3 May 1996

trial thumbs-up

Petiole analysis

PETIOLE analysis to fine-tune foliar feeding of potatoes should see more takers this season.

That is the opinion of Phosyn director Chris Merry after two years of field trials at Askham Bryan Agricultural College.

The technique requires careful sampling and uses independent analysis to arrive at specific recipes to correct nutrient deficiences. Applied to the variety Record in two years of tests at the college it gave yield lifts of 10.6% in 1994 and 6.6% last year despite the drought, according the firms David Bilsborough. "The results are very significant," said Mr Merry. "There has been some disillusionment with other forms of analysis. This is clearly an established technique."

Although skilled interpretation of the analysis to determine the best corrective treatment is required, the technique is not product orientated, he stressed. Growers can use a variety of nutrients provided they fit the crops requirements.

The UK experience echoes that in the USA where petiole testing has been successfully used since the 1970s, according to Phosyns Andrew Sefton. But accurate sampling is vital to avoid gathering misleading information.

To obtain meaningful analyses Phosyn recommends taking the fourth petiole from three or four plants at 20 sites across the field. This should be done at least three times – at 10% flowering and then at least twice more at three to four week intervals.

"It is important not to select an immature petiole which can read 3000-400ppm nitrate N lower than the fourth petiole," explained Mr Sefton. "It is also important to be consistent by taking samples from the same part of the field on each occasion and ideally at the same time of day."

Cost of a monitoring, excluding growers time, is £25.50.

&#8226 Needs careful sampling and skilled interpretation.

&#8226 Specific nutrient recipes devised to avoid deficiency.

&#8226 Boosted Record yield by 10.6% and 6.6% in 1994/5.