Maize Root Distribution between Phosphorus‐Fertilized and Unfertilized Soil

Abstract

AbstractPlacement of P in a fraction of the soil volume stimulates root growth in the P‐fertilized soil. Previous research on the degree of root proliferation as related to the proportion of soil fertilized with P was conducted with soils containing similar low levels of initial resin‐exchangeable P, Csi, and hence did not evaluate the influence of Csi on the degree of root proliferation in a P‐fertilized fraction of the soil. These measurements were made as part of research to determine the fractional volume of soil to fertilize with P to maximize P uptake. The objective of this research was to investigate the influence of initial soil Csi value and rate of P added on root distribution between P‐fertilized and unfertilized soil when the P‐fertilized volume is constant. Pot experiments were conducted in a controlled‐climate facility where maize (Zea mays L.) was grown on three soils varying in Csi levels and with three rates of applied P, from 50 to 300 mg kg−1, added to 0.20 of the volume of each soil. Root density, cm cm−3, in the P‐fertilized soil volume, RDF, and a comparable 0.20 volume of unfertilized soil, RDU, was measured and compared with Csi in the P‐fertilized soil, CsiF, and in the unfertilized soil, CsiU. There was a curvilinear relation between CsiF/CsiU and RDF/ROU that was described by the equation y = 1.20 + 2.74 log x (r2 = 0.97), where y is RDF/RDU and x is CsiF/CsiU. Hence, as soil Csi level increased, RDF/RDU decreased, and as rate of P applied increased, RDF/RDU increased. The relation between CsiF/CsiU and RDF/RDU can be used to predict root growth rates to use in the fertilized and unfertilized soil when using a mechanistic nutrient‐uptake model to calculate the effect of P placement on P uptake.