AN EXPERIMENTAL PROCEDURE FOR OBTAINING INPUT PARAMETERS FOR THE ROOTMAP ROOT SIMULATION PROGRAM FOR PEAS (PISUM-SATIVUM L)

The ''ROOTMAP'' model is designed to provide a realistic three-dimensi onal topological description of the growth of plant root systems. This paper describes and compares different techniques for obtaining ROOTM AP model input parameters from the measured properties of pea (Pisum s ativum L.) root systems grown in aggregated soil at three values of pe netration resistance (0.10, 0.25 and 0.51 MPa corresponding to bulk de nsities of 1.0, 1.2 and 1.4 Mg m(-3) respectively). The elongation rat e of the axis and the branching interval of laterals on the axis decre ased with increasing penetration resistance. The resulting simulation gave a distribution of root contacts on the walls of a cylindrical con tainer that was comparable to that observed. It was concluded that the model can simulate the growth and spatial distribution of the pea axi s and first order laterals but simulation of the number and length of second order laterals is likely to be unreliable since their behaviour did not conform to the assumption of uniform elongation rate. The mod el now needs to be tested and validated under a range of experimental conditions.