جستجوی مقالات مرتبط با کلیدواژه « irrigation interval » در نشریات گروه « کشاورزی »

Supplementary irrigation in the fig orchards of the shores of Bakhtegan Lake in Estahban is done with saline water. This research was carried out to investigate the effect of saline water on vegetative and reproductive characteristics of fig trees. The randomized complete block design was performed with irrigation water salinity treatments (2, 4, 6 and 8 dS.m-1) in two irrigation intervals (once every 15 and 30 days) with a non-irrigation treatment (control) on Sabz cultivar in three replications at Khanehkat village in the years 2018 to 2021. The results showed that irrigation with 8 dS.m-1 salinity had adverse effects and it was an unsuccessful treatment compared to the other treatments with lower salinity irrigation. The highest abnormality symptoms in vegetative and reproductive factors were observed in the control treatment. Also, this treatment has the lowest relative water content (58.6%), diameter (26.6mm) and weight (4.3g) of fruit, the least yield (4935g) and the percentage of first-class commercial fruits (Open ostiole, white and large fruits) and the highest leaf ionic leakage (27.1%), which was significantly different from most of the treatments. There was a great similarity in the characteristics of trees treated with 8 dS.m-1 saline water and without irrigation. Therefore, supplementary irrigation with this salinity is not recommended. In conclusion, supplementary irrigation with saline water less than 6 dS.m-1 had suitable quantity and quality of fruit and the least abnormality signs. So, Sabz cultivar can tolerate until this amount of salinity.

In order to study the effects of nitrogen and irrigation interval on Broomrape (Orbanche aegyptiaca) damage reduction in cucumber (Cucumis sativa L.), an experiment with two factors, nitrogen (urea in three levels 100,200 and 300 Kg/ha) and irrigation interval (with three levels 3,6 and 9 day) in three replications was performed in the greenhouse of Northern Khorasan Agricultural and Natural Resource Research Center. The results showed that the growing velocity was maximum in the treatment of 200 Kg N/ha. However, height and the number of cucumbers were lower. The effect of irrigation interval on the number of flowering days was significant, whereas nitrogen fertilizer did not have a significant influence on this parameter. Hence, irrigation level rising caused reduction in the number of flowering days. Maximum length and diameter of cucumber was observed in the treatment of highest nitrogen level and minimum irrigation interval or the treatment of lowest nitrogen level and medium irrigation interval. The maximum number of cucumbers and weight was obtained in maximum nitrogen and irrigation interval. In addition, rising irrigation interval caused the number of cucumber increase and decrease in cucumber weight. The maximum wet weight of shoot and root was observed in the highest nitrogen treatment. On the other hand, the maximum wet weight of shoot and root was derived from the highest nitrogen and medium irrigation treatment and the highest nitrogen and minimum irrigation interval treatment, respectively. The comparison of water percent in wet and dry weight of shoot showed that the highest value was observed in 300 and 100 Kg N/ha treatments respectively. Maximum shoot/root ratio was observed in the treatment of 100 Kg N/ha and a six-day irrigation interval.

Due to the climatic conditions of Iran, increasing water scarcity, and the effect of drought stress on the efficiency of irrigation water consumption and chemical fertilizers application, an experiment was conducted to investigate the effect of irrigation intervals (6, 9, and 12-day intervals), different levels of nitrogen fertilizer (200, 300, and 400 kg urea per hectare) and cultivation methods (on-ridge or heeling up and in-furrow) on yield and productivity of sugarcane as a factorial design based on randomized complete block design in 3 replications at Hakim Farabi Agro-Industry Company in Khuzestan province. The results showed that the maximum (106.73 tons/ha) and minimum (59.10 tons/ha) sugarcane yields were observed in 9-day and 12-day irrigation intervals, respectively. Also, the highest sugarcane yield (99.89 tons per hectare) was obtained in the treatment of 400 kg urea per hectare and the in-furrow planting method resulted in a higher yield compared to the on-ridge planting method. The highest water productivity in sugarcane stem yield and sugar production with 3.55 and 0.34 kg per cubic meter of applied water, respectively, was obtained in a 9-day irrigation interval. A significant increase in water use efficiency in sugarcane stem yield was observed in 400 kg urea/ha compared to the other two fertilizer levels. However, there was no significant difference in water productivity of sugar yield between different fertilizer treatments. The results showed that 6 and 9-day irrigation intervals in most of the studied traits were not significantly different. Therefore, using a 9-day irrigation interval is suggested in the studied area when the sugarcane cultivation area is high and the amount of available water is limited. In-furrow planting method can also be effective in reducing water consumption. Therefore, deficit irrigation and proper nitrogen fertilizer consumption can be very effective in sugarcane cultivation.

