drought stress

This research was conducted to investigate the kernel yield of six bread wheat cultivars under irrigation cut conditions at two important stages of development and to determine the scope of different irrigation stages on grain yield.

The experiment was conducted as randomized complete blocks design with three replicates under four different conditions (four irrigation regims) across two cropping years. Portable rainout shelters were installed to protect the crop from rainfall during drought stress treatments.

Combined analysis of variance across all environments indicated high significant genotypic and environmental differences for all the traits. Cultivars “Mihan” and “Sirwan” with 8321 and 7722 kg/ha had the highest and lowest kernel yield, respectively. The reduction of kernel yield was 20.27, 27.94 and 14.39% under stem elongation drought stress, terminal drought stress and terminal drought stress irrigated at milk development stage, respectively compared to normal irrigation conditions. The influence of environment on variation of the traits was twice as large as genotype and seven times as large as genotype by environment interaction. Rakhshan and Heydari cultivars were identified as early and late cultivars with 215 and 223 days, respectively.

Current research has improved our knowledge of these six latest popular wheat phenological developments, which can improve water conservation through an efficient irrigation approach based on the sensitivity of the phenological growth stage and their contribution toward final yield. GGE biplot was shown to be more informative than analysis of variance for distinguishing response of cultivars in different environments. The cultivar “Mihan” for incorporating its high potential traits is recommended for future breeding programs under drought stress conditions.

a field experiment performed to evaluate the effects of peppermint and sage intercropping with application of different fertilizer resources on the dry matter yield, essential oil content, and ecological indices under drought stress.A field experiment was carried out as a split split plot based on a randomized complete block design (RCBD) with 36 treatments and three replications . The main factor was three irrigation regimes included 25 (MAD25), 50 (MAD50), and 75% (MAD75) maximum allowable depletion (MAD) percentage of the soil available water (SAW) as normal irrigation, mild and severe water stress, respectively. The sub-factor was different planting patterns included peppermint monoculture, sage monoculture, and intercropping of peppermint + sage and also sub-sub factor were application of different fertilizer sources including no‐fertilizer as control, TiO2 nanoparticles (100 mg L−1), arbuscular mycorrhiza fungi (AMF) inoculation, and integrative application of AMF and TiO2 (AMF + TiO2).The maximum essential oil content of peppermint (1.51%) and sage (1.33%) was observed in intercropping plants with integrative application of AMF + TiO2. The essential oil content of peppermint and sage increased by 13.1 and 41.2% under mild stress in compared with normal irrigation, respectively. Also, the highest LER, K, AYL,, and monetary indices were achived in mild water stress with integrative application of AMF + TiO2. it can be concluded that the application of AMF + TiO2 in intercropping of peppermint/sage could be suggested as a sustainable strategy to increasing the quantity and quality of essential oil of both plants under drought stress conditions.

This research was carried out in order to evaluate the effect of intercropping of replacement and addition series on the yield and yield components of Camelina and Lentil under rainfed and irrigated conditions.

The experiment was carried out in the form of split plots in the form of a basic design of randomized complete blocks with three replications in the research farm of the Faculty of Agriculture of Ilam University in growing season in 2020-2021 and 2021-2022. The main plots include irrigation on two levels (rainfed and irrigated) and the subplots include alternative and incremental mixed cropping patterns in nine levels including (75% Camelina+ 25% lentils, 50% Camelina+ 50% lentils, 25% Camelina+ 75% lentils), 100% Camelina+ 25% lentils, 100% Camelina+ 50% lentils, 100% Camelina+ 75% lentils, 100% Camelina+ 100% lentils, monoculture of Camelina and lentils).

The results showed the highest grain yield (1827 kg ha-1) and biological yield of camelina (7012 kg ha-1) in the series of 100% camelina+ 25% lentil and the highest grain and biological yield of lentil was 750 and 1950, respectively, related to monoculture lentil cultivation. The evaluation of the ratio of land equality showed the superiority of all ratios of camellia and lentil intercropping over their monoculture, and the incremental rows of 100% camellina+ 75% lentils and 100% camellina+ 100% lentils had the highest LER.

The results showed that the intercropping of camelina and lentils under irrigation and rainfed conditions was beneficial and superior compared to their monoculture.

