28 March 1997

Chilean NPK fertiliser offers veg benefits

CHLORIDE-free NPK fertiliser newly imported into the UK is set to cause a stir among potato and field vegetable growers.

Based on potassium nitrate, the product is manufactured by Chilean company SQM Nitratos SA. Spanish and Italian potato growers have already reported improved yields and better resistance to mechanical bruising.

Potatoes are particularly sensitive to high levels of chloride, which can depress the uptake of other nutrients. They reduce yield, quality and starch content in the tubers and can hinder dry matter production.

"The main problem in potatoes is the salt effect," says Paddy Johnson of ADAS, Kirton. "High chloride levels will upset the general establishment of young plants. If salinity levels are too high, then roots dont establish properly. Salinity problems mainly apply to potatoes, which are particularly sensitive, but there are also potential difficulties with root vegetable crops like carrot and parsnip."

SQMs Antwerp-based agronomist Peter van Coillie says Contintental growers using chloride-free Chilean fertilisers have opted for a base dressing of 6-700kg/ha followed by two top dressings, one when the plants have attained 20cm of growth and a second when flowering starts. Tubers are even in shape and have a noticeably harder skin which resists damage during handling thereby reducing secondary infection, he claims.

Around 25% of the trial shipment of 400t of Chilean nitrate fertiliser, landed in February at Scunthorpe, has so far been sold in the north-west of England. It has received a positive response from growers in the region, says Ronnie Carmichael of UK agent Fergusson Wild.

However, with an on-farm price in the region of £225/t, he recognises that the product is likely to appeal to more speciality growers. "We are looking particularly at growers producing for the chip and crisp markets, and at those supplying established high quality outlets," says Mr Carmichael.