30 June 1995

Lime applications help to keep potato growers in profit

LIME has a crucial role in profitable potato production, according to independent consultant Bill Rennick, adviser to leading Irish potato grower Pat Reynolds of Garlow Cross, Navan, Co Meath.

"The two key inputs for potatoes are good sub-soiling to get the soil structure right and lime," Mr Rennick told a Potato Marketing Board group visiting Eire last week. "Lime helps us get the nutrient balance of the crop right. It makes phosphate more available, and supplies magnesium and calcium, too."

Typical application is 5t/ha (2t/acre) of Dolomitic limestone, according to soil analysis. "Most of these soils are index 1 for N and P, 1 to 3 for K and 1 for calcium. They are pretty sour." Application is on to the preceding crop stubble before winter ploughing. Sub-sequent de-stoning and bed tilling ensures a good mix.

Such a treatment provides 11% magnesium in a form the establishing crop can use immediately.

With soils typically about pH5.4 scab risk is not appreciably increased. Indeed, calcium aids cell wall development, so improving skin set and freedom from disease, he reckons. "We get the calcium on early so we dont have to worry about supplying it later as a foliar feed."

Yields from early-April planted Record, Maris Piper and Fianna average 39-42t/ha (16-17t/acre), Mr Rennick adds. &#42