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Boron and Nutrient Cycling

:: Thursday, October 22, 2020 :: Posted By Wendall Boehlje
Fourth and final in the series Unlocking Plant Root Potential: A Conversation with Dr. James White
As we wrap up the four-part series with Dr. James White, I wanted to circle the wagons and come back to boron and nutrient cycling to discuss how we can apply our learnings from Dr. White to boron deficiency and management strategies.

We know that boron deficiency is among the most widespread of all micronutrient deficiencies, and affects nearly all major crops grown around the world. We have also known, for some time, that soils play a major role in determining the plant availability of boron. So, how can we leverage what we have learned about the Rhizophagy Cycle and a plant’s ability to “farm” its own beneficial microbes?

Boron mobility

Among the drivers of boron availability to plants within a soil profile, these factors hold the strongest influence:
  1. Soil texture
  2. Soil pH
  3. Organic matter
  4. Soil tillage
  5. Drought conditions
  6. Microbial activity
And, if we look at that list, we can easily distinguish the correlation between the first five drivers and soil microbial activity to conclude that managing microbial populations can, at least to some extent, influence boron availability and nutrient cycling within the soil microbiome.

Improving soil condition to promote soil microbiome

Soil texture is something that cannot be changed by management practices. However, one thing that can be improved through microbial activity in soil is structure through increased soil aggregate stability.

Soil structure can be fostered through the management of crop residue. By carefully managing the balance of carbon:nitrogen ratio through crop rotation and residue management, a grower can maintain a no-till production system while seeing the residue-nutrient breakdown benefits typically seen with tillage. Balancing carbon:nitrogen ratios for a specific production plan also helps to maximize fertilizer inputs by controlling the nutrient cycling process. Corn residue has a higher carbon:nitrogen ratio than soybean which means corn residue will take longer to decompose and cycle.

Finally, the maintenance of the Rhizophagy Cycle—keeping the soil’s microbial farmers (the roots)—farming as much of the calendar year as possible reinforces the ability of a soil’s microbiome to withstand environmental stressors, such as excess rainfall or drought.

Following this process does three things for nutrient cycling:
  1. Increases organic matter, the natural storehouse of boron and many other micro and macronutrients. Organic matter complexes with boron to remove it from soil solution when levels are too high after fertilization. Organic matter also decomposes to supply growing crops with boron as the micronutrient is depleted by crop uptake or other loss mechanisms.
  1. Attracts the microbial populations that cycle nutrients and feed the growing plant.
  1. As microbes decompose plant residue, they produce organic substances that work as cement agents to creates soil aggregates that enhance soil structure and resilience. Improved soil structure and aeration are condition that then benefit soil microbe activity.

Optimizing nutrient cycling

One of the key learnings from our conversations with Dr. White is: The better we understand the chemical, physical, and biological interactions within the soil microbiome and their impact on specific crop performance, the more power we have in leveraging soil processes to support our commercial fertilizer applications.

What we knew, prior to the discussion, is how important adequate boron is to root development. Boron deficiency dramatically inhibits root elongation, with deformed leaves and fruits due to impaired cell division in the meristematic region, whereas adequate boron supply promotes advantageous root development (Fareeha Shireen, 2018).

Another key-learning from Dr. White is the importance of healthy root function and root hairs to nutrient cycling via the Rhizophagy Cycle.

Fertilizer management

Part of input management is knowing and understanding the relative boron needs for every crop in a crop rotation plan, including cover crops, if they are being utilized. This understanding allows you to better pair natural and commercial fertilization to apply the boron fertilizer that provides the nutrition both microbes and plants need, when they need it. Since this science is still emerging, there is some speculation as to who is being fed and at what interval: Microbes or plants.

This is why having the knowledge of which products are available to solve the specific boron needs of your crop and soil is important.

Granubor® is a water-soluble solution to boron deficiency with gradual release profile that provides season-long availability. The product blends perfectly and is of the correct hardness, which makes it ideal for application with bulk blenders. The particle size, density, and hardness also help to ensure uniform distribution in both the blend and field.

Solubor® is the right choice when boron is needed immediately and is the best option for foliar application. As the name suggests, Solubor dissolves readily in water to achieve maximum dispersion. A timely application of Solubor makes a big difference, almost immediately, in the nutrient cycling ability of a deficient crop. The product is also very economical—it can be less than half the cost of solvent-based liquid products, per pound of boron.

Fertibor® is an immediate-release granular product applied as a solid, liquid, or suspension. Because Fertibor is a high quality fine crystalline product, it’s an excellent source of boron for suspension fertilizers and for manufacturing ammoniated or granulated fertilizers and micronutrient mixes.

We’ve covered a lot of information in this four-part series, some new and some review. Therefore, in closing, I want to share my email address and that I am always excited to answer questions…and talk about boron. If you would like to learn more about any of the solutions listed above, or have questions about any of the information covered in this series, send me an email at: wendall.boehlje@riotinto.com and I’ll be in touch!

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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 500 customers with more than 1,700 delivery locations globally. We supply 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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