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Data extracted in May 2021
Note to the reader: This general fiche summarises all the environmental and climate impacts of INTERCROPPING found in a systematic review of 25 synthesis research papers1. These papers were selected, from an initial number of 111 yielded by a systematic literature search strategy, according to the inclusion criteria reported in section 4.
As each synthesis research paper involves a number of primary research papers ranging from 11 to 180, the assessment of impacts relies on a large number of results obtained in field experiments (carried out in situations close to real farming environment ), and sometimes in lab experiments or from model simulations.
1. DESCRIPTION OF THE FARMING PRACTICE
Description | Intercropping is a farming method that involves cultivating two or more crop species (i.e., crop mixture cropping) or genotypes (i.e., cultivar mixture cropping) in the same area and coexisting for a time so that they interact agronomically 2 3. |
Key descriptors |
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2. DESCRIPTION OF THE IMPACTS OF THE FARMING PRACTICE ON CLIMATE AND THE ENVIRONMENT
We reviewed the impacts of intercropping compared to monoculture, i.e., the cultivation of one crop or cultivar.
The tables below show the number of synthesis papers reporting positive, negative or no effect, based on the statistical comparison of the intervention and the control. In addition, we include, if any, the number of systematic reviews reporting relevant results but without statistical test of the effects (uncertain). The numbers between parentheses indicate the number of synthesis papers with a quality score of at least 50%. Details on quality criteria can be found in the methodology section of this WIKI.
Out of the 25 synthesis papers selected, 18 reported studies conducted in Europe. None of the synthesis studies exploring the impacts of intercropping on Carbon sequestration, Soil erosion, Soil nutrients and Water retention included experiments conducted in Europe. All synthesis papers have a quality score higher than 50%. Some synthesis papers reported more than one impact.
Table 1. Impacts of intercropping compared to monoculture
| All studies |
| Only studies including EU | |||||||
Impact | Intervention | Positive | Negative | No effect | Uncertain |
| Positive | Negative | No effect | Uncertain |
Increase Carbon sequestration | Crop mixture | 1 (1) | 0 | 0 | 0 |
| 0 | 0 | 0 | 0 |
Increase Plant nutrient uptake | Crop mixture | 5 (5) | 0 | 1 (1) | 0 |
| 4 (4) | 0 | 0 | 0 |
Decrease Pests and diseases | Crop mixture | 5 (5) | 0 | 1 (1) | 0 |
| 1 (1) | 0 | 0 | 0 |
Cultivar mixture | 3 (3) | 0 | 1 (1) | 0 |
| 3 (3) | 0 | 1 (1) | 0 | |
Decrease Soil erosion | Crop mixture | 2 (2) | 0 | 1 (1) | 0 |
| 0 | 0 | 0 | 0 |
Increase Soil nutrients | Crop mixture | 1 (1) | 0 | 1 (1) | 0 |
| 0 | 0 | 0 | 0 |
Increase Soil water retention | Crop mixture | 1 (1) | 1 (1) | 0 | 0 |
| 0 | 0 | 0 | 0 |
Increase Crop yield * | Crop mixture | 14 (14) | 2 (2) ** | 2 (2) | 0 |
| 9 (9) | 1(1) ** | 1 (1) | 0 |
Cultivar mixture | 3 (3) | 0 | 1 (1) | 0 |
| 3 (3) | 0 | 1 (1) | 0 | |
* Nine out of 19 studies measured crop yield as land equivalent ratio (LER), i.e., the ratio of the area under sole cropping to the area under intercropping needed to give equal amounts of yield at the same management level. It is generally calculated as the sum of the fractions of the intercropped yields divided by the sole-crop yields.
** These studies considered crop yield from only the main crop, instead of all crops included in the intercropping.
3. DESCRIPTION OF THE KEY FACTORS INFLUENCING THE SIZE OF THE EFFECT
Only the factors explicitly studied in the reviewed synthesis papers with a significant effect are reported below. Details regarding the factors can be found in the summaries of the meta-analyses.
