Paper of the Month November 2015

Temporal niche differentiation increases the land equivalent ratio of annual intercrops: A meta-analysis


Sustainable intensification of agriculture is needed to meet higher future food demands while mitigatingagricultureā€™s ecological footprint. Intercropping is a strategy for increasing agricultural productivity perunit land that is based on ecological mechanisms for improved resource capture. No quantitative synthesishas been made on the effect of intercrop system properties and species trait combinations on intercropproductivity. Here we use meta-analysis of the intercropping literature to study how the productivityof mixed systems is affected by intercrop system design and species traits. We focus on the effects oftemporal niche differentiation between species, intercropping pattern, relative densities, the use of C3and C4 species and the rate of nitrogen fertilizer. Land equivalent ratio (LER) is used as index for assessingthe relative productivity of a mixed system as compared to sole crops. Average LER was 1.22 Ā± 0.02, andno differences in LER were found between the 50 most highly cited studies and a random sample fromthe literature, indicating that high LERs in highly cited papers are representative of the entire literature.Temporal niche differentiation contributed substantially to high LER in systems combining a C3 and C4species, but not in systems based on C3 species mixtures. The amount of N fertilizer interacted positivelywith the effect of temporal niche differentiation on LER. The intercropping literature is dominated bystudies on cereal/legume mixtures. However, the few studies on C3 cereal/C4 cereal mixtures indicatethese mixtures have high LER.Substantial improvements in land use efficiency in agriculture may be obtained by using mixtures, par-ticularly C3/C4 mixtures. Thus, enhanced within-field crop diversity can make an important contributionto sustainable increases in food production.

Yang Yu, Tjeerd-Jan Stomph, David Makowski, Wopke van der Werf (2015) Field Crops Research 184: 133-144

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