Root competition resulting from spatial variation in nutrient distribution elicits decreasing maize yield at high planting density

Background and aims: Nutrient spatial heterogeneity occurs ubiquitously in soil, but its impact on plant growth and competition throughout the whole growth cycle remains unclear. We assessed the effects of different nutrient supply patterns and planting density on maize (Zea mays L.) growth rate, root competitive intensity and grain yield. Methods: Maize was grown with homogeneous or heterogeneous nutrient (ammonium and phosphorus) supplies under low and high planting densities in field conditions. Results: Nutrient patches promoted root proliferation and plant growth rate in the short term; however, with nutrient depletion and roots still proliferating in the patch zone, the plant growth rate was surpassed by that of plants in the homogeneous ammonium and phosphorus treatments with time. Consequently, final shoot biomass showed no difference between nutrient supply patterns at a given planting density. Furthermore, the temporal decoupling between root growth and soil nutrient availability induced greater competitive intensity in the heterogeneous than homogeneous treatments between the vegetative stage and anthesis. Under these conditions, heterogeneous ammonium and phosphorus supply markedly decreased grain yield at high planting density. Conclusions: Our results demonstrate that heterogeneous nutrient supply-induced root competition at high planting density modulates the dynamics of plant development and decreases final productivity.