Aerial application of granulated superphosphate.  B.D. Dexter and J.E. Opie.  February 1975.  47 pp. (unpubl.)

SUMMARY

This report deals with the aerial application of granulated superphosphate, and is in two parts.

PART I describes two studies carried out by the Research Branch.

1. Studies carried out with a Piper Pawnee aircraft at Melton airfield aimed at defining the effects of various factors (flying height, drop rate, crosswind) on the distribution of superphosphate across a single swath. From the results a mathematical model relating flying height and crosswind component to the first four moments of the distribution was developed. Fieldwork also included a comparative study of three different types of catcher for sampling the weight of superphosphate falling per unit area. No significant difference between catcher types was found.
2. Studies carried out with a Piper Pawnee aircraft at a plantation of Pinus radiata (Compartments 66 and 67, Scarsdale Forest District) aimed to examine various aspects of a field-scale operation. This work demonstrated that, with a narrow track separation of seven yards (6.4 m) it was possible to achieve a satisfactory distribution of superphosphate when applied by a free-drop technique. A time study was also carried out as a guide to planning and costing further studies.

PART II consists of operational prescriptions developed from the above studies, literature review, and other sources. With respect to quality control, the prescriptions deal with acceptable wind conditions, track separation, track marking, and post-operational assessment. The prescriptions also describe in detail a costing model presented in the form of a series of ready-reckoner tables. Various recommendations are included as guides to efficiency in the conduct of aerial spreading operations.