نشریه روابط خاک و گیاه
پیاپی 54 (تابستان 1402)

Sorghum is considered as a cereal in the world but in Iran forage sorghum is preferred due to lack of forage. This research was conducted considering the importance of forage sorghum and the conditions of sorghum cultivation under salinity stress in Mazandaran province. The aims of this research were: 1) to investigate the functional response of forage sorghum (variety Speedfeed) to irrigation water salinity and soil salinity, and 2) to quantify the sorghum functional response to salinity during maturation, using several empirical models. Water salinity treatments included well water (control), ratios of 1:4, 2:4, and 3:4 sea water to well water, and pure sea water which were applied in a column study. Salinity-Yield threshold models (Mass and Hoffman, van Genuchten and Hoffman, Dirksen et al., Homaee et al., modified Weibull, bi-exponential and Gompertz( were fitted to the data obtained (relative yield of sorghum at maturation stage vs. electrical conductivity, EC) and the parameters of  models were estimated. The van Genuchten model and the Hoffman and Gompertz model were better than other models in fitting the relative yield data as a function of the EC of the saturated soil extract, due to the lower root mean square errors (RMSE) and Akaike’s information criterion (AIC) in these models (2.84 and –157.34 for the van Genuchten model and 3.11 and –152.53 for the Hoffmann and Gompertz model, respectively). The van Genuchten and Hoffmann model (–205.77, -1.09) and the corrected Weibull model (-213.21 and 0.95) were superior in fitting relative yield data as a function of EC of irrigation water. The salinity tolerance thresholds of sorghum based on fitting relative yield data as a function of EC of saturated soil extract and irrigation water were also estimated to be 3.65 and 2.33 dS m-1, respectively. Also, no significant difference was observed between the relative yield obtained from the models as a function of the EC of saturated soil extract or irrigation water. In other words, the mentioned models are capable to estimate the yield based on the salinity of the irrigation water.

In this study, the possibility of growing greenhouse tomato cv. Dafnis with saving water consumption through grafting on different rootstocks was investigated by studying photosynthesis and plant growth. The experiment was carried out in the form of split plots based on completely randomized design in which the main-plot was irrigation levels (irrigation intervals of 3, 6 and 9 days) and the sub-plot consisted of 9 different grafting combinations. After grafting and establishment of tomato plants in greenhouse, the plants were exposed to the irrigation levels for 4 months and all were irrigated up to field capacity. Photosynthesis parameters were measured in four stages and shoot and root dry weights were determined at the end of the experiment. Based on the results, photosynthetic parameters were reduced by the intensity and duration of drought stress. The experimental results showed that the rate of photosynthesis was the same in all grafting combinations 36 days after the start of irrigation levels. However, after 72 days, the rate of photosynthesis in the “Emperador” rootstock was higher than in the control. The chlorophyll fluorescence indices were not sensitive to show the effects of drought stress and the role of rootstocks. Cherry tomato rootstock, in addition to having an extensive root system than the other rootstocks, resulted in more shoot growth at all levels of irrigation, although the least reduction in root weight was observed in the local eggplant rootstock of Yazd. In general, it can be concluded that the photosynthesis in this experiment was more affected by the interaction of environmental factors and grafting and the rootstocks used did not play a significant role in this regard. Furthermore, root and shoot growth traits were more affected by genetic potential of rootstock, and photosynthetic activities of the plant had a minor influence on them.

The use of organic fertilizers is one of the appropriate ways to produce medicinal plants due to their proper impact on the various soil properties, maintaining environmental health and better plant growth. This study was conducted to investigate the impact of various vermicompost levels on the growth and the morphological and physiological properties of the medicinal-ornamental plant of the Mullein, under drought stress conditions. The research was carried out in the form of split plots in a complete blocks design with four replicates. Experimental treatments included the use of vermicompost organic fertilizer at three levels of zero, 4, and 8 kg/m2 (equivalent to zero, 4, and 8 tons per hectare) and drought stress at two levels of normal irrigation (no stress) and irrigation at 50% of soil field capacity (FC). The results showed that the use of vermicompost and drought stress improved the morphological and physiological traits of the medicinal plant of Mullein. The highest height of the stem, the stem flower, the number of leaves, the height of the flower, the dry weight of shoot, and the root length were obtained by the use of vermicompost at 4 and 8 kg/m2 levels. The use of vermicompost at the rate of 8 kg/m2 increased chlorophyll and anthocyanin, respectively, by 53.7 and 122% compared to control. It was observed that by applying vermicompost at the levels of 4 and 8 kg/m2, significant changes in the morphological and physiological traits of the Mullein plant occurred. On the other hand, the combination of vermicompost application and mild drought stress also caused positive changes in the plant traits. Therefore, mild drought stress, and also for improving the vegetative growth and reproductive efficiency of the medicinal-ornamental plant of the Mullein, the use of vermicompost at 4 kg/m2 (equivalent to 4 tons per hectare) are recommended.

