Fo­cus on cleaner wa­ter

The Northland Age - - Local Life / Opinion - ■ mikef@nrc.govt.nz Cr Mike Fin­layson

I have been for­tu­nate to chair the Doubt­less Bay Catch­ment Group (DBCG) over the last two years. Much work had been done be­fore then, but this year we fi­nalised the DB Catch­ment Plan, which iden­ti­fies the wa­ter qual­ity is­sues and lists a range of reg­u­la­tory and non­reg­u­la­tory meth­ods to achieve the im­prove­ments listed in the plan.

Two non-reg­u­la­tory ap­proaches pro­mote the use of nat­u­ral fer­tilis­ers and im­proved soil health to re­duce sed­i­ment dis­charges and nu­tri­ent losses to wa­ter.

The group wants to trial bi­o­log­i­cal fer­tilis­ers to in­crease bi­o­log­i­cal soil ac­tiv­ity, to re­duce over­land ero­sion and nu­tri­ent leach­ing on gen­tly slop­ing pas­tures, cur­rently man­aged with con­ven­tional fer­tiliser, and com­mis­sioned a re­port from Land­care Re­search to in­ves­ti­gate the im­pact of this.

An ear­lier Niwa study into the Mangōnui Har­bour sed­i­ment sources showed that sed­i­ment gen­er­ated from pas­ture dom­i­nated sam­ples in five of 19 sub-catch­ments. The hy­poth­e­sis was that bi­o­log­i­cal fer­tilis­ers, par­tic­u­larly slow-re­lease rock dusts, will in­crease root growth, in­crease ben­e­fi­cial micro­organ­isms, and de­crease nu­tri­ent leach­ing and sur­fi­cial ero­sion.

We were de­lighted when the re­port con­firmed this, ce­ment­ing this ap­proach with sound re­search into the tool­kit avail­able to farm­ers and other land users to bet­ter pro­tect their land, wa­ter and bot­tom line.

Soil science is in­cred­i­bly com­plex, as is the way by which a plant can up­take nu­tri­ents. A cu­bic inch of healthy soil is home to more than a bil­lion mi­cro-or­gan­isms, and some syn­thetic fer­tilis­ers can di­min­ish this mi­cro­scopic com­mu­nity that is so es­sen­tial for plant and an­i­mal health. Nat­u­ral fer­tilis­ers, on the other hand, im­prove soil struc­ture, in­crease root depth and mass, which makes the plant more drought-re­sis­tant and pro­vides bet­ter nu­tri­tion for stock.

Build­ing or­ganic mat­ter in soil in­creases its wa­ter-hold­ing ca­pac­ity and de­creases nu­tri­ent leach­ing to wa­ter­ways. Plants also ben­e­fit by the in­crease in my­c­or­rhizal fungi, which can boost roots’ reach by up to 700 per cent, which can re­lease pre­vi­ously un­avail­able phos­pho­rus to the plant.

It is im­por­tant to note that ero­sion and leach­ing re­duc­tion on pas­tures can­not be achieved just by chang­ing the type of fer­tiliser. Farm plans look at ad­di­tional ero­sion mea­sures like ri­par­ian plant­ings and fenc­ing, along with a raft of other mea­sures. The NRC has boosted its farm plan­ning staff to in­crease sup­port to farm­ers across the re­gion. If you are a farmer, please con­sider us­ing this free ser­vice.

Hill coun­try farm­ers face ad­di­tional ero­sion is­sues, which can be also ad­dressed and sup­ported by farm plans. Farm forestry, be it ex­otic, indige­nous or a mix, is cur­rently get­ting lots of sup­port from both lo­cal and cen­tral gov­ern­ment, and now is the per­fect time to in­ves­ti­gate how to prof­itably in­cor­po­rate it into a sus­tain­able farm man­age­ment plant. If you would like a copy of the Land­care Re­search re­port please email me.

"Build­ing or­ganic mat­ter in soil in­creases its wa­ter­hold­ing ca­pac­ity and de­creases nu­tri­ent leach­ing to wa­ter­ways."

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