as, topography, soil type, depth of the groundwater table, obstacles and farming practices. Therefore, when planning ab bmeasurement programme, it is advisable to make a preliminary investigation to determine the optimal sampling pattern, the necessary number of sampling points, the sampling frequency and of course the most suitable measurement technique. 2.8.2 Soil moisture measurements 2.8.21 Measurement of soil moisture content Soil-moisture content can be measured directly by using the gravimetric method, the "acetylene" method or lysimeters. Physical changes of soil properties related to changes in the soil-water content are used for indirect measurement methods. 2.8.211 Gravimetric method The amount of soil water is determined from weighed soil samples which are oven dried at 105 C until there is nob bfurther change in weight (usually 24 hours. The moisture