Worms good as gold for farm soil

Matamata Chronicle - - Out & About - BALA TIKKISETTY

Worms are com­mon as muck but good as gold when it comes to en­sur­ing healthy farm soils.

And, just like with gold, it’s im­por­tant to keep count of what you have to en­sure your riches are be­ing main­tained.

Com­mon earth­worms in­tro­duced from Europe by Pakeha set­tlers in the 1800s im­prove the gen­eral con­di­tion of farm­ing soils, re­duce sur­face runoff of con­tam­i­nants from pas­ture to wa­ter­ways and pre­vent soil ero­sion gen­er­ally.

They in­crease the depth of top­soil and the car­bon con­tent of both top­soil and sub­soil by their bur­row­ing, di­gest­ing, and reworking and mix­ing of soil and plant residues.

This process in­cludes the de­posit­ing of worm casts, which are ma­te­rial that has passed through the worm’s body, and can be as much as 25 tonnes per hectare an­nu­ally.

So th­ese in­tro­duced earth­worms are es­sen­tial to the de­vel­op­ment of fer­tile pro­duc­tive soil.

They act as bi­o­log­i­cal aer­a­tors and phys­i­cal con­di­tion­ers of the soil, im­prove soil poros­ity, struc­ture, ag­gre­gate sta­bil­ity and wa­ter re­ten­tion.

Soils with­out enough of the right type of earth­worms are usu­ally poorly struc­tured and tend to de­velop a turf mat or thatch of slowly de­com­pos­ing peat-like ma­te­rial at the sur­face. Old dung and dead plant ma­te­rial lie about the sur­face.

Th­ese fac­tors can nat­u­rally in­hibit pas­ture and crop pro­duc­tion.

Lower pro­duc­ing grasses are of­ten more ev­i­dent than rye­grass on th­ese types of soils as well.

Pas­ture growth is slow to start in spring and stops early in au­tumn. Plant nu­tri­ents tend to re­main locked in the or­ganic layer and there is poor util­i­sa­tion of ap­plied fer­tiliser.

Plants roots in such soils are rel­a­tively shal­low and pas­tures are there­fore sus­cep­ti­ble to drought.

To help avoid th­ese types of prob­lems, soils should have a good di­ver­sity of rel­e­vant earth­worm species. Not all earth­worms are the same, with dif­fer­ent species hav­ing dif­fer­ent bur­row­ing and feed­ing be­hav­iour.

Un­der­tak­ing an earth­worm count will let farm­ers know if they have enough of the right type.

For yearly com­par­isons, earth­worm counts must be made at the same time of year.

Counts can be done by tak­ing out a 20 cen­time­tre cube of soil with a spade. Aim to have about 30 and 35 worms in that cube.

Bala Tikkisetty is a sus­tain­able agri­cul­ture ad­vi­sor at Waikato Re­gional Coun­cil. For more in­for­ma­tion con­tact him on 0800 800 401 or email bala.tikkisetty@waika­tore­gion.govt.nz

Count­ing earth­worms on farms is not as strange as it sounds, says Bala Tikkisetty.

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