Abstract
Intercropping of two or more species on the same piece of land can enhance biodiversity and resource use efficiency in agriculture. Traditionally, intercropping systems have been developed and improved by empirical methods within a specific local context. To support the development of promising intercropping systems, the individual species that are part of an intercrop can be subjected to breeding. Breeding for intercropping aims at resource foraging traits of the admixed species to maximize niche complementarity, niche facilitation, and intercrop performance. The breeding process can be facilitated by modeling tools that simulate the outcome of the combination of different species’ (or genotypes’) traits for growth and yield development, reducing the need of extensive field testing. Here, we revisit the challenges associated with breeding for intercropping, and give an outlook on applying crop growth models to assist breeding for intercropping. We conclude that crop growth models can assist breeding for intercropping, provided that (i) they incorporate the relevant plant features and mechanisms driving interspecific plant–plant interactions; (ii) they are based on model parameters that are closely linked to the traits that breeders would select for; and (iii) model calibration and validation is done with field data measured in intercrops. Minimalist crop growth models are more likely to incorporate the above elements than comprehensive but parameter-intensive crop growth models. Their lower complexity and reduced parameter requirement facilitate the exploration of mechanisms at play and fulfil the model requirements for calibration of the appropriate crop growth models.
Highlights
Intercropping is the simultaneous cultivation of at least two crops in the same field (Willey, 1979), without necessarily sowing or harvesting them at the same time
The STICS model provides additional examples for crop related parameters that can account for the competitive ability and how it changes in intercrops: minimum and maximum root and biomass growth rates and species specific nitrogen dilution functions derived from theoretical optimum nitrogen contents in the admixed target species (Brisson et al, 2003; Corre-Hellou et al, 2009)
Crop growth models use plant parameters to simulate growth and development of a crop for the given environmental conditions. These models have been used previously to assist plant breeding, especially ideotype breeding of crops to be grown in sole culture (Martre et al, 2015; Rötter et al, 2015)
Summary
Intercropping is the simultaneous cultivation of at least two crops in the same field (Willey, 1979), without necessarily sowing or harvesting them at the same time. To support the development of promising intercropping systems, the individual component species of mixtures can be subject of breeding and genotypes with contrasting resource foraging characteristics selected to maximize mixture complementarity, reduce negative competitive interactions, and improve the production of each component species (Litrico and Violle, 2015). Such a process can be facilitated by modeling tools simulating, in a system approach, plant functioning and expected outcomes of the combination of different species’ (or genotypes’) traits for growth and yield development over time. We do this by (i) summarizing the specific challenges associated with breeding for intercropping; (ii) providing an update on existing crop growth models that can simulate intercrops; and (iii) evaluating their application to assist breeding for intercropping
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