Experiments on the control of salinity and sodicity in surface-irrigated fields in the upper Yellow River Valley (II). Observation system and calibration

An experimental field was established in Pingbu village extending along the Yellow River (Baiyin, Gansu, China) to conduct experiments on the control of salinity and sodicity in surface-irrigated fields, and an observation system for measuring meteorological and hydrological elements relevant to soil salinization and alkalization was installed in it. The outline of the observation system is shown; principles of measuring such elements are examined and their limitations are pointed out in case of necessity. Furthermore, careful considerations are given to the system so that the system could measure such elements as accurately as possible.