In order to evaluate different irrigation regimes and planting date on yield, water use efficiency, and harvest index of Roselle (Hibiscus sabdarjffa L.), an experiment was conducted in form of split plot in randomized complete blocks with three replications in Karaj in 2017. Experimental treatments included irrigation round (Irrigation intervals of 8, 10, and 12 days) as a main plot, andplanting date treatments at three levels of 4th June, 18th June, and 2th July as a sub-plot. Results showed that the main effect of irrigation treatments was significant on all traits except harvest index. Planting date had a significant effect only on plant height, stem diameter, biological yield, flower water use efficiency, and sepal water use efficiency. The interaction of irrigation treatment levels and planting date only made a significant difference in biomass water use efficiency. Also, the flower harvest index was not affected by any of the applied treatments.The greatest plant height (181.2 cm), stem diameter (2.91 cm) and biological yield (14.6 t.ha-1) were obtained in the irrigation interval of 8 days. The highest sepal water use efficiency of (0.18 g.L-1), flower water use efficiency (0.034 g.L-1) and sepal harvest index (11.12 %) were observed in the irrigation interval of 12 days. The irrigation interval of 10 days had the highest sepal yield (1.59 t.ha-1) and flower yield (307.7 kg.ha-1).Delay in planting caused a decrease of 12, 16, and 7% in plant height, stem diameter, and biological yield, respectively and increase in the sepal water use efficiency and biological yield water use efficiency by 22 and 20%, respectively compared to optimum planting time. The highest biological yield water use efficiency (2.41 g.L-1) was obtained in irrigation interval of 12 days and one month delay in planting. Based on the obtained results, irrigation interval of 10 days is recommended to achieve maximum flower yield and sepal yield, increase the flower water use efficiency and sepal harvest index. Also, in order to shorten the cultivation period and save water consumption, the date of 18th June is recommended for plant cultivation in Karaj.

Drought and salinity stresses are among the main challenges in the agricultural sector, especially in arid and semi-arid regions. In this study, in order to investigate the interaction effect of salinity and drought stresses on safflower (cv Goldasht), a factorial experiment was conducted in 2020 as a completely randomized design with three replications in the 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 and salinity levels of irrigation water were included 0.7 (S1), 4 (S2), 7 (S3) and 10 (S4) dS/m. At the end of the growth period, safflower traits such as grain yield, 1000-seed weight, shoot dry weight, harvest index, water productivity, leaf area, evapotranspiration, electrolyte leakage and SPAD index were measured. Results showed that the main effect of the salinity levels of the irrigation water and irrigation intervals were significant on all traits. Also, the interaction effects of salinity and irrigation interval were significant on all traits except leaf area and electrolyte leakage at one percent level. By increasing irrigation water salinity and lengthening of irrigation interval, all traits decreased except electrolyte leakage percentage. In the highest salinity level (S4) compared to the control treatment (S1), the average of evapotranspiration during the stress period and grain yield decreased by 32 and 84.7 percent, respectively. Increasing irrigation interval up to 15 days reduced evapotranspiration during the stress period and grain yield by 38 and 86.4 percent compared to 5 days irrigation interval, respectively. The coefficient of readily available water for safflower grain yield was obtained 0.45. The salinity threshold of the soil solution for reducing safflower grain yield was obtained about 3.4 dS/m and the slope for decreasing grain yield was 5.8% per unit increase in salinity.

