Temporal and spatial dynamics in root length density of field-grown maize and NPK in the soil profile

There have been many studies to examine macronutrient depletion in the rhizosphere under controlled conditions. However, most cereal plants are grown in the field, which requires thorough investigation for nutrient use efficiency and crop yield. A two-year field study was conducted to investigate temporal dynamics of available nitrogen (N), phosphorous (P), and potassium (K) in the rhizosphere and bulk soil of maize, and changes in root length density (RLD) and soil NPK concentrations in 0–60 cm soil profile. The rhizospheric soil was collected by shaking the tightly attached soil after carefully removing the loosely held soil from the roots. During the vegetative growth stage, the RLD changed corresponding to shoot demand for nutrients. Maize plants accumulated NPK asynchronously during the whole growth period. More than 92% of total K was taken up during the vegetative growth stage, while approximately 65% of N and 55% of P were absorbed at the same time. There was significant N depletion in maize rhizosphere along soil profiles at each harvest; however, P or K depletion in maize rhizosphere could not be determined. Consistent with the obvious net K loss from maize plants in late reproductive growth stage, there was a significant K increase in the rhizosphere. These results indicated differential utilization strategies and accumulation patterns of mineral nutrients such as N, P, and K nutrients in the plant–soil rhizospheric system, laying a theoretical base for optimized fertilization practice.

► We examined whether NPK depletion occurred in the rhizosphere of field grown maize. ► We compared the temporal dynamics of available NPK in maize rhizosphere and bulk soil. ► Maize root length density changed corresponding to shoot demand for nutrients. ► Maize plants accumulated NPK asynchronously during the whole growth period. ► Differing from N depletion, P or K depletion in maize rhizosphere was not measured.