Now is the time to pre­pare pad­docks

Matamata Chronicle - - Rural Delivery - By BALA TIKKISETTY Bala Tikkisetty is a sus­tain­able agri­cul­ture co­or­di­na­tor at Waikato Re­gional Coun­cil, phone 0800 800 401 or bala.tikkisetty@waika­tore­gion.govt.nz

The months fol­low­ing win­ter are usu­ally the time for cul­ti­vat­ing pad­docks so they are at their best to pro­vide fresh pas­ture or crops.

Cul­ti­va­tion prac­tices in­volve many dif­fer­ent types of tillage equip­ment (from mould­board plough to di­rect drill).

But they have a com­mon pur­pose: to re­move the com­pe­ti­tion of pre­vi­ous plant cover from the seeded or planted area and to pre­pare soil tilth suit­able for ger­mi­na­tion.

There are some is­sues to look out for.

Con­tin­u­ous cul­ti­va­tion of soil by full tillage even­tu­ally leads to a de­cline in soil fer­til­ity, mainly be­cause con­tin­u­ous cul­ti­va­tion ac­cel­er­ates or­ganic mat­ter de­com­po­si­tion.

Any plough­ing can lead to sed­i­ment and as­so­ci­ated nu­tri­ents get­ting into water­ways, af­fect­ing wa­ter qual­ity.

Also, soil ero­sion gen­er­ally can be a con­trib­u­tor to sed­i­ment and nu­tri­ents get­ting into wa­ter. A good way to pre­vent ero­sion is to main­tain as much veg­e­ta­tive cover as pos­si­ble to pro­tect bare soil. So this should be taken into ac­count when cul­ti­vat­ing.

Win­ter-feed pad­docks can be very prone to ero­sion once they have dried out, due to a loss of soil struc­ture.

Con­ser­va­tion cul­ti­va­tion prac­tices are those aimed at main­tain­ing max­i­mum veg­e­ta­tive cover on the soil sur­face and en­cour­ag­ing mois­ture re­ten­tion in soils. The aim is to pro­duce an un­even soil sur­face in as ‘‘rough’’ a con­di­tion as prac­ti­cal and keep the cul­ti­va­tion pe­riod to a min­i­mum.

Us­ing a chisel plough or grub­bers give a fine deep seedbed while still re­tain­ing a cloddy sur­face. By con­trast, top-work­ing im­ple­ments, disc­ing and rolling can cre­ate a fine seedbed prone to ero­sion even in well-shel­tered sit­u­a­tions.

Cul­ti­vat­ing and sowing at right an­gles to the slope is an­other good method for min­imis­ing soil loss.

Car­ry­ing out cul­ti­va­tion at an ap­pro­pri­ate depth and when soil is suit­ably moist also helps get good re­sults.

If good pre­cau­tions are ob­served, two-pass cul­ti­va­tion – which re­duces ero­sion risks – is of­ten all that is needed to pre­pare a seedbed.

Other tech­niques in­clude prac­tices known as min­i­mum tillage or no tillage. If soil has been con­tin­u­ously cul­ti­vated for many years, the struc­ture is likely to be poor be­cause cul­ti­va­tion re­duces soil or­ganic mat­ter lev­els. No tillage will not re­pair the dam­age overnight but will even­tu­ally. Runoff of sed­i­ment and other con­tam­i­nants, such as mi­crobes and nu­tri­ents, to wa­ter can be ex­ac­er­bated when wa­ter in­fil­tra­tion into the soil is slower than the amount of rain or ir­ri­ga­tion. Fre­quent tillage can add to the amount run­ning off be­cause the in­fil­tra­tion rate can be low due to fre­quent tillage or other man­age­ment-re­lated con­straints like com­paction

A ri­par­ian mar­gin be­tween land and wa­ter can act as a cru­cial buf­fer that helps stop con­tam­i­nants get­ting into wa­ter.

So healthy ri­par­ian veg­e­ta­tion im­proves bank sta­bil­ity, in­creases wa­ter qual­ity, re­duces stock losses, fil­ters sur­face run-off and pro­vides habi­tat for wildlife.For ex­am­ple, stud­ies show up to 90 per cent of sed­i­ment can be caught in an ef­fec­tively con­structed fil­ter strip, while fae­cal bac­te­ria trapped in long grass fil­ter strips die off in sun­light.

Ri­par­ian veg­e­ta­tion also pro­vides shade to water­ways, thereby re­duc­ing wa­ter tem­per­a­tures and growth of nui­sance plants and al­gae.

Grasses in fil­ter strips should gen­er­ally be kept to a height of at least 10 to 15 cen­time­tres with a high den­sity of stems and leaves at ground level. Also, in Waikato re­gion, farm­ers must not cul­ti­vate pad­docks within two me­tres of a river, stream or lake bed.

BUSY TIME: Pad­docks are be­ing pre­pared for pas­ture or crops.

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