotes soil health and biodiversity. Little work has focused on the relative costs and benefits of these novel regenerative farming operations, which necessitates studying systems-level, farmer-defined best management practices.

Here, we evaluate the relative effects of regenerative and conventional corn production systems on pest management services, soil conservation, and farmer profitability and productivity throughout the Northern Plains of the United States. Insect diversity, soil properties, yield, and profitability were assessed in plots that were characterized as CONVENTIONAL: plots with no cover crop established with conventional pest management practices such as genetically modified (GM) corn and other insecticidal usage, or REGENERATIVE: plots in which a cover crop was established prior to corn, with non-GM corn and no insecticidal treatments, with a legacy of soil cover using cover crops. The overarching goal of regenerative farming systems is to increase soil quality and biodiversity in farmland while producing nourishing farm products profitably. The principles which are consistent across regenerative farming systems include 1) abandoning tillage (or actively rebuilding soil communities following a tillage event), 2) eliminating the occurrence of bare soil, 3) fostering plant diversity on the farm, and 4) integrating livestock into cropping operations. Further characterization of a regenerative system is difficult due to the various combinations of farming practices that comprise a system which targets the regenerative goal. 

Data were collected within systems that were defined and created by the producers, to give realistic insight on this systems-level question. Soil qualities were assessed by taking soil cores for analyzing soil organic matter (SOM) and determining soil bulk density. Insect communities in each field were assessed by analyzing insect dynamics using specimens collecting via soil cores, quadrat suction sampling, and by counting all insects on whole corn plants. Yields and profitability were examined and used to determine productivity and relative net profit on each operation.

Regenerative farming systems provided greater ecosystem services and profitability for farmers than the current input-intensive model of corn production. Pests were 10-fold more abundant on the conventional farms than on insecticide-free regenerative farms. Regenerative fields had 29% lower grain production but 78% higher profits over traditional corn production systems. These results indicate that ecologically based farming systems could be used to produce food while simultaneously conserving natural resources.

Outreach and explanation of these results are ongoing, and the results were shared with participating producers, as well as disseminated through an academic article. Our outreach highlights the fact that attaining this regenerative level of ecosystem functioning and profitability likely requires a systems-level shift on the farm — meaning the use of multiple practices. Simply applying individual regenerative practices within the current crop production model will not likely produce optimal results. 

Project Objectives:

The objective of the study was to evaluate the relative effects of regenerative and conventional corn production systems on invertebrate community dynamics, insect pests, soil conservation, and farmer profitability and productivity throughout the Northern Plains of the United States.

We compared two crop production models to one another, in-situ. We directly compared farms using the current model of crop production, to those which have developed a regenerative model of farm production that promotes soil health and biodiversity. We examined soil qualities by taking soil cores for analyzing soil organic matter (SOM) and determining soil bulk density. Insect communities in each field were assessed by analyzing insect dynamics using specimens collecting via soil cores, quadrat suction sampling, and by counting all insects on whole corn plants. Yields and profitability were examined and used to determine productivity and relative net profit on each operation.

Research

Materials and methods:

Experimental conditions. Ten pairs of farms were selected for our sampling. All fields were planted to Zea mays (corn), and were a minimum of 4 ha in size. These farms represented two fundamental systems; a regenerative model compared to the conventional model. The practices that were used in the systems were categorized as using a cover crop (regenerative) or leaving bare soil (conventional); no- tilling (regenerative) or tilling (conventional); and abandoning the use of insecticide (regenerative) or using insecticide (conventional). A farm was considered a regenerative system if more than one regenerative practice was used, and regenerative fields tended to use diverse crop rotations in addition to the other practices. All regenerative farms have used their respective regenerative practices for a minimum of 3 y, and are regarded by peers as local leaders in regenerative farming. Four independent plots (61× 61 m each), were segregated on each farm (separated by at least 15 m), for a total of 40 plots for each treatment. Seven farm pairs were sampled summer 2015, and three pairs were sampled in 2016. Each regenerative and conventional farm pair were within 50 km of one another.


