Eileen Perry1, James Nuttall2, Ashley Wallace2, Audrey Delahunty2,3, Kirsten Barlow4
1Agriculture Victoria, Department of Economic Development Jobs, Transport and Resources, Cnr. Midland Highway & Taylors Street, Epsom, Vic, 3551, Australia Eileen.Perry@ecodev.vic.gov.au
2Agriculture Victoria, Department of Economic Development Jobs, Transport and Resources, Grains Innovation Park, 110 Natimuk Road, Horsham, Vic 3400, Australia
3 The University of Melbourne, Parkville, Vic, 3000, Australia
4Agriculture Victoria, Department of Economic Development Jobs, Transport and Resources, 124 Chilton Valley Road, Rutherglen, Vic, 3685, Australia
Frost has the potential to significantly reduce production for field crops grown in Mediterranean-type environments, and significant economic losses due to frost damage for Australian wheat occur annually. If non-destructive sensors could make rapid, spatial assessment of frost damage near heading and anthesis, this could limit losses through timely management decisions. For this research we analysed canopy reflectance measurements as part of a field experiment in 2016 at Horsham. Mobile frost chambers applied chilled air (temperatures below 0°C) to wheat at heading and anthesis, and repeated canopy reflectance measurements were made following the treatments at leaf, head, and canopy scales. The reflectance measurements were used to determine a suite of reflectance indices, which were compared with frost intensity expressed as cold sums. Many of the indices demonstrated significant, linear relationships with frost intensity for heading treatments that were in excess of 20 °C.hr<0 (or minimum temperatures of -6.6 to -9.6°C). Immediately following the anthesis frost treatments (with frost intensities < 20 °C.hr and minimum temperatures of -0.7 to -4.2°C), only two indices, Photochemical Response Index (PRI) and Plant Senscence Reflectance Index (PSRI), showed significant relationships, and only for flag leaves. Eight days following anthesis treatments, six indices resulted in significant R2 values, although the values were lower than for the heading treatment. Initial results indicate that research should target frost intensities equivalent to cold sums between 20 and 50 °C.hr, to better understand at what point reflectance (and other non-destructive measurements) can detect frost damage.