DOI: 10.25338/b8np6j
title: Integrated Crop-Livestock Systems achieve comparable crop yields to specialized systems: a meta-analysis

description: Production systems that feature temporal and spatial integration of crop
 and livestock enterprises, also known as integrated crop-livestock systems
 (ICLS), have the potential to intensify production on cultivated lands and
 foster resilience to the effects of climate change without proportional
 increases in environmental impacts. Yet, crop production outcomes
 following livestock grazing across environments and management scenarios
 remain uncertain and a potential barrier to adoption, as producers worry
 about the effects of livestock activity on the agronomic quality of their
 land. To determine likely production outcomes across ICLS and to identify
 the most important moderating variables governing those outcomes, we
 performed a meta-analysis of 66 studies comparing crop yields in ICLS to
 yields in unintegrated controls across 3 continents, 12 crops, and 4
 livestock species. We found that annual cash crops in ICLS averaged
 similar yields (-7% to +2%) to crops in comparable unintegrated systems.
 The exception was dual-purpose crops (crops managed simultaneously for
 grazing and grain production), which yielded 20% less on average than
 single-purpose crops in the studies examined. When dual-purpose cropping
 systems were excluded from the analysis, crops in ICLS yielded more than
 in unintegrated systems in loamy soils and achieved equal yields in most
 other settings, suggesting that areas of intermediate soil texture may
 represent a “sweet-spot” for ICLS implementation. This meta-analysis
 represents the first quantitative synthesis of the crop production
 outcomes of ICLS and demonstrates the need for further investigation into
 the conditions and management scenarios under which ICLS can be
 successfully implemented.
description: We conducted a comprehensive literature search using three
 academic databases (Web of Science, CAB Abstracts, and Agricola) and the
 Google Scholar internet search engine in English, French, Spanish, and
 Portuguese. The most recent database search was conducted in September
 2018. We gleaned further records from the reference lists of review
 articles and research articles meeting the initial eligibility criteria.
 Targeted searches of governmental and independent agricultural research
 organizations were also performed in countries where medium-to-large
 scale, commercially oriented ICLS are known to occur. Finally, we
 performed a manual search of the grey literature including theses and
 dissertations and data from long-term experiments, both published and
 unpublished, in consultation with prominent integrated crop-livestock
 system researchers. No prior review protocol existed
 for this study. The following search terms were employed for abstracts,
 titles, and keywords: (crop-livestock AND yield) NOT mixed);
 (“crop-livestock” AND integ*) OR “integração lavoura-pecuária" OR
 "integración agropecuaria”; "crop-livestock" AND yield;
 (crop*livestock OR crop OR livestock) AND (French OR France) AND yield AND
 graz*; (crop*livestock OR crop OR livestock) AND (Spain OR Spanish OR
 “Latin America” OR “South America”) AND yield AND graz*; intégration
 ("polyculture-élevage" OR polyculture OR élevage OR agriculture)
 rendement pâturage expérimental -arbres. Search results were deduplicated
 and restricted to full-text journal articles. Google Scholar results were
 additionally restricted to the years 2008-2018 due to the volume of
 results; other databases were searched for the full range of available
 years. A total of 2,702 studies were identified from
 the database searches, unpublished dissertations, reference lists of
 eligible studies and literature reviews, and long-term datasets provided
 by ICLS researchers (Fig 1). The initial screening process involved manual
 scanning of titles and abstracts for clear instances of ineligibility,
 e.g. wrong field of study, wrong scope, wrong subject, or wrong language.
 A total of 2,569 records were excluded in the initial screening process,
 leaving the full text of 133 articles to be assessed in greater detail
 based on the following eligibility criteria: 
 Study scope was restricted to agropastoral systems with annual
 crops. Duck-rice-azolla, agro-silvo-pastoral systems, and systems
 integrating livestock with perennial crops were excluded;
 Study involved a replicated field trial with both an integrated
 system (grazed treatment) and an unintegrated control (ungrazed treatment)
 and included at least one season each of the cropping component and the
 grazing component; Crops and livestock were
 co-located, i.e. spatially integrated at the field level. Cut-and-carry,
 manure amendments, or farm-level mixed systems were excluded due to
 disparities in system objectives and constraints as well as difficulties
 in determining adequate experimental controls for farm-level
 integration; Study was original research,
 dataset, or dissertation, i.e. not a review, book chapter, or conference
 proceeding. Data on categorical
 environmental moderating variables were also collected for each study.
 Studies were grouped into climate and soil classes according to the Köppen
 climate classifications, which were extracted from the updated world map
 of the Köppen-Geiger climate , and soil texture characteristics extracted
 from the Harmonized World Soil Database v1.2. Additional moderating
 variables included crop species, livestock species, and the occurrence of
 dry weather anomalies. The latter was defined as a season during which
 precipitation accumulation was abnormally low according to specifications
 set by the authors of the relevant study. Crop species were grouped
 according to broad agronomic similarities: cereals (corn and sorghum),
 small grains (wheat, oat, barley, triticale, and rye), fiber (cotton
 harvested for lint), soybean, other legumes (peanuts and common bean), and
 oilseeds (canola). For animals, goats and sheep were grouped into small
 ruminants and beef and dairy cattle were grouped under cattle.