7 June 1996

CaN research to be expanded

WITH crop quality in vegetables and fruit more important than ever for some growers, fertiliser company Hydro Agri (UK) is expanding its research on calcium nitrate.

As a nitrogen source CaN (strictly speaking CaNO3) is significantly more expensive than ammonium nitrate or urea. Compared with ammonium nitrate at £150/t CaN costs about £130/t – but it contains only half as much N.

However, it offers useful benefits to crops prone to calcium deficiency disorders, such as pepper spot in cabbage, tip burn in lettuce and bitter pit in apples, explains the firms Dr Geoff Poulson. "Most N fertilisers acidify the soil. But calcium nitrate has a slight liming value." Another advantage is that all the N is in the form of nitrate so bypassing the need for the soil conversion processes required to make most of the N in other fertilisers readily available, he says.

Although CaN is the number-one source of N in Norway, it has only a tiny share of the UK market, mainly for use in hydroponics and fertigation, he adds.

The first two of four years of UK trials using it as a soil dressing in Bramley apple orchards gave some fairly promising results against bitter pit, says the firms horticultural agronomist, Miles Harriman. But for the past two mainly dry seasons, when possibly the fertiliser was not washed in sufficiently, results were less good. "So we need to look at it in more depth," he says. CaNs role in countering club root by maintaining pH levels in the immediate rooting zone of brassicas will also be examined, he adds.

The trials, with a range of leading growers and research bodies, include a set at the Scottish Agricultural Colleges, where the target problem is internal rust spot in potatoes. &#42