Sensors and frequencies of soil water content measurement affecting agro-hydrological simulations and irrigation management

Abstract

• The frequency of observation of soil water content affected the performance of inverse modeling. • Soil Hydraulic Properties (SHP) differed according to the water sensor used. • Differences observed in SHP affected the obtaining of important parameters for irrigation management. Principles and frequency of soil water content (SWC) measurements used in the transient water flow experiments may cause distinction on the determination of soil hydraulic properties (SHP) by inverse modelling (IM). Consequently, use of agro-hydrological models and irrigation management can be affected. This work has the following objectives: (i) to analyze if the type of sensor and the frequency of SWC measurement used in the transient water flow experiments for IM affect the results regarding SHP; (ii) to assess if variations on the SWC measurement frequencies affect the results of SHP to the point of causing effects on the agro-hydrological modelling through SWAP model and on the passion fruit irrigation management based on soil water sensing; (iii) point out strategies for the correct irrigation management based on SHP obtained by IM. The results regarding SHP were applied to the modelling of crop evapotranspiration (ETc) and SWC with the use of SWAP agro-hydrological model. The type of sensor and the frequency of SWC data measurements interfered in the results regarding SHP obtained by IM, with implications on the agro-hydrological modelling and on the irrigation management through soil water sensing (SWS). The results of this study alert for the differences that may occur in SWC values when those are obtained from matric potential through soil water retention curves. This is specially important for higher and lower critical matric potentials used as reference for the moment to turn on and off a irrigation. When using GS1 sensors for IM, it is recommended to use intervals of SWC data measurement of 1 h, as the TDR sensors performed better with SWC data acquisition frequency between 1 and 12 h. Finally, it is understood that the factors that affect agro-hydrological modeling and the performance of the type of soil water sensor are diverse and integrated in a complex nonlinear way, for instance: atmospheric condition, soil texture and structure, topography, presence/absence of plants, soil and irrigation management practices. Thus, similar studies should be carried out considering variations in these factors so that a generalist and integrated conclusion is possible.