AN fertiliser boosts yields by 0.7t/ha compared to urea

South Shropshire producer Rob Pugh, of R. H. Pugh and Sons, near Bridgnorth, gained an extra 0.7t/ha and boosted margin over fertiliser costs (MOFC) by over £60/ha after cutting out urea in favour of ammonium nitrate (AN) in farm trials last year.


Even limiting urea to a single application sandwiched between two AN-based treatments yielded 0.3t/ha less and dropped MOFC by nearly £30/ha compared to a full AN system despite ideal conditions for urea use, he says.


“If ever there was a year for urea to perform well here, 2019 was it!


“We got it on at the right time, temperatures were perfect and we had adequate rainfall after application so volatilisation should have been reduced to a minimum and crop uptake maximised.


“But despite this, the urea was convincingly outperformed by the AN in all cases, even when we cut it right back to a single application in between AN-based applications, the detrimental effect it was having on yield and economics was clear.”


“We rely quite heavily on CF Fertilisers’ N-Min programme to help us establish N availability in the soils and then use N-Calc to work out N requirement based on the yield potential of the crop.


“Ian Roe of ACT Ltd walks our ground, sampling the soils in late winter and reports back with the recommendations shortly afterwards.


In the fertiliser trials at the farm last year, using the CF N-Min test, a level of 68kg N/ha was measured plus a further 30kg N/ha was shown to be already in the crop giving a total Soil Nitrogen Supply (SNS) of 98kg N/ha.


CF Fertilisers’ N-Calc service then calculated an additional 172kg N/ha would be required to produce a 10.0t/ha crop taking into account the field’s soil type and previous cropping.


For the trial, it was decided to increase the rate to 191kg N/ha to allow the high yielding variety, Gravity, the opportunity to reach its full genetic potential with all three fertiliser treatments being based on this recommendation.


All three fertiliser treatments received their first application as CF DoubleTop providing 39kg N/ha and 53kg SO3/ha.


To supply the remaining balances of Nitrogen the urea treatment, received the remaining 152kg N/ha as urea, the urea/AN combination received 58kg N/ha from urea and 95kg N/ha from Nitram. The final AN only treatment received the full balance [152kg N/ha] as Nitram in two splits.


The DoubleTop/urea regime produced a yield of 11.96t/ha, the DoubleTop/urea/Nitram regime produced 12.37t/ha and the DoubleTop/Nitram only option delivered 12.65t/ha.


Using representative costs of £130/t for wheat, £0.64/kg for AN, £0.47/kg for urea and £0.85/kg for DoubleTop, MOFC for the three options was £1450, £1486 and £1514/ha respectively – an advantage of £64/ha in favour of the full AN-based regime.