FARMERS have not seen the end of skyrocketing fertiliser prices, which have the potential to cause loss of production in the sheep and beef sector -- a major player in Gisborne's rural economy.

The price of superphosphate went up $60 in December and after May 31 it is understood to be taking another $100 hike.

These price changes would definitely impact on farm decisions, said Summit Quinphos representative Mark Gemmell at a community group meeting at Meat and Wool monitor farm Elmore Station this week.

"With current lamb prices, many will be asking is it sustainable? By the time it is finished going up, it would have more than doubled in price."

However, two fertiliser representatives and some of the more seasoned farmers said it was a huge job to get fertility back and maintenance levels of fertiliser should be continued.

Tiniroto farmer Rick Spence said he had farmed through the last downturn when nearly all farmers stopped fertiliser and it cost a lot of money and time to rebuild fertility levels when prices turned around.

Ravensdown's Sue Quilter said in the past six to eight months, sulphur had gone from US$50 to US$650 a tonne and phosphate from US$100 to US$200 a tonne.

The scenario was not as bad as it seemed, she said.

"You need to do your sums for each farm but there will still be economic justification for the majority of properties to continue with fertilising."

Farmers would need to match their soil fertility levels with their stocking rate.

Mr Gemmell said some people were saying they would put half on.

"That is better than nothing but if you stop, it will take a lot to get back. This is the danger the industry is in. It's so important that the meat industry pulls its finger out and does something or it will all spiral down."

Farm consultant Peter Andrew said there were living examples of people who did not fertilise in the district and they had low stocking rates and were not making money.

Both fertiliser representatives advised farmers to talk to their fertiliser representative and they would run through a few scenarios to minimise the impact.

Mrs Quilter said while loss of phosphates would have a small impact on productivity in the medium term, the loss of sulphur would reflect in lost productivity in the first 18 months.

Sulphur leached from the soil, while phosphate did not.

While she did not want to cause a rush for fertiliser, she said that the next price hike for fertiliser was so big it was worth buying before the end of May because it would more than outweigh the interest paid for it.

Mr Andrew said having to drop fertiliser rates affected some farmers more than others. The Matawai area, where soil is pumice-based with low natural fertility, would be worse-affected by fertiliser loss than the more recent mudstone soils, which had high natural fertility.

Gisborne Ministry of Agriculture policy agent John Moroney said it was likely the same amount of money would be spent on less product.

Mr Moroney said when he was a farmer in the late '80s and '90s, they slashed private expenditure so they could afford to keep up fertility.