Effect of localised phosphorus application on root growth and soil nutrient dynamics in situ – comparison of maize (Zea mays) and faba bean (Vicia faba) at the seedling stage

Background and aims Root morphological response to localised phosphorus (P) application plays a crucial role in P acquisition. However, detailed knowledge of when and where roots respond to P patch (localised P supply) in situ is still lacking. Methods X-ray Computed Tomography (CT) was used to quantify the root response to localised and uniform triple superphosphate supply in maize ( Zea mays ) and faba bean ( Vicia faba ). Soil solution was extracted by micro suction cups. Results On the spatial scale, X-ray CT results showed that maize roots proliferated in the P patch, resulting in higher root length density compared to the uniform P supply. On the temporal scale, the proliferation of maize roots into the patch occurred as early as 11 days after sowing. Faba bean showed no response to the P patch during the experimental period. In soil solution, localised P fertiliser supply not only increased the concentration of P and calcium, elements present in the fertiliser, but also potassium and magnesium. Conclusions Our results indicate a fine-scale time pattern for P concentration in the local site to enhance root proliferation of maize but not faba bean, which suggests an evident difference in root response to local P supply between maize and faba bean at the seedling stage.