Summer Irrigation Management in Young Trees

By Travis Goldman

Summer irrigation practices are a huge factor in the success of establishing a solid foundation for a new orchard.

With how busy our summers get, we have to make sure that even the young trees fit into the schedule. Just like a producing orchard, we need to minimize downtime and maintain available water throughout the existing and expanding root zone. By properly monitoring our root zone, we can improve timing and reduce stress on these developing trees.

Finding the time to irrigate our younger trees can seem like a ton of work, but it is manageable. The simplest way (but not necessarily the best approach) that I’ve seen water applied to younger trees, is to irrigate once a week with a longer-than-needed shot of water. By applying more than is required by the crop, the trees might be able to access that water for an additional week depending on the weather.

This approach might “work” for managers, but in reality it isn’t working for the trees. In this double line drip almond orchard, for example, we can see that 24 hours works to rehydrate the root zone – but at the cost of leaching for more than 12 hours.

This additional water creates a less aerobic soil condition that slows down the metabolic rate of the tree and the development of roots.

In this orchard, we can identify less root pull one to two days post irrigation than in days three through six. By cutting our irrigations down to 12 hours in this block, we can reduce downtime and leaching. A better practice for this orchard would be to irrigate each set for 12 hours every five to six days. As the calendar moves into July and August, this block will require more water and irrigations every four to five days for 12 to 14 hours.

A more traditional form of stress that everyone is aware of is from being too dry. In this orchard, our irrigation duration is spot on for this soil type but there is just too much time before the next irrigation. These trees face a start and stop of growth because of a lack of water. By Day 3, the canopy begins to lose turgor pressure and leaf curl occurs.

By looking more into these trees, the prolonged stress has created shorter internodes in the younger growth.

To improve both root and canopy growth, we can apply water every three days for six hours. As the trees develop into later summer, we will begin to see more root pull from all three monitored depths and more water will need to be applied to rehydrate the soil.

With production in full swing, some orchards can go overlooked for higher priority blocks. Something as simple as missing 10 days without water can dry up your entire soil profile.

In this case, reapplying the missed 12 hours on July 1 will not fix the issue. Soil rehydration takes time, and high tension hydrophobic conditions are not easy to remedy.

To rebuild available water within the root zone, we will have to apply multiple irrigation sets to work around infiltration issues. With almost 22 hours of water, this block began to have pooling and runoff issues. Due to hydrophobic conditions, it took two days for water to percolate down to 12”. Additional puddling took three days post irrigation to either infiltrate the soil or evaporate off. Twenty hours of water was ordered for this block on July 14, to continue chipping away at rehydrating the soil. An additional 12 hours was applied five days later to meet the rehydration calculator.

Summer irrigations for young almond trees should be as important as your production blocks. By minimize downtime and maintain available water throughout the root profile, we can reduce crop stress.

This reduction in stress will improve root and canopy production for healthier trees. In my irrigation schedules, I am consistently looking at root response and adjusting irrigations to benefit the crop and work around pumping capacities.

Sometimes irrigations do have to be pushed off, but by adjusting runtimes we can counteract these delays. For more questions on irrigation scheduling please contact your local Hortau Irrigation Advisor.

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