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.

in addition to pasture grazing, animals are fed on such sources as manual forage, farm straw, etc. Therefore, due to various socio-economic reasons, overgrazing and forage shortage exert adverse effects on rangelands, leading to their degradation. On the other hand, excessive exploitation of rangelands and changes in their use has led to the expansion of invasive species, altering the rangelands’ species composition and influencing the relevant ecosystem’s functions and services, which, consequently, ends in the destruction of ecosystems worldwide. In this regard, in cases where the invaluable and important species are overgrazed, the improvement of the rangelands containing perennial, high-yielding, and palatable species is recommended to restore the rangeland’s production capacity, reduce the competitiveness of invasive species, and increase the vegetation both quantitatively and qualitatively. Thus, it could be argued that identifying the factors involved in the germination and growth of invaluable species in rangeland ecosystems is required for the management, improvement, and restoration of rangelands.

This study sought to investigate the effect of irrigation interval, water salinity, and the soil’s clay content on the seed germination and the height of germinated seedling of Hedyasrum criniferum which is an endangered, palatable species indigenous to Iran’s rangelands, under greenhouse and natural habitat conditions. To this end, a factorial experiment was performed in terms of irrigation interval at three levels of 7, 10, and 14 days, water salinity at three levels of <1 (0.4), 2, and 4 dS m-1, and added clay contents at three levels of 0, 10, and 20% under greenhouse conditions with three replications, using a random sampling method. Moreover, the GLM method was applied to examine the factors affecting the herbal parameters of the Hedyasrum criniferum species.

The study’s results revealed that out of the three treatments mentioned above, only the irrigation interval had a significant effect on the H. criniferum species’ germinated seedling height and its germination percentage (α = 5%), with the greatest amount of germination (77.77%) and the highest germinated seedling’s height (4.93 cm) being observed in the seven-day irrigation interval based on the comparison of means. According to the species’ response curves, while the species’ height showed an ascending trend in proportionate to the precipitation rate, it had a reverse trend in proportionate to salinity. As for the clay content, it was found that the species’ height decreased up to 25% with an increase in the clay content. However, the trend was increasing for over 25% clay content.On the other hand, the analysis of the species’ response curve in terms of the amount of germination density indicated that while the number of germinated seeds increased with an increase in the precipitation rate, it decreased with an increase in salinity. Moreover, the number of germinated seeds responded to clay content the same as it reacted to the species’ height, getting decreased with up to a 25% increase in the clay content.

as found in this study, irrigation interval is a more important factor than the other two treatments. The tolerance level of germination and seedling growth was found to be at a 14-day irrigation interval, 4 dS m-1 salinity level, and 20% added clay content. Therefore, it could be argued that lowering the irrigation intervals may help the root growth. Furthermore, maintaining the moisture at 40-0 cm away from the soil profile can facilitate root growth and thereby increase photosynthesis. However, increasing the irrigation intervals may disrupt photosynthesis by creating a shortage in the soil’s moisture and decreasing the production of photosynthate materials to be transformed into the plant’s growing parts, checking the growth of the plant’s height. Considering the fact that Hedyasrum criniferum is regarded as a very high-quality forage in Iranian rangelands based on the rangeland classification indices in terms of forage quality, and that the species contains more protein and metabolic energy and higher nutritional value than alfalfa, and also its desirable ability to stabilize the soil’s nitrogen, the species can be used to convert the abandoned rain-fed lands in semi-arid areas to forage-planted lands and restore the destroyed rangelands in natural habitats. On the other hand, it was revealed that in natural habitats, the chances for the growth of the aforementioned species increased with an increase in precipitation rate, reaching its highest points in areas with average annual 650 mm precipitation. It should be noted that the precipitation range of the species’ habitats indicates the possibility of  H. criniferum growth in different climatic regions, including arid, semi-arid, and semi-humid regions. Therefore, it was found that the chances for the species' growth increased with an increase in precipitation rate from arid to semi-arid and finally, to semi-humid regions. Moreover, the study found that based on its optimal precipitation rate, the species prefers semi-humid climates.

