1999 Volume 61 Issue 5 Pages 65-73
This paper discusses how many data should be collected for representing the feature over one grid space. Two test areas: 4.2 meter square with 0.6m sub-grid spacing in a maize growing field, and 10 meter square with 1m sub-grid spacing in a paddy field after harvesting. NO3-N as soil parameter was collected in respective sub-grid spacings. Data obtained provided non-normal distribution for the maize field and normal distribution for the paddy field. With the data sets, sampling size and estimation error was evaluated in terms of average. Results showed that in the maize field sample averages could be estimated using normal distribution techniques, and that estimation errors were greater in the maize field than in the paddy field. Estimation errors increased with depth for the maize field, but for the paddy field the effect of depth was not significant. In the maize field, keeping the estimation error below 20% required at least 10 points of sampling size.
