Many farms suffer devastating plant damage from toxic levels of boron. Sometimes these excessive levels appear in the specific farm soil, or they are delivered via irrigation water or both, and when they do, farmers are faced with low crop quality and yields.
The mineral boron is a micronutrient commonly found in small amounts in most soils in a variety of compounds—most often sodium borate (borax) and boric acid. Boron is a micronutrient that is critical to proper plant growth because, in addition to calcium, plants require sufficient levels of it to develop cell walls with high structural integrity. Just as people require sufficient calcium to maintain bone density, plants require sufficient levels of calcium and boron.
Boron deficiencies are associated with wilting and rotting of plant leaves and stems, as well as fruits and crops that are stunted or discolored, or which succumb to secondary fungal infections. Growers across the world struggle with naturally occurring boron deficiencies in cropped soil, which has led to boron being one of the most commonly used soil supplements in agriculture.
But some growers—such as those in desert regions and the West Coast’s Coastal Range—face the opposite problem: very high levels of boron in their soil and water.
In areas where soils are well irrigated and boron levels are low to normal, water drains through the soil and runs off, diluting out and carrying away boron and other minerals. The boron levels present in well-drained soils are reflective of the equilibrium which has been reached between the ever-ongoing processes of accumulation delivered from well water in areas with high boron levels, and subsequent leaching. It is because this process tends to result in lower than ideal boron levels that many growers supplement their soils with boron-containing fertilizers.
The reverse is also true for some farmers. In general, areas with naturally high boron levels are relatively rare, yet arid and semi-arid regions are particularly noted for having undesirably large amounts of boron in the soil. This is because, in dryer regions, there isn’t a consistent flow of water to leach boron out of the soil and prevent excessive accumulation.
Instead, water is occasionally deposited—along with dissolved boron and other minerals—which then evaporates directly out of the soil, leaving behind the minerals. Over time, boron levels can become quite high.
Boron accumulation tends to occur alongside salt accumulation, so if you live in a drought-prone area where soils are notably saline, there’s a good likelihood that high levels of boron are also present.
On the western side of North America, the Coastal Range is also known for having soil with elevated levels of boron. This is because much of the rock comprising the mountains was formed in the ocean. Thus, they contain large amounts of marine evaporites, which are mineral accumulations formed through the evaporation of ocean water. (Evaporites also form in arid conditions, which contributes to the previously mentioned high levels of boron found in arid conditions.)
Excessive boron levels are also sometimes found in areas with a history of volcanic activity, as well as in regions where mining has occurred. Areas with soil that has a high clay content are also known to have higher than average boron levels, as clay readily absorbs boron.
Regardless of the cause of boron accumulation, excessive boron in soil—or groundwater—poses a serious challenge for growers.
Excessive boron is toxic, causing a variety of health problems in plants, including damage to roots.
One of the most common symptoms of exposure to excess boron is the yellowing and browning of leaves, sometimes referred to as “leaf burn.” This is particularly evident at the tips and edges of older leaves, which eventually dry out and die. If the issue isn’t remedied, browning and tissue death will spread through affected leaves.
This occurs because boron is carried through plant tissue via a process called “transpiration.” Water is absorbed through the roots and is then drawn up through the plant due to water evaporating from leaf surfaces—creating a sort of vacuum that pulls water up. Because boron can’t evaporate along with water, it essentially piles up at the end of the line—at leaf edges, where there is nowhere else to go. This means that the pattern of plant tissue death actually tells you where in the plant elevated levels of boron are located. Because transpiration patterns in plants vary from species to species, the pattern of tissue discoloration and death can vary.
As boron levels in plant tissues increase, plants affected by boron toxicity experience a reduction in both total leaf area and overall growth.
But not all plants experience this progression of symptoms. In some plants, such as apples, pears, peaches, cherries, almonds, and so on, boron toxicity can lead to a variety of symptoms, such as the premature stunting and death of fruits, as well as stem dieback and degradation and death of bark tissue.
Reducing soil levels of boron requires access to a clean water source. Unfortunately, growers often rely on groundwater that also contains high or toxic levels of boron.
One effective way of reducing boron levels in soils is by leaching the high-boron soil with water that is low or absent or boron. Heavy watering with boron absent water can potentially dilute down the toxic boron levels in the soil. But the problem is that in using the dilution method, growers may only have access to water supply’s that are themselves high in boron levels, and thus only contributing to the already excessive levels of boron in the soil.
Unfortunately, growers have even less recourse when it comes to remedying water sources that are high in boron. Many times standard membrane technology’s (RO’s), are installed with hopes of reducing toxic boron levels. However they only provide a low percentage of reduction leaving boron usually at unacceptable damaging levels. We have many growers in this exact situation contact us, wanting to know what we can do to reduce or eliminate the toxic levels of boron in their water before using it for irrigation.
Watson Well has been very successful in engineering a combination of technologies that reduce boron in water to non-toxic levels, and in many instances completely remove the boron present in irrigation water. Our customers are now able to improve their crops quality and significantly reduce their crop loss.
If you have any questions on how we can help your boron toxicity—or help address other quality issues with your irrigation water, contact Watson Well to learn more.