Using the traditional performance index of Emission Uniformity (EU) as an indicator of the irrigation performance may be misleading, as it implicitly assumes that water application uniformity immediately leads to a similar uniformity of the water stored in the root zone. Due to the heterogeneity of soil hydrological properties, the same EU might correspond to a different distribution of water stored in the soil root zone. In order to overcome this problem, a methodology has been developed to introduce an EU index which accounts for the actual distribution of pressure heads (and thus of water contents) in the upper layer of the soil, under drip irrigation. The methodology includes TDR measurements and 3D modeling of the pressure head (and thus of water contents) distribution inside the wetted bulb, under drip irrigation.
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As the 3D modeling requires soil hydraulic properties to be known in all the sites needed to calculate the uniformity index, hydraulic property measurement methods have been adopted using the same drippers as those used for determining the uniformity index. TDR measurements have allowed for reproducing, during simulations, the water content actually measured under drip irrigation.
