An in­for­ma­tive dataset is be­ing gen­er­ated.

NZ Grower - - Your Levy At Work -

Fluxme­ter re­sults re­viewed

In 2014 a new re­search project was ini­ti­ated, the root zone re­al­ity project, also known as the Fluxme­ter Net­work Project.

The Veg­etable Re­search & In­no­va­tion (VR&I) Board was re­spon­si­ble for ad­min­is­ter­ing the project with Veg­eta­bles NZ Inc. (VNZI) co-fund­ing a to­tal of $13,500 for three years along­side other veg­etable sec­tor prod­uct groups. The Min­istry for Pri­mary In­dus­try’s (MPI) Sus­tain­able Farm­ing Fund (SFF) con­trib­uted $597,000 and re­gional coun­cil fund­ing was also se­cured for a com­bined project value of $939,000 over three years.

At the end of the SFF con­tract in 2017 the project team suc­cess­fully ap­plied to the Min­istry for the En­vi­ron­ment’s (MfE) Fresh­wa­ter Im­prove­ment Fund for $485,000 to en­able the col­lec­tion of data for a fur­ther three years to con­tinue on with this valu­able data col­lec­tion work. The to­tal project is val­ued at $1.04 mil­lion, in­clud­ing fur­ther in­vest­ment of $36,000 from VNZI of $36,000 a year.

This ex­ten­sive re­search work has been un­der­taken by the Foun­da­tion for Arable Re­search (FAR) and Plant & Food Re­search and our val­ued grow­ers who in­stalled the orig­i­nal fluxme­ters at 12 host sites in 2014 and 2015. Since then in­for­ma­tion has been col­lected about nutri­ent losses from arable and veg­etable crop­ping sys­tems, with the in­ten­tion that this will con­tinue as long as pos­si­ble.

The data be­ing col­lected is an in­for­ma­tive dataset for New Zealand’s arable and veg­etable farm­ers and it’s im­por­tant that re­searchers, in­dus­try and grow­ers can have con­fi­dence the fluxme­ters are per­form­ing well and the drainage and nutri­ent loss in­for­ma­tion be­ing col­lected is re­li­able.

At the con­clu­sion of the SFF project and with a col­lec­tion of three years of data it was op­por­tune to re­view how well the net­work was work­ing, and a tech­ni­cal re­view was un­der­taken by Plant & Food Re­search in June.

This re­view eval­u­ated the mea­sured drainage vol­umes from each of the fluxme­ter sites against mod­elled (SPASMO) out­puts for the pe­riod be­tween Septem­ber 1, 2014 and Fe­bru­ary 28, this year. For most sites this is at least three years of con­tin­u­ous data col­lec­tion in­clud­ing the pe­riod when the fluxme­ters were set­tling in, and it cov­ers mul­ti­ple crop ro­ta­tions.

The re­view has shown that with the ex­cep­tion of Site Eight, fluxme­ters at all sites have ef­fec­tively cap­tured drainage wa­ter. How­ever, at times there can be large vari­a­tions in the cap­tured vol­umes be­tween the in­di­vid­ual units at each site. There are 12 fluxme­ters at each site and the dif­fer­ences re­late to dif­fer­ent drainage pat­terns within the pad­dock which can be af­fected by to­pog­ra­phy, soil phys­i­cal prop­er­ties and crop fac­tors.

Site per­for­mance

The re­view con­firmed that 11 of the 12 fluxme­ter sites are op­er­at­ing in a man­ner suit­able for the gen­er­a­tion of ro­bust data on ni­tro­gen and phos­pho­rus losses in drainage wa­ter as seen in Ta­ble 1.

At seven of the sites, one to six and 10, the cap­tured drainage vol­umes were highly con­sis­tent with the SPASMO model pre­dic­tions for the tim­ing of drainage events and pat­terns of drainage ac­cu­mu­la­tion.

