Let the Plant Tell You

excerpt from the Soil Report Newsletter of Soilmoisture Equipment Corp

Plants may be smarter than we think, as the cover article of Soil Report suggests. Gardeners swear that house plants like to be talked to or prosper with music. Bach's Brandenburg Concerto is said to be a particular floral favorite. Research indicates plants react to a threat of fire or even pruning shears. It is now known a whole forest will put out chemicals to fight certain insects when only one tree is infested. Clearly something is going on with plants.

They will even tell us when they need water--if SEC's Plant Water Status Console is used. At the very least it takes the guesswork out of when to irrigate, an increasingly expensive operation for growers the world over. And the information comes from the plant itself.

The Plant Water Status Console measures the negative pressure or tension with which water is held in the plant, revealing how much water stress the plant and thus the whole crop is under. The soil may look dry, but the plant is doing just fine. Or, the ground may appear moist, but the plant is thirsty, perhaps indicating the presence of a root pathogen.

The principle behind the Plant Water Status Console is simple. If you cut a cross section of a twig or petiole, it reveals a central core called a xylem, through which nutrient-laden water goes up from the roots. Surrounding the xylem is the phloem, consisting mostly of sugars or carbohydrates, which travel down to the roots. Ever notice that when you cut a twig, stalk or limb some fluid may leak out? This is an effort by the plant to heal itself by forming a scab. (Painting the tree where a limb has been lopped does absolutely nothing for the tree and may become a source of infection for it.) The latex coming from the xylem, has important uses--the maple sugar industry, for example. SEC Soil Scientist Richard White offers a more intriguing example, the "Diesel Tree" in the tropics. Its xylem produces a low-grade fuel oil.

The amount of moisture in the xylem provides a way to measure the plant's need for water, as the Plant Water Status Console reveals. As Richard White explains, "A small twig is snipped, trimmed neatly, then inserted into the lid of the pressure cylinder, which is filled with compressed air or nitrogen gas under pressure. A gauge registers the pressure under which water begins to flow up the xylem, revealing whether the plant needs water." The Console is self-contained with its own "gas tank" and easily transported to the field.

The Console is especially useful with certain crops. Cotton, for example. It requires a lot of water, and in the Southwest irrigation is becoming increasingly expensive. Avoiding one or two irrigations a year will easily pay for the cost of the Console, as will better yields when irrigation is found to be needed. Orchardists, especially those growing stone fruits such as peaches, almonds, plums or cherries, are finding the Console valuable. The device is particularly effective with pine trees, allowing ecological studies of natural stands and seedling transplants. The National Park Service is using the equipment in Sequoia National Park to measure the health of those majestic trees.

If you would like to know more about the Plant Water Status Console and how it might aid your operation, please contact your nearest SEC dealer or Soilmoisture Equipment Corp. directly. It may save you money.