While water efficiency necessarily occupies much of a grower’s attention, proper management of an almond or walnut orchard within the first five years after planting isn’t just about irrigation. Proper pruning, weed control, and pest management will help optimize tree health, growth, and yield over the life of the orchard, University of California researchers say.

The UC Cooperative Extension’s 33-page “Young Orchard Handbook” gives detailed advice on fertilizers, pruning, and weed and pest management, as well as irrigation. Released in March, it’s meant as an ‘introductory resource for understanding management steps to take in young orchards,” notes the team led by Katherine Jarvis-Shean, UCCE farm advisor for Sacramento, Solano, and Yolo counties. Other team members were farm advisors Allan Fulton, Dani Lightle, and David Doll; almond and walnut specialist Bruce Lampinen; weed specialist Brad Hanson; wildlife specialist Roger Baldwin; and intern Brianna Vinsonhaler.

They point out that the handbook “is by no means exhaustive,” but they provide additional resources for growers to consult at the end of each chapter.

Here are some of the highlights.

FERTILIZING YOUNG ORCHARDS

Jarvis-Shean and Doll note that trees need nutrients to support the growth of vegetative tissue, such as trunk, roots, branches, and leaves, and reproductive tissue, such as nuts and hulls. In the first few years, trees are generally growing more vegetative tissue than reproductive tissue. Nutrient deficiency can mean that the growth potential is not met, leading to smaller, stunted trees, with weaker growth. However, too much fertilizer can cause toxicity and kill tender tissues, they warn. It’s more common that growers apply fertilizer rates that lead to excessive vigor, which causes lanky growth and too much space between buds, interfering with future canopy branching structure and crop load bearing capacity.

In nutrient management, the key is to provide what is needed by the tree, at the right time, without negatively impacting growth or canopy structure. 

TRAINING AND PRUNING

The primary goal of training and pruning is to have a tree that will produce optimum yields and “facilitate cultural practices,” Jarvis-Shean and Lampinen advise. In the first years, the tree is trained to a structure that will support future crop weight and allow for cultural practices, while minimizing cuts which could decrease early yields.

After the structure has been established, pruning primarily helps cultural practices like spraying and harvesting, and removes dead and diseased wood. Numerous long-term trials have shown minimally pruned trees yield as well or better than heavily pruned trees.

WEED MANAGEMENT

As is the case with vineyards, weeds in young orchards compete with trees for orchard resources — sunlight, water, and nutrients — which can set back growth and yield, Jarvis-Shean and Hanson point out. Weeds can also provide cover for vertebrate pests that can damage tree trunks or irrigation lines.

The first step in effective weed control is correctly identifying the weed that’s creating a problem and selecting registered herbicides that will neutralize it. UC-Davis has a weed-identification website (weedid.wisc.edu/ca/weedid.php). As tree crops aren’t resistant to herbicides, it’s best to place herbicides below foliage and green tissues, but above the root zone, they advise

Other segments of the handbook deal with irrigation, managing vertebrates and other pests, and diseases. To read the full handbook online, visit http://ccfruitandnuts.ucanr.edu/files/238596.pdf