Worms es­sen­tial for good pas­tures

Matamata Chronicle - - Rural Delivery - By BALA TIKKISETTY Bala Tikkisetty is a sus­tain­able agri­cul­ture co­or­di­na­tor at Waikato Re­gional Coun­cil. For more in­for­ma­tion con­tact him on 0800 800 401 or bala.tikkisetty@waika­tore­gion.govt.nz

The hum­ble earth­worm is worth its weight in gold when it comes to on-farm soil pro­duc­tiv­ity and pro­tect­ing wa­ter­ways from the im­pacts of farm­ing.

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

These in­tro­duced earth­worms are, in fact, 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.

Earth­worms also in­crease the pop­u­la­tion, ac­tiv­ity and di­ver­sity of soil mi­crobes, such as acti­no­mycetes and my­c­or­rhizal fungi.

These mi­crobes play a vi­tal role in the sup­ply of nu­tri­ents to pas­ture, di­gest­ing soil and fer­tiliser, and un­lock­ing nu­tri­ents such as phos­pho­rus that are fixed by the soil.

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 peat­like 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 ab­sorp­tion of ap­plied fer­tiliser.

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

And, as in­di­cated ear­lier, wa­ter runs off this type of pas­ture more eas­ily rather than be­ing ab­sorbed into the soil, in­creas­ing wa­ter qual­ity prob­lems.

To help avoid these types of prob­lems, soils should have a good di­ver­sity of rel­e­vant earth­worm species.

The most com­mon in­tro­duced earth­worm in New Zealand is Apor­rec­todea calig­nosa, a top­soil dweller.

This earth­worm grows up to 90 mil­lime­tres long and may vary in colour from grey to pink or cream.

An­other very com­mon in­tro­duced earth­worm is Lum­bri­cus rubel­lus, a sur­face dweller.

Of­ten found un­der cow pats, this earth­worm will grow up to 150mm long. It is red­dish-brown or red­dish­pur­ple colour­ing with a pale un­der­side and flat­tened tail.

Apor­rec­todea longa live in bur­rows as deep as two to three me­tres be­low the sur­face.

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

Counts should prefer­ably be done from late win­ter to early spring when soil mois­ture and tem­per­a­ture con­di­tions are ideal.

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

If soils are scor­ing way be­low that there is a range of ways to in­crease their pop­u­la­tions:

En­sure soil cal­cium lev­els are near 7 as cal­cium pro­motes earth­worm re­pro­duc­tion.

Main­tain soil pH be­tween 5.8 and 6.3.

Limit use


fu­mi­gants and other pes­ti­cides.

Re­duce am­mo­nium-based fer­tilis­ers as they make soils acidic. Also, moist soils pro­mote earth­worm spread and ac­tiv­ity, and more will re­main ac­tive in top­soil dur­ing sum­mer un­der ir­ri­ga­tion.


Soil sense: Look­ing af­ter soil is fun­da­men­tal for farm­ers and food pro­duc­tion, says Bala Tikkisetty (pic­tured) of Waikato Re­gional Coun­cil.

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