This study was conducted to investigate the response of salicornia persica, directly irrigated with Persian Gulf saline water in Bushehr region, to reducing its required water and to determine the relationships between applied water and dry matter. The experiment was performed in a randomized complete block design with 3 replications. The treatments included T1, T2, T3, T4, T5 and T6, with total applied water of 6700, 8800, 9600, 10000, 11800 and 14700 m3.ha-1, respectively. The results showed that the applied water has important role in the dry matter; So that in the treatments of T1 to T5 with a significant difference it applied water, no significant increase was obtained for the crop yield. The average dry matter of the treatments was relatively constant and about 3000 kg.ha-1. However, increasing the volume of applied water in T6 treatment had a positive and significant effect on dry matter and increased it to 4600 kg.ha-1. Under the mentioned field conditions, Salicornia water productivity (WP) was obtained between 0.15 to 0.44 kg.m-3. Therefore, to achieve yields of 5 tons per hectare and more, a timely and sufficient water supply system (by shortening of the irrigation cycles) will be required for the Salicornia fields. The latter conclusion confirms the positive response of Salicornia to the increase of applied water, which can well illustrate the challenge of water supply importance in Salicornia fields.

Application of water-absorbent material to increase Water productivity (WP) has been considered by researchers in recent decades. In this regard, different materials with different nature in water absorption and storage have been introduced. Aquasource is a kind of water-absorbent polymers that intruduces as an additive for modification of soil-water-plant relationship. Therefore, the present study was conducted to investigate the effect of application of Aquasource superabsorbent on WP of soybean using experimental plots. This study was performed in a factorial experiment with a completely randomized design and three replications. The first factor was two different irrigation intervals (4 and 7 days) and the second factor was different levels of superabsorbent (zero, 200 and 300 kg/ha). During the growth period, the amount of soil moisture was measured using a hydrometer. At the end of the plant growth period, yield and yield components and WP were determined. The results showed that the effect of irrigation interval on all indices was significant. The interaction between Irrigation and superabsorbent on water use and yield was significant. By changing the irrigation interval from 4 to 7 days, the average irrigation water, yield, oil yield, protein yield, WP of oil and protein decreased by 30, 50, 52, 50, 26, 23 and 30 percent, respectively. Aquasource superabsorbent reduced the average water use by 10% compared to the control treatment. Under the application of two levels of 200 and 300 kg of superabsorbent per hectare, increasing the depth of irrigation water to more than 630 mm did not have much effect on crop yield. Use of superabsorbent also reduced the appropriate irrigation depth to achieve the highest WP from 700 to 630 mm. This study suggests that the use of superabsorbent at a rate of 200 kg/ha (probably the optimal limit) increase grain yield, WP of oil and protein.

Drip irrigation delivers moisture to the soil surrounding the plant root, leaving the uncultivated ridges mostly dry. The dynamics of dryness and moisture can help adjust the soil salinity and redistribute moisture and salinity (Li et al., 2013; Wang et al., 2011). Further, the distribution of soil salinity in arid regions is affected by a multitude of factors, including the water table (Ming et al., 2016), groundwater salinity, (Abliz et al., 2016), irrigation system (Lie et al.,2013;Zhang et al.,2017), and soil texture (Hu et al., 2011; Zhang et al., 2014). Given the complexity of investigating moisture and salinity distribution in the soil and their uptake by plant roots, the subject has been addressed by several studies around the world. The present study attempts to investigate and evaluate the effects of different irrigation regimes (two-, three-, and four-day) using a tape drip irrigation system on the diffusion and distribution of salinity and moisture around the root of summer maize over two crop years (2018–19) in the South Khuzestan region, where a heavy soil texture is predominant.

Located between the 29°57’ N and 33°0’ N relative to the equator, and between 47°40’ E and 50°33’ E relative to the prime meridian, Khuzestan Province occupies 64,057 square kilometers in Southwest Iran. The present study was carried out in a research farm at the Center for Agriculture and Natural Resources Research and Training, Ahwaz, Khuzestan Province, in summers 2018 and 2019. With clay and silty clay soil textures, shallow and saline groundwater (1.5 m depth), and its particular climate, this research farm can be representative of the farmlands of Central and Southern Khuzestan. The required volume of water during each irrigation by the drip tape irrigation system under different irrigation regimes (two-, three-, and four-day) was calculated for different plant development stages and treatments, thus enabling control over the different irrigation hours in different regimes. the farm soil was sampled at four stages, namely before planting, upon germination, during the middle development stage, and after planting), for physical and chemical characterization and monitoring salt levels from three depths (0–25, 25–50, and 50–75 cm) at a 20 cm distance from the tape by manual excavation using an auger (10 cm in diameter and 20 cm in length). Soil salinity and other quality criteria were measured in the lab. Further, the SMC was measured by the weight percent method, which involves weighing and drying the samples.

