Although silicon (Si) is found at much higher concentrations in healthy rice crops than N, P or K, it has received far less study, particularly for upland rice. There are few reports on the existence, causes, and effects of varying Si supplies in different environments. Chemical analyses of soil, water and plant tissue samples from experiments grown on a typical weathered, acidic upland soil in Colombia found concentrations of Si which were 80-90% lower than those in a typical lowland environment. These results corroborate published