A new drip-injection irrigation system for crop salt tolerance evaluation

An irrigation system was developed for the establishment of salinity gradients in field experiments that are aimed at obtaining salinity-yield response functions of crops. The drip-injection irrigation system (DIS) consists:of a parallel pump system (a centrifugal pump for fresh water and an:injection pump for saline water) and a conventional drip irrigation system composed of various irrigation sectors, The number of emitters installed in each irrigation sector determines the discharge of the centrifugal pump that blends with the fixed discharge of the injection pump, So, for the rest of fixed variables, the number of emitters (N) installed in a given irrigation sector determines the salinity of the irrigation water (ECiw): ECiw = a N-b, with a measured coefficient of determination of approximate to 99%, The DIS was validated in an experiment where the salinity-yield response functions of ten barley cultivars were obtained using nine ECiw salinity treatments, with two replications per treatment, The DIS proved to be accurate and robust in that: (i) the measured ECiw gradient was similar to the target ECiw gradient (r positively correlated at P < 0.0001); (ii) the soil salinity (ECe) horizontal and vertical (0-50 cm depth) uniformities within each-salinity treatment were low (average coefficient of variation [CV] of the pooled salinity treatments equal to 16-22% for the horizontal soil salinity and equal to 10% for the vertical soil salinity) and the temporal variability of soil salinity was low to moderate (average CV of the pooled salinity treatments equal to 18% during the studied period); and (iii) ECiw and ECe were positively correlated (P < 0.001). We concluded that the DIS is an excellent, low cost irrigation system for conducting field crop salt tolerance evaluations.