Young pecan trees require two key ingredients for establishment; 1) water and 2) elimination of weed competition. There is no published data on required irrigation amounts for young pecan trees that I have been able to find. So, we began a study in 2014 to determine this for trees grown under Southeastern U.S. conditions. Looking at trees in the year of planting (1st year trees), we used microsprinklers that supplied either 6.7 gallons per hour (gph) or 14.3 gallons per hour (gph) and compared these with non-irrigated trees. Trees were irrigated 3 times per week (M,W, and F) at 4 hours per application. Preliminary results show that young pecan trees respond to more water than I expected. Trees receiving 80 gallons per week had significantly more growth than non-irrigated trees. But, trees receiving 172 gallons per week had even more growth than those receiving 80 gallons per week.
Many people try to water young trees by hauling water to them once a week. While this is better than nothing, and will keep the tree alive, the trees require more water for the best results on most soils in our area. While 80 gallons per week improved growth over non-irrigated trees, it appears that young pecan trees require as much as 172 gallons per week for optimal growth on a loamy sand soil. Heavier clay soils may not require quite this much, while deep sandy soils may require even a little more.