evaluation of yield and growth indix of potato under water deficit

in order to study the yield and growth indix of potato under water deficit, an experiment was conducted with line-source sprinkler irrigation in khorasan razavi agricultural and natural resource research center. water deficit levels were included, at 0.75m from line-source (control), at 3.75m from line source (very mild deficit), at 6.75m from line-source (mild deficit), at 9.75m from line-source (severe deficit), at 12.75m from line source (very severe deficit).the yield were 26.47, 22.3, 17.31, 9.88 and 2.04 ton per hectare in control, very mild, mild, sever and very sever deficit respectively. water deficit had very effects on root, shoot and tuber dry matter, total dry matter (tdm), relative growth rate (rgr), crop growth rate (cgr), leaf area index (lai), leaf area duration (lad), and net assimilation rate (nar). the maximum lad (478) was in control in 1600 gdd and maximum rgr was calculated between 0.004 and 0.005 g/g gdd in water deficit. in sever and very sever deficit, maximum cgr showed very soon (1300 and 1200 gdd respectively).