Impact | Factors |
Increase Plant nutrient uptake | Crop/cultivar combinations (ref. 5, 2, 6), Sowing time (ref. 7, 2), Geographical area (ref. 7), Soil texture (ref. 14), Previous crop (ref. 14), Growing degree days (Climate) (ref. 14), Fertiliser application (ref. 2, 6), Method used to quantify Nitrogen fixation (ref. 6) |
Decrease Pests and diseases | Crop/cultivar combinations (ref. 1, 23, 20), Crop type (ref. 1), Sowing density (ref. 23), Disease severity (ref. 23), Type of herbivore pest (ref. 11), Season (ref. 8), Pathogen species (ref. 8) |
Increase Soil water retention | Soil depth (ref. 3) |
Increase Crop yield | Crop type (ref. 10, 3, 13, 25, 18, 9), Disease severity (ref. 10, 13), Trait heterogeneity (ref. 10), Fertiliser application (ref. 16, 13, 5, 4, 18, 19, 2, 9), Pesticide use (ref. 16), Tillage (ref. 16), Crop/cultivar combinations (ref. 16, 13, 12, 5, 4, 20, 25, 19, 17, 2, 21, 9), Herbicide use (ref. 16), Soil organic matter (ref. 13, 7), Soil pH (ref. 13), Latitude (ref. 13, 25), Crop spatial arrangement (ref. 5, 19, 17), Sowing time (ref. 18, 7), Crop density (ref. 18, 19), Geographical area (ref. 7, 19), Soil texture (ref. 14, 9), Previous crop (ref. 14), Growing degree days (ref. 14), Climate (ref. 9), Temporal treatment establishment (ref. 9), Row distance (ref. 9) |
4. SYSTEMATIC REVIEW SEARCH STRATEGY
Keywords | TS=("grazing*" OR "grassland*" OR "pasture*" OR "rangeland")) AND TS=(("meta-analy*" OR "systematic* review*" OR "evidence map" OR "global synthesis" OR "evidence synthesis" OR "research synthesis") or TITLE-ABS-KEY: ( "grazing*" OR "grassland*" OR "pasture*" OR "rangeland") AND TITLE-ABS-KEY ( "meta-analy*" OR "systematic* review*" OR "evidence map" OR "global synthesis" OR "evidence synthesis" OR "research synthesis") |
Search dates | No time restrictions |
Databases | Web of Science and Scopus, run in September 2021 |
Selection criteria | The main criteria that led to the exclusion of a synthesis paper were when the paper: 1) did not deal with terrestrial grasslands or the effects on grasslands could not be disentangled from other land uses; 2) did not deal with grazing management; 3) was either a non-systematic review, a non-quantitative systematic review, or a meta-regression without mean effect sizes; 4) was not written in English. Due to the high number of potentially valid synthesis papers, we applied additional exclusion criteria: 5) the paper did not include studies conducted in Europe; 6) the paper only reported impacts on grassland or animal production, but any environmental impacts. Synthesis papers that passed the relevance criteria were subject to critical appraisal carried out on a paper-by-paper basis. The search returned 1022 synthesis papers potentially relevant for the practice object of our fiche. From the 1022 potentially relevant synthesis papers, 661 were excluded after reading the title and abstract, and 330 after reading the full text according to the above-mentioned criteria. Finally, 31 synthesis papers were selected for grazing. |
5. LIST OF SYNTHESIS PAPERS INCLUDED IN THE REVIEW
Ref. Num | Authors | Year | Title | Reference | DOI |
1 | Gibson, AK; Nguyen, AE | 2021 | Does genetic diversity protect host populations from parasites? A meta-analysis across natural and agricultural systems | Evol. Lett. 5, 16-32 | 10.1002/evl3.206 |
2 | Tang, XY; Zhang, CC; Yu, Y; Shen, JB; van der Werf, W; Zhang, FS | 2021 | Intercropping legumes and cereals increases phosphorus use efficiency; a meta-analysis | Plant Soil 460, 89–104 | 10.1007/s11104-020-04768-x |
3 | Daryanto, S; Fu, BJ; Zhao, WW; Wang, S; Jacinthe, PA; Wang, LX | 2020 | Ecosystem service provision of grain legume and cereal intercropping in Africa | Agric. Syst. 178, 102761 | 10.1016/j.agsy.2019.102761 |
4 | Li, CJ; Hoffland, E; Kuyper, TW; Yu, Y; Li, HG; Zhang, CC; Zhang, FS; van der Werf, W | 2020 | Yield gain, complementarity and competitive dominance in intercropping in China: A meta-analysis of drivers of yield gain using additive partitioning | Eur J Agron. 113, 125987 | 10.1016/j.eja.2019.125987 |
5 | Li, CJ; Hoffland, E; Kuyper, TW; Yu, Y; Zhang, CC; Li, HG; Zhang, FS; van der Werf, W | 2020 | Syndromes of production in intercropping impact yield gains | Nat. Plants 6, 653–660 | 10.1038/s41477-020-0680-9 |
6 | Rodriguez, C; Carlsson, G; Englund, JE; Flohr, A; Pelzer, E; Jeuffroy, MH; Makowski, D; Jensen, ES | 2020 | Grain legume-cereal intercropping enhances the use of soil-derived and biologically fixed nitrogen in temperate agroecosystems. A meta-analysis | Eur. J. Agron. 118, 126077 | 10.1016/j.eja.2020.126077 |
