Maize growth and nutrient uptake as affected by root zone volume

Background. In many agricultural situations root zone volume is restricted by adverse soil conditions. Many papers have reported that a restriction in volume of soil available to plants reduces shoot and root growth, but the precise mechanism by which root confinement causes reduction of shoot growth has not been identified. This study was conducted to examine the effect of root zone volume on yield, shoot and root growth, and N and P uptake in maize. Methods. Two maize hybrids were grown in containers at four root zone volumes. Samples were taken at collar of 12th leaf visible and at silking stages. Dry weight, N and P concentrations and contents of leaves, stems, ears, and root were measured. Grain yield and yield components were measured at physiological maturity. From emergence to 12th leaf and from this stage to silking SDWI, N and P SAR were calculated. Results. Restricted root zone volume reduced shoot and root growth at silking, while it reduced only shoot growth at the vegetative stage. In both stages, restricted root zone volume decreased N concentration and N and P content, reduced recovery of both nutrients, decreased N SAR, and did not affect P SAR. Grain yield increased with the increase of root zone volume. Conclusions. The impediment to root deepening did not affect root growth rate but resulted in a high concentration of roots in the surface soil layer; because of excessive root density a high percentage of soil pores in the upper layer were filled with mass roots and root growth rate and nitrogen uptake efficiency were consequently reduced.