22 February 2002

Give worms a chance to work their wonders

MASSIVE increases in worm numbers have been recorded under a minimum-tillage trial in Ireland, highlighting the considerable contribution can make to cultivation work when given the chance, say commentators.

After just one year of min-till worm number and weight was four times more under min-till than conventional plough and power-harrow cultivation in the same field.

"It just goes to show how quickly the worms come back when you convert the cultivation system," says consultant John Geraghty, who has been running the trial for Monsanto on Co Kildare grower Jim McCarthys farm.

The worms are now doing the work of the plough, says tillage consultant Steve Townsend. "They do it for nothing and they do it for 24 hours a day if you look after them. The big fellows can move an awful lot of soil."

The key beneficial species, and the one most disrupted by the plough, is a big fat worm up to 20cm (8in) long, known as Lumbricus terrestris.

It works up and down the soil profile eating, digesting and conditioning the soil. Slime and mucus trails are rich in protein and sugars, which feed bacteria, raising the organic matter and biological activity of the soil.

In turn that raises nutrient availability, retains moisture, resists compaction and helps soil structure.

"Worms are natures fertiliser factories. We all know what farmyard manure does for the soil, so why dont we use worm manure? Treat them right and they will give you all the manure you require," Mr Townsend enthuses.

Middens of straw built by the worms on the min-tilled side of Mr McCarthys field gradually disappeared during the winter as the worms dragged the crop debris down into the soil, notes Mr Geraghty.

Trials show aeration rises 60-75% and water infiltration is four to 10 times faster in worm rich soils, Mr Townsend adds.

"Wet holes become a thing of the past after a few years of minimum tillage. The water can get away to the sub-soil where it belongs."

That is echoed by Mr McCarthy. "Three years into Eco-tillage and the wet holes have disappeared on my farm."

To encourage worms tillage passes should be reduced, shallow and only carried out when dry, advises Mr Townsend. Carbamate slug pellets and mbc fungicides should be avoided where possible and care taken with liquid manures.

"They can cut off the oxygen supply if they are applied too thickly and high copper content is a risk in pig slurries."

Acidity should be corrected and increasing the amount of crop residue returned to the field will increase the worms food supply, he adds.

That has been taken on board by Mr McCarthy, who says all straw should be chopped and spread, unless it is making £60/ha (£25/acre) or more. "Selling your straw is like selling your land," he concludes. &#42

WORM WORKS

&#8226 Cultivate when dry.

&#8226 Max 10cm cultivation depth.

&#8226 No carbamate slug pellets.

&#8226 Caution with slurries.

&#8226 Avoid acidity.