Errors in Determination of the Water Content of a Trickle Irrigated Soil Volume

Abstract

AbstractA short review of the possible methods of measuring soil water content under high frequency trickle irrigation suggested that the gravimetric method was most appropriate. Three sources of errors in this method have been evaluated and discussed. The sources are those of water content by weight, bulk density, and integration based on the sampling grid. Furthermore, as the sampling mesh became coarser the results became unstable because the differences in volume of water became larger than the defined standard deviation (SD). Error analysis of measurements on uniform Bet Dagan grumusol and sandy soils of Nahal Sinai (Israel) and Yuma (Arizona) showed that coefficient of variation in volume of water within an irrigated volume element may be reduced if the sampling grid is taken properly. The analysis suggests that for a given coefficient of variation and interval of sampling depth, an optimum distance between lateral samples can be evaluated from a mathematical reorganization of the coefficient of variation.