VEGETABLES NZ INC.
An informative dataset is being generated.
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.
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 www.vri.org.nz; 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.