How con­trolled-re­lease ni­tro­gen is help­ing pota­toes

How con­trolled-re­lease nu­tri­tion is de­liv­er­ing grow­ing ef­fi­cien­cies for hor­ti­cul­ture in the Bund­aberg re­gion

Central and North Rural Weekly - - FRONT PAGE -

A MOVE to con­trolled-re­lease nu­tri­tion is help­ing to limit nu­tri­ent losses and ex­tra fer­tiliser ap­pli­ca­tions for Bund­aberg potato grower Mark Fritz.

The add-on ben­e­fits of this change in fer­tiliser strat­egy for pro­tect­ing the Great Bar­rier Reef in the re­gion are also well recog­nised.

Mark is a fourth-gen­er­a­tion grower in the area, farm­ing 240 hectares with his wife Judy, and par­ents, Gor­don and Al­li­son.

They grow crisp­ing po­ta­toes and sug­ar­cane un­der their M and J Pro­duce brand and have pre­vi­ously grown toma­toes, cap­sicums, wa­ter­melon, soy­beans and peanuts.

Mark said the pre­dom­i­nantly sandy soils on the prop­erty, which “you can’t stand on in sum­mer”, were good for grow­ing and har­vest­ing po­ta­toes in win­ter.

He said the po­ta­toes were grown from March-April through to Novem­berDe­cem­ber in 12-14 pad­docks to­talling about 80ha.

An­other 80ha of land is spelled in the ro­ta­tion and the re­main­der is de­voted to cane pro­duc­tion.

The fam­ily has been pro­duc­ing po­ta­toes for Smith’s Crisps in Bris­bane since the mid 1990s, grow­ing the com­pany’s pre­ferred va­ri­eties and meet­ing set pro­duc­tion tar­gets through­out sea­sons.

Cover crops are grown on the spelled land, with a fi­nal for­age sorghum crop be­ing

mowed and al­lowed to re­grow be­fore be­ing sprayed with Roundup and in­cor­po­rated with a disc or speed till in prepa­ra­tion for the potato plant­ing.

“We try to keep cover on the soil all the time to avoid ero­sion caused by wind or wa­ter. It stores some mois­ture and by plough­ing it back in, it stores some resid­ual nu­tri­tion and helps soil health,” Mark said.

The seed po­ta­toes are sourced from South Aus­tralia, Vic­to­ria and Char­ters Tow­ers.

The fam­ily car­ries out a pre-plant fer­tiliser ap­pli­ca­tion of phos­pho­rus with some trace el­e­ments, but with­out any ni­tro­gen, and ap­plies a com­pound fer­tiliser with the seed po­ta­toes at plant­ing.

The re­main­ing nu­tri­tion is mostly sup­plied through the side dress­ing of Haifa Mul­ti­cote Agri con­trolle­drelease fer­tiliser blends, sourced through Paul Warhurst at Sun­fam in Bund­aberg.

Util­is­ing Haifa’s poly­mer coat­ing tech­nol­ogy, the Mul­ti­cote Agri fer­tiliser re­leases nu­tri­ents into soils in a grad­ual man­ner ac­cord­ing to soil tem­per­a­ture, match­ing plants’ re­quire­ments.

It meets en­vi­ron­men­tal reg­u­la­tions, with near zero ni­tro­gen leach­ing.

Mul­ti­cote Agri com­bines poly­mer-coated gran­ules of ni­tro­gen, phos­pho­rus, potas­sium and boron, and non-coated, read­ily avail­able

nu­tri­ents.

It is avail­able with a va­ri­ety of nu­tri­tional com­po­si­tions and re­lease fea­tures.

Mark said they make up the CRF blends and ap­ply them two to three weeks af­ter plant­ing.

They use a four-month re­lease Mul­ti­cote Agri fer­tiliser with 40 per cent coated potas­sium ni­trate, 40 per cent coated sul­phate of potash and 20 per cent mag­ne­sium sul­phate, ap­plied at 350 kilo­grams/ha, as well as a two-month re­lease Haifa-coated urea fer­tiliser ap­plied at 150kg/ha.

The ap­pli­ca­tion rates can change de­pend­ing on plant den­si­ties.

Mark said a lot of bulk­ing up oc­curs later in the crop

and that’s when the con­trolled-re­lease potas­sium ni­trate “kicks-in”.

They have also tri­alled the two-month re­lease coated urea prod­uct in cane and were able to achieve sim­i­lar pro­duc­tion de­spite us­ing 20 per cent less urea than tra­di­tional ap­pli­ca­tions.

Mark said the sandy soil was prone to sig­nif­i­cant leach­ing.

“With a fall of over 75 mil­lime­tres, we could get a lot of nu­tri­ent loss,” he said.

“Through­out the crop, we could lose a lot of fer­tiliser by 90 days (af­ter plant­ing) and we are not har­vest­ing un­til 120 days.

“We did some work with a New Zealand com­pany show­ing how dif­fer­ent soil types hold dif­fer­ent amounts

of rain­fall.

“Ours only holds 25mm be­fore leach­ing, so with a 75mm rain­fall event, we can lose 40-50 units of N.”

He said they had been tri­alling CRF prod­ucts the past five years and us­ing the Haifa Mul­ti­cote Agri fer­tiliser the last two sea­sons.

“The Haifa fer­tiliser has been the most con­sis­tent prod­uct and has han­dled the blend­ing,” he said.

“Some other fer­tilis­ers have had dif­fer­ent nu­tri­ent re­leases and can break down in the blend­ing.”

Mark is also us­ing Haifa’s CRF to avoid mul­ti­ple fer­tiliser ap­pli­ca­tions in the potato crops dur­ing the sea­son.

“We might have been ap­ply­ing up to three

ap­pli­ca­tions with a spreader. Now we only ap­ply cal (cal­cium) ni­trate and boron about half­way through the crop, and we have two less prod­ucts in the shed,” he said.

Yields of 15 tonnes per acre are tar­geted and last sea­son, de­spite some rain­fall dam­age, a yield of 14.8t/ac was achieved.

Mark said they are now pro­duc­ing bet­ter-sized po­ta­toes, but ad­mit­ted this also could be at­trib­uted to the im­proved seed potato qual­ity.

The Fritz fam­ily’s potato crops are wa­tered via lat­eral and over­head trav­el­ling ir­ri­ga­tors, with some trickle tape also used, draw­ing from un­der­ground wa­ter and dams.

GOOD SOIL: Bund­aberg grower Mark Fritz, Tony Gras­sick and Haifa Queens­land Re­gional Agron­o­mist Peter An­der­son in­ves­ti­gate the qual­ity of a young potato crop on the fam­ily's prop­erty. PHOTO: CON­TRIB­UTED

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