7 | Xu, Z; Li, CJ; Zhang, CC; Yu, Y; van der Werf, W; Zhang, FS | 2020 | Intercropping maize and soybean increases efficiency of land and fertilizer nitrogen use; A meta-analysis | Field Crops Res. 246, 107661 | 10.1016/j.fcr.2019.107661 |
8 | Zhang, CC; Dong, Y; Tang, L; Zheng, Y; Makowski, D; Yu, Y; Zhang, FS; van der Werf, W | 2019 | Intercropping cereals with faba bean reduces plant disease incidence regardless of fertilizer input; a meta-analysis | Eur. J. Plant Pathol. 154, 931–942 | 10.1007/s10658-019-01711-4 |
9 | Ashworth, AJ; Toler, HD; Allen, FL; Auge, RM | 2018 | Global meta-analysis reveals agro-grassland productivity varies based on species diversity over time | PloS One 13, e0200274. | 10.1371/journal.pone.0200274 |
10 | Borg, J; Kiaer, LP; Lecarpentier, C; Goldringer, I; Gauffreteau, A; Saint-Jean, S; Barot, S; Enjalbert, J | 2018 | Unfolding the potential of wheat cultivar mixtures: A meta-analysis perspective and identification of knowledge gaps | Field Crops Res. 221, 298-313 | 10.1016/j.fcr.2017.09.006 |
11 | Koricheva, J; Hayes, D | 2018 | The relative importance of plant intraspecific diversity in structuring arthropod communities: A meta-analysis | Funct. Col. 32, 1704-1717 | 10.1111/1365-2435.13062 |
12 | Martin-Guay, MO; Paquette, A; Dupras, J; Rivest, D | 2018 | The new Green Revolution: Sustainable intensification of agriculture by intercropping | Sci. Total Environ. 615, 767–772 | 10.1016/j.scitotenv.2017.10.024 |
13 | Reiss, ER; Drinkwater, LE | 2018 | Cultivar mixtures: a meta-analysis of the effect of intraspecific diversity on crop yield | Ecol. Appl. 28, 62–77 | 10.1002/eap.1629 |
14 | Thapa, R; Poffenbarger, H; Tully, KL; Ackroyd, VJ; Kramer, M; Mirsky, SB | 2018 | Biomass production and nitrogen accumulation by hairy vetch-cereal rye mixtures: a meta-analysis | J. Agron. 91, 25–33 | 10.2134/agronj2017.09.0544 |
15 | Xiong, M; Sun, R; Chen, L; | 2018 | Effects of soil conservation techniques on water erosion control: A global analysis | Sci. Total Environ. 645 753–760 | 10.1016/j.scitotenv.2018.07.124 |
16 | Himmelstein, J; Ares, A; Gallagher, D; Myers, J | 2017 | A meta-analysis of intercropping in Africa: impacts on crop yield, farmer income, and integrated pest management effects | Int. J. Sustain. Agric. Res. 15, 1-10 | 10.1080/14735903.2016.1242332 |
17 | Raseduzzaman, M; Jensen, ES | 2017 | Does intercropping enhance yield stability in arable crop production ? A meta-analysis | Eur. J. Agron. 91, 25–33 | 10.1016/j.eja.2017.09.009 |
18 | Yu, Y; Stomph, TJ; Makowski, D; Zhang, LZ; van der Werf, W | 2016 | A meta-analysis of relative crop yields in cereal/legume mixtures suggests options for management | Field Crops Res. 198, 269–279 | 10.1016/j.fcr.2016.08.001 |
19 | Yu, Y; Stomph, TJ; Makowski, D; van der Werf, W | 2015 | Temporal niche differentiation increases the land equivalent ratio of annual intercrops: A meta-analysis | Field Crops Res. 184, 133–144 | 10.1016/j.fcr.2015.09.010 |
20 | Iverson, AL; Marin, LE; Ennis, KK; Gonthier, DJ; Connor-Barrie, BT; Remfert, JL; Cardinale, BJ; Perfecto, I | 2014 | Do polycultures promote win-wins or trade-offs in agricultural ecosystem services? A meta-analysis | J. Appl. Ecol. 51, 1593–1602 | 10.1111/1365-2664.12334 |
21 | Pelzer, E; Hombert, N; Jeuffroy, MH; Makowski, D | 2014 | Meta-analysis of the effect of nitrogen fertilization on annual cereal-legume intercrop production | Agron. J. 106, 1775–1786 | 10.2134/agronj13.0590 |
22 | Slattery, RA; Ainsworth, EA; Ort, DR | 2013 | A meta-analysis of responses of canopy photosynthetic conversion efficiency to environmental factors reveals major causes of yield gap | J. Exp. Bot. 12, 3723–3733 | 10.1093/jxb/ert207 |
23 | Huang, C; Sun, ZY; Wang, HG; Luo, Y; Ma, ZH | 2012 | Effects of wheat cultivar mixtures on stripe rust: A meta-analysis on field trials | Crop Prot. 33, 52-58 | 10.1016/j.cropro.2011.11.020 |
24 | Letourneau, DK; Armbrecht, I; Rivera, BS; Lerma, JM; Carmona, EJ; Daza, MC; Escobar, S; Galindo, V; Gutierrez, C; Lopez, SD; Mejia, JL; Rangel, AMA; Rangel, JH; Rivera, L; Saavedra, CA; Torres, AM; Trujillo, AR | 2011 | Does plant diversity benefit agroecosystems? A synthetic review | Ecol. Appl. 21, 9-21. | 10.1890/09-2026.1 |
25 | Kiaer, LP; Skovgaard, IM; Ostergard, H | 2009 | Grain yield increase in cereal variety mixtures: A meta-analysis of field trials | Field Crops Res. 114, 361–373 | 10.1016/j.fcr.2009.09.006 |