An independent panel of experts set up to review the nutrient management planning tool OVERSEER® has made wide ranging recommendations for improvements to the way it deals with arable crops. The panel found that OVERSEER® is currently the best tool available for estimating long term, average nitrate leaching losses from the root zone across the diversity and complexity of farming systems in New Zealand, but that further work on the cropping model is needed to enhance confidence in OVERSEER® estimates of nitrate leaching from arable farms.
The review was initiated by the Foundation for Arable Research (FAR) in August last year and carried out by science and industry specialists from New Zealand, Australia and the UK. Dr Roger Williams, FAR’s Director of Research Development, says the review grew out of concerns that OVERSEER® was becoming a major element of many regional authority plans for improving water quality.
“Although this computer model has a well-established role in managing nutrients in pastoral systems, its use in estimating nutrient losses from cropping farms is a new and relatively untested application. FAR decided it was time to ‘lift the bonnet’ on OVERSEER® and take a look at the science underpinning the modelling of cropping systems.”
The independent expert panel has spent the past few months examining OVERSEER’s® capabilities, consulting with some key stakeholders and has come up with a wide range of recommendations to OVERSEER’s® owners, AgResearch Ltd, The Fertiliser Association of New Zealand and the Ministry for Primary Industries.
These recommendations include:
• Further validation of the cropping model through field experiments and comparison with other crop model predictions of nutrient losses.
• An overhaul of the way that users enter data about crop rotations.
• Introducing independent peer review into the on-going process of OVERSEER® development.
• Information and training so that all users, including regional authorities, understand the strengths and limitations of OVERSEER®.
• Increasing the funding available for further work on the crop model and other aspects of OVERSEER® improvement.
“We considered alternative crop models for estimating long term leaching from arable farms, but we are confident that building on the existing strengths of OVERSEER® is the way to go. FAR is already talking to the owners about implementation of the panel’s recommendations and we look forward to a joined-up approach to making sure OVERSEER® will meet the future needs of the arable sector” says Dr Williams.
Panel members were:
Dr Mike Dunbier, Dunbier and Associates Ltd (Chair)
Dr Hamish Brown, Plant and Food Research
Dr Doug Edmeades, agKnowledge
Dr Reece Hill, Waikato Regional Council
Dr Alister Metherell, Ravensdown Fertiliser Co-operative Ltd
Dr Clive Rahn, PlantNutrition Consulting, UK
Dr Peter Thorburn, CSIRO
Dr Roger Williams, Foundation for Arable Research
Click here for full OVERSEER report
About OVERSEER®
OVERSEER® is an agricultural management tool that assists in examining nutrient use and movements within a farm to optimise production and environmental outcomes.OVERSEER® calculates and estimates the nutrient flows in a productive farming system and identifies potential for risk of environmental impacts through calculation of nutrient loss as run-off and leaching and greenhouse gas emissions. Its current uses are in the development of on-farm nutrient budgets, whole-of-farm nutrient management plans and, through the use of additional proprietary software, the development of farm specific fertiliser recommendations.
More information is available at An independent panel of experts set up to review the nutrient management planning tool OVERSEER®has made wide ranging recommendations for improvements to the way it deals with arable crops. The panel found that OVERSEER®is currently the best tool available for estimating long term, average nitrate leaching losses from the root zone across the diversity and complexity of farming systems in New Zealand, but that further work on the cropping model is needed to enhance confidence in OVERSEER®estimates of nitrate leaching from arable farms.
More information is available athttp://overseer.org.nz/
OVERSEER® and regional authority plans regarding water quality
New Zealand’s National Policy Statement for Freshwater Management, which came into effect on 1 July 2011, set the tone for a consistent approach to improving water quality and managing water use across the country. Accordingly, regional authorities are developing regional plans aimed at reducing agriculturally-derived nitrate and other nutrient levels in water. The favoured approach is regulation of nutrient losses from farmland rather than capping nutrient inputs per se. This output-based approach has the potential to offer more flexibility for farmers to use nutrients efficiently, and maintain or improve productivity, than input limits. However, determining nutrient losses is more difficult than monitoring inputs. As measurement of losses is impractical at present, a modelling approach is needed and OVERSEER® is set to be the model of choice. At present, Environment Canterbury, Otago Regional Council, Environment Southland, Waikato Regional Council, and Environment Bay of Plenty specify use of OVERSEER® for recording estimated nutrient discharges from individual properties. Other regional authorities are also looking at using OVERSEER® in this way.