effect of irrigation duration on some of characteristics growth thomson navel orange grafted on three citrus rootstock

in this research, the effect of irrigation duration on growth characteristics of thomson navel orange grafted on three rootstocks was evaluated in complete randomized block design in iran citrus research institute. factors included rootstock in three levels (poncirus (poncitus trifoliate), citrange (citrus sinensis  poncitus trifoliata) and sour orange (citrus aurantium)) duration of irrigation in four levels (2, 4, 6 and 8 once days) and time in six levels (t1, t2, t3, t4, t5 and t6). in the during irrigation, vegetative traits such as scion height, leaf number, diameter of rootstock and scion, leaf water content and chlorophyll value were measured. also, at the end of the experimental period, amount of nitrogen, phosphorus and potassium in soils mixtures were determined. the results showed that time of sampling, type of rootstock and duration of irrigation can affect on growth characteristics of studied rootstock and scion. height of scion, leaf number, diameter of rootstock and scion were increased so that the increase for all traits to time t3 was significant, but from time t3 to t6 was not. the difference among different rootstocks in the absorption of nutritional elements in short time (two days) was more. poncirus rootstock in uptake of nutritional elements in drought stress was more efficient than other rootstocks and with increase in intervals of irrigation, amount of nitrogen, phosphorus and potassium in soil mixture of poncirus rootstock, was less. overall, studied rootstocks in this research which are common citrus rootstocks in north of iran, in drought stress conditions, did not show superiority over others in growth characteristics.