By: Andrew Swallow

There’s a disconnect between what we can find out about soil fertility today and what we can do about it. Rectifying that will be a key development in the way we manage fertiliser in future, Balance Agrinutrients’ innovation leader Jamie Blennerhassett says.

In an interview before the annual Fertiliser and Lime Research Council Workshop in Palmerston North, he also touched on exciting possibilities for controlled release fertilisers. He says there’s a disconnect in the understanding of variability in fertility across a paddock and ability to create a blend of nutrients to correct that and the spreading technology to deliver them to correct the variability.

“It takes a lot of management to connect all those dots and this is where precision technology will have quite an impact.”

He says data management products such as Ballance’s My Ballance programme are starting to do that.

“It gives the farmer the ability to view that linkage better, providing information to the spreaders and providing proof of placement in return.”

He says without it, standard block recommendations for fertiliser which, in a dairy situation, would typically be split over eight or nine applications during the spring, summer and autumn, often go awry. The same can be true for blocks of more-extensive sheep and beef country, except the timescale is longer: instead of an annual soil sample and recommendation for multiple applications in a season, soil sampling might only be every third or fourth year and a recipe for annual fertiliser applications drawn up from that.

What’s more, over two or three years some paddocks will get more, or less fertiliser than they should because they might miss a round, or the contractor might make a mistake in which paddocks he was to go to.

Blennerhassett says My Balance prevents that, and makes paddock-specific recommendations much more manageable.

More-detailed soil sampling is revealing gradients of fertility within management blocks. For example, in dairy paddocks soil nutrient levels typically reduce the further from the gate you go due to grazing patterns transferring nutrients, while in hill blocks slopes become depleted and flats – at the top or the bottom – accumulate nutrients for the same reason.

“In Canterbury dairy paddocks under irrigation there’s a big transfer of nutrients from the back of the paddock to the front. Olsen P can be 10 units lower at the back.”

Such variable fertility can be illustrated on computer software maps and transferred to spreaders equipped with the appropriate technology to inform on-the-go variations in fertiliser rates, counteracting or compensating for the differential in soil fertility.

The technology to do that has been available for more than a decade but availability of spreader hardware capable of accurately delivering variable rate prescriptions is still limited, as is uptake of services where they are available.

He says the big challenge is most fertilisers are relatively cheap. In general farmers get a good return on investment from blanket applications.

It’s a similar story with fertiliser quality.

While there are frequently calls for stronger, more uniform products, the reality is developing such products adds cost which is a hard-sell in terms of improved output and returns onfarm.

With any increase in the cost of fertiliser there’s a push back from customers.

“The exception to that rule is perhaps in arable where we’re seeing an increased focus on product physical quality as they use increasingly wide tramlines in crops.”

He says one of the spreaders used in that sector claims 54-metre spread capability but that is only possible with the highest quality, densest products.