The Role of Boron: Much More Than a Synergist

avocado-flowerAmerican consultant, Gary Zimmer, coined the term “Calcium the trucker of all minerals and boron the steering wheel” and he correctly highlighted the critically important, synergistic relationship between these two minerals. It is a simple fact that you will be disappointed in your lime response if your soils are boron deficient because calcium does not provide its many benefits in the absence of boron. During a recent trip to New Zealand I was speaking with a dairy farmer who had made a considerable investment in lime but had seen very few benefits from the exercise. Upon further investigation I found that his soil tests revealed a massive boron deficiency! In fact, he had just 0.1 ppm of boron in his soils when he required a minimum of 1 ppm. He had created this deficiency through burning out his organic matter reserves with large applications of urea and then leaching boron with centre pivot irrigation. Organic matter is the boron storehouse as it is the only component of the soil that has the positively charged sites to attract and retain this negatively charged trace mineral (anion). As your organic matter declines so does your boron, as it is the most leachable of all trace elements. However this dairy farmer’s boron neglect cost him more than a poor lime response. There was virtually no clover on his entire property because legumes are boron-hungry and will struggle when boron drops to these levels. The lack of clover was also related to urea abuse as legumes never thrive in high N situations. When most people think of legumes they think of nitrogen fixation and the associated reduced requirement for applied N. However, legumes offer more than this. Legumes constantly release organic acids which are invaluable in solubilising locked-up phosphorus (over 70% of applied phosphate becomes insoluble) and they also make calcium more bio-available which is beneficial to both soil organisms and plants. So you get nitrogen, calcium and phosphorus from legumes and you don’t get a good legume to grass ratio without boron. These calcium and legume links should offer enough motivation for you to manage boron nutrition but this highly leachable trace element provides several other benefits.

Boron and Biology

Photosynthesis is the most important process on the planet because this is where we get our food. In an almost miraculous process, the plant combines sunlight, water and carbon dioxide to produce the glucose building blocks that are the basis of carbon chemistry. The grower’s chief role is to manage chlorophyll, the green pigment that houses the sugar factories. If there are pale colours, stripes or blotches in the leaf then you failed as a chlorophyll manager and will pay the price in terms of yield or increased pest pressure. The plant translocates 50% of all of the glucose it produces down to the roots each night, and 60% of this is squirted out into the root zone (the rhizosphere) to feed the hoards of microorganisms surrounding the roots. In the most classic example of the universal law, “give and you shall receive”, the plant is rewarded many fold for its glucose gift. In return for their daily feed, the soil microbes fix nitrogen from the atmosphere, solubilise locked-up phosphorus, recycle minerals from crop residues, remove toxins, produce plant growth stimulants and protect the plant from pathogens. What has this mutually beneficial deal got to do with boron? Well, quite a lot as it happens. There is a little trapdoor in each chloroplast which opens just before dusk to allow the glucose, intended for the roots, to flow freely from the factory. Boron governs the opening of this trapdoor. If your plants are boron deficient the glucose stays trapped in the chloroplast and the beneficial bugs, who deliver all nutrients to the plant, miss out on their daily tucker. In this situation a foliar spray of $3 worth of soluble boron becomes one of the best cost-to-benefit investments you will ever make because the whole give and take system falls flat on its face without boron. A refractometer is an invaluable tool for early detection of a boron deficit. Brix levels in the leaf should always be lower in the morning, following translocation of half of the sugars down to the roots overnight. If levels have not changed overnight, then you have detected a boron deficit and should correct it as a matter of urgency.