Invertebrate sampling. Invertebrate sampling was conducted at each field twice during the growing season; once during corn vegetative stage (stages ranged from V2-V6.5), and once during pollen shed (anthesis). These two sampling events were selected as focal time periods for ecosystem services in agricultural systems, and have distinct arthropod communities. The early season is the timeframe when pests and other insects colonize cornfields (1, 2, 3), and anthesis is the time when pests are typically present in cornfields, and when the greatest diversity and abundance of insects are fostered (4, 5) Sampling was conducted over three main habitat domains within the field: foliar (using deconstructive whole plant assessment, n = 25 corn plants per plot), epigeal (using quadrat suction sampling n = 5 quadrats per plot), and the soil column (using soil core samples in a Berlese extraction system for 7 d, n = 5 soil cores per plot), to get a broad understanding of the invertebrate communities. All samples were taken at least 12 m into the field to minimize border effects.


Invertebrate identification. Invertebrates were stored in 70% ethanol for later curation and identification. Invertebrates were identified to the lowest taxonomic unit possible, and morphospecies were assigned to many of the taxa for community analysis.

Soil sampling. Soil was analyzed for bulk density (BD), soil organic matter (SOM) and particulate organic matter (POM). Soil cores (8.5 cm deep, 5 cm in diameter; n = 4 BD; 4 SOM/POM) were collected along a grid, with each core collected at least 10 m apart; four cores were collected during early vegetative growth of the corn and four during anthesis. BD samples were stored in plastic bags at ~1.8-2.6° C until analysis; the soil samples intended for POM and SOM analysis were stored in paper bags and dried to constant weight.

Soil analyses. For each sample, ~60 grams of soil was ground and visible plant residue was removed by hand for 5 min. Soil samples were then placed in open aluminum soil containers and were dried overnight at 105°C. Containers were covered in aluminum and stored until they could be analyzed for SOM and POM. SOM was determined using the weight loss on ignition (LOI) technique (7). Coarse and fine POM were measured on each sample separately from SOM. (8). BD cores were stored cold, then were thawed for ~ 2 h before they were weighed. They were then placed in aluminum soil containers and dried at 105° C for ~55 h, cooled with aluminum lids on for 10 min and dry weights were recorded. BD was determined by dividing the mass of the dry sample by the volume of the cylinder (D = ; V = πr2h) with which it was collected.

Yield sampling/profit. To determine yield, corn ears were hand gathered from three, 3.5 m sections of row from each replicate-field. Corn was shelled, weighed, and dried until moisture reached 15.5%, as determined using a grain moisture tester.

Responses from a producer survey were used to determine costs and revenues that went into the direct net profitability of each operation. The factors used for determining profit were: hand collected yield, return on grain, additional revenue streams (to determine gross revenue per ha) and cost of corn seed/bag, cost of cover crop seed/bag, cost of drying/cleaning grain, crop insurance, cost of tillage, cost of planting corn, cost of planting cover crop, cost of fertilizers, cost of herbicides, and cost of irrigation (to determine total direct costs).
We used only direct costs and revenues to calculate profitability. Equipment, labor, land rent, and repairs were considered overhead or indirect expenses and were not included in our calculations.

References:

  1. Harwood, J. D., Phillips, S. W., Lello, J., Sunderland, K. D., Glen, D. M., Bruford, M. W., Harper, G.L., and Symondson, W. O. Invertebrate biodiversity affects predator fitness and hence potential to control pests in crops. Biological Control, 51(3):499-506 (2009).
  2. Landis, D. A., and Van der Werf, W. Early-season predation impacts the establishment of aphids and spread of beet yellows virus in sugar beet. Entomophaga, 42(4):499-516 (1997).
  3. Settle, W. H., Ariawan, H., Astuti, E. T., Cahyana, W., Hakim, A. L., Hindayana, D., and Lestari, A. S. Managing tropical rice pests through conservation of generalist natural enemies and alternative prey. Ecology, 77(7):1975-1988 (1996).
  4. Peterson, J.A., Romero, S.A., Harwood, J.D. Pollen interception by linyphiid spiders in a corn agroecosystem: implications for dietary diversification and risk assessment. Arthropod Plant Interactions, 4: 207–217 (2010).
  5. Lundgren, J. G., Razzak, A. A., and Wiedenmann, R. N. Population responses and food consumption by predators Coleomegilla maculata and Harmonia axyridis (Coleoptera: Coccinellidae) during anthesis in an Illinois cornfield. Environmental Entomology, 33(4):958-963 (2004).
  6. Lundgren, J. G., Shaw, J. T., Zaborski, E. R., and Eastman, C. E. The influence of organic transition systems on beneficial ground-dwelling arthropods and predation of insects and weed seeds. Renewable Agriculture and Food Systems, 21(4):227-237 (2006).
  7. Davies, B. E. Loss-on-ignition as an estimate of soil organic matter. Soil Science Society of America Journal, 38(1):150-151 (1974).
  8. Cambardella, C.A., Elliott, E.T. Particulate soil organic-matter changes across a grassland cultivation sequence. Soil Science Society of America Journal, 56(3):777-783 (1992).
Research results and discussion:

We found that insect pest populations were 10-fold higher in the conventional system than on the insecticide-free regenerative farms. Pest abundance tends to be lower in cornfields that have greater insect diversity, enhanced biological network strength and greater community evenness (1). Suggested hypotheses to explain how invertebrate diversity and network interactions reduce pests include predation (2), competition (3), and other processes that may be unpredictable. In this study, farmers that replaced insecticide use with the incorporation of plant diversity using cover crops and more diverse rotations and had fewer invertebrate pests than farms with strict monocultures. 

Despite having lower grain yields, the regenerative systems were nearly twice as profitable as the conventional corn systems. Regenerative farms produced 29% less corn grain than conventional operations (8481 ± 684 kg/ha vs. 11,884 ± 648 kg/ha). This kind of yield reduction is commonly reported in more ecologically-based food production systems relative to conventional systems (4).  In this case, these regenerative corn production systems could increase the human food produced per ha in cornfields by increasing the diversity of livestock on the field or increasing the grazing duration of current livestock. The relative profitability in the two systems was driven by 1) the high seed and fertilizer costs that conventional farms paid (32% of the gross income went into these inputs on conventional fields, versus 12% in regenerative fields), and 2) the higher revenue generated from grain and other products produced on the regenerative corn fields. The high seed costs on conventional farms are largely due to costs associated with prophylactic pesticides. Regenerative farmers reduced their fertilizer costs by reducing their need for additional fertilizer. They accomplished this by including legume-based cover crops on their fields during the fallow period (5), adopting no-till practices (6), and grazing the crop field with livestock (7). They also received higher payment for their crop by receiving organic premiums or by selling their grain directly to consumers as seed or feed. Some regenerative farmers also gleaned more than just corn revenue from their field, generally through grazing cover mixes with livestock. 

Soil organic matter (SOM) is generally considered the basis for productivity in the soil (8), and soils with high SOM typically have lower bulk density, increased water infiltration rates, and SOM supports greater microbial and animal abundance and diversity (9). The coarse and fine components of particulate organic matter (POM) are the labile portion of this SOM, and are frequently used to study the effects of management-based differences in SOM (10). Regenerative fields had greater POM, and POM was positively correlated to invertebrate diversity. Soil organic matter and its components are generated in cropland through fostering biology, which is inherently driven by plant communities through sequestration of CO2 from the atmosphere. Decreasing or eliminating tillage (11), implementing cover crops (12), and cycling plant residue through livestock (13) all enhance this process and are important practices used in regenerative food systems which increase soil organic matter. 