The lack of fresh water resources in arid and semi-arid regions is the most important factor limiting agricultural activities. On the other hand, one of the challenges that exist in cities is the accumulation of sludge resulting from urban sewage treatment. According to the available sources, the sludge obtained from urban sewage treatment contains large amounts of mineral and organic substances, which can improve soil fertility and water retention and are useful for agricultural products. In this regard, in order to investigate the effect of sewage sludge in reducing the effects of drought stress on the growth characteristics of Hibiscus sabdariffa L., a study was conducted in the form of a completely randomized design in a factorial format and under greenhouse conditions. The test factors included drought stress with four levels (100, 75, 50 and 25% of crop capacity) and sewage sludge with two levels (zero and 10 grams per kilogram of soil) and four replications. During the six-month growth period of the plants in the greenhouse, dry treatments were applied using tap water with a salinity of 700 micro Siemens per meter, based on the weighing of the pots. After the plants reached the stage of flowering and boll production, morphological traits such as plant height, shoot weight, stem diameter, number of bolls, root weight and number of leaves were measured. The results showed that the effect of sewage sludge application on the wet and dry weight of shoot, height, number of bolls, stem diameter and root wet weight at the level of one percent (p<0.01) and the dry weight of the root at the level of five percent (p>0.05) was significant. Using sewage sludge increased plant dry weight by 46%, height by 24%, stem diameter by 14%, and root dry weight by 50% compared to the control treatment.​ The investigation of the interaction effect of drought and sludge on the morphological characteristics of the plant showed that the application of sewage sludge at stress levels of 100, 70 and 50% of the field capacity increased the fresh weight of aerial parts by 118, 90 and 75%, respectively, compared to the control. The interaction effect of drought and sludge on the number of plant bolls showed that the highest amount of this trait was obtained with an average of 25 numbers in the treatment of sewage sludge application and 100% field capacity, and the lowest amount was equal to 1.25 in the treatment of 25% field capacity and no sewage sludge application. The interaction effect of drought and sewage sludge on plant physiological traits such as proline, sugar, chlorophyll a, chlorophyll b and carotenoid levels was not significant. In general, the results of this research show the positive role of sewage sludge on improving the growth and performance of this plant under drought stress conditions.

A Acer velutinum Boiss. (Persian or velvet maple) is one of the industrial and important species of Hyrcanian (Caspian) forests with wide distribution. This species is rarely seen in the forests of other parts of the world and has only been reported from the forests of the Caucasus. Therefore the information about this species is very limited. This research aims to investigate the response of A. velutinum seedlings to drought stress as one of the consequences of climate change. Seedlings of velvet maple were analyzed in terms of height, basal diameter, leaf area (LA), specific leaf area (SLA), biomass, photosynthesis pigments, relative water content RWC), free proline, malondialdehyde (MDA), superoxide dismutase(SOD), and peroxidase(POD) activities to drought stress. One year old of Potted plants were exposed to four water supply regimes (100, 75, 50, and 25% field capacity (FC); performed as a control, mild, moderate, and severe water stress. The results showed that drought reduced all aspects of growth in the velvet maple. It negatively affected on growth and reduced plant height, stem diameter, biomass, and leaf area, but SLA significantly increased under moderate treatment. Drought stress reduced chlorophyll content, however, no significant difference was found for carotenoids. RWC reduced significantly just under severe drought stress. Proline and MDA content increased significantly when plants were exposed to moderate and severe drought stress. Drought stress induced POD and SOD activity under drought treatments, although the highest activities were measured under mild and moderate treatments. Our data demonstrate that A. velutinum seedlings have relative drought resistance. They used drought avoidance and tolerance mechanisms through changes in morpho-physiological characteristics. The results of this research briefly showed the mechanisms of drought tolerance in A. velutinum and will provide essential information for more research in the future.

Drought condition is one of the most important abiotic stresses through the world. In the first place, the best way to prevent the reduction of crop yields in drought conditions is to use natural compounds that play a key role in growth, development and response to environmental stresses. Quinoa (Chenopodium quinoa Wild.) belongs to the Chenopodiaceae family, a plant with high nutritional value and rich in protein as a future crop. Due to the high resistance to various biotic and abiotic stresses, global demand for quinoa is currently increasing and its global production is less than market purpose.

