Improving crop productivity is a global priority. While intensive agriculture provides high yields, it also causes negative environmental impacts on air, water, and soil quality — such as soil acidification, habitat loss or pollution, fertiliser run-off and surface-water eutrophication — and resulting declines in biodiversity. Due to its essential role in supporting growing communities but also its negative impact on biodiversity, the European agricultural sector is seeking innovative ways to improve yields while supporting the EU Biodiversity Strategy for 20301, which aims to protect European land and sea and to restore nature.Intercropping has emerged as a potentially sustainable way forward, offering ecological mechanisms for suppressing weeds, controlling pests and diseases, conserving soil resources, increasing yields, and using light, space and water more efficiently than pure stands of crop species that are nowadays the norm in agriculture. However, the absolute yield gain that intercropping can bring on a global scale, compared to sole crops, has not been quantified. This study therefore performed a statistical analysis of a global dataset2 on yields in intercropping.

The records on intercropping were retrieved from a total of 132 research papers which reported results of 226 field experiments, constituting the largest statistical analysis on intercropping to date.The researchers identified two different intercropping strategies: one type of intercropping system including maize (Zea mays), with high inputs, and a staggered relay sequence for sowing and harvesting multiple species of crop (a configuration commonly practiced in China and known as relay-strip intercropping); and another type of system without maize, with low inputs with simultaneous sowing and harvesting of multiple crop species (commonly practiced in Europe, Asia and Africa). The researchers surmise that these systems evolved in different parts of the world to meet different demands and constraints — food security in China, reduced environmental impact in Europe and shortage of resources in parts of Africa.Compared with monocultures, absolute yield gains were greatest when maize was mixed with short-grain cereals or legumes with a substantially different temporal niche (growing period) to maize and grown with high nutrient inputs in multi-row species strips. Mixing temporal niches in this way may enable greater agricultural adaptivity to the extended growing seasons and higher average temperatures that accompany ongoing global warming and could allow agricultural producers to more precisely time their application of fertiliser to reduce the total amount needed.

Intercropping, the simultaneous production of multiple crops on the same field, provides opportunities for the sustainable intensification of agriculture if it can provide a greater yield per unit land and fertilizer than sole crops. The worldwide absolute yield gain of intercropping as compared with sole crops has not been analysed. We therefore performed a global meta-analysis to quantify the effect of intercropping on the yield gain, exploring the effects of crop species combinations, temporal and spatial arrangements, and fertilizer input. We found that the absolute yield gains, compared with monocultures, were the greatest for mixtures of maize with short-grain cereals or legumes that had substantial temporal niche differentiation from maize, when grown with high nutrient inputs, and using multirow strips of each species.

This approach, commonly practised in China, provided yield gains that were (in an absolute sense) about four times as large as those in another, low-input intercropping strategy, commonly practised outside China. The alternative intercropping strategy consisted of growing mixtures of short-stature crop species, often as full mixtures, with the same growing period and with low to moderate nutrient inputs. Both the low- and high-yield intercropping strategies saved 16–29% of the land and 19–36% of the fertilizer compared with monocultures grown under the same management as the intercrop. The two syndromes of production in intercropping uncovered by this meta-analysis show that intercropping offers opportunities for the sustainable intensification of both high- and low-input agriculture.