Field Evaluation of Ion Uptake of Avocado Rootstocks as Affected by Salinity

摘要

With potable water becoming a scarce resource in semi-arid regions, we must evaluate the potential to use degraded water for irrigation without reducing yield. Avocado is one of the most salt sensitive crops, and one of the highest value per acre. The objectives of this experiment were to screen avocado rootstocks for salinity tolerance, study the effect of sodium and chloride on growth and yield, quantify the salt distribution in the root zone, and relate the soil salinity to leaf ion composition and in turn to salt tolerance. A field experiment was conducted to evaluate the salt tolerance of 13 different avocado rootstocks grafted onto Hass scion. The experiment consists of 252 trees arranged in a randomized block design with four rows per block and four replications. The experimental plot is arranged in rows which alternate between those irrigated with a fresh water control, and a salt treatment with electrical conductivities of 0.5 dS m-1 and 1.5 dS m-1 and chloride levels of 0.73 mmolc L-1 and 4.94 mmolc L-1 respectively.;The salt movement during the salinization process was recorded by selected intensive soil sampling, and soil resistivity profiling using the SuperSting RTM 56 electrode resistivity imaging system. We collected soil samples and leaves from the plot and analyzed them for major ions. The rootstocks R0.06, R0.07, PP14, and R0.17 were found to have high concentrations of chloride and sodium in the leaves and therefore the least salt tolerant having 100 % mortality in the salt treated rows after being irrigated for 23 months. The rootstocks that had low concentrations of sodium and chloride ions in the fully expanded leaves were R0.05, PP40, R0.18 and DUSA, which were also the rootstocks whose growth and yield was minimally affected also exhibiting the highest yield, highest trunk diameter and highest survival percentage.