Mathematical modeling of the indole-3-butyric acid applications on rooting of northern highbush blueberry (Vaccinium corymbosum L.) softwood-cuttings

The objective of the present study is to develop a mathematical model to predict the effect of indole-3-butyric acid (IBA) on mean rooting (%) and mean root growth of northern highbush blueberry cultivars (Vaccinium corymbosum L.). The best estimating equations for the rooting (%) and root growth are formulized as: RG = (5.672183) + [0.002851 × (IBA)] − [2.0E⁻⁶ × (IBA)2] + (−0.27211 × Cv.) and R = (82.00649) + [0.030801 × (IBA)] − [2,4E⁻⁵ × (IBA)2] − [2.36218 × (Cv.)] where RG is root growth, R is rooting, IBA is indole-3-butyric acid (ppm) and Cv. is cultivar. Cultivars are Ivanhoe [1], Jersey [2], Rekord [3], Northland [4], Berkeley [5] and Bluejay [6]. The numbers given in square brackets represent the blueberry cultivars for the equations. Multiple regression analysis was carried out until the least sum of squares (R2) was obtained. R ² value 0.90 for rooting and 0.95 for root growth. Standard errors were found to be significant at the p < 0.001 level. The actual rooting differed to the blueberry cultivars and it was between 57.76 and 83.23% while estimated rooting percentage calculated by the produced mathematical model was between 59.04 and 83.80%.