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Data extracted in May 2021
Fiche created in December 2023
Note to the reader: This general fiche summarises all the environmental and climate impacts of INTERCROPPING found in a review of 25 synthesis papers[1]. These papers were selected from an initial number of 111 obtained through a systematic literature search strategy, according to the inclusion criteria reported in section 4. The impacts reported here are those for which there is scientific evidence available in published synthesis papers, what does not preclude the farming practice to have other impacts on the environment and climate still not covered by primary studies or by synthesis papers.
The synthesis papers review a number of primary studies ranging from 11 to 180. Therefore, the assessment of impacts relies on a large number of results from the primary studies, obtained mainly in field conditions, or sometimes in lab experiments or from model simulations.
1. DESCRIPTION OF THE FARMING PRACTICE
- Description:
- Key descriptors:
- This review includes different types of intercropping2 [4]:
- Mixed cropping: sowing multiple crop species or cultivars in the same field at the same time, in a mixture with a given seeding ratio but random spatial arrangement.
- Row intercropping: sowing multiple crop species in the same field at the same time in alternate rows.
- Strip intercropping: sowing two (or more) crop species in the same field at the same time in multi-row strips wide enough to allow independent cultivation.
- Relay cropping: intercropping of two crop species in which the second species is under-sown in the first at a later point in the growing season.
- This review includes intercropping applied to cash crops, fodder (one study) and cover crops (one study). [5]
- This review does not include: 1) alley cropping, i.e., the cultivation of food, forage or specialty crops between rows of trees, and 2) dual-purpose cropping, i.e. the cultivation of two or more crops used for grazing by livestock and for grain. These two practices are assessed in separate sets of fiches.
- This review includes different types of intercropping2 [4]:
2. EFFECTS OF THE FARMING PRACTICE ON CLIMATE AND ENVIRONMENTAL IMPACTS
The table below shows the number of synthesis papers with statistical tests reporting i) a significant difference between the Intervention and the Comparator, that is to say, a significant statistical effect, which can be positive or negative; or ii) a non-statistically significant difference between the Intervention and the Comparator. In addition, we include, if any, the number of synthesis papers reporting relevant results but without statistical test of the effects. Details on the quality assessment of the synthesis papers can be found in the methodology section of this WIKI.
Out of the 25 selected synthesis papers, 18 included studies conducted in Europe, and 25 have a quality score higher than 50%.
Table 1: Summary of effects. Number of synthesis papers reporting positive, negative or non-statistically significant effects on environmental and climate impacts. The number of synthesis papers reporting relevant results but without statistical test of the effects are also provided. When not all the synthesis papers reporting an effect are of high quality, the number of synthesis papers with a quality score of at least 50% is indicated in parentheses. Some synthesis papers may report effects for more than one impact, or more than one effect for the same impact.
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| Statistically tested | Non-statistically tested | ||
Impact | Metric | Intervention | Comparator | Significantly positive | Significantly negative | Non-significant | |
Increase Carbon sequestration | Soil organic carbon | Crop mixture cropping | monoculture | 1 | 0 | 0 | 0 |
Decrease Pests and diseases | Pest and disease control | Crop mixture cropping | monoculture | 5 | 0 | 1 | 0 |
Cultivar mixture cropping | monoculture | 3 | 0 | 1 | 0 | ||
Increase Plant nutrient uptake | Nutrient uptake | Crop mixture cropping | monoculture | 5 | 0 | 1 | 0 |
Decrease Soil erosion | Soil erosion | Crop mixture cropping | monoculture | 2 | 0 | 1 | 0 |
Increase Soil nutrients | Soil nutrients | Crop mixture cropping | monoculture | 2 | 0 | 0 | 0 |
Increase Soil physico-chemical quality | Soil physico-chemical quality | Crop mixture cropping | monoculture | 1 | 0 | 0 | 0 |
Increase Soil water retention | Soil water retention | Crop mixture cropping | monoculture | 1 | 1 | 0 | 0 |
Increase Crop yield* | Crop yield | Crop mixture cropping | monoculture | 14 | 2** | 2 | 0 |
Cultivar mixture cropping | monoculture | 3 | 0 | 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. FACTORS INFLUENCING THE EFFECTS ON CLIMATE AND ENVIRONMENTAL IMPACTS
The factors significantly influencing the size and/or direction of the effects on the impacts, according to the synthesis papers included in this review, are reported below. Details about the factors can be found in the summaries of the meta-analyses available in this WIKI.
Table 2: List of factors reported to significantly affect the size and/or direction of the effects on environmental and climate impacts, according to the synthesis papers reviewed. The reference number of the synthesis papers where those factors are explored is given in parentheses.
