Solid v liquid fertiliser: Which is best?

Which is best – solid or liquid fertiliser? Louise Impey visits an eastern counties farming business which uses both.

The workload and logistics involved with the timely and accurate application of fertiliser across 2,900ha (7,166 acres) of combinable crops and sugar beet has led farm manager David Knott to adopt different approaches on the two farming businesses he oversees in Cambridgeshire.

On the larger of the two units, where the ability to cover a large area in a tight timeframe is important, solid fertiliser is used. On the other, which is more exposed and has less labour and machinery, liquid fertiliser is preferred.

See also: Case study – Norfolk farm sees the benefits of liquid nitrogen switch

“Both systems have their pros and cons,” says Mr Knott. “Our main concern is to ensure that we are making the best use of any applied fertiliser, targeting it to where it is needed through variable rate application, for optimum crop performance.”

He likes the fact that solid fertiliser can be moved about easily, and that he can hold all the product he requires on the farm. “Once spreading starts, we can make rapid progress and get a large area covered in a day.”

Liquid fertilisers, however, allow good use of existing on-farm application equipment and offer more flexibility with the nutrients applied, he acknowledges. “The accuracy and timing can be perfect, but the saving on machinery has to be balanced by the fact that the fertiliser is often marginally more expensive.”

liquid fertiliser

© Tim Scrivener

Both systems on the two businesses are helped by the use of precision farming technology and high-quality fertiliser products from Frontier Agriculture, which have allowed variable rate application of N, S, P and K for the last three years.

“We’re using the same amount of fertiliser that we were before, but our crops are more even and yields have increased by up to 5%.”

Trumpington Farm Company

At Trumpington Farm Company, just outside Cambridge, solid fertiliser is used across all the crops, with the latest application equipment being employed to ensure that all nutrients are applied according to the crop’s development and yield potential.

“On this unit, which is 2,100ha, our self-propelled sprayer is fully utilised once the growing season gets under way,” explains Mr Knott. “We can’t justify buying another sprayer just for fertiliser application, plus we may need to be doing both operations at the same time.”

Covering such a large cropped area with a small team is a further consideration, he notes. “We are working on 40m tramlines here, so we need to be able to spread to that width and cover plenty of ground in a day, when conditions allow.

“Wind can restrict the operation, as well as rain. When things are in our favour, we can spread with wind speeds of up to 12 miles/hour and can travel at speeds of up to 18mph.”

For these reasons, he finds solid fertiliser the best solution and has purchased an Amazone ZA-TS Ultra Profis Hydro spreader, which has the capability of covering more than 300ha per day.

“We have one man driving the tractor, and another man delivering the fertiliser to him. It lets us get a large area done in a short time, almost 400ha/day sometimes, but with the accuracy and consistency of application that we need.”

High peripheral speed

Given the spreading distance required, the quality of the solid fertiliser used at Trumpington Farm Company is essential, continues Mr Knott. “The spreader has two large discs, which operate at a high peripheral speed. A sub-standard fertiliser just shatters when it hits the disc and won’t spread at all.”

As a result, he works closely with Frontier Agriculture to ensure that he gets a high-quality fertiliser product with a consistent density.

“A business of this size uses a great deal of fertiliser in a year,” he points out. “It would be a false economy to use a product which wasn’t able to give us the even application or spreading width that we’re looking for.”

To be certain of getting a sufficient supply of the right product, he has a policy of buying fertiliser forward in the summer, when the prices are first released. Having ordered in July and taken delivery in September and October, the 1t bags of fertiliser are in store and under cover long before they are needed.

“The economics work out in our favour in most years,” comments Mr Knott.

AF Pemberton (Thorney Farms) Ltd

At the other business, AF Pemberton (Thorney Farms) Ltd near Peterborough, liquid fertiliser is used for all of the crops’ nitrogen and sulphur applications.

Covering around 800ha, the farm has a 24m tramline system and a John Deere trailed sprayer, which Mr Knott describes as only just having capacity to be used for fertiliser applications, as well as its normal spraying duties.

“We manage to get everything done with one man and one machine,” he reveals. “Although there are times when it is extremely busy and we are right up against it.”

In its favour, both application accuracy and timing are spot on with liquid fertilisers, while there is a saving on machinery by using the existing sprayer.

However, the fertiliser itself costs slightly more than the solid product. “It varies year on year. Of course liquid fertiliser can be customised, so there’s more flexibility with the balance of nutrients applied and the opportunity to address any particular macro or micronutrient shortfalls.”

Always windy

Another important factor is that the Thorney site is more exposed than Trumpington, so it always seems to be windy, he continues. “The wind speeds that we experience at Thorney mean that it would be a struggle with solid fertilisers. We would lose the spreading accuracy.”

Dedicated liquid fertiliser storage tanks, supplied by Frontier Agriculture, are situated in two locations, so that they service the whole farm area and minimise down time.

“We do need to have quite a volume of storage, which can be a challenge with liquids,” reports Mr Knott. “It’s also essential that we have the speed of delivery of product in busy periods. Our work windows can be very small, so timing is everything.”

His final point is that there can be considerable corrosion to the sprayer from the nitrate component of a liquid fertiliser. “The bits which aren’t stainless steel seem to get eaten at an alarming rate.”

Finding the right system for your farm

Existing farm infrastructure will often dictate which fertiliser system is the most appropriate for individual situations, says Frontier Agriculture’s fertiliser business development manager, Jack Russell.

“The ability to store product, as well as cropping choice and the machinery policy, all have a bearing,” he notes. “There are advantages to both.”

Solid fertiliser probably has the edge for those who like to have all their fertiliser supplies on the farm at the start of the season, or are looking for the very best deal, he suggests.

His colleague, liquid fertiliser manager Bernie Zahra, highlights the better accuracy of liquid fertiliser applications and the good use of existing farm equipment.

“Just like solids, liquids can be bought forward for a specific delivery date,” he explains. “Our service is well equipped to keep up with demand – most users have one-third of their requirement in storage on the farm, with the remaining two-thirds delivered throughout the spring, as required.”

Good sprayer hygiene is essential with liquid fertiliser, just as it is with pesticides, he stresses.

On the question of economics, Mr Zahra calculates that the p/kg of nutrient price for liquids generally falls between that of urea and ammonium nitrate. “They are very close. It’s the practicalities that tend to sway the decision, not the price.”

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