Our Wa­ter

New rules for ru­ral landown­ers na­tion­wide take ef­fect soon, and the most im­por­tant cov­ers ni­tro­gen loss.

NZ Lifestyle Block - - Contents - Words Emma Buchanan

Why you need to know your (ni­tro­gen) limit

Ni­tro­gen is one of the key nu­tri­ents that landown­ers need to keep on their prop­erty and out of their wa­ter­ways. No mat­ter where you live, it will be mea­sured un­der soon-to-be-in­tro­duced re­gional coun­cil reg­u­la­tions.

These reg­u­la­tions are be­ing de­vel­oped in re­sponse to the Na­tional Pol­icy Statement for Fresh­wa­ter Man­age­ment. While tim­ing and de­tails will be dif­fer­ent de­pend­ing on where you live, all re­gional coun­cils will be set­ting lim­its for al­low­able ni­tro­gen loss and will mea­sure that loss.

Most coun­cils are leav­ing it up to in­di­vid­ual farm­ers and block own­ers as to how they man­age the nu­tri­ents on their land. How­ever, Farm En­vi­ron­men­tal Man­age­ment Plans will be re­quired by most prop­er­ties 4ha and larger. These will es­tab­lish a limit on the amount of ni­tro­gen which can be lost from an in­di­vid­ual prop­erty, known as the ni­tro­gen loss limit.

Even if your re­gion hasn’t set lim­its yet, it’s im­por­tant to un­der­stand how the process works. It will be vi­tal to get your nu­tri­ent bud­get right once one is set. If you go over your ni­tro­gen loss limit, it might trig­ger the re­quire­ment to ap­ply for a re­source con­sent. Ni­tro­gen loss lim­its might also be­come rel­e­vant in de­ter­min­ing the saleable value of your prop­erty.

But how will the al­low­able lev­els be set and how will the ni­tro­gen loss be mea­sured?


This sounds warm and fuzzy, but it’s a way of set­ting ni­tro­gen lim­its. How­ever, this type of grand­par­ent will have favourites.

For ex­am­ple, in Waikato, the ni­tro­gen limit will be set on a ref­er­ence year in the past that pro­vides a base­line. Ide­ally, this base­line will be his­toric enough to avoid peo­ple try­ing to ‘game’ it. They could do this by ar­ti­fi­cially in­flat­ing their leach­ing with un­usu­ally in­ten­sive prac­tices in or­der to es­tab­lish a higher loss al­lowance.

Com­pa­ra­ble prop­er­ties might re­ceive dif­fer­ent lim­its de­pend­ing on their his­tory. Un­for­tu­nately, in some cases it might be seen to re­ward poor his­tor­i­cal en­vi­ron­men­tal prac­tices.

What­ever hap­pens, this level will be the up­per al­low­able limit of ni­tro­gen loss for that land in the fu­ture. This will mean it won’t be pos­si­ble to tran­si­tion from a less in­ten­sive land use (like forestry) to a more in­ten­sive land use (like dairy­ing).

Nat­u­ral Cap­i­tal

The other sys­tem cur­rently used for set­ting ni­tro­gen lim­its is the Nat­u­ral Cap­i­tal ap­proach. Hawke’s Bay Re­gional Coun­cil are us­ing this for the Tuk­i­tuki re­gion.

This method uses the Land Use Ca­pa­bil­ity (LUC) clas­si­fi­ca­tion. LUC is

a sys­tem de­vel­oped in the 1950s-1970s. It helps farm­ers to un­der­stand the pro­duc­tion po­ten­tial of New Zealand’s agri­cul­tural land. It takes into ac­count the gra­di­ents, cli­mate and ero­sion risks of an in­di­vid­ual prop­erty. These fac­tors give a good guide to the type of land use sus­tain­able for that area.

LUC 1 is the best land, with good longterm pro­duc­tion po­ten­tial. LUC 1-4 can be cropped, 5-7 is gen­er­ally for pas­toral farm­ing, and LUC 8 is re­ally only for con­ser­va­tion.

Each LUC class has been as­signed a leach­ing limit, on the as­sump­tion that bet­ter land is used more in­ten­sively and so gets a slightly higher al­lowance. The LUC sys­tem al­lows sim­i­lar prop­er­ties to be treated in a sim­i­lar way.

In some cases, it will be worth in­vest­ing in a pad­dock-scale remap of a farm, where the na­tional-level LUC map is not ac­cu­rate enough for the prop­erty.

A spe­cial­ist nu­tri­ent cal­cu­la­tion soft­ware (OVERSEER® or another ap­proved model) can be used to work out the limit for a prop­erty in a grand­par­ented re­gion, and to model losses against the prop­erty limit. These model an­nual nu­tri­ent losses from farms based on farm in­puts such as fer­tiliser, stock and sup­ple­men­tary feed, and spe­cific in­di­vid­ual pro­duc­tion in­for­ma­tion.

OVERSEER® up­dates as sci­en­tific stud­ies pro­vide more in­for­ma­tion about nu­tri­ent flows in farm sys­tems, so it is al­ways im­prov­ing.

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