6 November 1998

Artificial lime

will bear fruit

By Edward Long

NEW research shows 70% dry factory lime reduces soil acidity faster than ground limestone and does more to boost sugar yields.

Independent trials conducted by Horticulture Research International at Kirton, Lincs, compared the effect on soil pH of 3, 5, and 7t/ha applications of British Sugars LimeX70 product with 5t/ha of ground limestone.

When soil was tested 35 days later the untreated area averaged pH 6.17. The ground limestone boosted that to 6.36, the 3t/ha treatment of LimeX70 to 6.43 and the 5t/ha rate to 6.58. There was no advantage from using the top rate.

After 71 days the pH in the untreated soil had fallen to 5.86. It was 0.09 higher where limestone had been applied and 0.17 better where the low rate of factory lime had gone on. Again 5t/ha of LimeX70 did best, lifting pH 0.25.

"The results show conclusively that at a comparable rate of 5t/ha LimeX70 increases the soil pH more quickly than ground limestone," says Andy Spetch of British Sugars co-products division.

"Speed of activity is important, particularly for vegetables which are only in the ground for a short time."

Separate trials by BS on beet growing farms in North Yorks and Notts checked the new products effect on sugar yield. At the northern site, ground limestone produced an extra 1.21t/ha and LimeX70 a further 0.44t/ha.

At the Notts site ground limestone increased yield by 0.3t/ha and factory lime by 1.54t/ha.

Cost of ground limestone used at the Yorks site was £120/ha, factory lime costing £11/ha more. At C-beet prices that left a net loss of £15/ha with ground limestone, but a £14/ha gain from the LimeX70.

At Langar, Notts, more lime was needed, so the limestone cost £170/ha and the factory material £20/ha more. At C-beet prices both products left a net loss. But at the A&B price there would have been a net gain from LimeX70, notes BS.

As well as correcting acidity, LimeX70 contains nutrients worth £6/t, says BS. Each tonne contains 9kg of sulphur, 8.5 of phosphate, 7.5 magnesium and 4.5kg of nitrogen.

BS attributes the faster liming effect to a smaller particle size. The industry standard requires at least 40% of an acidity correcting material to pass through a 150 micron sieve. Levington Research results show over 90% of LimeX70 passes through.

The first batch of LimeX70 to be produced at Bury St Edmunds is seen here in an on-site storage area which can hold up to 50,000t of the product. The new £2.1m dry liming plant (inset) has five presses which can produce 500 tonnes of LimeX70 a day.