The present study addressed moisture and salinity distribution in the soil profile around the plant root under different irrigation regimes. The moisture distribution results showed that all irrigation regimes (two-, three-, and four-day) could maintain the moisture around the FC, slowing down the vertical flow and minimizing penetration into depths. The soil salinity results showed that, considering the soil salinity conditions at the start of the growing season, using the drip tape irrigation first reduced and then increased salinity in the first year of cropping. In contrast, in the second growing season, soil salinity at the end of the growing season using two-, three-, and four-day irrigation regimes was cut to a fourth and a third of its initial level. This shift in the behavior was, however, due to the differences in the quality of irrigation water. This outcome shows the susceptibility of using the drip tape irrigation system in soils that are prone to sodicization and salinity, which requires preparing the conditions to ensure the sustainable function of the irrigation system. The final set of samples showed that, under all irrigation regimes, the emitter output effectively reduced soil salinity, and that this reduction is more effective with frequent irrigations, washing the salts further away from the source. Further, the 0–25 cm deep layer was found to have the least salinity among the studied layers. All irrigation regimes (two-, three-, and four-day) were successful in controlling salinity in the root zone, but the two-day treatment, with a shallower irrigation depth and shorter irrigation intervals, offered the best leaching. The results of performance analysis in two years showed that the year did not have a significant effect on grain and dry matter yield. The results also showed that irrigation regimes did not have a significant effect on dry matter yield but significant on grain yield at 5%.

The present study was conducted to evaluate the efficiency of the HYDRUS model in simulating soil water movement and redistribution of moisture around the roots of maize in homogeneous and heavy soils. This study was carried out in the Agricultural Research Center of Khuzestan Province under drip strip irrigation with three irrigation regimes of 2, 3 and 4 days with three replications during two cropping years. In order to monitor the moisture around the roots, dig a soil profile to a depth of 75 cm perpendicular to the drip irrigation strip. Observed and simulated moisture values were compared byR2,EF, MAE and RMSE statistics. The results showed that the average moisture distribution in each irrigation regime is in the range of crop capacity. RMSE values for different diets ranged from 1.29 to 2.40% and MAE values for different diets ranged from 1 to 2%. Moisture simulations were classified as excellent based on MAE and RMSE values.Also, the results of the coefficient of explanation are between 60 to 90% and the efficiency of the model is between 40 to 90%. Based on the results, the lowest efficiency of the model was in the simulation 24 hours after irrigation and the best simulation was 72 hours after irrigation. The results show the high capability of the model in simulating soil volumetric moisture.

To evaluate different irrigation regimes and planting dates on plant height, stem diameter, yield, and yield components of okra (Abelmoschus esculentus L.) a split plot experiment based on randomized complete blocks with three replications was conducted in Karaj during 2017 growing season. Experimental treatments were irrigation intervals (8, 10 and 12 days) as a main plot, and planting dates with three levels (4th, 18th of June and 2th July) as a sub-plot. The results of analysis of variance showed that the main effect of irrigation interval was significant on all traits under study. Planting date treatment had a significant effect only on plant height, stem diameter, number of plant branches, number of plant leaves, number of fruits, fresh fruit yield and dry fruit yield. The interaction of irrigation interval treatment and planting date had no significant effect on the trails under study. The highest chlorophyll concentration (3.68 mg.g-1 FW), plant height (100.4 cm), number of branches (3.1), number of leaves per plant (24.8), number of fruits per plant (10.5) and fresh fruit yield (4023 kg.ha-1) were belonged to the irrigation interval of 8 days. Irrigation interval of 12 days decreased by 30.4, 21.7, 21.3 and 28.4 % in stem diameter, fruit length, fruit diameter and dry fruit yield, compared to irrigation interval of 8 days interval, respectively. The highest plant height (99.2 cm), number of branches (2.5), number of leaves per plant (23.3) and number of fruits (9.77) were observed of June 4th planting date. The highest fruit yield was obtained in June 18th planting. Based on the results obtained it can be concluded that irrigation interval of 8 days is recommended to achieve maximum fruit yield and to shorten the length of growing period, saving in water consumption and maximum yield performance in the Karaj region, the date of 18th June is recommended.

