Aqueous ammonia was used to determine its effectiveness as a soil steriliser for use in glasshouses and to see if it can be used as an alternative sterilising method. A sandy soil was used to examine the effect of aqueous ammonia on the numbers of weeds, nematodes and microbes. The aqueous ammonia was applied to 1 kg of soil in doses of 2, 4, 6 and 8 ml with three contact periods of 24,48 and 72 hours for each dose. The application of ammonia water to the soil produced a clear decline in the numbers of weeds, nematodes and microbes. There was a direct correlation between the decline in numbers with an increase in dosage and time.