A Dynamic Variation of Root Water Uptake in Drip Irrigated Paddy

Abstract

Research on drip irrigated paddy is gaining importance due to the reason that, it reduces inefficient use of water and nutrients by optimum irrigation and fertigation scheduling. Modelling of root zone process is essential for drip irrigation management. Spatial and temporal changes in Root Water Uptake (RWU) distribution patterns is needed for estimating root zone parameters and also for obtaining average RWU location. It is useful for developing guidelines for soil water sensor placement. It is extremely challenging to measure RWU distribution directly from the field. In the present work inverse modelling was developed by solving Richards' equation inversely for estimating root water uptake. Spatial and temporal variation of volumetric water content was measured at the root zone using Time Domain Reflectometry (TDR) sensors. The dynamic variation of Root Water Uptake Distribution (UD) patterns in drip irrigated paddy was evaluated at 15 minutes interval. Temporal changes in the location of the average root water uptake and volumetric water content was evaluated for a period of 24 hours. The UD pattern during day time is completely different from the UD pattern at night. The changes in UD patterns are due to soil moisture content availability and root behaviours. It is noted that during day time the maximum RWU was observed between dripper and plant locations and at night time the RWU was observed away from the dripper location. The results from this work indicate that the root zoneparameters are needed to be found out separately for day and night.