Effects of amendments, soil additives, and irrigation on tree survival and growth

"During the first and second year after transplanting into good soil, there was no apparent benefit from adding amendments to the backfill soil around newly planted 5 cm (2 in.) caliper live oaks (Quercus virginiana Mill.), nor was there a benefit from applying liquid additives over the root ball.

Top growth in the first 2 years after planting was not enhanced on trees with amendments added to the backfill soil compared to the control. In the first growing season following planting, trees irrigated frequently (3 times per week for 38 weeks) grew about twice as fast as those irrigated only during the first 3 months after planting. There was no lingering effect of irrigation on top growth rates once irrigation ceased. Trunk diameter and height growth on trees treated with paclobutrazol (Profile 2SC) was less than on trees in all other treatments due to the growth-regulating effect of paclobutrazol. Root growth in the backfill soil was not affected by soil amendments added to the backfill soil at planting and was not affected by irrigation after planting in 5 of the 7 treatments." [Abstract]