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Practically managing soil N using quick tests

2014 Conference presentation by Matt Norris and Paul Johnstone
The New Zealand Institute for Plant & Food Research Limited

Norris NTestStripNitrogen fertiliser is used extensively to maximise productivity across a range of vegetable, arable and forage crops in New Zealand. Matching crop N demand with supply from residual soil mineral N, N mineralisation from organic matter and fertiliser N is central to economic and environmental outcomes in these sectors.

To improve nitrogen use efficiency, effective tools and approaches are required to help guide nutrient management decisions. One potential method is the ‘quick test’ soil nitrate (NO3-N) approach. This in-field approach uses a ‘test strip’ impregnated with a NO3-N sensitive alert zone which, with a simple colorimetric scale, may be used to measure soil solution NO3-N concentrations. Measured NO3-N concentrations can then be compared with critical threshold limits that have been established for a number of crops.

The quick test strips have already been used for a number of years overseas to support growers in making N fertiliser decisions. Depending on NO3-N levels at sampling, a test strip reading may indicate the need for fertiliser to be applied, withheld for a period or eliminated entirely. The test can therefore provide more certainty in decision making. In addition to being cost effective and simple to use, the quick test approach provides the user with rapid information thus enabling decisions to be made at short notice.

In 2013–14, Plant & Food Research undertook a series of proof-of-concept trials to examine the ‘quick test’ soil nitrate (NO3-N) approach under NZ conditions. The aim of the work was to:

  1. substantiate the relationship between test strip nitrate values and laboratory-determined mineral N (the ‘gold standard’) and
  2. assess the suggested quick test critical thresholds for making N fertiliser decisions in beetroot and carrot crops.

Results from this preliminary work were encouraging. Follow on trials will test further the suitability of the strip in making field-scale N fertiliser decisions.


New Zealand Soil Management Field Days

Don’t miss LandWISE 2017: Are we ready for automation?
24th-25th May 2017, Havelock North

8th-9th March 2017, Pukekawa, Pukekohe

The NZ Soil Management Field Days offer a two day field aimed at all areas of crop production that needs to cultivate the soil.

The two Days aim to bring together a broad selection of machinery companies keen to demonstrate their products both new and existing.Also present will be new technology looking to improve our understanding of the soil and better ways to control weeds and disease.

Catering on site will be available for the two days with coffee and hot food. Upon registration the first 250 entrants will receive a free event hat.

On the first afternoon FAR will give three presentations on:

  1. Research outcomes for soil management and environmental issues
  2. Cultivation techniques long term trial Northern Crop research site
  3. Soil quality results from focus on potatoes project and then these will be repeated in in the morning of the second day.

Once again many thanks to all the main sponsors and exhibitors and to Sundale Farms for the use of the site.

Location: 585 Highway 22, Pukekawa 2696

This is an opportunity to see new technology and techniques from a broad base of suppliers from throughout New Zealand.

The  Pukekohe area has a unique 12 months of the year growing potential, a wide variety of crops grown, and some of the biggest grower operations in the country. Within New Zealand there are many companies with  new ideas and great equipment which don’t get seen.

Special note to suppliers and potential sponsors

Contact the organisers to ask any questions, they are hoping to accommodate as many companies as possible and expect growers from all over the country to come.

Email the organisers:


The Value of Smart Farming

header1525 and 26 May 2016

Havelock North Function Centre

LandWISE 2016: The Value of Smart Farming is our 14th Annual Conference! Details are on-line and registrations open.

This year we are proud to host a delegation from Australia with two dozen growers and advisors crossing the Tasman to join us. The conference is the central point of their week long tour from Auckland through the Bay of Plenty to Hawke’s Bay and the Manawatu.

Tour leader, Ian Layden is also one of our keynote speakers. Ian and the Queensland growers have been trialing precision vegetable growing, assessing the same sort of things that are of interest to LandWISE members. We look forward to learning from their experiences.

A carrot harvester fitted with a yield monitor as part of Queensland Precision Vegetables research. (C) Image from SPAA 2015 Conference Proceedings
A carrot harvester fitted with a yield monitor as part of Queensland Precision Vegetables research. (C) Image from SPAA 2015 Conference Proceedings

On a different angle, Charles Merfield will present results from a review of the agricultural uses of plant biostimulants. Plant biostimulants are diverse substances and microorganisms used to enhance plant growth. The global market for biostimulants is projected to increase 12 % per year and reach over $2 billion by 2018!  Despite the growing use of biostimulants in agriculture, many in the scientific community consider biostimulants to be lacking peer-reviewed scientific evaluation. Merf’s review will get us up to date with the science that is available on this topic of great and growing interest.

