Category Archives: Nutrients

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.


LandWISE 2017: Are we ready for automation?

In 2017 our 15th Annual Conference focuses on automated tools for data collection, decision making and doing actual tasks on the farm (and beyond).

  • What do you want?
  • What’s on offer?
  • How will farms and management have to change?

We have a comprehensive programme. We’ve gone a bit outside the box to bring a variety including from outside the horticultural and arable sectors. We find cross-pollination and hybrid vigour valuable!

So register, come along and listen to excellent presenters, discuss the ideas with colleagues and go away with new understanding and plans.

Thanks to Our Loyal Platinum Sponsors!
Many thanks to AGMARDT, sponsors of our international presenter, Thibault Delcroix, France

Hawke’s Bay Regional Council, John Deere and BASF Crop Protection are our Platinum Sponsors again in 2017. Many thanks to these loyal supporters who have backed the Conference for a number of years.

We also welcome our Gold Sponsors, meal sponsors and  trade displays new and old. These are the organisations that make conferences like this possible and affordable.

Join them and us at the Havelock North Function Centre on 24-25 May 2017 to mix with leading practitioners, farmers, growers, researchers, technology developers and providers.

Register now – click here!


Variable Rate N Fertiliser – the Value Proposition

Adrian Hunt is a crop scientist at Plant and Food Research.

He recently completed a PhD at the University of Tasmania, investigating Pre-Harvest and Post-Harvest factor effects on the quality of onion bulbs exported to Europe for counter seasonal supply.  He now works across the vegetable and arable sectors to improve yield, profitability and environmental outcomes.

Together with colleagues Joanna Sharp, Paul Johnstone and Bruce Searle, Adrian has been investigating the value proposition for variable rate fertiliser application.

The technology to deliver variable rate fertiliser in an automated manner has advanced substantially in recent years. This has been aided by new or adapted spreading technologies coupled with location awareness using GPS (Global Positioning System). It is now technically possible to distribute fertilisers in a wide range of spatial patterns within a paddock, however the value proposition of variable rate fertiliser application is not thoroughly understood.

The Plant and Food team looked at the difference in productivity, profitability and potential environmental impact of a range of spatial management scales.

Based on a sampling grid of 105 points in a Hawke’s Bay paddock and used mineral N and a N mineralisation assay to quantify the underlying variability in N processes/cycling within the paddock they “grew” both irrigated and unirrigated maize in the crop simulation model APSIM Next Generation for the 105 sampling locations for 35 growing seasons, using long term weather data.

Adrian will present this work and the results at the LandWISE 2017 Conference in Havelock North.

Drainage and Erosion Planning

The Arawhata Catchment Integrated Storm Water Management project is drawing to a close, the majority of work is done but farm follow-ups continue. The aim of the project was to reduce crop loss from ponding and minimise erosion of soil to Lake Horowhenua. 

We completed OptiSurface drainage analyses for 26 Levin properties covering 450ha of intensive vegetable cropping. OptiSurface calculates flood patterns and erosion risk and creates cut & fill maps for GPS levelling. An example is shown in our earlier post “Mapping for Drainage”.

Drainage and Erosion Management Plans were developed for each block. The plans identify drainage problem areas and erosion risks and recommend management strategies to respond.

Individual farms have done significant work to prevent erosion and reduce crop damage. Farmer actions to reduce sediment runoff and ponding include realigning bed direction, levelling, grassed headlands and drains and swales and sediment traps.

Stages in headland redevelopment

Original design used narrow headlands subject to pugging in wet weather with high risk of slumping soil into vegetation-free drains
Headland lowered to ensure adequate drainage from furrows. Vegetation being encouraged to protect drain from sediment inflows
Land-shaping created a much wider headland for a greater vegetation buffer between cultivated land and drains
Completed headland with its well-established vegetated buffer filtering sediment from drainage water

Now farms are required to have consent in this catchment, the Drainage and Erosion Management Plans are a useful component of the overall Farm Nutrient Management Plans required.

Fertiliser Spreader Calibration

We successfully completed our SFF project “On-farm Fertiliser Spreader Calibration” and launched the online tool, earlier this year.

Some key messages:

  • Our testing found wide performance variation
  • Most new machines do a good job if set up correctly
  • Caution is essential spreading blended fertilisers or when bout widths exceed 30 m
  • Visible striping indicates > 40% application variability and at least a 20% yield penalty.
  • Fertiliser ballistics play a critical role
Setting out a line of catch trays to test fertiliser application uniformity
Driving over a line of catch trays

We ran a number of workshops from Waikato to Ashburton reaching a wide range of farmers and industry people. Information, training handouts and how-to YouTube video clips are on the LandWISE website. See for the on-line calculator and field recording sheets.

