Minimize Boron Leaching

:: Tuesday, June 4, 2019
Rainfall across much of the U.S. has reached record high levels this spring. As the floodwater flows from waterlogged fields into ponds and waterways, it takes precious plant nutrients with it. Many plants are struggling, and unless soil nutrient reserves are replenished, the growth of upcoming crops may be in jeopardy.

When soil loses essential nutrients due to excessive rain, the process is called leaching. Understanding what leaching is, how it affects crops, and how to minimize the damage is important for farmers and agronomists worldwide. Boron leaching in particular can affect overall crop quality and yield. Understanding the causes and solutions will help you create a micronutrient management plan that reduces costs and improves yields.

Impact on crop development

Leaching removes vital nutrients and micronutrients from the soil, causing potential deficiencies in crops. Boron, a water-soluble micronutrient, is especially prone to leaching. Because boron is a neutrally charged ion, it floats in ecosystems until it finds a substance to which it can cling. During periods of heavy rain, boron is flushed out of the soil quickly. If standing water is present in fields for more than 24 hours, the soil can become completely depleted of boron. Most plants also die from lack of oxygen in this same amount of time so replanting is likely.

Erosion is also a concern when leaching occurs in your fields. Organic matter that contains the boron molecules is among the first parts of the soil to float off the field. Since leaching washes away micronutrients that are required for healthy crop growth, crops can’t grow strong root systems to hold the soil in place during future storms.

Crops suffering from boron deficiency display symptoms such as:
  • Impaired root growth
  • Misshapen, thick, brittle, and small leaves
  • Weak or dead growing points
  • Shortened internodes
Unfortunately, by the time your plants exhibit these visible signs, yields will already have been diminished, so the best way to determine whether you need to replenish boron is through testing. Soil testing is a good way to verify how much boron is in the soil, but it can’t tell you if the micronutrient is being absorbed. Tissue analysis, however, will indicate whether or not the plants are actually taking up adequate amounts of boron for proper development. Even if boron was applied earlier in the season, the level should be rechecked frequently to see if supplementation is needed.

A best practice to follow concerning tissue testing is to build data over time by testing according to planting date and heat unit accumulation. Testing every year at the same growth stage and heat unit interval will give the best data to identify trends in boron utilization on your fields.

Soil condition and type can also determine how much leaching is likely to occur. For example, sandy soils exposed to heavy rains or irrigation will leach boron more easily than denser soils. Thus, they’ll require boron supplementation more frequently, unlike silt loam or clay-based soils, which are able to retain more micronutrients.

Not all supplements created equal

No matter your crop or soil type, a slow-release, water-soluble supplement will help you maintain the proper balance of micronutrients during both wet and dry weather. Controlled release boron fertilizers are widely available, but the rate at which they release can vary. The ideal release should be slow enough to protect against leaching and toxicity, but fast enough to supply essential nutrients to plants when needed.

Results from soil experiments have shown that not all boron sources provide the same amount of water-soluble boron. There is a wide disparity between refined granular sodium-only borate products such as Granubor® and granular ulexite, a sodium-calcium borate product. Ulexite mineral consists of sodium-calcium borate which is classified as only partially water soluble, while Granubor is a sodium-only borate classified as 100% water soluble, improving absorption and reducing waste.

Another key difference is how the two types of products are manufactured. Granubor is a refined product, which means the ore is dissolved in water and recrystallized, removing any impurities and creating an extremely pure natural product. It contains no calcium, which can cause boron deficiency in plants, and its unique granulation ensures that it releases just the right quantity of micronutrients at each stage of a plant’s lifecycle.

To determine the proper level and frequency for boron application, check with your local crop consultant, or contact us to speak with a U.S. Borax agronomist.



 soil science

U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 650 customers with more than 1,800 delivery locations globally. We supply around 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles. Learn more about Rio Tinto.

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