The more I work with farmers to produce quality forage, the more I realise that success depends on paying attention to detail, especially when it comes to the balancing of soil minerals. It seems to me my clients and I still suffer from a nitrogen-phosphorus-potassium (NPK) hangover. And we don’t give credit to the minor minerals – those that are required in miniscule quantities.
Yet, when these are in short supply, the expense of correcting the major minerals – major in terms of quantity applied – can be very high. Gary Zimmer, dairy farmer and author of The Biological Farmer, lists calcium, boron, phosphorus, magnesium and sulphur as the five most important minerals required for the production of quality forage.
Note that boron follows calcium in the Zimmer list. There’s a good reason for this. Boron has also been described as the pump that pushes calcium up in the plant. And here we have a good example of the relationship between a major mineral and a minor mineral. It’s not uncommon for farmers to be advised to apply 1 000kg/ha of calcium (about 3t/ha of lime) and 4kg/ha of boron. In my experience 90% of farmers apply the recommended level of calcium – but fail to apply any boron at all!
Why so Lax?
Why are farmers so lax about applying boron? I can think of four reasons:
- Sourcing the product is difficult – most fertiliser outlets don’t stock boron for soil application (foliar boron is more freely available).
- Applying only 4kg/ha is a hassle.
- Boron is potentially toxic. Applied in excess – even slight excess – can result in severe damage to, and even kill, the pasture.
- A lack of knowledge about the crucial role boron plays in getting calcium into the plant.
I’m currently dealing with a number of cases where farmers are experiencing poor animal performance, especially low fertility. In all but one, calcium is severely lacking in both soil and plants. And all the lands are seriously short of boron!
How are my clients going to correct the problem? Firstly, by applying the right amount and type of lime as recommended by the soil report. Secondly, by applying the recommended amount of boron.
I must point out here that boron toxicity is less likely to occur in soil that has been adequately limed. The toxicity threat can be further negated by the use of calcium/sodium boronate. This is actually a sodium boronate that’s been coated with calcium. The safety factor is that it’s less soluble and there’s less “rush” of boron into the plant.
It also prolongs the effective lifespan of boron in the soil. Boron is unstable and does not recycle via the animal. As noted, boron must be applied at a maximum of 4kg/ha – and it’s better to apply it twice a year, in two applications of 2kg/ha each. To reiterate – producing quality forage is about getting all the minerals at correct levels into the soil and then into the plant. Don’t stop at calcium and boron!
John Fair is a leading expert on pastures in South Africa, and founder and head of the SA Biofarm Institute in Harrismith.
Contact John on [email protected]. Please state “Biological farming” in the subject line of your email. •FW