Flowering and Fruit Formation

It is my firm belief that there is no crop that will not benefit from a foliar spray of boron prior to flowering (except in very rare cases of boron toxicity in the soil). We like to see luxury levels of boron in the leaf tissue but this is rarely achieved. The boron requirement is much higher for reproduction than for vegetative growth as boron increases flower production and retention, pollen tube elongation and germination and seed and fruit development. Avocados are an incredibly boron-hungry crop and their very low fruit to flower ratio can be substantially improved with a foliar spray of boron at pre-flowering. The boron increases the length of the male pollen tube and improves the pollination process. It is common to see the top 25% of corn cobs not fill due to a boron shortage. I always recall visiting a corn grower in Kunnanurra who was facing a 25% yield loss on 1000 acres of table corn for the sake of an inexpensive boron foliar. He had assumed that because his starter fertiliser contained some boron the poor pollination must be due to a lack of bees. In actual fact, his irrigated, low carbon soils had lost the boron through leaching by the time his crop reached the boron draw-down time at reproduction. It was a stark and expensive lesson in the importance of leaf analysis before flowering. It can make a big difference getting things right at the business end of the season. Poor pod set in soybeans is another consequence of poor boron nutrition that could be avoided through early diagnosis with leaf analysis and a timely foliar spray of boron.

Cell Strength and Cell Division

In a synergistic process, not unlike bone development in humans and animals, boron is involved in cell wall strength as it moves calcium into the cell walls. Boron has also been shown to increase the solubility of silica in the soil, which further increases cell strength. It is a good idea to apply boron to the soil in late winter to sponsor the uptake of soluble silica before spring. This also improves calcium transport into the plant through improved, silica-based development of phloem and xylem (like building better highways). Good levels of calcium are required for the extra cell division needed during the spring flush. Boron is actively involved in cell division in its own right and this is why it is common to see misshapen fruit and vegetables where cell division was compromised due to boron deficiency during fruit formation. Rosetting (stunting) of plants can occur due to inadequate cell division in the growing shoots and this is particularly common in lucerne.  A combination of boron compromised cell strength and cell division is responsible for hollow stems in broccoli. Never purchase these boron deficient vegetables as they are virtually guaranteed to have required more chemical intervention than otherwise. Dieback in vines crops can also be related to a boron related deficiency.

Plant Hormone Regulation

Plant hormones, like animal hormones, regulate many growth and reproductive functions. Flower initiation, fruit development, cell wall and tissue formation and root elongation are all influenced by hormones. Boron plays an important role in regulating plant hormone levels. This is yet another reason for your pre-flowering foliar spray of boron as there is such a strong hormonal presence during reproduction.

We have concluded that boron nutrition is never to be overlooked but what is the best type of boron to use and at what rates?

Boron Options

Borax and Ulexite (calcium borate) are the most common materials for soil application but there is a very important proviso when determining appropriate application rates of these materials. Boron can serve as a herbicide if you get it wrong, so this is very important information. If your calcium levels in the soil are less than 60% base saturation then the maximum application of borax is 15 kg per hectare. If you have good calcium levels then you can safely increase the upper rate to 25 kg per hectare. We have found that the very best and sustained boron performance comes from NTS Stabilised Boron Granules™. When boron is complexed with humic acid it becomes more plant available and far more stable as boron humates do not leach. The application rate for NTS Stabilised Boron Granules™ is typically 20 kg per hectare but you get many other benefits at this rate due to the substantial application of humic acid involved. i.e. urea and DAP can be stabilised with boron humates and this product offers a major boost to beneficial fungi in the soil and improves soil structure.

The best form of boron for fertigation or foliar application is sodium borate (Solubor, Inkabor etc). Once again there are tremendous benefits in combining humic acid with these 22% boron products. This will immediately create a boron humate which is better absorbed and much more stable in the soil when fertigating. Typical application rates for foliars are 1 kg of Solubor per hectare in field crops combined with 2 to 3 litres of humic acid or 1 kg of Soluble Humate Granules. When fertigating use 3 – 5 kg Solubor combined with 2 kg of Soluble Humate Granules.

Boron in Animal Nutrition

How did that massive boron deficiency (0.1 ppm) in that NZ dairy pasture affect the animals eating that pasture? Animals need 25 to 50 ppm of boron in their food.  USDA researcher, C-D Hunt, in his paper “The biochemical effects of physiological amounts of dietary boron in animal nutrition models” demonstrates that boron has a powerful synergistic relationship with vitamin D3 in influencing animal growth and cartilage and bone mineralisation. In fact the link to bone health goes way beyond the vitamin D3 synergy. It appears that boron may be as important as calcium and magnesium to maintain healthy bones and joints. Research in New Zealand has shown that sheep suffer the same form of osteoarthritis suffered by humans and there is far higher levels of this ailment in areas where soil boron is low (usually high rainfall areas).The initial animal research triggered subsequent human research where it was found that there were also much higher levels of arthritis in humans in boron deficient regions. More recent human research in Australia has shown that where boron is at higher levels in soil and water there is a 50% decrease in musculoskeletal diseases than where boron in soil and water was low.