Cotton or white gold is the most important and the oldest fibrous plant that is suitable for cultivation in arid and semi-arid regions. Among industrial plants, cotton has a special position. Not only cotton is one of the most important fibrous plants in view of fiber production, but also its seeds, which contain oil and protein, play a major role in providing edible oils and animal feed. Due to increasing need of society for cotton plant products and the importance of cotton in the global market and industries, it is very important to remove barriers to the continuous development of the cultivation of this product. Considering the importance of cotton in crop rotation and the sever reduction of cotton cultivation in recent years, it is necessary to use new approaches to increase the cultivation area, production amount and to reduce the production cost of this strategic crop. One of the strategies for developing the area under cotton cultivation is delayed cultivation as transplanting, which increases yield, early maturity and water use efficiency. Proper irrigation scheduling plays a very important role in delayed cultivations. In order to determine the physical and chemical properties of the soil in the study area, soil samples were taken from a depth of 0 to 30 and 30 to 60 cm and were analyzed in the laboratory. Fertilizer recommendation was done on the bases of soil test. In this experiment, the percentage of saturation moisture, electrical conductivity, acidity of saturated paste was determined and soil texture was measured by hydrometric method. Therefore, an experimental design of factorial strip plot, with three replications, was carried out in the Hashemabad cotton research station, in 2020. Irrigation methods of tape and furrow were as main factor. Cultivation methods of direct and transplanting as sub-factor and sub-sub factor was irrigation intervals after 70, 105, 140 mm cumulative evaporation from the pan, and irrigation quantities of 0, 50, 75, 100, 125% of the evaporated water from the pan. The treatment of 105 mm cumulative evaporation from the pan is usually 14 days, depending on the region. While the treatment of 70 mm means irrigating as soon as possible during 8 days. In addition, the treatment of irrigation after 140 mm of cumulative evaporation from the evaporation pan, ie once every 20 days, means that irrigation leads to plant stress. It should be noted that irrigation with less than 50% of the evaporated water from the pan can reduce the yield and is not applicable to the furrow irrigation method in the field, due to water not reaching the end of the field. In addition, irrigation with more than 125% of water evaporated from the pan is not highly recommended. The results showed that irrigation method had no effect on yield and yield components, but transplanting method had higher yield, early maturity, boll weight and water use efficiency at rates of 14, 180, 4.8 and 11.3% compared with direct method, respectively. Among the irrigation interval treatments, the irrigation after 105 mm evaporation from the pan had higher yield, boll weight and water use efficiency than the 70 and 140 mm treatments; So, that the yield of this treatment was 8.8 and 16.6% higher than the 70 and 140 mm treatments. While, water use efficiency of 105 mm treatment was 9% higher than 140 mm. In fact, cotton is a plant that reacts a lot to the amount and frequency of irrigation. It means irrigation management, and the balance between reproductive and vegetative growth is regulated by irrigation management. Excessive irrigation not only prevents increased yield, but also reduces yield and water use efficiency. Different irrigation water quantities had no effect on yield but on yield components had significant effect. The highest water use efficiency was related to 50% irrigation water, which was 19.6%, 43% and 69.8% higher than 75, 100 and 125% irrigation water, respectively. Irrigation quantity of more than 50% does not significantly increase yield but increases water use efficiency. Finally, the best treatment was transplanting method with an irrigation interval of 105 mm evaporation from the pan and 50% irrigation water of cotton increases. Also, transplanting cultivation increased yield compared to direct cultivation. Although it is not economically viable, it is recommended if the price of cotton increases.

