All farm­ers need a nu­tri­ent plan

Matamata Chronicle - - Rural Delivery - By BALA TIKKISETTY

As the soil starts warm­ing up over the next few months, farm­ers will be pre­par­ing to fer­tilise their pad­docks. From both busi­ness ef­fi­ciency and en­vi­ron­men­tal pro­tec­tion per­spec­tives, it’s im­por­tant to bear in mind the risks of ap­ply­ing too much fer­tiliser, and ap­ply­ing it in the wrong place or at the wrong time.

Get­ting it wrong means ben­e­fits of fer­tiliser are wasted and it can end up con­tam­i­nat­ing ground­wa­ter and pro­mot­ing al­gal growth in nearby wa­ter­ways.

As there are a range of risks when ap­ply­ing fer­tiliser, and strate­gies to help you avoid them, I rec­om­mend all farm­ers have a nu­tri­ent bud­get and a nu­tri­ent man­age­ment plan for their prop­er­ties and dis­cuss their sit­u­a­tion with their fer­tiliser rep.

It’s also a re­quire­ment of our re­gional plan to have such a bud­get and plan if ni­tro­gen (N) use ex­ceeds 60 kilo­grams per hectare per year.

Reps or con­sul­tants can help with nu­tri­ent bud­gets for those who don’t have them, while AgRe­search last month re­leased the new Over­seer nu­tri­ent bud­get model ver­sion 6, which can be down­loaded from over­

One fac­tor to bear in mind when do­ing nu­tri­ent bud­gets in Waikato is that re­cent soil qual­ity mon­i­tor­ing re­sults re­veal that high fer­til­ity and com­paction continue to re­main as prob­lems on dairy and some dry­s­tock sites.

An­other is­sue to con­sider is ni­trate leach­ing. Plants need N for healthy leaf growth. But N is an ex­tremely mo­bile nu­tri­ent. If more ni­troge­nous fer­tiliser is ap­plied than plants can take up most of the un-used N ends up leach­ing down through the soil into ground­wa­ter. Some­times N will also be lost to wa­ter­ways as run-off and some is al­ways re­leased back into the air as gas.

An im­por­tant rea­son for in­ef­fi­cient N cy­cling in grazed pas­tures is the de­po­si­tion of N by graz­ing an­i­mals in con­cen­trated urine patches.

The amount of N that is de­posited is gen­er­ally much greater than can be taken up by the plants in the area of the urine patch, and the ex­cess N can be lost through leach­ing.

These losses are likely to be high­est dur­ing pe­ri­ods of high drainage with ex­cess rain­fall and low soil tem­per­a­tures that limit pas­ture growth and N up­take: au­tumn, win­ter and early spring.

Dung patches may also con­trib­ute to a lesser de­gree – dung con­sists mainly of or­gan­i­cally bound N that is re­leased slowly.

The amount of N leach­ing from pas­tures can be re­duced by;

Tim­ing fer­tiliser ap­pli­ca­tion to avoid pe­ri­ods when plant up­take of N will be low, such as when soils are sat­u­rated, dur­ing heavy rain, colder pe­ri­ods and times of low soil tem­per­a­tures

Ap­ply­ing N fer­tiliser in split dress­ings (as many split doses as pos­si­ble), rather than all at once

Ir­ri­gat­ing farm dairy ef­flu­ent to a large enough area

Ad­just­ing fer­tiliser pol­icy for ef­flu­ent ir­ri­gated ar­eas to ac­count for the nu­tri­ent value of ef­flu­ent

Us­ing fenced wet­lands and well-man­aged open drains as nu­tri­ent traps.

The nu­tri­ent phos­pho­rus be­haves very dif­fer­ently to N be­cause it binds with the soil and only dis­solves slowly in wa­ter over time. This means it doesn’t read­ily leach to ground­wa­ter. But it can still dam­age the health of wa­ter­ways through soil ero­sion and sur­face run-off into wa­ter.

Farm­ers can re­duce the amount of phos­pho­rus run-off by not ap­ply­ing phos­phate fer­tiliser when heavy rain is com­ing. Other tips in­clude: Fol­low­ing the Fer­tiliser Man­u­fac­tur­ers’ Re­search As­so­ci­a­tion Code of Prac­tice for Nu­tri­ent Man­age­ment

Ap­ply­ing fer­tiliser when the grass is in an ac­tive grow­ing phase Not ap­ply­ing fer­tiliser near wa­ter­ways Leav­ing a grassed buf­fer strip be­tween pad­dock and wa­ter­way – the strip fil­ters the phos­pho­rus be­fore the run-off reaches the wa­ter

Con­trol­ling run-off from tracks, races, feed and stand-off pads.

Mean­while, if soil Olsen P lev­els are high, it’s likely more phos­phate fer­tiliser has been ap­plied than needed for op­ti­mum pas­ture growth.

It also means there is a greater chance of los­ing a lot of added phos­pho­rus to nearby wa­ter­ways.

Soil tests com­bined with an Over­seer nu­tri­ent bud­get can help en­sure soil fer­til­ity isn’t ex­ces­sive and re­duce the amount of nu­tri­ents lost from the farm.

Be aware that fer­tiliser can be poi­sonous if in­gested by stock.

Make sure an­i­mals don’t have di­rect ac­cess to fer­tiliser bins.

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