This study was conducted to evaluate drought tolerance of recombined genotypes of orchardgrass (Dactylis glomerata L.) and smooth bromegrass (Bromus inermis Leyss.), and investigate the effect of long-term drought stress on persistence, summer dormancy, and post-drought recovery. For this purpose, 36 genotypes of each species randomly selected from polycross populations, were clonally propagated, and evaluated under normal and drought-stressed conditions during 2013-2015 at the research farm of the Isfahan University of Technology, Isfahan, Iran. In the fourth year (2016), irrigation was withheld in both moisture regimes for two months, and then plants were re-watered and investigated. For most of the measured traits, high genetic variation was observed among the genotypes of both species. In orchardgrass, the genetic coefficient of variation varied from 4.31 to 65.45% under normal conditions, and from 3.93 to 79.93% under drought stress conditions. In smooth bromegrass, the range of genetic coefficient of variation was variable from 3.56 to 67.18% under normal conditions and from 3.42 to 54.63% under drought stress conditions. This indicated a high potential for improving these traits through targeted selection in breeding programs of the two species. In both species, the higher increase in genetic coefficient of variation under drought stress was observed for recovery-related traits (i.e., degree of recovery and recovery ratio in orchardgrass; and recovery yield, degree of recovery, recovery ratio, and percentage of recovery in smooth bromegrass). Results showed that smooth bromegrass had a better performance regarding recovery-related traits. Furthermore, post-drought recovery-related traits in both species were reduced under drought stress, except for the recovery ratio in smooth bromegrass. However, reductions were higher in orchardgrass than in smooth bromegrass. In the current study, the persistence of orchardgrass genotypes increased under drought stress, and decreased in the smooth bromegrass. Less fodder production during summer by the genotypes of this germplasm showed that these genotypes had incomplete dormancy.

Tomato is one of the most important crops, which is cultivated as seedlings. It is important to choose an economic and favorable cultivation medium for the production of good seedlings. In order to use the compost produced from palm pruning wastes as a substrate for the production of tomato seedlings, an experiment was carried out in the greenhouse conditions as completely randomized design with three replications in 2019-2018 at the research greenhouse of Soil and Water Research Institute. Five cultivation beds as treatments included: 1) compost produced from palm pruning wastes (palm peat) (PP), 2) peat moss (PM), 3) cocopeat (CP), 4) mixture of palm peat and peat moss (PP+PM), and 5) mixture of cocopeat and peat moss (CP+PM). Some plant indices, the concentration of plant nutrients and plant growth indicators were measured at the end of the growth period. The results showed that the highest amounts of nitrogen, phosphorus and potassium (1.47% nitrogen, 0.18% phosphorus and 2.83% potassium) were observed in PM, CP and PP+PM treatments, respectively, which were significantly (p<0.01) different from other treatments. In terms of tomato seedling height, the best treatment was PM (8.34 cm), and PP (7.56 cm) and PP+PM (7.56 cm) were ranked second. The lowest seedling height was recorded in CP (5.37 cm). The highest and lowest values of root length were related to PP+PM (8.69 cm) and CP (6.62 cm), respectively, that were significantly (p<0.01) different. The economic results evaluation showed that palm peat is 50% cheaper than cocopeat and 100% cheaper than peat moss, and it can be used as a substitute for imported cocopeat and peat moss in tomato seedling cultivation.

Stability of forest ecosystems, especially in arid and semi-arid areas with non-dense cover, depends on the soil quality maintenance. Therefore, knowledge of the soil properties of these areas can play an effective role in their management. The purpose of this study was to investigate some physical, chemical and biological properties of the soil under wild pistachio (Pistacia atlantica Desf.) and wild almond (Prunus orientalis (Mill.) Koehne) canopy in Tang Khoshk forest reserve of Semirom. Surface soil samples (0 to 15 cm) were randomly collected from the sites under the canopy of P. atlantica and P. orientalis species and outside the canopy (control sample). Some chemical properties including electrical conductivity, pH, total nitrogen, organic carbon, available phosphorus, potassium, iron, zinc, copper and manganese, soluble calcium and magnesium and calcium carbonate equivalent, physical properties including bulk density, soil texture and gravimetric water content, and biological properties of basal respiration, induced respiration, microbial biomass carbon and nitrification potential of soils were measured. The electrical conductivity, organic carbon and potassium in the soil under the canopy of P. atlantica and P. orientalis species were significantly higher than those in the control soil. The reverse trend was observed for the available phosphorus, iron and copper. The mean total nitrogen in the soil under the canopy was at least 1.46 times higher than that of the control soil. Soil bulk density decreased significantly at the presence of canopy compared to the control soil. The basal and induced respirations of the soil under the canopy were significantly higher than in the canopy outside, while the microbial biomass carbon and nitrification potential were significantly greater in the control soil compared to the sites under the canopy. According to the results of current research, the type of plant and its canopy can have different effects on soil properties.