You may not notice it happening in your canola crop, but boron deficiency can limit yield whether you see it or not. This micronutrient is important to all crops, especially flowering crops like canola and peas, and particularly when the plants are switching from vegetative to flowering stages.
Boron is immobile in the plant, and when it is taken up by the roots it travels very slowly. We know this because all deficiency symptoms appear on the newest leaves.
Plants with severe boron deficiency may have cracked stems, poor seed set (blasting in canola) and most importantly, they may not yield as well as expected. However, boron deficiencies are hard to detect in-season, and symptoms may not even be apparent at all.
Under a microscope, you can see that boron-deficient crops have thick cell walls, poorly differentiated cells in the phloem, pollen tubes that do not extend properly and shorter root hair tips. These problems may be microscopic but they could be costing you bushels!
Boron in the soil
As we grow bigger canola, pea and soybean crops we can mine the soil into deficient levels. Unfortunately, the boron soil test is somewhat limited, but it is the best we have to determine how much is needed.
Typically, you want to see at least 1 ppm of boron in the top 6 inches. Some agronomists will look at cation exchange capacity (CEC) to measure boron needs. If the CEC is higher than 18 you would want boron to be 3 ppm.
I prefer to look at both the CEC and calcium values to make a recommendation. This is because boron competes with other nutrients – like calcium – to enter the plant.
Boron is incredibly mobile in the soil, which means it can leach past the root zone with heavy precipitation or a good snow melt. Boron deficiency can also happen when drought conditions are present. Boron is taken up by plant roots as boric acid via mass flow, meaning it requires water to enter the plant. This can be problematic if there are high concentrations of other nutrients in the soil because they prevent boron from entering.
For this reason, I suggest ensuring you have 3 ppm boron in soils with more than 2500 ppm calcium.
When and how to use Boron
You should consider applying boron if:
- You are targeting high yields in flowering crops (canola, peas, soybeans). For 1 bushel of canola you need 3.7 grams of boron.
- If soil samples are indicating low boron levels (1-3 ppm on the soil test), high calcium levels, and you have a CEC higher than 18.
- Environmental conditions are not suitable for boron uptake (eg: drought or excessive moisture).
- You are seeing visual symptoms of boron deficiency.
- Procote™ B - This oil-based product treats granular fertilizer with a micronutrient. It allows for equal feeding sites and for the plant to take up boron through the roots, all season long.
- Bortrac - This foliar-applied product is easily tank mixable. It is often beneficial to apply more than once, since boron is not mobile in the plant. I’ve seen good results in trials by applying with the second pass of herbicide and again at 10% bloom with an early application of fungicide.
- Combination of the two – Because boron is not easily transported within the plant, it can be helpful to apply Procote B for early season uptake and if the crop is looking exceptional, add some Bortrac™ with the fungicide pass.
Your local Cargill agronomist is ready to help you determine your micronutrient needs. Get in touch if you have questions.
Procote and Bortrac are trademarks of Yara Canada, Inc.