This experiment was conducted during 2020-2021 cropping season as split plots based on a randomized complete block design with three replications at research farm of Zabol University (UOZ), IR. Iran. The main plot factor was irrigation regimes at three levels: 1- Irrigation equal to 100% crop water requirement (control), 2- Deficit irrigation equal to 75% crop water requirement (mild stress), 3- Deficit irrigation equal to 50% crop water requirement (severe stress) and six levels of foliar application were assigned to the sub plot: Control (sprayed with distilled water without ethanol), 70% ethanol, 0.5 mM SA, 0.5 mM MeJA, 1 mM SA and 1 mM MeJA. In this study plant height, stem diameter, panicle dry weight, root dry weight, dry matter, seed yield, harvest index, stomatal conductance, electrolyte leakage, chlorophyll florescence and water use efficiency were measured. Determination of irrigation interval and crop water requirement was based on CROPWAT 8.0 software and Penman-Mantis equation. For plant coefficients used FAO default data. Irrigation planning was determined with 85% efficiency and water volume of each plot calculated using a digital water meter.

The results revealed that the irrigation 50% crop water requirement (severe stress), regime increased electrolyte leakage, water use efficiency and root dry weigh, whereas it did not significantly affected Fv/Fm, stomatal conductance and harvest index. The highest plant height with mean 144.02 cm was obtained from 100% crop water requirement and 1 mM SA and the lowest with a reduction 71.5% was obtained at 50% crop water requirement and no spraying conditions. Quinoa had 54.3% higher seed yield than control under drought stress conditions owing to unaffected Fv/Fm and stomatal conductance and less electrolyte leakage. Spraying 1 mM MeJA and SA increased chlorophyll fluorescence (22.4%), stomatal conductance (53.4%) and harvest index (38%). In severe drought stress (supply 50% crop water requirement), foliar application significantly increased the water use efficiency (from 0.2 to 1.1 kg m-3). In severe drought stress, increased quinoa seed yield was due to to increase in water use efficiency. According to the results drought stress decreased physiological and seed yield traits, 1 mM MeJA could increase the seed yield (292.93 g m-2) and then partially compensated for the reduction caused by drought stress. Also, seed yield with mean 281.96 g m-2 was in the second rank at 1 mM MeJA application and 75% crop water requirement (mild stress) conditions. Fv/Fm ratio was not significantly affected in drought stress. The highest harvest index was observed in 1 mM MeJA and SA compared to the control. Therefore, for minimizing the effect of drought stress, we could recommend the use of 1 mM MeJA.

The least stress treatment for quinoa economic yield supply was 100% crop water requirement (control) and 1 mM MeJA application. Also the average seed yield (281.96 g m-2) was at the second rank, in 1 mM MeJA and 75% crop water requirement (mild stress) treatment. It seems that stress tolerance mechanisms study and MeJA foliar application is necessary, especially in areas with less water and we need to develop crops that possible to produce high quantity with require low water in farm.

The aims of this study was to investigate the radiation and nitrogen use efficiency at different irrigation regime and nitrogen rate in Ilam climatic condition.

The experiment was conducted as a split-plot based on randomized complete block design with three replications in Agronomy Research Farm of Ilam University. The experimental factors included 3 irrigation regime (100, 80, and 60 percent of field capacity) and nitrogen rate at three levels (0, 100 and 150 kg.ha-1).

The highest grain and biological yield were obtained with 5275 and 17209 kg/ha in I100 N150 treatment, respectively. Radiation use efficiency of Maize was affected by irrigation regime and nitrogen rate. Radiation use efficiency was in the range of 1.97 (I60N0 treatment) to 2.66 g/MJ (I100 N150 treatment). The highest and lowest of radiation absorbed were obtained in I100 N150 and I60N0 respectively. The highest of nitrogen use efficiency of agronomic (47.5 kg/kg) and uptake (1.6 kg/kg) were observed in I100N0 treatment and the highest of nitrogen use efficiency of physiologic was obtained I80N0. Nitrogen uptake in harvested biomass increased with additional N fertilizer application. The nitrogen uptake increased from ∼65 kg/ha at I60N0 treatment to ∼280 kg/ha for I100N150 treatments.

