An Algorithm for Predicting Crown Root Axes of Annual Grasses

Root formation by any plant determines its success or failure for creating seed for its next generation. Those interested in managing plants for optimum harvestable yield require information about effects of their practices on root growth. Crop growth models can be convenient summarizations of such knowledge. Models of plants and environment currently describe the plant shoot more completely than they describe the root. The morphologically based root formation algorithm presented in this paper provides opportunities for improving both the description of root formation and the response of roots to their environment. The equation relating shoot and root development will be convenient for crop modeling. It can also be used as a standard for comparison of field rooting observations, as environmental effects on rooting are quantified. The equation predicts the number of root axes on a plant from the plant phyllochron interval, the timing of nodal root appearance relative to leaf appearance, and the effect of environmental stresses that reduce tillering. A comparison of algorithm predictions with observed root formation by wheat ( Triticum aestivum L.) from a warm, dry seedbed revealed that fewer roots were formed during the early tillering stage of development than predicted for unstressed plants. Correction for observed tillering did not reduce predicted root numbers to those observed. Observed early‐season root observations were matched by using one‐half of possible tillering as a stress correction.