Applying nitrogen is a well-established practice to ensure sufficient spring pasture. To get the grass growing, frequent applications are typically the norm.
But when the cows are already calving, you’re up to your elbows in mud, and the rain just keeps coming, it’s easier said than done!
So what if you could apply the nitrogen in one go and not have to worry about it again for several months? Well, you can if you choose a controlled release fertiliser (CRF).
What is CRF?
In brief, a controlled release fertiliser does what it says on the tin: it releases it’s nutrients in a controlled way. Also known as delayed release, controlled availability, and coated fertiliser, it’s easy to get the idea about what it does. It’s quite different to conventional fertilisers like urea where all the nutrients are available to plants as soon as they hit the soil.
How CRFs work
CRFs are manufactured by spraying a coating onto granules of fertiliser. Soil moisture penetrates the coating of the granule and starts to dissolve its contents. This causes the granule to swell and pressure to develop inside the granule. With the increased pressure, the dissolved nutrients move out into the soil through pores in the coating which have a fixed size. When the pressure eventually drops inside the granule, the coating degrades away.
Note that this process can take up to 3 months, and that the nutrient release follows a controlled pattern.
These characteristics of CRF have huge benefits for farmers.
Only one application needed
An obvious benefit is that since the nutrients are protected inside the granule and not released all at once, a single application can provide what plants need for up to 3 months.
This is ideal for meeting the nitrogen demands of spring pasture, a difficult job during wet weather. It’s also perfect for nutrient-hungry maize crops by removing the necessity for a side dressing, avoiding crop damage and reducing spreading costs.
But while the sustained release time of CRFs saves time and money, it’s the controlled pattern of nutrient release that delivers the greatest benefits.
Nutrient release matches plant growth
As plants grow, their nutrient demands increase. For pasture, this occurs as the weather gradually warms up in spring, and for crops this occurs as newly-sown seed matures. Then once growth slows down, less nutrients are needed. For pasture this is when it’s either too hot, too cold, too wet, or too dry. For crops, this is when they reach maturity.
This pattern of plant growth is not matched by conventional fertilisers very well. It’s typically a case of too much too soon when plants don’t need the nutrients, then not enough when they actually do.
With CRFs, the situation is quite different. The nutrients are released in a more controlled way described as a sigmoidal curve, or ‘S’ shaped pattern. So the release starts out slowly, rapidly increases, then gradually tails off. This is much closer to how plants grow, so CRFs are more efficient at matching plant nutrient needs.
Efficiency saves money
Because CRFs are more efficient, you save money. What you pay for is being used, so you don’t need to apply as much as you normally might to get the same result. Studies show that for a CRF like that included in Fertco’s 44 Magnum, you can apply around a third less than you would if you used urea.
The environment benefits
Since the mechanism of nutrient release is more efficient, CRFs can help us meet environmental objectives too. By choosing CRFs instead of conventional fertilisers like urea, you can reduce losses from volatilisation and leaching because the nutrients are protected by the coating around the fertiliser granule.
CRFs aren’t new
While we’re not so familiar with CRFs in NZ, these products are used to grow rice in the wet field paddies of Japan, citrus in California, palms in Malaysia, and food crops like tomatoes, capsicum, and onions. So they’re well tested.
If CRFs can save time and money while simultaneously reducing environmental wastage, why wouldn’t we use them more often here in NZ?
This article was published in the Coast & Country News.
