determining soil indices and water balance for scheduling an irrigation control center

nowadays, the limitation of water resources are added on the importance of detailed planning including the estimated timing and amount of irrigation water. this is possible with considering the soil indices and water balance. the measured soil field capacity of some with two lab and field measurement methods were 21% and 19/8% respectively and the permanent wilting point were determined 12% as a result. then an irrigiation control center was scheduled to stop irrigation when the soil moisture of pots reaches to 21% and start irrigation when moisture reaches to 12%. control center use an inexpensive hygrometer yl-69 model that calibrated with a precise sensor wet-2 and the correlation between data were 0.994. evaluation the accuracy of the yl-69 sensor in 5 moisture levels (21%, 18%, 15%, 12% and 9%) showed a correlation of 0.98 between measured and real moisture and proved it is possible to use the sensor to monitor the moisture around the plant root and hold the moisture in appropriate amount for optimum plant growth.