Root traits for sustainable low-input agro-ecosystems
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Soil stress is a key constraint to global food production, and selection for root traits is a promising strategy for improving sustainability of low input agro-ecosystems. In this thesis, the use of root traits for improving nutrient uptake in low-input agro-ecosystems is explored, with an emphasis on root architecture and low-phosphorus soil. Chapter 1 presents a general introduction of sustainable low-input agriculture, soil stress, and root traits. In Chapter 2, root cortical aerenchyma formation was observed to decrease radial nutrient transport in maize seminal roots. Chapter 3 shows that multilines (genetic mixtures) of genotypes with contrasting root architecture have improved yields over single lines under combined drought and phosphorus stress, that root competition among genotypes did not cause a reduction in yield, and identifies root competitiveness as variable on a genotype level. In Chapter 4, erosion of low-phosphorus soils was not directly affected by different root architectures of common bean or soybean. Chapter 5 shows that root shallowness can reduce erosion on an agro-ecosystem level through improved shoot groundcover, and erosional losses of phosphorus are lower than removal of phosphorus by biomass harvest. The wide range of methods and environments used for this thesis research reflect the complexity of roots, soils, and their interactions, and was ideal for understanding mechanisms underlying the sustainability of low-input agro- ecosystems.