Irrigation of Chestnut Trees

Chestnut trees are drought tolerant. If you are not dependent on the size of the chestnut harvest then irrigating chestnut trees could be more harmful to the chestnut trees than helping. If chestnut trees get their roots saturated with water when they are actively growing there is a good chance the tree(s) could die. Only water chestnut trees if the leaves are looking like they are sad and limp.

Water is one of the most important components of the soil in the chestnut orchard. Soil nutrients are carried to the chestnut tree root system through soil moisture. When there is sufficient water in the soil, water forms a microscopic layer over the soil particles. When present, this microscopic layer of water, aids in the interaction of the soil particles with each other. In a simple way, the water helps the soil come alive by filling the gaps between particles allowing them to interact with each other. When the soil particles can interact they cause each other to change a little bit. As these changes take place nutrients are released into the microscopic layer of water. As the nutrients enter the water the chestnut tree roots uptake of water will bring the nutrients into the tree.

The challenge then is to keep the amount of water in the soil in a range that best benefits the chestnut trees. Soil moisture is measured in percentage. When evaluating soil moisture content there are 3 important parts to the evaluation. Most important is the soil type. Fine sandy soils have a very low capacity for holding water. Clay soils have the highest capacity for storing water. The water capacity of the soil if often described as inches of available water per foot of soil. The higher the water capacity of a soil the more water it takes to rehydrate. The next part of the evaluation is the wilt point of the soil. This is where there is still water in the soil but none of it is available to the plant roots. The final part is of the evaluation is determining if the water in the soil is in what is called "readily available water" range. The goal with irrigation is to always keep the soil water in the readily available water range. Once the soil water goes above the 100 percent available water is wasted, becomes run off and possible cause the soil to become saturated. Water saturated soils kills trees. The only way to know if the water content of the soil is in the readily available range is to measure it.

Measuring water in the soil can be as simple as taking a handful of soil and feeling it. It could also be simply weighing the soil sample, drying the soil, weighing it again and then calculating the percent moisture. There are meters for measuring soil moisture that are either permanently installed in the ground or are inserted at the time the measurement is taken. For help with measuring soil moisture content contact your local extension agent. They know the soils in your area the best and can help determine the soil moisture capacity.

As the soil moisture is depleted, water will be required once the moisture drops below the readily available range. Determining how much water is required is simple if you know the soil water capacity and the current soil moisture readings. Watering simply refills the spaces between the soil particles. Available water in the soil can be expressed in inches of water. Fine and very fine soils including clays have a moisture available of 1.6 - 2.5 inches of water per foot. Medium soils described as silt loam, clay loam, and sandy loam have a range of 1.4 - 2.4 inches of water per foot of soil. Moderately coarse soils, those soils having larger soil particles, have a range of 1.0 to 1.6 inches of water per foot of soil. If the soil moisture measurement of available soil moisture indicated the soil to have 50% of the moisture depleted then the amount of water needed to bring it back up to 100% available would be half the total soil capacity. For example, a medium soil with an available moisture capacity of 2 inches with half of this depleted would require 1 inch of water to refill the soil.

There are many methods of irrigating chestnut trees. Please contact your local extension agent for guidance. There are a few tips that can help avoid trouble when considering irrigating chestnut trees. When it comes to applying water from overhead, leave this to the clouds. Overhead sprinklers damage the leaves of the trees to much. Whenever you do irrigate measure the amount of water applied. You can do this using a bucket and putting a drip emitter in it or if using sprinklers place the bucket near a tree where the water is applied. Check the bucket every 1/2 hour or so to see if the amount of water applied is what you expected or needed. If you have the resources to place a timer on the irrigation system this can help prevent "I forgot to turn off the water" failures.

As a final word about irrigation, water travels at different speeds through the soil. The more compact the soil the slower the water moves. Try to set your application rate of water equal to or less than the rate the soil can accept water. This is the one area where the most water is wasted. When checking the orchard while water is being applied, any puddling, running water over the surface, or saturated soil even if it is only in the top inch or two of soil, you are applying to much water to fast. Slow down the application rate of the water. Most sprinklers have changeable nozzles so the volume of water passing through can be changed.