But in that case I would do it different:
have an array
spice [x][y]
it stores how much spice is on the ground at each map coordinate.
the spice is drawn with Lua.
If a harvester runs over the spice at [x][y]:
spice[x][y]--
harvesterCargo++
drawing and reading [x][y] would work similiar as described in this thread: http://springrts.com/phpbb/viewtopic.php?f=23&t=24820

instead of red you would draw a "spice texture" and instead of green you would draw nothing.
Looking at their map design this approach is probally better as they have "fields" of resources. Conflict Terra has small "clusters" of resources, like Starcraft, age of empires etc.