The relation between the pressure of fertilizer on the bottom of the vessel (P) and the height of fertilizer filled in the vessel (H) can be shown in the following equation.
log P=log+cHlog b (1)
a, b, c: coefficients determined by fertilizer
The unit-weight and collapsibility of fertilizer are the positive factors which increase P, and aggregation and friction of fertilizer to the inside wall of the vessel are together the negative which decrease P. P is determined correspondently by such factors as above mentioned, that the fluidity of fertilizer can be assumed by how P relates to H. In addition, c in equation (1) almost indicates the degree of aggregation of packed fertilizer.