TECHNICAL
N-SIGHT: MAKING THE INVISIBLE, VISIBLE Andrew Barber : Sustainable Vegetable Systems programme manager
Nitrogen is invisible, its effects are not. Therefore, the cause-and-effect link is much harder to make than say sediment on the road. Change will only occur by working together to improve practices, not through unenforceable leaching numbers. The Sustainable Vegetable Systems (SVS) Programme is empowering growers through greater understanding of how nitrogen flows through a very complex vegetable growing system.
Nitrogen budgets to change the regulatory direction Some councils have set strict nitrogen leaching values. These values have been debated by planners and lawyers for years, resulting in little change in grower practice. Those growers who have tried to work within these limits have spent a significant amount of time and money modelling their system. As you dive into the vegetable modelling world it quickly becomes apparent to any model user just how complicated it is. An absolute nitrogen number is not defendable in court hence this should not be defined as a desirable outcome. Therefore, in the future there is likely to be greater emphasis placed on Farm Environment Plans (FEPs) to deliver changes in grower practice. Practice change leads to environmental improvement and that is a desirable outcome.
Variability and uncertainty Natural systems are extremely variable. Then add to that market uncertainty. Every day, growers deal with that variability and uncertainty and adjust their management decisions accordingly. We need to better understand and document that variability if we are going to tell that part of the story with integrity and an evidence base. It is the process of data sampling, analysis and presentation that leads to meaningful conversations. Having the data is critical if the industry is going to engage with regulators, rather than being led back down that now well-worn path to the lawyer’s office (apologies to lawyers). All nitrogen flows are best represented as a range. Some of the components that make up the total variation in the complex system can never be improved upon, that is nature for you. Others however, will be improved over time as understanding and the underpinning data become more robust.
FEPs document growers’ nutrient management practices. One of the key practices is the preparation of a nitrogen budget. The processes, methods and thinking that support the preparation of that nitrogen budget leads to greater understanding of individual steps driving nitrogen flow, and to practice changes that can be measured. The process, research, data monitoring and thinking lead to further questions that drive a system of continual improvement.
The Sustainable Vegetable Systems (SVS) Programme is empowering growers through greater understanding of how nitrogen flows through a very complex vegetable growing system NZGROWER : JUNE 2022 39
