Supporting soil arthropods in forage systems

written by: Makayla Harrison

​​We often forget about the vibrant and essential world that lives beneath our feet, which includes microorganisms and soil arthropods. While farms often use machines and chemicals, the benefit of working with the world underground often goes unnoticed. Robert Salerno – a graduating master’s student and member of the Lamp lab– discussed his thesis work exploring the response of soil arthropods to ecological intensification in agricultural forage systems during a recent colloquium with the Entomology department. Forage systems are used to feed livestock, and they are managed in many different ways. While some systems are managed in a conventional manner, using heavy machinery and chemical inputs, other systems use the ecosystem's natural functions to support and regulate the land. The method of using the natural functions of the ecosystem to sustainably produce agricultural goods is called ecological intensification. 

Agriculture impacts several aspects of the soil; physical soil properties are altered by tillage and irrigation while chemical soil properties are altered by fertilizers and pesticides. The physical and chemical properties of the soil influence the types of soil arthropods that are present. It is important to support soil arthropod communities because of the valuable ecosystem services that they carry out, like providing biological pest control, assisting with nutrient cycling, and supporting plant growth and development. There are distinct relationships between agricultural management practices, soil properties, and the presence and activity of soil arthropods. In the talk, Robert focused on tillage as a management practice. Tillage is the mechanized disturbance of land to prepare for planning crops. While many farmers depend on tiling to prepare their land, it decreases the abundance and richness of soil arthropods, disrupts soil structure, and increases the rate of runoff. Robert argued that tillage may negate most of the benefits that come from strong soil arthropod communities.
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The main objectives of Robert’s master’s research were to look into the response of soil arthropods, soil quality, and decomposition to ecological intensification in forage systems. To do this, he collected data from four types of land use: pastureland, corn fields, grass margins, and woodlots. Pastureland is an ecologically intensified treatment because it uses livestock and other natural methods to manage the land. The corn fields are conventionally managed areas because tills and other heavy machinery prepare the land for planting. The grass margins and woodlots are semi-natural habitats, serving as a middle ground between the pasture and cornfield areas. In the study, there were three sections of land that had each land use type (Fig. 1).

Figure 1: Sampling areas for collections. Each sampling area (A-C) had a cornfield, pasture, grass margin, and woodlot that were used as treatments (photos extracted from Google Earth and arranged by Robert Salerno, used with permission).

To look into the response of soil arthropod communities, subterranean pitfall traps were used in each study area, which allow for the capture of arthropods from multiple soil depths. The collected arthropods were identified and assigned an index value based on how adaptive it is to lower soil quality. The soil quality was assessed by measuring soil moisture, bulk density, and soil temperature. These characteristics of soil are important because they are primary constraints on the assembly of soil arthropod communities.  Decomposition was measured using the removal of baits over time from bait-drilled plastic strips inserted into the soil. After two weeks, the strips were removed and the fraction of bait remaining was estimated to represent the feeding activity of soil arthropods.

Robert showed that ecological intensification impacts soil arthropods, as hypothesized. Arthropod diversity was lower in conventionally managed corn fields– tilled areas – compared to the other land use types that had higher ecological intensification. Soil quality assessments generally showed parallel results, with conventionally managed land having lower quality soil. The study showed that sustainable land management through ecological intensification may support soil arthropod communities and soil quality, but future studies are needed.
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Robert earned his bachelor’s degree in Organismal Biology from the State University of New York at Oswego in 2022. His research interests include IPM and sustainable agriculture. During his time at UMD, he has been a TA for Principles of Ecology and Evolution (BSCI161).
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Further reading:
Picasso, V. D., Berti, M., Cassida, K., Collier, S., Fang, D., Finan, A., Krome, M., Hannaway, D., Lamp, W., Stevens, A. W., & Williams, C. (2022). Diverse perennial circular forage systems are needed to foster resilience, ecosystem services, and socioeconomic benefits in agricultural landscapes. Grassland Research, 1(2), 123–130. https://doi.org/10.1002/glr2.12020

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