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

An irrigation system was developed for the establishment of salinity gradie nts in field experiments that are aimed at obtaining salinity-yield respons e functions of crops. The drip-injection irrigation system (DIS) consists:o f a parallel pump system (a centrifugal pump for fresh water and an:injecti on pump for saline water) and a conventional drip irrigation system compose d of various irrigation sectors, The number of emitters installed in each i rrigation sector determines the discharge of the centrifugal pump that blen ds with the fixed discharge of the injection pump, So, for the rest of fixe d variables, the number of emitters (N) installed in a given irrigation sec tor determines the salinity of the irrigation water (ECiw): ECiw = a N-b, w ith 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 robu st in that: (i) the measured ECiw gradient was similar to the target ECiw g radient (r positively correlated at P < 0.0001); (ii) the soil salinity (EC e) horizontal and vertical (0-50 cm depth) uniformities within each-salinit y treatment were low (average coefficient of variation [CV] of the pooled s alinity treatments equal to 16-22% for the horizontal soil salinity and equ al to 10% for the vertical soil salinity) and the temporal variability of s oil salinity was low to moderate (average CV of the pooled salinity treatme nts equal to 18% during the studied period); and (iii) ECiw and ECe were po sitively correlated (P < 0.001). We concluded that the DIS is an excellent, low cost irrigation system for conducting field crop salt tolerance evalua tions.