Orchard Leaf Tissue Sampling

 

Written By: Kaelyn Lupyrypa, Horticulture Research Assistant and Erika DeBrouwer, Tree Fruit Specialist, OMAFRA

Why Leaf Tissue Sampling is Important

When managing an orchard getting information on the health and wellbeing of your trees is a crucial management tool. One way to better understand what is happening in your orchard for the current season to do a leaf tissue analysis. A complete analysis will give you information on the amount of essential micro and macro nutrients in your trees including nitrogen, potassium, phosphorus, calcium, magnesium, and copper.

Timing of Leaf Tissue Sampling

It is important to take leaf tissue samples at the right time to get an accurate reading of the nutrients within the leaves. It is recommended that mid to late July is the ideal time to take a leaf tissue sample. The reason for this is that at this stage the nutrients in the leaves are becoming more stable and immobile due to the terminal bud set that is happening around now. Terminal bud set is the end of vegetative growth, so nutrients are sent primarily into growing fruit and not leaves or shoots.

Humidity Impact on Tree Health

It is worth noting how the environment and weather may impact plant growth and nutrient uptake as well. As fruit trees grow, they use their roots to take up nutrients from the soil. To accomplish this the plants must transpire, a process by which water is pulled from the roots into the leaves and further into the atmosphere via the xylem and phloem in the trees. All nutrients utilize the phloem and/or xylem for transport of nutrients to fruit, leaves and shoots. This is significant as the humidity in the air and the water in the ground both have a role in the overall movement of nutrients throughout the plant. Too little humidity in the air and the plants have less force acting on them to pull water and nutrients upward. Opposingly, too much humidity means that plants cannot rid themselves of the water vapour, stopping the evaporation process and ultimately affecting their growth.

This year in Ontario the season has been very dry, there has been little to no rain across most of the province. As a result of the lack of moisture in the atmosphere the trees are unable to move nutrients effectively through their systems. Most orchards have some sort of irrigation which is important to give water to the roots of the trees. The dry and hot temperatures will cause the water to evaporate from the ground as well as be pulled more quickly through the systems in the trees themselves.

Mobility of Nutrients in Leaves

The mobility of nutrients will impact the ease at which the plant has access to their resources. Below is Table 2-4 from the Ontario Soil Fertility Handbook, showing mobile and immobile nutrients within the plant and within the soil.

More specifically in trees, nutrient uptake changes throughout the season as the trees go through different processes (i.e. maturing fruit, dormancy etc.), most notably this change has been seen in ‘Honeycrisp’ apple trees. Bitter pit is a very common disorder and has now been linked to the decrease in xylem function and vascular bundle development as the season progresses, leading to a decrease in calcium uptake in the fruit.

 

Best Practices in Sample Collection

To achieve accurate results in your leaf tissue analysis there are some best practices that are recommended.

• Make sure to sample your leaves at the same time every year, ideally from the same trees.
  • Aim to sample 10 leaves from each tree, taking samples from 10 trees that are representative of your block (100 leaves total).
  • You could also separate old leaves and new leaves to get a better understanding of which nutrients are moving to new growth, this is to give you a better understanding of nutrient distribution throughout the tree.
• Ensure that you collect your samples into properly labeled paper bags so that nothing gets mixed up at home or at the lab.
• Avoid damaged or dying leaves from pests, they may lead to false nutrient deficiency information.
  • However, if you suspect a different problem, take a sample from the area of concern and label it appropriately.
• Avoid contaminating the samples, keep them free of dust, soils, brass, copper, or galvanized metals.

Once all of blocks have been sampled it is best to get the samples to a testing facility as quickly as possible. A list of registered testing facilities can be found at this link: list of registered testing facility link.

Results and Outcomes of Leaf Tissue Sampling

As a result of proper leaf tissue testing, soil management and scouting, you will be in the best place to make management decisions about your orchard. This could be economically significant when deciding what and when to apply pesticides and fertilizers. When these practices are performed regularly it will help you maintain a record of events in your orchard and allow you to assess your nutrient program more effectively. Overall, leaf sampling will contribute to efficient management practices, the ability to plan ahead, and allow you pivot your program while gaining more experience.

Resources

Leaf tissue sampling is an important tool that can give you lots of information about your current years crop, however, it will not tell you everything and should not be the only tool in your toolbox. Other practices that should be done in conjunction with leaf tissue testing include soil testing, visual scouting for deficiencies, pests, and pathogens, as well as staying up to date on the latest conditions events within if your area. If you have any questions about what is going on in your orchard, please talk to an expert to get a second opinion. 

There are numerous other publication that can help you in this process. Check out these other ONFruit blog posts for further details.

Tissue Sampling for Tender Fruit (Peaches, Nectarines, Cherries and Pears)

Why You Need a Tissue, a Leaf Tissue Analysis

Leaf Tissue Sampling and Nutrient Analysis

Nutrient Management (cornell.edu)

Griffith, C., & Einhorn, Todd C. 2023. The effect of plant growth regulators on xylem differentiation, water and nutrient transport, and bitter pit susceptibility of apple. Scientia Horticulturae. 310: 111709. https://doi.org/10.1016/j.scienta.2022.111709

You can also reference the nutrient sufficiency ranges for apples in Table 18 of the OMAFRA Soil Management, Fertilizer Use, Crop Nutrition, and Cover Crops for Fruit Production webpage.