ROBUST MODELS MEAN THE BEST FARMER-FACING TOOLS By Gemma Carroll : Communication & Engagement Officer, Potatoes NZ Inc.
Sustainable Vegetable Systems (SVS) monthly update: improving the modelling via Workstream 3 and extension activities in Workstream 4 Sustainable Vegetable Systems is a four-year, $7.5 million project focused on reducing the environmental impact of intensive growing of potatoes, onions, brassicas and leafy greens. It involves research work to quantify and model nitrogen leaching, and engages vegetable growers from around New Zealand with tools to identify and implement techniques they can use.
Sustainable Vegetable Systems is a four-year, $7.5 million project focused on reducing the environmental impact of intensive growing of potatoes, onions, brassicas and leafy greens In Workstream 3 of the SVS project the modelling team alongside agronomists and growers are focused on improving crop modelling. Whatever nutrient tool is used on your farm, the accuracy of the results depends on the accuracy of the inputs and/or crop model behind the tool. Our collaborative approach in SVS aims to provide the data that underpins the crop nutrient models. In turn better crop understanding and modelling will improve Overseer, and any other nutrient management tool. For consistency and confidence across all stakeholders, existing and new tools need to be underpinned by robust data and crop modelling.
50 NZGROWER : JULY 2021
SVS aims for the same crop model to underpin all grower facing tools, for consistent results and to inform best management The calculation of nitrogen leaching does not have to be done in Overseer unless your Regional Council rules require it. Some Regional Councils require the use of Overseer to estimate nutrient leaching from an individual farm. SVS is aiming to improve the ability of models like Overseer, to represent vegetable rotations and associated nitrogen leaching so that growers can have confidence that the modelled results reflect their growing system and management practices. SVS aims for the same crop model to underpin all grower facing tools, for consistent results and to inform best management. Data gaps are being addressed through trials in Lincoln and Hawke’s Bay, alongside monitoring using nine regional sites.
The challenges in the current modelling so far identified by agronomists and growers include: • Current modelling uses the same formula for all crops, and only a handful of crop types are included. • The model is based on one paddock using one-month time steps, and therefore can only model one crop per year on that block. • Water data and modelling was developed for arable crop irrigation and needs to be refined for vegetable crops. Overseer uses a fixed and quite limited longterm climatic data, using average annual climate data – which is not accurate enough for the sub-annual, rotational nature and relatively fine scale of some vegetable production systems.