Manning roughness coefficient is a complex and effective parameter in furrow irrigation, and its exact determination is complicated due to spatial and temporal changes of soil characteristics and hydraulic parameters of the flow. Hence, this study was conducted to determine the Manning roughness coefficient in the advance and storage phases and in the first to third irrigation events. In this study, Manning roughness in furrow irrigation in the advance and storage phases was determined using the SIPAR_ID model and the Manning equation, respectively. For this purpose, the value of Manning roughness coefficient for two inflow treatments (an average of 0.27 and 0.53 L/S), two irrigation cycle treatments (5 and 10 days), and two different fields (E and F) was examined in the first to third irrigation events and in three replications. The results showed that the value of Manning roughness coefficient in the advance and storage phases of three irrigation events (first to third irrigation) was between 0.017 to 0.636 and 0.015 to 0.317, respectively. Also, it was found that the average roughness coefficient in the advance phase was more than the one in storage phase (0.083 and 0.054, respectively). In addition, the roughness coefficient in the two phases reduced by increasing irrigation events. In field F, due to the heavier soil texture, the difference in Manning roughness coefficient in both phases in the first and second irrigation was lower than the ones in field E. The results also indicated that the roughness coefficient had an inverse and poor relationship with the initial soil moisture and inflow. However, the inflow was more effective than the initial moisture.

Due to the lack of water resources, increasing of the water productivity index in a strategic and high water consuming cultivation like as rice is getting more important. Planting date and irrigation program are important factors in increasing the productivity of rice. This study investigates the effect of transplanting date on irrigation programe and rice yield and provides an acceptable strategy for determining the appropriate planting date with respect to climatic conditions and field characteristics. Therefore, SWAP model was calibrated in the Astaneh-Koushfahan plain with data of three paddy fields (Hashemi variety) and validated with data of two other paddy fields. The R2 index greater than 0.98 and RMSE-N less than 10% indicated that the model had acceptable accuracy for rice growth simulation. After validation, the optimummanagement of intermittent irrigation was obtained in planting dates 1, 5, 10, 15, 20 and 25 May. The results showed that in 2011 1 May was the suitable planting date due to higher irrigation water productivity. At this date, 9% allowable moisture depletion and 7 days irrigation intervals were proposed. Also, in this plain, the maximum and minimum moisture allowable depletion was 15 and 2%, respectively in clay and sandy loamy clay soil texture.

Current study was carried out by the aim of investigating the effect of different degrees of irrigation on some quantitative characteristics of eastern cottonwood (Populus deltoides Bartr. ex Marsh) seedlings in Guilan province. The cuttings were planted in a completely randomized design with four treatments and five replications. Three irrigation levels including 20%, 40% and 60% of soil saturated moisture content in each pot including 187.5, 375 and 570 ml water for 2.5 kg soil and control treatment (without manual irrigation) every three days applied on seedlings form the beginning of spring to end of summer. At the end of the period, height of seedlings using ruler, collar diameter using caliper, stem and root fresh weight by scale, stem and root biomass by drying in oven, root length using graph paper, the number of leaves by counting were measured for all treatments and examined by one-way analysis of variance (ANOVA) test. The results showed that the highest mean of seedlings height (with 89 cm), maximum mean of collar diameter (with 8.28 mm), highest mean of stem fresh weight (with 37 g), highest mean of root length (462 80 cm), the highest mean of leaf number (with 10.23) was related to 60% treatment. The highest mean of root fresh weight and the highest stem and root biomass were observed at 40% with 4.26, 14.05 and 1.62 grams, respectively. The optimum amount of poplar seedlings irrigation was also determined by 40%.

In order to evaluate root yield and quality of Paya, a newly released drought tolerance sugar beet cultivar and compare it with foreign check Rasta, this experiment was conducted on farmers' fields under both normal and drought conditions in 2016. In this study, half hectare of each cultivar was planted and from the second irrigation, irrigation was done with intervals of 7 and 14 days for each half of the cultivated area. At the end of the growth stage, four samples were harvested (along two 5-meter lines at two rows) and the root pulp for qualitative traits was provided. Economic evaluation was carried out using benefit- cost ratio and partial budgeting. The results showed that the yield for two cultivars in the irrigation interval of 7 days (normal irrigation) was 93.3 tons and in the irrigation intervals 14 days (stress conditions) was 57.6 tha-1. In the irrigation interval of 7 days, the percentage of sugar was 16.5% and the 14-day irrigation interval percentage of sugar was 14%. Irrigation interval did not have a significant effect on the elements in the root (sodium, potassium and nitrogen). There was no significant difference between two cultivars in terms of yield, but the sugar percentage of Rasta cultivar (16.9%) was higher than Paya cultivar (13.7%).  Under drought stress condition for Paya and Rasta cultivars yield reductions were 31% and 46%, respectively. Economic evaluation showed that the Paya cultivar had economic advantage of 95% to Rasta cultivar in 14-days irrigation interval and advantage of 63% in complete irrigation (7-days interval). Therefore, the Paya cultivar under stress conditions has more capability compared to Rasta sugar beet cultivars (one of the good foreign cultivars) and can be recommended for regions with water shortages and disease-free soils.

