Boron Nutrient Management in Plants
BORON UPTAKE BY PLANTS
Boron uptake by plants is controlled by the boron level in soil solution rather than the total boron content in soil. Boron uptake is a passive (non-metabolic) process. It moves with water in plant’s tissues and accumulates in the leaves; therefore, Boron uptake and accumulation are directly dependent on the rate of transpiration.
Boron mobility in the phloem is now known to be plant-specie dependent.
BORON TOXICITIES AND DEFICIENCIES
Boron deficiency symptoms: Limited budding, bud break, distorted shoot growth, short internodes, increased branching, flower buds falling and inhibition of fruit and seeds development.
Symptoms of boron deficiency in pepper
Boron toxicity symptoms include: Chlorotic leaf tips, leaf necrosis, and later leaves falling and even plant death.
BORON IN SOIL
Boron is soils can be categorized into 3 groups:
- Boron as a mineral component;
- Boron adsorbed to soil particles, such as clay minerals, iron or aluminum oxides and organic matter. Adsorption of Boron to clay particles is reversible so the adsorbed boron can be released to the soil solution. It also has high affinity to iron and aluminum oxides;
- Boron in soil solution as boric acid (H3BO3) and borate ions (BO3-). The boron in soil solution is available to plants (mainly as H3BO3).
The ratio between the Boron concentration in the soil solution and the Boron adsorbed to soil particles is affected by the components of the soil (clay minerals, free oxides and organic matter) and also by other factors such as type and concentration of salts in the soil, pH and temperature.
Actually, most of the boron in soil is adsorbed to organic matter, acting as a pool of boron from which the boron can be readily released into the soil solution.
PREVENTING BORON ACCUMULATION IN THE ROOT ZONE
Since toxic levels of Boron are only slightly higher than deficiency levels, it is important to keep a non-toxic level of Boron in soil solution. In order to achieve that, root zone should be flushed either periodically or continuously.
The water amount and the irrigation intervals should be determined in the same way done for treating salinitybuildup in soil.
COMMON BORON FERTILIZERS
|Boric acid||H3BO3||17.5% B|
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