 

References: 

  1. Lundgren, J. G. & Fausti, S. W. Trading biodiversity for pest problems. Science Advances 1, e1500558 (2015).
  2. Letourneau, D. K., Jedlicka, J. A., Bothwell, S. G. & Moreno, C. R. Effects of Natural Enemy Biodiversity on the Suppression of Arthropod Herbivores in Terrestrial Ecosystems. Annual Review of Ecology, Evolution, and Systematics 40, 573-592 (2009).
  1. Barbosa, P. et al. Associational resistance and susceptibility: having right or wrong neighbors.Annual Review of Ecology, Evolution & Systematics 40, 1-20 (2009).
  2. De Ponti, T., Rijk, B. & Van Ittersum, M. K. The crop yield gap between organic and conventional agriculture. Agricultural Systems 108, 1-9 (2012).
  3. Ebelhar, S. A., Frye, W. W. & Blevins, R. L. Nitrogen from legume cover crops for no-tillage corn. Agronomy Journal 76, 51-55 (1984).
  4. Lal, R., Reicosky, D. C. & Hanson, J. D. Evolution of the plow over 10,000 years and the rationale for no-till farming. Soil & Tillage Research 93, 1-12 (2007).
  5. Russelle, M. P., Entz, M. H. & Franzluebbers, A. J. Reconsidering integrated crop-livestock systems in North America. Agronomy Journal 99, 325-334 (2010).
  6. Karlen, D. L. et al. Soil quality: a concept, definition, and framework for evaluation. Soil Science Society of America Journal 61, 4-10 (1997).
  7. Lehman, R. M. et al. Understanding and enhancing soil biological health: The solution for reversing soil degradation. Sustainability 7, 988-1027 (2015).
  8. Cambardella, C. A. & Elliott, E. T. Particulate soil organic-matter changes across a grassland cultivation sequence. Soil Science Society of America Journal 56, 777-783 (1992).
  9. Pikul, J. L., Jr., Osborne, S. E., Ellsbury, M. M. & Riedell, W. E. Particulate organic matter and water-stable aggregation of soil under contrasting management. Soil Science Society of America Journal 71, 766-776 (2007).
  10. Ding, G. et al. Effect of cover crop management on soil organic matter. Geoderma 130, 229-239 (2006).
  11. Tracy, B. F. & Zhang, Y. Soil compaction, corn yield response, and soil nutrient pool dynamics within an integrated crop-livestock system in Illinois. Crop Science 48, 1211-1218 (2008).
Participation Summary
10 Farmers participating in research

Educational & Outreach Activities

1 Journal articles
1 Published press articles, newsletters
5 Webinars / talks / presentations
3 Workshop field days
1 Documentary regarding regenerative agriculture highlighting this study.

Participation Summary

75 Farmers
5 Ag professionals participated
Education/outreach description:

1 journal article – LaCanne, C. E., & Lundgren, J. G.. Regenerative agriculture: merging farming and natural resource conservation profitably. PeerJ6, e4428 (2018). 

1 published press article – written about our PeerJ article – Bryce, Emma.  Regenerative soil can double farmers’ incomes. Anthropocene. March 2, 2018.

5 talks and presentations – Claire LaCanne has given 4 talks about the study so far, Jon Lundgren has given several talks. LaCanne and Lundgren will continue to share the results both to scientific peers and farmers.  

3 workshops/field days so far – Blue Dasher Farm, non-profit run by Jon Lundgren has held 3 field days which share the process and results of this study. More field days to come.

Project Outcomes

Project outcomes:

This study revealed that not only can crop production and natural resource conservation be compatible goals, they can coexist in a profitable system. Revealing the economic benefits of regenerative farming will likely convince more producers to adapt sustainable methods. 

Knowledge Gained:

We found that regenerative systems not only foster more ecological functioning and effective pest control, but can be more profitable than many current crop production models.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.