Boron in Human Health

Boron’s role in human nutrition was poorly understood until recently and it is now known that it is linked to a diverse range of functions. A shortage of boron in the diet has been linked to inflammatory processes including swollen joints and restricted movement. It is needed for the production of antibodies in the immune system, for the production of serine protease (which is linked to platelet aggregation) and for the metabolism of leukotrienes which are involved in the inflammatory response. Boron is also intimately linked to energy as it affects energy substrates including triglycerides, glucose, amino acids, free radicals and even estrogen. It is these energy links which may help explain recent findings where luxury boron intake was linked to better brain performance. Dr Alexander Schauss conducted research which highlighted a lack of energy, mental alertness and focus in students lacking boron. Following 3 months of boron supplementation, 92% of treated students showed obvious improvement in mental alertness in comparison to their untreated class mates.  EEG readings also confirm increased brain alertness following boron supplementation. However it is boron’s role as a bone building nutrient that is attracting most attention at present. This capacity is particularly pronounced in post-menopausal women who are notoriously prone to osteoporosis. A recent clinical trial has shown that after 7 weeks of boron supplementation at 3 mg per day, participants experienced a marked increase in the hormones, 7 beta estradiol and testosterone, both of which increase the uptake of calcium into the bones. In fact, there was a two fold increase in testosterone and a significant increase in calcium retention. In another study, men given 10 mgs of boron each day, for 4 weeks also exhibited major increases in testosterone and 7 beta estradiol. Testosterone is not just about libido, it plays a big role in heart health, bone density and muscle integrity and production of this hormone steadily declines after age 25. The capacity of boron to help with hormone formation partially explains why this mineral is so important for arthritis. Boron can complex with hydroxyl groups and form corticosteroids which can alleviate arthritis symptoms. The arthritis connection is more involved than this and appears profound. Jamaica, for example, has the lowest levels of soil boron in the world and the highest levels of arthritis. It is speculated that the arthritis link may also be related to boron’s role in the healthy functioning of the parathyroid glands which regulate calcium and calcium uptake. I have a personal anecdote to share here.

A Cut Throat Through A Lack Of Understanding

In the midst of the Three Up Tour, a nation-wide seminar series with Gary Zimmer and Jerry Brunetti a few years back, I was contacted by my mother to inform me of my father’s impending surgery. Dad had recently been diagnosed with a parathyroid malfunction and had been scheduled to have the offending gland surgically removed. Apparently there was quite a chance that during the procedure, which literally involved a cut throat, his voice box could be damaged and he would be unable to talk naturally again. Mum suggested I speak with him immediately in case it proved my last opportunity for 2 way conversation. I was obviously horrified and explained the situation to Jerry Brunetti, who is an exceptional nutrition consultant. Jerry pointed out that boron was hugely important for parathyroid health and that Dad should be tested for boron before he undertook this dangerous operation. I called home and scheduled a hair test which revealed a major boron deficiency. We postponed the operation while this deficiency was addressed (with** 5 mg of boron** per day) and sure enough his blood calcium levels returned to normal and the operation was no longer necessary. In a modern medical machine which involves less than one hour of nutrition training in a 7 year degree, one wonders how many unnecessary operations are conducted for want of a basic nutrition understanding.

In Conclusion

As we can see, there is so often a direct parallel between mineral relationships in the soil and those in animals and humans. The statement “calcium is the trucker of all minerals and boron is the steering wheel” is as relevant in human nutrition as it is in the soil. Animals source their boron from legumes so there is an issue if clover is missing from the equation due to abuse of urea. Humans source their boron from certain fruits, legumes and nuts. Apples contain the highest levels of boron followed by grapes, almonds, soya beans, prunes and avocados. Many of us are deficient in boron and could benefit from supplementation, particularly if arthritis is an issue.