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.