We are grateful for strong support from Miles Grafton and Ian Yule at Massey University.

This project was co-funded by the Foundation for Arable Research (FAR), the Fertiliser Association (FertResearch) and MPI Sustainable Farming Fund.

More at

Onion Crop Research Plan

After identifying areas within paddocks that had yields limited by different probably causes, we conceived the idea of Management Action Zones (MAZs).

Yield assessments show considerable variation, limits imposed by population, growth of individual plants, or both
Yield assessments show considerable variation, limits imposed by population, growth of individual plants, or both

Some areas showed that yield was limited by plant number: establishment was poor. Others had the expected population, but low biomass: the plants were small due to some other limiting factor.

If we can identify zones easily, and determine the causes, we should be able to target a management response accordingly. So for this season, we set out a revised research aim.

What we want to know:

  • Can we successfully determine a management action zone in a field?

Why do we need to know this?

  • Develop a tool to increase uniformity and yield outcomes
  • Develop a tool to evaluate management practices and crop productivity

If we want to successfully determine a management action zone in a field then there are two main steps to achieve in this year’s work:

  • Confirm the relationship between digital data and crop model parameters
    • Does the relationship stay constant over time and sites?
    • How early in growth can a difference be detected?
    • Can the relationship be used to show a growth map across a field?
  • Develop an approach to gather information and ways to input and display results, initially using a website approach.
    • Can we integrate a plant count and yield information to start developing a management action zone?
    • How should this be put together in a way growers can start to use to gather information about their crops?

At the MicroFarm, we established six research zones based on paddock history and excessive wetness at establishment.

We have three paddock histories: two years of onion production with autumn cover crops of Caliente mustard, two years of onion production with autumn cover crops of oats, and no previous onion crops planted after previous summer sweetcorn and autumn sown rye grass. In each of these areas, we deliberately created sub-zones  by applying about 45mm of spray irrigation as a “large rain event”.

Artificial heavy rain event applied after planting and before emergence
Artificial heavy rain event applied after planting and before emergence

The impact of the artificial rainstorm is evident on images taken at the end of November.

The lasting effect of a heavy (artificial) rain event pre-emergence (right panel) shows low population and poor growth compared to areas without heavy rain (left panel)
The lasting effect of a heavy (artificial) rain event pre-emergence (right panel) shows low population and poor growth compared to areas without heavy rain (left panel)

Technology to Reduce N Leaching

N-Leach_WorkshopThe Precision Agriculture Association NZ is presenting workshops focused on technologies available to help reduce nitrogen leaching. There are two North Island workshops being offered at:

Massey University on Thursday 1st September 2016 [PDF here]


Ellwood Centre, Hastings on Friday 2nd September 2016 [PDF here]


The ‘Technology to Reduce N Leaching’ workshops are similar to the well received program conducted in Ashburton in March 2016 and will address where we are and what we can do about nitrate leaching limits in a North Island context utilising a range of technologies and farm systems options.

The particular areas for focus for the program are:

  • Variable rate technologies and systems
  • Precision irrigation
  • Precision spreading systems and services
  • Soil mapping
  • Soil moisture monitoring, sensors, metering
  • Nutrient budgeting and environmental monitoring

A Q & A time slot is devoted in the afternoon session for attendees to interact with members and presenters on the day to share learnings and understandings about the issues. This will also be possible over the lunch break on both days with one and half hours devoted for this.


Offer to PAANZ Members

As part of the Hastings program only on 2nd September, PAANZ members are offered the opportunity to participate as trade/sector participants for technologies and products as may be appropriate to support the program.

PAANZ is not able to offer trade/sector stand space at the Palmerston North venue due to space restrictions unfortunately so only the Hastings venue will be able to accommodate this option for members.

If you would like to participate please advise Jim Grennell, E-mail:

Mobile: 021 330 626, places are limited to ten organisations for the Hastings workshop to be involved as a trade/sector participant so it will be on a first come basis.

The cost of participation will be $100.00 plus GST per stand with attendance fee of $100.00 per person additional.

As these are indoors Workshops, with a technology focus and space at the Hastings venue is limited no large equipment or hardware can be accommodated.

Confirmation of members wishing to take up this opportunity is required by Monday 22nd August 2016 after which time the opportunity to participate will be made available to non-members.

Profit Mapping Variability in Onions

Profit Bands Across A Paddock

 Justin Pishief

Justin Pishief and Dan Bloomer
Centre for Land and Water


As part of the Onions NZ project “Benchmarking Variability in Onion Crops” a process was developed to generate yield and profit maps. This presentation explains the process using the example of a 7.3 ha paddock in Hawke’s Bay.