In 2015, LandWISE and Plant and Food Research began a three year project investigating variability in onions crops. We will report results from our first year’s activities, ranging from individual onion measurements to images from satellites and a swag of things in between.

Mapping canopy development with smartphone app - camera shrouded to avoid shadow effects
Mapping canopy development with smartphone app – camera shrouded to avoid shadow effects

We hear more and more about “big data” and “data analytics” and “value chains”.  These need not be scary! and we have several experienced speakers to let you in on the secrets. Join Alistair Mowat, James Beech and Megan Cushnahan as they explain value chains, the value of massive amounts of image data to identify signatures of specific crop factors, and how big data gives insights that were previously unseeable.

The party wouldn’t be complete without a peek at field robots and UAVs. Do you know the Civil Aviation rules about flying a drone – even on your own place?

Check out the programme, register and we’ll see you in Havelock North!

Thanks to Our Loyal Platinum Sponsors!
Thanks to Our Loyal Platinum Sponsors!

The One Minute Questionnaire

In the lead up to the LandWISE Conference, we are polling our readers about things that would add value.

We only know the first question: the next one will be determined by your responses.  So please take one minute to tell us what would make things better for you.

We’ll collate responses, determine what needs to be followed up, and let respondents know what we find.

Thanks for helping!

Question of the Week:

What one thing you do on a regular basis would you like to change to make your job easier?

Email your reply -click here

Or use the form below

Fields marked with an * are required

Winter Cover Crops Established

This winter we have established both Caliente Mustard and Oats in paddocks 1 and 2, the site of our last two years of summer onions.

Oats and Mustard well established 12 days after drilling

The ground had not had onions before 2014-2015 as far as we know. We grew our second crop in succession in 2015-2016.

Our plan is to grow onions for a third year, and to pay attention to the development of weeds, pests and diseases. Plant and Food Research reported some evidence of “Pink Root” in a few plants while harvesting samples of the 2015-2016 crop.

After harvest, Gerry and John Steenkamer ripped the beds, leaving the wheel tracks. This is step 1 of a route into permanent bed cropping at the MicroFarm.

Unfortunately, the alignment of the main AB line for the entire block did not match the buried drip irrigation installed some years ago, and it has been damaged beyond repair.

Mike Kettle Contracting drilling oats and mustard
Mike Kettle Contracting drilling oats and mustard

After ripping, Mike Kettle Contracting power harrowed the paddocks to about 100mm to reduce the rubbley surface. The Caliente and Oats were drilled by Kettle Contracting on 16 March.

We chose a split-paddock planting, with Caliente on the northern side and oats on the south. This repeats last winter’s pattern, so we will have two years of onions followed by either Caliente or Oats when we establish the 2016-2017 crop.

Caliente emerging on 23 March, 7 days after planting
Oats emerging on 23 March, 7 days after planting

Many thanks to True Earth Organics for supplying the Caliente seed, and to G & J Steenkamer and Mike Kettle for groundwork and drilling.


Onion Crop Harvested

The MicroFarm onion crop was lifted on 3rd February and harvested on 13th February prior to promised rain.  Many thanks to Gerry and John Steenkamer for providing equipment and staff to do these tasks.

We don’t have final yields yet, but the load out was about 70 tonnes per hectare.

Here is a simple photo essay showing some of the scenes from the ground and from our UAV.


Lifting DSC_4997_web








And off to the packhouse


Scouting by Consumer UAV

Consumer UAVs are increasingly seen as farm tools.  Some come with camera and packaged tech for easy flying, pretty much straight out of the box.

But before you leap in, please be aware there are RULES.

We suggest you spend time on the AirShare and CAA websites before you get started.  Designed specifically for UAV users they have easy to digest information setting out what you can and cannot do.

DJI Phantom 3

Our package came with all equipment, an extra battery and optional propeller guards packed in a tough custom carry case.  The camera is on a gimbal for steady shots, panning and tilting. Zoom in by getting closer!

A downloaded smartphone or tablet app shows flight information such as height, position and battery charge and lets you see exactly what the camera sees with no delay.

In windy conditions, we achieved about 13 minutes of flight time rather than the 23 minutes stated for each battery charge. Rules say you must be able to see the aircraft with your own eyes so you are probably limited to under 100ha. You could make a reasonable inspection in that time.

Peas and onions from 30m Web

We used the UAV to scout at the LandWISE MicroFarm. Viewed from 30m up, crop variation is immediately obvious.  Pea flowering striping seems to match drill widths. We had variable emergence too so ponder the link. Sprayer runs are visible too.

On the onion side we see thinner areas to the bottom right, and patches where Plant & Food have harvested sample plants as part of our joint OnionsNZ research project.


