عنوان مقاله [English]
Water resources scarcity is the biggest challenge for food production. In addition to the problem of water shortage, salinity stress is also an important limiting factor in agricultural systems that disrupts the growth and development of most plants. So, drought and salinity stresses are among the main environmental and biological stresses that reduce agricultural and horticultural productions all over the world, especially in arid and semi-arid regions. High evaporation, low rainfall, water scarcity, soil salinity and low quality of available water resources are the serious concerns in arid and semi-arid regions that threaten the sustainability of agriculture in these areas. It can be said with certainty that proper management of irrigation and drainage is the main key to protecting water and soil resources, maintaining their quality and continuing irrigated cultivation to meet the growing nutritional needs of the world. Due to the fact that native cultivars of plants in each region show better adaptation reactions in critical conditions, this experiment was performed to evaluate the tolerance of pistachio Badami rootstock as a native cultivar of Ardakan region to salinity and drought stresses.
In this research, in order to investigate the interaction effect of salinity and drought stresses on pistachio seedlings, a factorial experiment was conducted as a completely randomized design with three replications in greenhouse of Pistachio Research Station of Ardakan city located in Yazd province. The irrigation treatments were applied as 5 (I1), 10 (I2) and 15 (I3) days of irrigation interval. Four salinity levels of irrigation water included 0.5 (S1), 4 (S2), 7 (S3) and 10 (S4) dS/m. The amount of irrigation water was determined by weighing the pots before each irrigation and raising the pots soil water content to field capacity. Furthermore, 30% more water was applied as leaching fraction. Electrical conductivity of the drainage water was determined throughout the applying of stress treatment by taking the samples of the drainage water. At the end of the treatments period, in addition to the actual evapotranspiration of each treatment, morphological traits of seedlings including leaf area, shoot dry weight, plant height, stem diameter, root dry weight and main root length were measured. The main and interaction effects between water and salinity stress levels were separately evaluated, using SPSS software. The analysis of variance (ANOVA) was performed using Duncan’s method to determine statistically significant differences between the means (p ≤ 0.05).
Results showed that the main effect of the irrigation intervals and salinity levels of irrigation water were significant on all of the traits except seedlings height at one percent level. However, the interaction effects of irrigation interval and salinity were only significant on evapotranspiration, leaf area and root dry weight. The increasing irrigation water salinity from 0.5 to 10 dS/m, the average evapotranspiration decreased by 17% and increasing the irrigation interval from 5 to 15 days, the average evapotranspiration decreased by 49%. Increasing the irrigation interval caused a greater decrease in evapotranspiration than increasing the irrigation water salinity. Comparison of shoot and root dry weights at the lowest salinity level compared to the highest salinity level showed a decrease of 60 and 58%, respectively. Increasing the irrigation interval from 5 to 15 days also reduced the average dry shoot and root weights by 27 and 29%, respectively. By increasing irrigation interval from 5 to 15 days and increasing salinity from 0.5 to 10 dS/m, leaf area decreased by 46 and 79%, respectively. In general, based on the results, the effect of salinity on reducing the shoot and root morphological traits of pistachio was more than the effect of drought, the most important reason can be the toxicity of salinity ions, especially sodium and chlorine in disrupting the internal metabolism of pistachio especially photosynthesis process. The results of comparing the mean of traits such as dry weights of shoot and root and leaf area, showed that the best irrigation interval for pistachio in greenhouse condition was 10 days. The readily available water for 2-year-old pistachio seedlings for shoot dry matter production was also determined 41 percent.
The salinity threshold of soil solution for reducing shoot and root dry weights for 2-year-old pistachio seedlings of Badami cultivar were obtained 8.8 and 7.0 dS/m, respectively. These threshold values indicate that the pistachio root growth begins to decrease at lower salinity. In other words, by increasing salinity, while continuing the process of water uptake by root, dry matter increases in the shoot section, it means, the pistachio shoot growth begins to decrease at higher salinity. The slope for decreasing shoot and root dry matter was 4 percent per unit increase in soil solution salinity. The results of this research can be used for water management in greenhouses and by farmers for growing pistachio seedlings of Badami cultivar.