In this study, an inverse relationship was observed between radiation use efficiency and agronomic nitrogen use efficiency. The results of the experiment showed that the application of higher nitrogen rate was not the appropriate strategy for compensating for the reduced grain yield under low irrigation.

Guar (Cyamopsis tetragonoloba) is an annual and tropical plant of the legume family that is suitable for seed production in arid and semi-arid regions due to its resistance to drought.

Methods & Materials: 

Therefore for studying the effects of salicylic acid on morphological, physiological characteristics, yield and yield components of Guar under at three levels of field capacity (drought stress), a split plot experiment based on randomized complete block design with four replicates was conducted in Jiroft in Kerman province, Iran. The experimental treatments were included three levels of irrigation (45, 65 and 85% of field capacity as main factor) and four concentrations of salicylic acid (0, 0.5, 1 and 2 mM as the sub factor). Foliar application of salicylic acid was carried out in three five-leaf, flowering and pod stages.

Results showed that by reducing soil moisture (from 85 to 45% FC) significantly decreased all traits except grain protein. The effect of salicylic acid was also significant on all traits except for 1000-grain weight. Foliar application of 1mM salicylic acid at 85% and 65% of field capacity resulted in the highest grain yield.

There was no statistically significant difference between 2 and 1 mM concentrations in most of the studied traits, so, it can be concluded that foliar application of salicylic acid at a 1 mM concentration can reduce the negative effects of decreasing soil moisture, Finally 65% of field capacity it can be introduced as superior level for irrigation of Guar.

It is necessary to evaluation of the occurrence of climate change, Inadequate distribution and Stop of rainfall in the final stages of wheat growth in Varamin.

From the output of HadGEM under RCP4.5 and RCP8.5, to simulate the future climate using AgMIP model with long-term baseline data (1980-2009), in the periods of 2025, 2055 and 2085 were used. SSM model was used to simulate the phonological stages of wheat and in order to calibrate and validate the model, an experiment in the form of a randomized complete block design with five treatments including; [No stress, booting stage, Flowering, Milking, and Doughing], with 3 replications, was carried out during the 2020-2019 growth season in Varamin.

The SSM model simulated the occurrence of phonological stages with high accuracy. In 2085 period under RCP8.5, the highest increase of Tmax and Tmin was observed with 6.9 °C and 5.6 °C compared to the baseline period, respectively. While the amount of precipitation decreased in 2025 and 2055 under RCP8.5, but it increased in RCP4.5. The smallest difference between day to Flowering, BSG, TSG and day to was related to the period 2025 under RCP4.5 with 3, 9, 12 and 11 days, respectively. The highest differences were observed in the period 2085 under the RCP8.5 with 90, 77, 47 and 43 days, respectively.

Increasing the temperature and decreasing rainfall have neutralized the beneficial effects of increasing CO2 concentration and these factors have shortened the duration of phonological stages.

The aim of this study was to investigate the effect of biochar produced from wastes from pruning of pomegranate trees and compare it with vermicompost Oenothera biennis under drought stress.

Treatments included different levels of organic modifier application (seven levels including no modifier application, application of 10, 20 and 30 ton ha-1 vermicompost and application of 10, 20 and 30 ton ha-1 biochar) and three levels of drought stress (irrigation in 80, 60 and 40% of field capacity (FC)).

The results showed that drought stress significantly decreased leaf length, leaf area, stem diameter, plant height, chlorophyll index and relative water content (RWC) while increased the ratio of root dry weight to shoot and ion leakage. Application of 30 ton ha-1 biochar and all application levels of vermicompost decreased root dry weight to shoot ratio under severe drought stress. All application levels of vermicompost were increased the chlorophyll index under severe stress while different levels of biochar had not significant effect. All amendments significantly increased RWC compared to the control under moderate and severe stress conditions. Application of 30 ton ha-1 biochar and vermicompost decreased ion leakage compared to the control.

It seems that organic amendments can help the plant in stressful conditions by affecting the availability of nutrients and increasing the soil moisture holding capacity. In this study the effectiveness of vermicompost was better compared to biochar, which can be attributed to the higher content of nutrients in vermicompost.