Active optical sensing of canopies in pasture management

Abstract

Commercial units of Active Optical Sensor (AOS) systems are designed for sensing arable crops to estimate the required amount of nitrogen fertiliser and are well established in intensive arable cropping systems in Europe. A research version AOS (RU-AOS) of a commercial system was tested as a potential canopy sensor for New Zealand dairy pastures. To study the applicability of this sensor a sensitivity experiment was conducted. Additionally, a plot experiment investigated the relationship between the spectrometer and biomass attributes on ryegrass and white clover canopies fertilised with five different nitrogen amounts. The pasture plots were sensed with the RU-AOS and results compared with measured biomass dry matter and nitrogen amount. For some events a strong linear relationship between dry matter (DM) and the water index (WI) was evident (i.e. r² = 0.80) as well as between nitrogen (N) amount and simple ratio (SR) (i.e. r² = 0.89). The results suggest there is potential for this sensor to estimate New Zealand dairy pasture attributes. This could be used to develop a pasture system similar to commercial arable cropping nitrogen sensor AOSs.