Because almond trees do not take up applied nutrients from
the soil until leaves are present to support transpiration
through the leaf system, growers should hold off applying N
fertilizers until leaf-out.
Almond growers who regularly make their first nitrogen applications in February should wait at least a month until leaf-out occurs, according to findings coming out of major research on almond nutrient management funded by the Almond Board and USDA.
That research, led by UC Davis plant scientist Patrick Brown, shows that almond trees do not take up applied nutrients from the soil until leaves are present to support transpiration through the leaf system. This means that growers applying nitrogen before leaf-out, particularly through fertigation, which targets the roots, are potentially wasting money and could be contributing to the risk that applied nitrogen will move off target through leaching, runoff or off-gassing before it can be absorbed by the tree.
Brown’s research, which refines observations made by earlier researchers, demonstrates that mature almond trees rely on stored nitrogen to feed bloom and leaf-out activities rather than taking that nitrogen from the ground. Among other things, the trial
examined how nitrogen accumulates in different parts of the tree at different times of the year, given various rates of applied N. It clearly suggests that nitrogen applied too early prior to leaf-out will be wasted if rain or irrigation moves that N below the root zone.
“Given the high cost of fertilizers and increasing pressure to account for every bit of applied nitrogen, it makes sense for growers to make this small change to their standard practice, which can save money with no risk to crop yield or tree health,” says the Almond Board’s Gabriele Ludwig.