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Sue Chok

Doctor of Philosophy
Study Completed: 2017
College of Sciences


Thesis Title
Improving Granular Fertiliser Aerial Application for Hill Country Farming

Read article at Massey Research Online: MRO icon

Granular fertiliser is applied to hill country by aircraft. Conventional applications apply a single application rate to a whole farm. However, this is inefficient as soil nutrient concentrations vary significantly. Therefore variable rate application technology was introduced to enable aircraft to apply multiple application rates. Ms Chok's research investigated the accuracy, precision and capability of a variable rate application system. She found the system was able to meet New Zealand standards for a good aerial application. However, wind conditions significantly affected the results. Consequently, a ballistics model was validated to predict the landing position of fertiliser particles based on initial conditions. The model was developed into a tool that re-positions the application area to minimise off-target application, due to wind conditions. Overall, Ms Chok's research showed that using variable rate application technology and the ballistics model improves the aerial application of granular fertiliser in New Zealand.

Professor Ian Yule
Dr Miles Grafton