The effect of soil volume on the growth of roots and canopy of Opuntia ficus-indica

The influence of soil volume on root development and canopy growth rates of cactus pear (Opuntia ficus-indica) was studied at Palermo University, Italy, in 2014-2016. In November 2014, 60 1-year-old O. ficus-indica cladodes were planted in pots containing five different soil volumes, 50, 33, 18, 9 or 5 L, in a complete randomized design with three replications. Root dry mass, total number of cladodes and canopy dry mass were measured after 6, 12, 18 and 24 months. The results revealed a significant effect of soil volume and sampling time and their interaction (P<0.01) on root dry mass, total number of cladodes and canopy dry mass. Root dry mass ranged between 23 and 206 g, with the highest value for plants grown in 50 L soil volume, sampled after 24 months of planting. The highest number of cladodes was produced by the plants raised in the highest soil volume (50 L) after 24 months of planting and the lowest number was in the lowest soil volume (5 L). A linear increase in canopy dry mass was observed with respect to increased soil volume. Increased soil volume had a significant and positive effect on the roots:canopy dry mass ratio. It is concluded that the restriction of soil availability in O. ficus-indica resulted in major growth limitation for root and canopy.