At the other sites and at cer­tain times, the cap­tured drainage vol­umes de­vi­ated from the mod­elled pre­dic­tions. At Sites seven, 11 and 12, there were times when the fluxme­ters flooded and too much drainage wa­ter was cap­tured. When this hap­pened, ni­tro­gen and phos­pho­rus losses were es­ti­mated by us­ing a com­bi­na­tion of mod­elled drainage values and mea­sured con­cen­tra­tion data. Nutri­ent con­cen­tra­tion data eval­u­a­tion was car­ried out to en­sure their values were con­sis­tent with the wa­ter drain­ing through the soil pro­file, as op­posed to wa­ter from by­pass flow or ground wa­ter in­fil­tra­tion.

At Site Nine less drainage than ex­pected was col­lected. Soil phys­i­cal char­ac­ter­i­sa­tion will be used to con­firm whether the cap­tured vol­umes are be­ing un­der­es­ti­mated.

At Site Eight con­cerns have been raised about the per­for­mance of some of fluxme­ters which have cap­tured no drainage in the 41 months of mon­i­tor­ing. The per­for­mance of this site will be mon­i­tored dur­ing next win­ter and spring and if a sig­nif­i­cant num­ber of units con­tinue to col­lect no drainage wa­ter, re­in­stal­la­tion might be re­quired. Soil mois­ture mon­i­tor­ing at the site does con­firm the site has re­mained very dry through­out the mon­i­tor­ing pe­riod. For more in­for­ma­tion and a copy of the full re­port re­fer to Root­zone re­al­ity: tech­ni­cal re­view on net­work per­for­mance (Nor­ris, John­stone, Liu, Arnold, Soren­son, Green, van den Di­js­sel, Del­low, Wright, Clark 2018) on the VR&I web­site; Key­word search: fluxme­ter.

Next steps for the project

The project is con­tin­u­ing with new fund­ing from the Fresh­wa­ter Im­prove­ment Fund and con­tin­ued sup­port from in­dus­try and re­gional coun­cils. It has a new name - Pro­tect­ing our Ground­wa­ter - Mea­sur­ing and Man­ag­ing Dif­fuse Nutri­ent Losses from Crop­ping Sys­tems.

The chal­lenge for the next three years is to bring to­gether what been learned from the fluxme­ter data as well as FAR and the VR&I’ s col­lec­tive in­vest­ment in the de­vel­op­ment of good man­age­ment prac­tices for crop­ping and veg­etable farm­ers.

An im­por­tant new ob­jec­tive is around man­ag­ing iden­ti­fied en­vi­ron­men­tal risks with good man­age­ment prac­tices. Work will con­tinue with the host farm­ers and their nutri­ent loss data to iden­tify man­age­ment changes they could test to ad­dress any en­vi­ron­men­tal risks re­vealed by the data.

Ideas for the man­age­ment changes will come from the farm­ers, start­ing with a sin­gle man­age­ment change and mon­i­tor progress, in­clud­ing any con­straints that are iden­ti­fed for im­ple­ment­ing the change. It’s of­ten more im­por­tant to un­der­stand why things don’t work than why they do. At some sites nutri­ent losses are low and man­age­ment is al­ready bet­ter than good, so it will be a chal­lenge to find things that could be done bet­ter. This mes­sage is im­por­tant for the wider com­mu­nity.

An­other new ob­jec­tive con­cerns soil qual­ity and soil ero­sion losses in crop­ping sys­tems. The host farms will be used as mon­i­tor­ing sites for soil qual­ity in­di­ca­tors and sed­i­ment move­ment to im­prove un­der­stand­ing of the risks to crop­ping soils from our man­age­ment prac­tices. This in­for­ma­tion builds on the data be­ing col­lected from the fluxme­ters and com­pletes the dataset about dif­fuse losses from crop­ping sys­tems.

▴ Ta­ble 1. Sum­mary of per­for­mance for the 12 fluxme­ter sites for the pe­riod Septem­ber 1, 2014 to Fe­bru­ary 28, 2018.

◀ Plant & Food staff pre­pare to in­stall fluxme­ters at a Cen­tral Hawke’s Bay site at a depth is one me­tre be­low the soil sur­face, be­low the cul­ti­va­tion zone.

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