Need of Boron for Crops
Boron (B) is a micro nutrient critical to the expansion and health of all crops. It is a component of plant cell walls and reproductive structures. It is a mobile nutrient within the soil, meaning it’s susceptible to movement within the soil. Because it’s required in small amounts, it’s important to deliver Boron as evenly as possible across the hector . Traditional fertilizer blends containing Boron struggle to realize uniform nutrient distribution but Maxgrow’s Boron overcomes this problem. Despite the necessity for this critical nutrient, Boron is that the second most widespread micronutrient deficiency problem worldwide after zinc.
Major Functions of Boron in Plants
Boron plays a key role during a diverse range of plant functions including cell membrane formation and stability, maintenance of structural and functional integrity of biological membranes, movement of sugar or energy into growing parts of plants, and pollination and seed set. Adequate Boron is additionally required for effective organic process and nodulation in legume crops.
Boron deficiency commonly leads to empty pollen grains, poor pollen vitality and a reduced number of flowers per plant. Low Boron supply also can stunt root growth, as shown within the soybean and canola photos (see Picture 1).
Picture 1: Shoot and root growth of soybean and canola plants with low and adequate boron supply (courtesy: Y. Ceylan and I. Cakmak).
Plant Analysis for Boron
To determine a plant’s Boron nutrient status, younger leaves are recommended for sampling and analysis. Typically, adequate Boron levels in dried leaf tissues range from 25 to 75 ppm Boron, which may be a considerable quantity for several crops. Generally, a soil application of Boron is suggested when leaves contain but 25 ppm Boron in high-boron-demanding crops like alfalfa, sugar beets, potatoes, sunflower, soybeans and canola.
Boron Deficiency Symptoms
Most crops aren’t ready to mobilize Boron from vegetative tissues to actively growing, meristematic plant tissues like shoots, root tips, flowers, seeds or fruits. Rather, Boron transport occurs primarily within the xylem channel, resulting from transpiration. Because of this, deficiency symptoms first develop in newly developed plant part like young leaves and reproductive structures (see Picture 2).
Soybean Canola Boron
Picture 2: Alfalfa plants grown with deficient (left) and adequate (right) supply of Boron fertilization (courtesy: A. Yazici and I. Cakmak).
Under severe Boron deficiency, stunted development and death of meristematic growing points are common. Other common reactions include reduced root elongation, failure of flowers to line seeds and fruit abortion. Low Boron supply can also adversely affect pollination and seed set, without visible leaf deficiency symptoms.
Soil Factors Affecting Boron Deficiency in Plants
Boron deficiency is very prevalent in sandy acidic soils with low organic matter, thanks to the potential for Boron leaching. Soils with high adsorption and retention capacity (e.g., soils with high pH and rich in clay minerals and iron or aluminum oxides) also are commonly impacted by B deficiency.
In most crops, Boron shows very poor phloem mobility. Consequently, Boron in leaf tissue can’t be transported sufficiently into the reproductive organs (i.e., shoot tips, buds, flowers, seeds, etc.). Because of this poor mobility, keeping soluble B in soil solution during all stages of plant growth, particularly during reproductive growth (e.g., during seed setting), is critical for optimal plant nutrition.
Environmental Factors Affecting Boron Deficiency
Environmental factors that reduce transpiration, like high air humidity and low soil moisture, have adverse impacts on xylem transportation of B. Extended periods of drought impede Boron uptake by reducing root growth, limiting supply of Boron from organic matter reserves, and by depressing diffusion and transport of B to root surfaces. Plants under low Boron supply are more vulnerable to damage from high candlepower related to long and hot, sunny days (see Picture 3). Under B deficiency, use of absorbed light energy in photosynthesis is significantly reduced, resulting in an excess amount of energy and potential for leaf damage. Low soil temperature also can reduce root boron uptake.
Picture 3: Growth of sunflower plants with sufficient and deficient boron supply under low and high light conditions. Plants under low boron supply are quickly damaged when exposed to high candlepower (courtesy of I. Cakmak; cf. Cakmak and Römheld, 1997, Plant Soil, 193:71–83).
Sufficient Boron for Better Root Uptake of Phosphorus and Potassium
Studies show that adequate B nutrition improves root uptake of phosphorus (P) and potassium (K) by maintaining proper function (through ATPase activity) and structure of root cell membranes. Boron has a crucial role in colonization of roots with mycorrhizal fungi, which contributes to root uptake of P. In short-term experiments with corn plants, reduced root uptake of P and K under low B supply was restored within one hour after B was added to the expansion medium. Experimental evidence also suggests that adequate B supply is required for mitigation of aluminum toxicity in plants grown in low-pH soils.
Tips for Preventing Boron Deficiency
Soil-test your fields every two years to realize a radical understanding of the nutrient levels of your field. Make sure to match your yield goals with current nutrient needs, and discuss options with an agronomist. Because there’s a fine line between deficiency and toxicity, it’s important to use the proper amount of B at the proper rate using the right source. Aspire® with Boron ensures uniform nutrient distribution across each field. Using Nutriform® technology, Aspire combines potassium and boron in each granule to assist achieve balanced crop nutrition.