A critical review of the impacts of cover crops on nitrogen leaching, net greenhouse gas balance and crop productivity

Abstract

Cover crops play an increasingly important role in improving soil quality, reducing agricultural inputs and improving environmental sustainability. The main objectives of this critical global review and systematic analysis were to assess cover crop practices in the context of their impacts on nitrogen leaching, net greenhouse gas balances (NGHGB) and crop productivity. Only studies that investigated the impacts of cover crops and measured one or a combination of nitrogen leaching, soil organic carbon (SOC), nitrous oxide (N2O), grain yield and nitrogen in grain of primary crop, and had a control treatment were included in the analysis. Long‐term studies were uncommon, with most data coming from studies lasting 2–3 years. The literature search resulted in 106 studies carried out at 372 sites and covering different countries, climatic zones and management. Our analysis demonstrates that cover crops significantly (p < 0.001) decreased N leaching and significantly (p < 0.001) increased SOC sequestration without having significant (p > 0.05) effects on direct N2O emissions. Cover crops could mitigate the NGHGB by 2.06 ± 2.10 Mg CO2‐eq ha−1 year−1. One of the potential disadvantages of cover crops identified was the reduction in grain yield of the primary crop by ≈4%, compared to the control treatment. This drawback could be avoided by selecting mixed cover crops with a range of legumes and non‐legumes, which increased the yield by ≈13%. These advantages of cover crops justify their widespread adoption. However, management practices in relation to cover crops will need to be adapted to specific soil, management and regional climatic conditions.

Integrated management for sustainable cropping systems: Looking beyond the greenhouse balance at the field scale

“…These results are consistent with recent simulation studies by Tribouillois, Constantin, and Justes (2018) when applying the STICS soil-crop model to 12 cropping systems in five locations in France, and with Lugato, Bampa, Panagos, Montanarella, and Jones (2014) when conducting large-scale simulations with CENTURY in Europe. Similar results were reported from field experiments conducted under various environmental conditions (García-González, Hontoria, Gabriel, Alonso-Ayuso, & Quemada, 2018;Mazzoncini, Sapkota, Bàrberi, Antichi, & Risaliti, 2011;Quemada, Cabrera, & McCracken, 1997;Thomsen & Christensen, 2004) and summarized in two meta-analysis (Abdalla et al, 2019;Aguilera et al, 2013;Poeplau & Don, 2015). All these studies agree that the mitigation potential of soil C sequestration is finite because this pool eventually reaches a steady state.…”

“…The yield reduction observed in a minority of sampling locations might be due to the competition for water by the cover crops over the main crop (Mediterranean, Central Europe). Results from a meta‐analysis by Abdalla et al () identified a stabilization or a slight reduction of grain yield (4% on average with respect to the fallow control) as a drawback for cover cropping adoption, and suggested that management practices adapted to local conditions could mitigate this disadvantage. In our study, the yield reduction under the GHG 0 and GHG min scenarios compared to the CC leg scenario highlighted the transition toward a more N limiting environment in many of the simulated locations by 2100.…”

Meta‐analysis on the potential for increasing nitrogen losses from intensifying tropical agriculture

“…Most of what we know about the inefficiency of N fertilizer use comes from temperate North America, Europe, and Asia (Liu et al, 2010). Although there have been a number of recent meta-analyses on N losses from agroecosystems, they include very few observations from tropical agriculture (Abdalla et al, 2019;Liu et al, 2017;Shcherbak et al, 2014;Zhou & Butterbach-Bahl, 2014). For example, Shcherbak et al, 2014 included only five studies from the tropics.…”

Cover Crop Effects on Corn Plant Sap Flow Rates and Soil Water Dynamics

“…The types of CC used and the planting and termination times could also affect the grain yield. Studies have emphasized mixed results of CC use on grain yield, reporting reduced grain yields with spring‐sown CC due to high competition with primary crop for resources (Känkänen et al, 2003), no effects on grain yield (Ohlander et al, 1996), and reduced yields by monocropped CC and increased yields by legume and nonlegume CC mixtures (Abdalla et al, 2019).…”

“…Miguez and Bollero (2005) reported mixed effects of winter CC use on corn ( Zea mays L.) yields in the United States and Canada with a 21% increase of corn yield after a biculture mix of legume and grass species winter CC, a 37% yield increase after legume winter CC, and no yield benefit after a grass winter CC. A review by Abdalla et al (2019) reported ∼4% reduction of grain yield of the primary crop compared with the control by both legume and nonlegume CC, as well as an increase of yield up to ∼13% by cover crop mixtures.…”