IntroudationSalvia sahendica is a perennial native odorant plant of Iran with a right stem, crustal and about 90-40 cm height. Due to the importance of the use of Salvia sahendica in various pharmaceutical, food and sanitary industries, and because of its potential for cultivation in stressful climates, this plant has attentions to cultivate in low-yielding lands. Until now, there is not a comprehensive study on the response of Salvia sahendica to drought stress. Therefore, in order to evaluate the possibility of production and development of its cultivation under drought stress conditions, this research was carried to investigate the effects of drought stress on some physiological parameters, percentage and yield of essential oil of Salvia sahendica and determining the tolerance threshold of this plant to stress in 1395 in field conditions. Material and MethodsThis experiment was conducted at the research farm of Mobarakeh steel complex which located at 40th kilometers of southwest of Isfahan, at latitude of 32˚ 21′ northern and longitude of 51˚ 27′ eastern. After field preparation, the plants were cultivated in plots with size of 1.5 × 1.5m by 50 × 50 cm spacing in a randomized complete block design with three replicates and 9 plants per replicate. At the beginning of planting, all plots were irrigated three times a week for two weeks until the plants were established. Then, the effect of various irrigation intervals including 4 (as control, which is traditionally the optimum irrigation rate of plant in studied area), 8, 12 and 16 days intervals were applied. At the end of the summer, a sample was taken from the cultivated plant. The plants were fractioned to roots and shoots and some physiological and biochemical indices including, relative water content of leaves (RWC), water potential of leaves, total chlorophyll and chlorophyll a and b, proline and soluble sugars contents, electrolyte leakage, the essential oil percentage and yield were determined. Statistical analysis was performed on the data using MSTAT-C software at 5% level and the correlation between traits was determined by SPSS software. Results The results of analysis of variance showed that the effects of different levels of irrigation intervals on water potential of leaves, relative water content of leaves, soluble sugars, electrolyte leakage, percentage and essential oil yield were discriminated at 1% statistical level while on proline and total chlorophyll, chlorophyll a and b contents at 5%. Based on the results of the comparison of the mean, by increasing irrigation interval from 4 to 8 and 12 days, the differences in the means of all investigated parameters were not significant and only in 16 days irrigation interval the noted parameters differed significantly(pr<0.05). The highest amount of RWC (95%), chlorophyll a, b and total chlorophyll were 2.47, 1.32, and 0.98 mg.g-1 respectively in control treatment. The highest water potential of leaves (-1.78 MPa), proline accumulation (3.1 mg.g-1) and electrolyte leakage (57.7%) were observed in16- day irrigation interval. Maximum amount of soluble sugar, percentage and essential oil yield by the mean of 2.55 mg.g-1, 0.3% and 14.3 kg.ha-1 respectively were obtained in the 12-day irrigation interval. The correlation of traits showed a negative relationship between chlorophyll a, chlorophyll b with proline, soluble sugars, percentage and essential oil yield. Conclusion By considering that non-significant differences were observed in stress resistance indices of this plant up to 12-days interval in comparison with control, it can be concluded with 95% confidence that an optimal irrigation interval for using of this plant in areas arid and semi-arid regions is 12 days irrigation interval, which saves irrigation water. Also, the results of this study showed that Salvia sahendica resisted to water stress by increasing accumulation of proline and soluble sugars (osmotic regulation). Therefore, the accumulation of proline and soluble sugars can be considered as a sensitive indicator for determining the degree of leaf turgidity. Also, in order to produce the highest amount of essential oil from Salvia sahendica, the mild stress (12-day irrigation) can be used.