EVALUATION IN-FIELD CONDITIONS OF A 3-DIMENSIONAL ARCHITECTURAL MODELOF THE MAIZE ROOT-SYSTEM - COMPARISON OF SIMULATED AND OBSERVED HORIZONTAL ROOT MAPS

Most existing water and nutrient uptake models are based on the assump tion that roots are evenly distributed in the soil volume. This assump tion is not realistic for field conditions, and significantly alters w ater or nutrient uptake calculations. Therefore, development of models of root system growth that account for the spatial distribution of ro ots is necessary. The objective of this work was to test a three dimen sional architectural model of the maize root system by comparing simul ated horizontal root maps with observed root maps obtained from the fi eld. The model was built using the current knowledge on maize root sys tem morphogenesis and parameters obtained under field conditions. Simu lated root maps (0.45 x 0.75 m) of horizontal cross sections at 3 dept hs and 3 dates were obtained by using the model for a plant population . Actual root maps were obtained in a deep, barrier-free clay-loamy so il by digging pits, preparing selected horizontal planes and recording root contacts on plastic sheets. Results showed that both the number of cross-sections of axile roots, and their spatial distribution chara cterized with the R-index value of Clark and Evans (1954), were correc tly accounted for by the model at all dates and depths. The number of cross-sections of laterals was also correctly predicted. However, late rals were more clustered around axile roots on simulated root maps tha n on observed root maps. Although slight discrepancies appeared betwee n simulated and observed root maps in this respect, it was concluded t hat the model correctly accounted for the general colonization pattern of the soil volume by roots under a maize crop.