Drainage key to high tech de­vel­op­ment on Tas­ma­nian farm

An op­por­tu­nity to ir­ri­gate and de­velop a Tas­ma­nian High­lands farm led Will Bignell on a high tech jour­ney to en­sure the high­est re­turn on in­vest­ment.

NZ Grower - - Landwise - By Rose Man­ner­ing

Speak­ing at the LandWISE Con­fer­ence in Have­lock North, Will says the op­por­tu­nity to de­velop the farm, which has been in the fam­ily for seven gen­er­a­tions, arose with a Gov­ern­ment­funded wa­ter project.

“We have been here since day dot, 1817.” The farm in Both­well, Cen­tral High­lands was first flood ir­ri­gated by the Scot­tish set­tlers in 1826. Red meat and poppy grow­ing are the pri­mary ac­tiv­i­ties on the farm.

Large scale Gov­ern­ment in­vest­ment in the South­ern High­lands Ir­ri­ga­tion Sys­tem has pre­sented a once in a gen­er­a­tion chance to take wa­ter out to the back of the 2500-hectare prop­erty. He can buy 150 days of wa­ter, volumes of 4.2 mega litres a day, “com­ing at you 24/7”.

Will had se­lected an area at the back of the farm know as “The Square” for de­vel­op­ment. Al­though flat, the land is poorly drained with some salt in­tru­sion so care­ful con­sid­er­a­tion was needed to en­sure de­vel­op­ment would de­liver an eco­nomic re­turn. Wa­ter needs to be piped 9.5 km, and a 130 me­tre-high el­e­va­tion, to a drained marsh­land for dry­land con­ver­sion.

“It is not cheap wa­ter.”

His fa­ther and grand­fa­ther be­fore him have at­tempted un­suc­cess­fully to drain the flats, but Will, a self con­fessed “data nerd” be­lieved he had the ex­tra tools to make the project work.

He is a well-known in­no­va­tor, and one of the early adopters of drone tech­nol­ogy; he has built up a suc­cess­ful UAV business, DroneAg, which flies a di­verse range of missions across the globe. He set out to cre­ate a “pre­ci­sion agri­cul­ture sand­wich” to en­able him to de­velop the dif­fi­cult piece of land.

To in­ves­ti­gate the site, he went about de­tect­ing high salt ar­eas us­ing an EM38 ground con­duc­tiv­ity me­ter to iso­late wet patches. >

He also grid tested the soil acid­ity (pH) and phos­phate lev­els; to cre­ate a de­tailed soil map. A bedrock sur­face model was cre­ated, which didn’t cre­ate to­pog­ra­phy or other fac­tors.

Then us­ing 3cm drone im­agery, he could see de­tail right down to a cig­a­rette pack on the ground; this de­tail was pulled through to a dig­i­tal ter­rain model.

“I had just blown $27,000, my fa­ther wanted re­sults.” From the data gath­ered he set about de­tailed plan­ning, cre­at­ing the fol­low­ing:

• Wa­ter log­ging mod­el­ling

• Vari­able rate P ap­pli­ca­tion map

• Vari­able rate lime ap­pli­ca­tion map (soil pH in places was around 5, and needed to be brought up to 6.5) Will says they achieved huge sav­ings on ap­pli­ca­tion of phos­phate and lime of close to $37,000.

“We ran some eco­nomic mod­els on var­i­ous pivot, pipe and pump com­bi­na­tions with de­cent num­bers be­hind the plan. When we made our choice, we knew what will flood and what ar­eas are at risk. From there I could pur­chase enough wa­ter for what I can ir­ri­gate safely and con­fi­dently and ac­count­ing for how much I want to risk.”

The end re­sult was a 942 m pivot with 18 spans cover­ing 160 ha de­liv­er­ing 3mm over 24 hours. Vari­able Rate Ir­ri­ga­tion could be op­er­ated on the out­side 12 spans, to al­low risk man­age­ment of salt-heavy and wa­ter­logged ar­eas.

His wa­ter log­ging mod­el­ling en­abled Will to plan big drainage works over risky soils. “Good drainage is key for my risk man­age­ment,” he says.

Drainage has been a lim­it­ing fac­tor in crop­ping sys­tems across the globe, for both ir­ri­gated and dry land, and most sur­face drainage has in­volved cut­ting drains down gul­lies and emp­ty­ing pud­dles once the dam­age is done.

The abil­ity to model sur­face flow and de­sign drainage sys­tems has pre­vi­ously had a high price en­try bar­rier and the de­vel­op­ment of pre­ci­sion drainage has been sti­fled as a re­sult. Re­cent ad­vance­ments in UAV tech­nol­ogy al­lowed the cap­ture of high res­o­lu­tion spa­tial in­for­ma­tion to al­low cost ef­fec­tive mod­el­ling, de­sign, ma­chine con­trol pro­gram­ming and whole farm plan­ning to oc­cur eas­ily and cheaply.

“In one day we got an ex­ca­va­tor in and dug a big cen­tral drain.” He then cut sur­face drains with a scraper and land­scape drains with RTK con­trols (Real-Time Kine­matic po­si­tion­ing is a satel­lite nav­i­ga­tion tech­nique used to en­hance the pre­ci­sion of sys­tems like

“It fits in where an area is too small for a chop­per and too large for a knap­sack, or ac­cess is dif­fi­cult such as a gorse in a gully,” Stephen says.

GPS). This added an 8.3 kilo­me­tre drainage net­work to The Square.

He could model dig­i­tal sur­face flow to sim­u­late what will hap­pen in a rain or flood­ing event. “In ef­fect we can sim­u­late 40 years’ farm­ing ex­pe­ri­ence. Good drainage is bang for your buck,” he says.

The drone is just like a trac­tor, it’s what you put on the back of them that mat­ters, Will says. The drone rev­o­lu­tion repli­cates aerial map­ping. With this ad­di­tional in­for­ma­tion, he had the tools that al­lowed him to de­velop this sen­si­tive area where his fore­bears were un­able to.

Luck­ily Will had pre­pared for the worst, and once his crop was es­tab­lished, a down­pour of 127 mm of rain overnight led him to ex­e­cute his emer­gency plan. He got the trac­tor out in the dark and cre­ated a 1.2km trench with a grader blade, and the wa­ter fol­lowed me out. “I needed to plan for the worst-case sce­nario; if you can model it you can do it.”

▴ Tas­ma­nian high-tech en­tre­pre­neur and farmer Will Bignell (left) and LandWISE man­ager Dan Bloomer

◀ Demon­stra­tion at the LandWISE Con­fer­ence on May 24, Stephen Wrigley from Tiro360 demon­strates his DJI Agras drone, set up for weed spray­ing, re­motely con­trolled from his cell phone. The spray unit has a 10 litre ca­pac­ity and can cover six hectares/hour.

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