Impact | Factors |
Pests and diseases | Crop type (Ref1), Crop/cultivar combinations (Ref1, Ref23, Ref20), Disease severity (Ref23), Pathogen species (Ref8), Season (Ref8), Sowing density (Ref23) and Type of herbivore pest (Ref11) |
Plant nutrient uptake | Crop/cultivar combinations (Ref4, Ref2, Ref6), Fertiliser application (Ref2, Ref6), Geographical area (Ref7), Growing degree days (climate) (Ref14), Method used to quantify Nitrogen fixation (Ref6), Previous crop (Ref14), Soil texture (Ref14) and Sowing time (Ref7, Ref2) |
Soil nutrients | Crop/cultivar combinations (Ref6), Fertiliser application (Ref6), Method used to quantify Nitrogen fixation (Ref6) |
Crop yield | Climate (Ref9), Crop density (Ref18, Ref19), Crop spatial arrangement (Ref4, Ref19, Ref17), Crop type (Ref10, Ref3, Ref13, Ref25, Ref18, Ref9), Crop/cultivar combinations (Ref16, Ref13, Ref12, Ref4, Ref5, Ref20, Ref25, Ref19, Ref17, Ref2, Ref21, Ref9), Disease severity (Ref10, Ref13), Fertiliser application (Ref16, Ref13, Ref4, Ref5, Ref18, Ref19, Ref2, Ref9), Geographical area (Ref19, Ref7), Growing degree days (Ref14), Herbicide use (Ref16), Latitude (Ref13, Ref25), Pesticide use (Ref16), Previous crop (Ref14), Row distance (Ref9), Soil organic matter (Ref13, Ref7), Soil pH (Ref13), Soil texture (Ref14, Ref9), Sowing time (Ref18, Ref7), Temporal treatment establishment (Ref9), Tillage (Ref16) and Trait heterogeneity (Ref10) |
4. SYSTEMATIC REVIEW SEARCH STRATEGY
Table 3: Systematic review search strategy - methodology and search parameters.
Parameter | Details |
Keywords | WOS: TOPIC: (( intercrop* OR "inter crop*" OR "mult* variet*" OR "mult* crop*" OR "Companion crop*" OR "Companion plant*" OR "polycultur*" OR "crop diversity" OR "mix* crop*" OR "crop* mix*" OR "cult* mix*"OR "variety mix*" OR "row crop*" OR "strip* crop*" OR "row crop*" OR "relay crop*")) AND TOPIC: (("meta-analy*" OR "systematic* review*" OR "evidence map" OR "global synthesis" OR "evidence synthesis" OR "research synthesis")) |
Time reference | No time restriction. |
Databases | Web of Science and Scopus: run on 18 May 2021 |
Exclusion criteria | The main criteria that led to the exclusion of a synthesis paper are: |
5. SYNTHESIS PAPERS INCLUDED IN THE REVIEW
Table 4: List of synthesis papers included in this review. More details can be found in the summaries of the meta-analyses.
Ref Num | Author(s) | Year | Title | Journal | DOI |
Ref1 | 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 |
Ref2 | 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 |
Ref3 | 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 |
Ref4 | 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 |
Ref5 | 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 |
Ref6 | 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 |
Ref7 | 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 |
Ref8 | 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 |
Ref9 | 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 |
Ref10 | 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 |
Ref11 | 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 |
Ref12 | 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 |
Ref13 | 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 |
Ref14 | 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 |
Ref15 | 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 |
Ref16 | 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 |
Ref17 | 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 |
Ref18 | 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 |
Ref19 | 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 |
Ref20 | 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 |
Ref21 | 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 |
Ref22 | 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 |
Ref23 | 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 |
Ref24 | 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 |
Ref25 | 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 |
Disclaimer: These fiches present a large amount of scientific knowledge synthesised to assess farming practices impacts on the environment, climate and productivity. The European Commission maintains this WIKI to enhance public access to information about its initiatives. Our goal is to keep this information timely and accurate. If errors are brought to our attention, we will try to correct them. However, the Commission accepts no responsibility or liability whatsoever with regard to the information on these fiches and WIKI.
[1] Synthesis research papers include either meta-analysis or systematic reviews with quantitative results. Details can be found in the methodology section of the WIKI.
[2] Vandermeer, J. H. (1992). The ecology of intercropping. Cambridge University Press
[3] Brooker, Rob W., et al. “Improving intercropping: a synthesis of research in agronomy, plant physiology and ecology.” New Phytologist 206.1 (2015): 107-117.
[4] Ditzler, Lenora, et al. “Current research on the ecosystem service potential of legume inclusive cropping systems in Europe. A review.” Agronomy for Sustainable Development 41.2 (2021): 1-13.
[5] Cover crops are plants that are planted to cover (and protect) the soil rather than for being harvested.