Viewed from directly overhead we see more of Plant & Food’s research plots, some harvested and some still being followed through to final harvest. The image indicates all these plots are within a reasonably good and even part of the crop.

To the bottom right, a lower wetter area shows lower populations where plants are smaller and fewer made it through establishment.


Dropping to a metre of two above the crop and tilting the camera, we see up close. Because we are seeing what the camera is seeing, we can choose exactly what we want to check and go there immediately.

So we’ve scouted the whole paddock, had a closer look here and there, and if we need to, we can walk to the spots we want to check in detail. The thing is, we know where we should be looking.

Process Pea Yields

We earlier posted an article on flowering patterns in our process pea crop. (See

The crop included three lines of Ashton peas, and an area where irrigation was withheld to stop flowering. It also had plots where crop covers were placed at planting to minimise effects of pigeons on plant population or shoot removal.

The crop was harvested in December and yield observations made. We didn’t see significant differences either in hand harvested plots or in viner yield estimates between the seed lines or the cover options. Unfortunately we failed in our tracking of the planter position and delayed emergence strips.



Satellite Imagery

A large part of Heretaunga Plains horticulture was photographed for us by satellite at the end of November.

World View 2 satellite coverage of the Heretaunga Plains on 23 November 2105
World View 2 satellite coverage of the Heretaunga Plains on 23 November 2105

Part of our OnionsNZ Variability project, the World View 2 coverage targeted our crop and other onion crops east of Hastings.

By capturing four bands of light, Blue, Green, Red and Near Infrared, we are able to get a “normal” colour image like an aerial photo, and a biomass map using the NDVI index.

The satellite image pixel size in 0.5m x 0.5m, so we get at least two pixels across each onion bed.

World View 2 NDVI image captured 23 november 2015 of MicroFarm onion and vining pea crops
World View 2 NDVI image captured 23 November 2015 of MicroFarm onion and vining pea crops

In the NDVI image, the onion crop is lower left paddock, the vining peas upper right. Red areas indicate low or no biomass, yellow light, green moderate and blue heavy cover. Note however that the value of each colour is slightly different for each crop.

Because the pea canopy is full ground cover while the onions are only roughly half ground cover, we had to use different value bands to see variation within each crop. If we used the same range, either the peas would all be blue, or the onions mostly yellow and red.

The striping effect in the onions is the onion beds. Some adjacent beds have quite different canopy densities.  The red edge around the onions is bare soil and light canopy in the outer beds. The blue area in the centre is influenced by charcoal from an old bonfire site. Even taking these things into account, there is a reasonably large amount of variation in this crop.

Red spots in the pea crop are patches with no plants. The red headlands show light canopy areas and the red strip centre right the irrigator access track. There are three different seed lines of Ashton peas making up the pea crop. These are not discernable in the satellite image. The crop was harvested on 14 December, and there was no significant difference seen in hand harvested plots or in the viner.

Flowering Patterns in Process Pea Paddocks

LandWISE farmers and processors want to increase vining pea yields, and importantly reliably higher yields. Last year many farms growing processing pea crops exceeded 10t/ha. But regularly crop yields are less than half that.

PodFillWe have been trying to determine factors controlling plant density, flowering, pod number, pea number and fill in process crops. Unlike seed peas, vining peas are harvested before the life cycle is complete. Any variation in maturity causes yield loss – both quantity and quality.

A small trial at the MicroFarm saw three lines of Ashton pea seed planted on the same day, using the same drill, seeking to achieve the same plant density of 110 plants/m2.

Sub-plots in each line were covered in Cosio cover mesh or an open bird netting to remove the effect of birds stealing seed or seedlings. This is important because recent years have seen a major increase in bird numbers and damage. We had 60 pigeons eating a 1ha crop. One farm shot 600 pigeons on one crop in one day and there were still hundreds eating.

At emergence, striping effects were immediately noticeable. We attribute this to drill settings because it repeated at the same spacing across the paddock. Half the width emerged later than the rest. What surprised us was the length of delay in some areas, plants emerging up to three weeks behind.

Variable coulter depth at planting leads to smaller canopy and delayed flowering
Variable coulter depth at planting seen in delayed emergence, smaller canopy and delayed flowering

On enquiry, we found the coulters were set differently to account for the area compacted by the tractor tyres versus uncompacted/untrafficked areas. The settings were clearly incorrect!

The trouble with this kind of issue is the delay in observing the problem.  In the period between planting this crop and our observation, many, many other crops could have been planted, all to suffer a similar problem.

How big is the problem?

We’ll take samples from the three seed lines, the cover options and the planter positions just before harvest. We’ll determine their yields and see what variation we find.