Can above‐ground ecosystem services compensate for reduced fertilizer input and soil organic matter in annual crops?

Abstract

Summary1. Above-ground and below-ground environmental conditions influence crop yield by pollination, pest pressure and resource supply. However, little is known about how interactions between these factors contribute to yield. Here, we used oilseed rape Brassica napus to test their effects on crop yield. 2. We exposed potted plants to all combinations of high and low levels of soil organic matter (SOM) and fertilizer supply, and placed all treatments at a variety of field sites representing a gradient in pollinator visitation rate and pest exposure. We determined the relative contribution of pollinators and pests, SOM and fertilizer supply to yield. We also tested whether SOM can moderate effects of fertilizer on yield and whether soil conditions influence the relationship between above-ground conditions and yield. 3. Increases in pollinator visitation rate and decreases in pest pressure enhanced yield more than increase in fertilizer supply. Although higher SOM content resulted in plants with more biomass and flowers, under our experimental conditions SOM neither enhanced yield, nor influenced effects of fertilizer, pollinators or pests on yield. 4. The relationships between yield, pollinator visitation rate and pest pressure did not depend on the level of fertilization, suggesting that the effects of fertilizer application and aboveground (dis)services on yield were additive. In contrast, pollinator visitation rate was more strongly related to yield at low pest pressure than at high pest pressure indicating trade-offs between above-ground services and disservices. 5. Synthesis and applications. Our results show that it is possible to increase oilseed rape yield by enhancing pollination, irrespective of supplying mineral fertilizer. Moreover, the fact that belowground conditions did not alter the effect of above-ground conditions suggests that farmers may obtain even higher yields by maximizing both above-ground ecosystem services and external inputs. Further studies are needed to understand at which point the positive relationships between pollinator visitation and yield, as well as between fertilizer and yield, will level off. Considering above-ground and below-ground services and inputs in agro-ecosystems in conjunction is crucial in order to optimize external inputs for crop yield from an economic and ecological perspective.

Landscape‐level crop diversity benefits biological pest control

“…Perennial non-crop structures are important sources of natural enemies in agroecosystems (Bosem Baillod et al, 2017;Tscharntke et al, 2005), and therefore have the potential to enhance pest regulation (Rusch et al, 2016). Yet a growing evidence base suggests that F I G U R E 4 Conversion of crop diversity (CropDiv) to "effective number of crops" (ENCS, Jost, 2006).…”

“…At the same time, crop diversity benefits might only emerge in resource-depleted, simplified landscapes with low semi-natural habitat cover. Here, crop diversification adds essential resources otherwise lacking in the non-crop matrix (Josefsson, Berg, Hiron, Pärt, & Eggers, 2017;Tscharntke, Klein, Kruess, Steffan-Dewenter, & Thies, 2005). However, correlations between crop diversity and semi-natural habitat often impede our ability to infer causal relationships (Fahrig et al, 2011(Fahrig et al, , 2015.…”

Insect pollination as an agronomic input: Strategies for oilseed rape production

“…Although several studies have demonstrated the benefits of individual ecosystem services on crop yield and quality (Garratt, Breeze, et al, 2014;Klatt et al, 2014), recent studies have indicated that these benefits are affected by interactions among different services (Bartomeus, Gagic, & Bommarco, 2015;Lundin, Smith, Rundlöf, & Bommarco, 2013;Sutter & Albrecht, 2016) and between ecosystem services and anthropogenic inputs such as fertilizer and irrigation (Klein, Hendrix, Clough, Scofield, & Kremen, 2015;Marini et al, 2015;van Gils, van der Putten, & Kleijn, 2016). Despite the potential importance of biodiversity-derived services to contribute directly to yield, only by understanding and quantifying these interactions can effective ecologically intensive management strategies be applied with predictable outcomes for production.…”

Soil management shapes ecosystem service provision and trade-offs in agricultural landscapes

“…Although the effects of different soil management strategies on the provision of single services have been reported (e.g. tillage on erosion and pest control [8,9]; nitrogen fertilization on pest pressure and pollination [10]), studies exploring potential repercussions on multiple ESs are scarce.…”