A Great Yarmouth-based fertiliser company which was sold to US group Koch last year saw its profits soar by more than �4m thanks to increased demand for its products.

South Beach Parade-based company J & H Bunn Ltd imports, manufactures and distributes fertilisers to farmers across the UK.

Recently published accounts for the year ending March 2011 show that it increased its turnover by 26.3pc from �141,566,170 to �178,797,065.

The firm entered a new era last March when the US agri-chemical giant Koch Fertilizer completed its acquisition.

Koch Fertilizer, a susidiary of Koch Industries – the world's largest private company – pledged to retain all of Bunn's national workforce, and it is thought the 50 staff at Yarmouth could eventually grow to at least 75.

In the financial year the company increased its staff numbers from 155 to 165 with most posts in production. Pre-tax profits increased from �7,856,265 to �12,143,464.

In a directors' report, the company said world fertiliser prices had fluctuated significantly over the past few years.

It said prices increased rapidly before the collapse of Lehman Brothers in September 2008 before falling sharply with the worldwide recession, but the factors originally pushing up prices including increasing demand from the Far East and South America, remained and impacted upon the market during the year.

'UK farmers reacted to the fluctuating prices by applying less fertiliser to their crops, but in order to maintain yields this could not be a long term approach and this has resulted in increased volumes sold in the year.'

During the financial year the company disposed of what it described as its 'non-core' business such as the manufacture of liquid fertiliser and brine.

The report said: 'As part of the Koch group the company and its subsidiaries are able to draw upon considerable expertise, finance and logistics so as to be able to continue its proud history of offering competitively priced high quality and innovative products.'

Bunn was founded in 1816 and has an 18pc share in the UK fertiliser market, but it is understood that Koch has ambitious expansion plans.

Dividends for the year increased significantly from �2m to more than �6m.