Abstract
Intercropping cereals and legumes can increase agricultural productivity and reduce inputs of nitrogen fertilizer but there is a need for further literature synthesis on the size of intercropping advantages and the factors affecting these advantages. Here we present a global meta-analysis of 36 studies, 66 experiments and 260 treatments addressing the land productivity of maize (Zea mays L.) and peanut (Arachis hypogaea L.) intercropping. Data were extracted from the literature and analyzed with mixed effects models to assess the land equivalent ratio (LER) and the factors affecting LER. The worldwide average LER of maize/peanut intercropping was 1.31 ± 0.03. The LER did not vary with continent, intercrop planting pattern and temporal niche differentiation, but sowing maize earlier than peanut (relative sowing time: RSTm<0) increased the partial LER of maize without significantly decreasing the partial LER of peanut. Increased N rate increased the partial LER of maize and decreased the partial LER of peanut but did not affect the total LER. This meta-analysis shows that maize/peanut intercropping is more land use efficient than the sole crops, it attains on average a “win-no win” yield advantage and mainly due to the maize.
Highlights
Intercropping is the cultivation of two or more crop species simul taneously in the same field for the whole or a part of their growing period (Willey, 1990; Hauggaard-Nielsen et al, 2008)
In this study, we address two main questions: (1) What is globally the land equivalent ratio of maize/peanut intercropping? (2) How is LER affected by intercrop management, the inter cropping pattern, co-growth period, relative sowing time of two species and fertilizer-N input?
The search yielded 256 publications. We selected only those studies that met four inclusion criteria: (1) data were from field experiments; (2) papers reported original data; (3) papers were written in English; (4) papers included both the grain yield of intercrops and sole crops, or reported the LER directly
Summary
Intercropping is the cultivation of two or more crop species simul taneously in the same field for the whole or a part of their growing period (Willey, 1990; Hauggaard-Nielsen et al, 2008). The key reasons for mixing cereals and legumes in an intercrop are to increase long-term land productivity by biological fixation of atmospheric N by the legumes and to enhance diversity of product and reduce climate risk (Kermah et al, 2017). Cereals may perform better when intercropped with legumes than as a sole crop, especially at low N supply, due to reduced competition for soil N as legumes can obtain their nitrogen from the at mosphere and are not strong competitors for soil N (Cowell et al, 1989; Hauggaard-Nielsen et al, 2001). A high uptake of inorganic N by cereals may enhance the biological N fixation of legumes (Haug gaard-Nielsen et al, 2003), enhancing soil fertility by incorporating legumes in cropping systems in the long term (Giller, 2001)
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