Calculating farm fertiliser expenses

Fert Options
with Robin Boom
Agronomic Advisory Services

Last month I was having a discussion with a farm advisor for hill country farms in the King Country, challenging him on why he didn’t look at some of the smaller importers which could make considerable savings for some of his clients compared to the two big fertiliser co-operatives.

He asked me to go through the exercise and show how this was possible. Fertiliser prices are always a moving target so company comparisons should be done on a case-by-case basis, depending on the nutrients required at the time and cartage and spreading costs.

For this exercise I made the following assumptions of a cartage cost ex-port of $40/tonne to airstrip, and an application cost of $90/tonne for low analysis (superphosphate, dicalcium phosphate and RPR) fertilisers; and $120/tonne for high analysis (triple super, feedgrade DCP, DAP, MAP).

I also worked on the equivalent of 400kg/ha of superphosphate providing 36kg P/ha, and acknowledged that with the exception of volcanic ash soils, there is value in the sulphur of superphosphate. Although with it being sulphate sulphur and prone to leaching, the equivalent of 30kg/ha of Sulphur 90 (elemental sulphur) should suffice as the equivalent.

For volcanic ash soils, the sulphur in superphosphate has no value and in some respects could be seen as a negative as high sulphur can interfere with copper absorption in stock and as it leaches through the soil it can carry positive cations with it such as calcium and magnesium, removing these from the root zone. So I worked on prices with and without the sulphur. This price comparison was based on the Ravensdown Direct pricing as of 22/5/2020.

Superphosphates

Ravensdown Superphosphate ($315/tonne) at 400 kg/ha on ground price = $178/ha.

Triple Super @ 180 kg/ha from Fert Wholesale Direct or Dickie Direct ($585/tonne) = $134/ha. Or $153/ha with Sulphur, or Triple Plus @ 200kg/ha from Inphos ($610/tonne) = $154/ha on ground.

Dicalcium Phosphates

Ravensdown DCP ($196/tonne) at 800 kg/ha on ground price = $260/ha.

Feed grade 17 per cent P DCP applied 210 kg/ha from Dickie Direct or Fertilisers Direct = $178/ha. Or $197/ha with Sulphur.

DAP

Ravensdown DAP ($800/tonne) @ 180 kg/ha on ground price = $173/ha. Or $194/ha with Sulphur on ground.

Dickie Direct or Fert Wholesale Direct DAP ($700/tonne) = $155/ha or $174/ha with Sulphur.

MAP

Ravensdown MAP (Ammophos) ($895/tonne) @ 160 kg/ha = $169/ha. Or $190/ha with sulphur.

Fert Wholesale Direct or Inphos MAP ($700/tonne) = $137/ha. Or $158/ha with sulphur.

Granular RPR

Ravensdown RPR (11.6 per cent P priced at $395/tonne) @ 310 kg/ha = $163/ha. Or $184/ha with sulphur.

Dickie Direct RPR (12.5 per cent P priced at $335/tonne) @ 290 kg/ha = $135/ha. Or $156/ha with sulphur.

Last year Ravensdown paid an average rebate of $30/tonne, which taxed at 33c gives a cash rebate of $20/tonne which equates to around $8/ha, so there is an average saving of $20/ha using importers products. The advantage of using high analysis fertilisers however drops off when being applied by truck, where using single superphosphate-based fertilisers can be just as economic as the imported high analysis fertilisers once rebates are factored in.

After going through the above exercise for the consultant, he would be able to see that for a 500ha sheep and beef farm he could save them $10,000. Or for a 1000ha farm the saving would be $20,000, which should cover his annual consulting fees several times over. He did respond that it is more convenient to get from the local co-op store, but I said that if it took an extra week or two to get from another supplier, I’m sure most farmers would be well prepared to either order a week or two ahead, or wait another week or two for this sort of saving.

Disclaimer – these are the opinions of independent agronomy and soil fertility consultant Robin Boom, of Agronomic Advisory Services. Any decisions made should not be based on this article alone and appropriate professional assistance should be sought. Robin Boom, CPAg, is a member of the Institute of Professional Soil Scientists. Ph: 0274448764. Email: agronomics@xtra.co.nz

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