Variable quality across different solid fertiliser types and within individual manufacturing processes can have a major effect on spreader accuracy and application efficiency, says Cheshire contractor Rob Briscoe.

* Nitram most preferred product with consistent flow and accuracy of spread

* Some imported AN products show 20% fluctuation in flow rates

* Lower demand for urea due to poor spreading

* Blends seen visibly separating out in hopper as spreading proceeds

With around 2000ha (5000 acres) of spreading to complete each year on both grass and arable land, poor quality fertiliser not only affects his work-rates it can make achieving even distribution of material virtually impossible, he says.

“You can learn a lot just by looking at material and how it goes through the spreader but with the latest application equipment and management systems you can now accurately quantify in real time how variable products are and how this is affecting fertiliser distribution. It’s actually a bit of an eye opener."

“Within the same hopper of imported AN, for example, you can see up to 20% variation in flow going through the machine, with the spreader constantly having to make adjustments for the differing prill sizes and density.”

Using a brand new Kuhn Axis 40.2 M-EMC-W with a 3.2 tonne hopper and capable of spreading up to 36.0m, Rob’s work is largely arable and principally involves AN, blends and straights.

“There just doesn’t seem to be much demand for urea by the customers I contract spread for any more. We used to spread it on our own arable land when we were on 12m tramlines but it wouldn’t throw accurately to 24m so we gave up and locally I think a lot of others did too. The risk of volatilisation and N loss with urea is a real problem too.”

The last urea product Rob was asked to spread for a customer was in the protected form, designed to cut down on volatilisation, but it was obvious the coating was breaking down and coming off in the bag and during spreading, he says.

“By the time we had finished, the discs and back of the spreader were covered in green dust, which meant a proportion of the coating was no longer on the urea where it was supposed to be doing its job, but on our machine instead!”

Whilst all straight Nitrogen spread for clients is now in the form of AN, there is a wide variability in the quality of material he is asked to work with when imported material is specified.

“There are different flow settings for different materials recommended on the Kuhn App which we use. For Nitram (34.5%N), for example, the flow factor is given as 1.08 so I can set that up and watch the flow monitor in the cab when I’m spreading and it is doesn’t budge from that all day.

“I can go to another farm using Nitram and it will be the same. Not only is there no difference in prill size and density within a bag, there is none from bag to bag either.”

It’s a very different situation with imported AN, however, he says.

“For imported AN the flow factor is given as 1.17 as the average prill size is smaller and it flows more quickly through the spreader. I can set it up for 1.17, as recommended, but as soon as I start spreading, it will jump to 1.3 or 1.4 and then fluctuate constantly between 1.17 and 1.35 as I am working – that’s a variation of up to 20% from the optimum flow. As the Kuhn has flow meters for both discs, I can see it varying between both sides, too."

“That means the machine is constantly making adjustments for the differing prill size and density which can only have an effect on distribution and evenness of spread.”

Not surprisingly, Nitram is the only source of straight Nitrogen used on Rob’s own 140ha (350 acres) of arable production at the family’s Lower House Farm near Tarporley. 


Fluctuations in density and spreading performance can also be seen when using blends, he says.

“We’ve used Ammonium Sulphate and AN blends where you can see the larger AS granules bridging up the sides of the hopper whilst the smaller denser AN prills collect in the centre and are the first to go out."

“Your application rates might tell you you’ve put on the right amount but the actual constituents of the product are separating out so the distribution of Sulphur and Nitrogen is all over the place. Virtually all our work is at 24m or above now and there’s no way you will get a blend to spread accurately at this width let alone 30m and above.”

Sulphur needs at Lower House Farm are taken care of by CF DoubleTop (27N + 30SO3) for the winter wheat, barley and oilseed rape with CF KayNitro Sulphur (25-0-13+7SO3) being used for Spring barley, Rob explains.

“The difference is these are true granular compounds meaning each granule contains Sulphur and Nitrogen combined unlike a blend which is just a physical mix of different constituents with variable densities and particle sizes. In truth, we’re spreading more compounds like DoubleTop and KayNitro Sulphur now and you can really see a difference."

“We had some barley earlier in the year that was starting to look a bit yellow, but almost as soon as we put the DoubleTop on it perked up. Crops to seem to respond very quickly to it.”


How material is stored on farm can also have a significant effect on how easy it is going to be to spread accurately, Rob Briscoe says.

“Considering it is a relatively expensive product, people don’t always store fertiliser the way they should do. Many store it outside so if the bags are in poor condition water will get in, but even with secure bags if there’s any rain on the plastic, that often gets into the spreader which doesn’t help.”

Finally, not all bags are the same, he says.

“The bottoms of blue bags have a kind of cross stitched across them and as soon as this cut, you know it will empty completely. This is unlike others with a square-shaped base that you usually have to stretch across the dusty lip of the hopper to try and empty the bag fully as some material always gets trapped."

“If you don’t try and get the last bits out, you’re just wasting product, but if you’re using dozens of bags a day it can be quite tiring as well as slowing you down significantly and in contracting it’s all about work rate.”

All in all, there are few arguments for choosing anything less than the best quality fertiliser you can, Rob Briscoe believes.

“Whether you’re a farmer in your own right or contracting for others, lower quality material is a real pain. It’s invariably difficult to use and you’re not going to get the same crop response largely as a result of either poor manufacture, variable quality or uneven distribution - and in many cases all three!"

“If all my clients used CF products my life would be much easier and I’m sure they would get better results too. At the end of the day, you get what you pay for.”

Take this information away with you.