Fer­tiliser bal­ance is cru­cial for peat soil

South Waikato News - - RURAL DELIVERY - By BALA TIKKISETTY

Get­ting peak pro­duc­tiv­ity from the re­gion’s pro­lific peat soils is cru­cial for farm­ing prof­itabil­ity. This re­quires care­ful man­age­ment, tak­ing into ac­count the par­tic­u­lar char­ac­ter­is­tics of the peat soils. There are dif­fer­ent peat types that re­quire dif­fer­en­tial man­age­ment.

About 80 per cent of the peat soils in our re­gion have been de­vel­oped, mostly for farm­ing.

Peat soils are both highly pro­duc­tive and frag­ile.

They re­quire dif­fer­ent man­age­ment than min­eral soils to max­imise their pro­duc­tiv­ity. In par­tic­u­lar, farm­ing peat land ad­ja­cent to lakes and wet­lands re­quires care­ful man­age­ment to avoid dam­ag­ing them.

The re­mains of wet­land plants in ar­eas with high water ta­bles con­trib­ute to the for­ma­tion of peat. The high water ta­ble in these ar­eas stops the rapid break­down of the dead plant ma­te­rial. Con­se­quently, peat soils have more than 20 per cent or­ganic car­bon in the top­soil.

Though drainage and cul­ti­va­tion of peat is es­sen­tial to es­tab­lish pro­duc­tive pas­ture, it leads to ir­re­versible shrink­age of the peat and re­sults in a con­tin­ued sub­si­dence of the land sur­face.

Sub­si­dence is the re­sult of con­sol­i­da­tion and chem­i­cal break­down of soil car­bon, which is es­ti­mated at about 200 mil­lime­tres per year af­ter the ini­tial cul­ti­va­tion, re­duc­ing to around 20mm per year as the peat be­comes more con­sol­i­dated.

De­vel­op­ment and drainage of peat also dam­ages the nearby wet­lands and peat lakes. The Waikato peat lakes are the largest re­main­ing col­lec­tion of such unique habi­tats in the coun­try and have at­tracted in­ter­na­tional at­ten­tion. Their unique ecosys­tems are highly de­pen­dent on the care­ful bal­anc­ing of water lev­els.

When it comes to the suc­cess­ful farm­ing of peat soils, the ef­fec­tive use of fer­tilis­ers is nec­es­sary, with care needed over the amount, ap­pli­ca­tion tim­ing and type of fer­tiliser used. This is be­cause Waikato peat soils have a low nu­tri­ent sta­tus. Ap­ply­ing the cor­rect amounts of the right type of fer­tiliser will main­tain good pas­ture for longer pe­ri­ods, re­duc­ing the need for fre­quent cul­ti­va­tion and pas­ture re­newal.

Lime is also re­quired to in­crease the soil ph to an ap­pro­pri­ate level for pas­ture and crop species. Soil and herbage tests de­ter­mine what fer­tiliser peat soils on in­di­vid­ual prop­er­ties need.

Tim­ing of fer­tiliser ap­pli­ca­tion should be so that plant up­take is max­imised and po­ten­tial ef­fects on the en­vi­ron­ment min­imised. Fer­tiliser should be uni­formly and evenly ap­plied with none out­side the tar­get area. The pre­ci­sion place­ment of fer­tiliser de­pends on a num­ber of fac­tors. It re­quires care­ful in­te­gra­tion of op­er­a­tor skills, sound equip­ment and ap­pro­pri­ate for­mu­la­tion of fer­tiliser.

I rec­om­mend that farm­ers fol­low the code of prac­tice for the place­ment of fer­tiliser in New Zealand. The Spread­mark Code of Prac­tice is a fer­tiliser place­ment qual­ity as­sur­ance pro­gramme, which is gov­erned by the Fer­tiliser Qual­ity Coun­cil.

Peat soils typ­i­cally have a low an­ion stor­age ca­pac­ity. This means the leach­ing of nu­tri­ents to ground water will be sig­nif­i­cant in peat soils. In­creased leach­ing of nu­tri­ents can oc­cur when water ta­bles are near the ground sur­face.

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