Data from a satellite image captured in late November were used to identify high, medium and low biomass zones.  Paddock yield samples were taken from these zones at harvest and used to generate a paddock yield map. The average yield of the paddock was estimated at 95 t/ha, with a predicted total field harvest of 669 tonnes. This compares to the grower recorded harvest of 614 tonnes.

The relative yield data were combined with grower supplied costs and returns to determine gross margins across the paddock. Data were mapped in ArcGIS and a Gross Margin map with five “profit bands” produced. The highest band had a mean Gross Margin of $11,884/ha compared to the lowest at $3,225/ha.

The breakeven gross margin yield is estimated to be 62.5 t/ha at current costs and prices. The estimated cost to business of low performing areas is $27,945, assuming the whole paddock could achieve the top band mean yield.

The poorest performing areas were identified by the grower as impacted by a failed council drain and areas of slowed drainage in the main paddock areas. An OptiSurface® assessment using historic HBRC LiDAR elevation data analysed of the impact of ponding on the site and also suggested ponding was a significant issue.

An OptiSurface® landform assessment was conducted using both single plain and optimised surface designs and the soil movement required to allow effective surface drainage was determined.

The assessment showed ponding could be avoided by land shaping with 224 m3/ha soil movement and few areas requiring more than 100 mm cut or fill. The cost is estimated at $2,000/ha or approximately $14,000 total.

On-Farm Fertiliser Applicator Calibration

Guidance for farmers – check performance of fertiliser spreading


Dan Bloomer

Fertiliser application calibration procedures suitable for farmers applying nutrients with their own equipment have been developed.  Guidelines and a web-based calculator (see support on-farm checks to ensure and demonstrate application equipment is performing to expectations.

Farmers and agronomists had noticed striping in crops, especially when spreading bout widths increased to match wide sprayer bouts. Visible striping is indicative of very significant non-uniform distribution and yield loss.

A calibration check includes assessment and correcting of both application rate (kg/ha) and uniformity (CV). Farmers indicate determining the rate is reasonably easy and commonly done. Very few report completing any form of uniformity assessment.

FertSpread calculates uniformity from data from a single pass and mathematically applies overlap using both to and fro and round and round driving patterns. Test spread-pattern checks performed to date show there is a need for wider testing by farmers. Unacceptable CVs and incorrect application rates are the norm.

Fertiliser applicator manufacturers provide guidelines to calibrate equipment and some newer machines automatically adjust to correct distribution pattern based on product properties and comparing a test catch with “factory” test data.

The efficiency of catch trays is called into question. While we believe the collection tray data is acceptable to assess evenness of application, the application rate should be determined by direct measurement of weight applied to determined area.  Weighing samples involves very small quantities so scales weighing to 0.01g are required. Satisfactory options are readily available at reasonable price.

An alternative approach uses small measuring cylinders or syringe bodies to compare applied volumes. While not able to assess alternative driving patterns, this can give a direct and very visual immediate view of performance.

The Sustainable Farming Fund “On-Farm Fertiliser Applicator Calibration” project arose from repeated requests by farmers for a quick and simple way to check performance of fertiliser spreading by themselves or contractors. It was co-funded by the Foundation for Arable Research and the Fertiliser Association.

Rootzone reality – measuring nutrient losses

Drainage fluxmeters in commercial fields across the regions

P Johnstone, M Norris, S Green, G Clemens, C van den Dijssel, P Wright, G Clark & S Thomas
Plant & Food Research

Minimising nutrient losses from cropping systems makes good financial sense. It also minimises any adverse impacts on our waterways, which is increasingly important in many regions as new national water policy requirements are implemented.

A common theme in many regions is the requirement that growers should, as a minimum, be managing nutrients according to agreed good management practices. However, there is relatively little long-term measurement of how good management practices throughout New Zealand impact losses of nitrogen (N) and phosphorus (P) from cropping paddocks.

To help fill this gap a network of permanent drainage fluxmeters has been established in commercial fields in the Canterbury, Manawatu, Hawke’s Bay, Waikato and Auckland regions over the last 18 months. There are a total of 12 sites in the network, covering a broad range of cropping systems, soil types, climatic conditions and management practices.

At each site fluxmeters have been installed at a depth of 1 m.  Any water from rainfall or irrigation events that drains to 1 m is captured by the fluxmeters. It is then pumped to the surface and analysed for nutrient concentrations. Net losses can be estimated by combining these measured concentrations and measured drainage volumes.

Preliminary results from the network have highlighted a wide range in N and P losses in drainage water. Many of the losses have been comparatively low to date, evidence that economic and environmental risks can be successfully balanced through the integration of good management practices.

Where high losses have been observed this has resulted from large drainage losses and high nutrient concentrations in the drainage water.

Importantly, this is a long-term initiative and the value of the information from the network will increase over time as growers and regional authorities consider long-term trends.