The following conditions are given:

Hay: Dry density (kg/m^3) = 92

Straw: Dry density (kg/m^3) = 68

Straw and manure*: Dry density (kg/m^3) = 171

Hay and manure*: Dry density (kg/m^3) = 248

(*Note: Straw or hay was mixed with manure in a 1:2 ratio by dry weight)

How can we deduce that manure, on its own, would have a dry density that is greater than the dry density of hay?