There have been carried out measurements of ammonium phosphate single granule strength versus granule size applying to this purpose a measuring device of our own construction and basing on an original method of interpretation of test results. Test results have been represented graphically in the form of curves expressing the breaking force F, relative strain ι, absolute strain ε and breaking stress σ versus granule size at the breaking moment.
The critical speed of ammonium phosphate granules has been determined by a dynamic pressure measurement realized by means of a device of our own construction. Knowing the lifting surface determined with use of the perpendicular projection shadow method and knowing the critical speed there becomes possible to calculate aerodynamic resistance of coefficient of fertilizer granules. The critical speed and the aerodynamic resistance coefficient have been determined in respect of the granule size and these relationships have been shown graphically in the form of regression curves.