Optimum N

Optimum N

  • Primary Sector

Modern intensive dairy farming in New Zealand relies on nitrogen based fertilisers to optimise pasture yield and profit. Overuse or inefficient use of nitrogen fertilisers has unwanted economic and environmental impacts. This five-year programme termed Optimum N was funded by the Ministry of Business, Innovation and Employment and Ballance Agri-nutrients; aimed to provide dairy farmers with information and tools to optimise nitrogen fertiliser application.

Led by Lincoln Agritech, along with researchers from Lincoln University, AgResearch, Massey University and University of New England, the team investigated different tools and technologies that determined nitrogen demand and spatial variations across paddocks. The ability of remote optical sensors - optical reflectance, machine vision, LiDAR - to detect and estimate pasture nitrogen content, dry matter, urine patch density and clover content.

A fertiliser algorithm was developed to determine fertilisation rates based on the nitrogen status of the pasture using the Agricultural Production Systems Simulator (APSIM). This model was used in conjunction with aerial hyperspectral tools to make fertiliser recommendations and increase the nitrogen use efficiency of dairy pastures and reduce nitrogen losses.

The Optimum N research programme also developed a zonal management tool to indicate nitrogen ‘hotspots’ or ‘exclusion zones’ for fertiliser application. This was calculated by using a set of rules to identify areas of high nitrogen availability.

Results showed that remote sensors have the potential to accurately estimate nitrogen demand across a paddock and coupled with the Optimum N models it can assist farmers with variable rate nitrogen applications - applying nitrogen in the right amount where it is required.

Photo: Cross-section of a paddock (false colour contour map) depicting the pasture height (biomass) and nitrogen hot spots (red).