3D Mapping of Almond Root Systems: A Groundbreaking Study at UC Davis

In the pursuit of healthier, more resilient almond orchards, California's almond growers have a new ally — cutting-edge research from the University of California, Davis. Led by Professor Astrid Volder from the Department of Plant Sciences, this study, funded by the Almond Board of California, focuses on understanding the root structures of different almond rootstocks using advanced 3D mapping technology. The goal? To optimize orchard management practices and enhance the productivity of almond trees across various soil types.

A Deep Dive into the Roots

At the heart of this research is a 20-year vision to understand how root systems respond to different orchard management practices and how growers can leverage the knowledge to maximize production. The study employs a meticulous process of excavating root systems and utilizing LiDAR technology to create detailed 3D models. By comparing different rootstocks — such as Krymsk® and Nemaguard® — the team aims to uncover how these roots develop and interact with their environment.

"We're essentially trying to see what happens below the soil as the tree grows," explains Volder. "This is crucial because a well-developed root system can significantly impact a tree's overall health and yield."

The Role of Staking and Irrigation

One key aspect of the study examines the impact of staking on new plantings. The findings suggest that allowing young trees some degree of movement is essential for developing a robust root system. "If a tree is staked too rigidly, it tends to grow straight up without putting energy into expanding its roots," Volder notes. "But if you allow some movement, the roots spread more widely and anchor the tree better."

The research also delves into irrigation practices, particularly in the early years of tree growth. Volder’s team has observed that reducing irrigation in spring can encourage deeper root systems, which are better suited to withstand summer drought conditions. This insight is especially valuable for growers facing water scarcity, as it suggests that strategic irrigation could prime trees for survival in dry years.

Comparing Rootstocks: Krymsk® vs. Nemaguard® 

The study's preliminary findings have revealed significant architectural differences between Krymsk® and Nemaguard® rootstocks once trees are mature (> 6 years old). Nemaguard®, which is propagated from seeds, tends to develop an initial taproot with large roots concentrated near the trunk at steep angles, while Krymsk®, which is produced via tissue culture, exhibits a broader, more horizontal oriented root network with many more large lateral roots originating from the trunk. 

"The density of large roots in Krymsk® is estimated to be four to five times greater than in Nemaguard®," says Volder. This difference could have implications for nutrient uptake, tree stability, and ultimately, yield. Root images have also been collected for mature trees grown on Marianna 2624, Lovell, Titan and Brights 5 rootstocks, revealing large differences in root system architecture once trees are mature.

Implications for Orchard Management

The broader goal of this research is to translate these findings into practical recommendations for almond growers. By understanding how different rootstocks interact with specific soil types and management practices such as pruning and irrigation, growers can tailor their approaches to maximize efficiency and productivity.

For instance, the research suggests that growers using Krymsk® rootstocks might consider moving irrigation lines further out from the trunk earlier than they would with Nemaguard®, to accommodate the wider spread of roots. Conversely, during years with limited water availability, delaying irrigation might help encourage deeper root development, particularly in Krymsk® rootstocks.

The Future of Almond Rootstock Research

The UC Davis team plans to continue this groundbreaking work, with future studies aimed at linking root development to young tree growth, and eventually to yield outcomes as much of the mature root system architecture is developed in the first year(s) after planting. The next phase will involve applying different irrigation treatments to six different rootstocks – Nemaguard, Lovell, Titan, Hansen 536, all each as clonal and seed grown, and Krymsk 86 and Mariana 2624 – all grafted with Nonpareil and observing root system development over time in response to water management.

As Volder aptly summarizes, "This research is about moving from basic knowledge to practical applications. By understanding the unique needs of different rootstocks, we can help growers customize their management practices, leading to more efficient use of resources and better overall orchard health."

For California almond growers, this research holds the potential of more resilient orchards, capable of thriving even in challenging conditions. Volder's research will be part of a breakout session at The Almond Conference 2024, December 10-12 at the SAFE Credit Union and Convention Center in Sacramento. Growers can attend the conference for free and learn more about the research into mapping root systems of almond rootstocks. Register now at Almonds.com/Conference.