Abstract
Ground beetles (Carabidae) are beneficial insects providing ecosystem services by regulating insect pests and weed seeds. Despite several studies conducted on ground beetles worldwide, there is a lack of knowledge on how these insects are affected by differently managed organic systems (e.g., tillage-based versus grazed-based) compared to that of chemical-based no-tillage conventional cropping systems. In a 5-year (2013–2017) study, we assessed the ground beetle communities in cover crops and winter wheat (Triticum aestivium L.) in Montana, USA, with three contrasting cropping systems: a chemically managed no-tillage, a tillage-based organic, and a livestock-integrated organic with reduced tillage. The first three years (i.e., 2013–2015) corresponded to the transition to organic period, while the last two (i.e., 2016–2017) were conducted in United States Department of Agriculture (USDA) organic-certified tillage-based and livestock-integrated organic systems. The experiment was designed with three management systems across three blocks as the whole plot variable and 5-year rotation of crop phases as the subplot variable. Using pitfall traps, we sampled ground beetles across all cover crop and winter wheat subplots for five years (n = 450). The data were analyzed using mixed effects models and PERMANOVA and visualized with non-metric multidimensional scaling ordination. Our study indicated that organically managed farms, whether tilled or grazed, enhance activity density, species richness, diversity, and evenness of ground beetles in the dryland row crop productions. Also, irrespective of farming system, cover crops supported higher species richness, diversity, and evenness of ground beetles than winter wheat. The ground beetle communities were mostly similar during the transition to organic period. However, during the established organic phase, cropping systems acted as contrasting ecological filters and beetle communities became dissimilar. Cover cropping affected ground beetle communities positively not only in organically managed systems but also in chemical-based conventional systems. Our study provides evidence supporting the adoption of ecologically-based cropping systems such as crop-livestock integration, organic farming, and cover cropping to enhance beneficial insects and their pest-regulation services.
Highlights
Industrialized crop production relies heavily on the use of off-farm chemical and mechanical inputs to control pest populations, maintain soil fertility, and prepare fields for planting
42 (555 in thewheat reduced-till organic (Supplementary cover crops, 20 (315 specimens) were collected in the conventional no-till system, (674 specimens) among the beetle species that were sampled in winter wheat, 20 (168 specimens) were collected in in the tilled organic, and 42 (555 specimens) in the reduced-till grazed organic
Our study found that A. apricaria, A. patruelis, Apristus pugetanus, Bradycellus congener, and Poecilus scitulus were indicative of cover crops, but ecological drivers of these associations are, to our understanding, unknown
Summary
Industrialized crop production relies heavily on the use of off-farm chemical and mechanical inputs to control pest populations, maintain soil fertility, and prepare fields for planting. Agronomy 2020, 10, 1210 intensive management practices may secure yields, they are major drivers of declines in local and regional biodiversity, soil erosion, selection of pesticide resistance, greenhouse gas emissions, and eutrophication [1,2] These negative consequences of modern industrialized agriculture have spawned interest in the development of ecologically-based cropping, an approach to food, fiber, and bioenergy production that relies on augmenting ecological processes to provide the functions necessary for sustained production, helping to reduce excessive use of off-farm inputs [3,4]. Cover cropping is one of the most widely used ecologically-based management practices as it can help increase soil organic matter, reduce soil erosion, improve soil nutrient retention [5], suppress weeds, and fix nitrogen if a legume is included [6]. Tillage reduces soil carbon and nutrient, releases greenhouse gases into the atmosphere, and accelerate soil erosion [14,15]
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