جستجوی مقالات مرتبط با کلیدواژه « دمای پوشش سبز » در نشریات گروه « آب و خاک »

Inefficient use of limited water resources, along with increasing population and increasing water demand for food production has severely threatened agricultural water resources. One way to overcome this problem is to improve water productivity by introducing new crops that tolerate water stresses such as quinoa. In this study, the effect of water stress at different stages of plant growth (vegetative, flowering, and grain filling) was studied on plant parameters, yield, and water productivity of quinoa (cv. Titicaca). This study was conducted under field conditions and the treatments were performed as a block experiment in a completely randomized design with four replications. Experimental factors were: treatment without water stress or full irrigation (F) and water stress treatment (D) at 50% of the need for full irrigation at different stages of quinoa growth. The application of deficit irrigation during different stages of plant growth decreased stomatal conductance, leaf area index, leaf water potential, seed yield, and water productivity, while deficit irrigation increased the green canopy temperature. According to the results of the present study, the flowering stage of quinoa was very sensitive to water stress leading to produce lower yield compared with the amount of yield obtained when vegetative and or grain filling stages are under water stress conditions.

 Barley could be grown under low-input and harsh conditions because of its wide adaptability to drought, and heat stresses. Nonetheless, the water stress leads to yield reduction when drought stress occurs during stem elongation and grain filling stages. In rainfed areas, water and heat stress occur together, specifically after anthesis, amplifying the adverse effects of water stress via disrupting water uptake of crops. In this regard, measurement of canopy temperature (Tc) by infrared thermometry is a non-destructive method that can effectively characterize the water status of plants. There is a linear relation between Tc and transpiration, which increases upon stomata closure. Since stomata is very sensitive to environmental variations and moisture reduction in the plant and it is very difficult to measure, therefore, Tc is the preferred factor to determine the crop water status. The Tc was used to calculate the practical Crop Water Stress Index (CWSI) by Idso et al. (1981) and Jackson et al. (1981). Dold et al., (2017) reported a positive significant correlation between CWSI and transpiration, daily soil water content, and plant production. Negative significant correlations between CWSI and pure photosynthesis rate, transpiration, and stomatal conductance were also reported. This study was aimed to: (i) assess the water stress effects on dryland barley genotypes using Tc, (ii) identify the upper limit for Tc affecting performance and reducing barley grain yield, (iii) determine the critical point of water stress, and (iv) apply CWSI to select the most suitable barley genotypes for both rainfed and supplemental irrigation conditions.

 To determine the crop water stress index (CWSI) and assess water status of dryland barley genotypes, an experiment was carried out in a split plot arrangement based on randomized complete block design with 15 genotypes in three replications at the Dryland Agricultural Research Institute, Maragheh (46° 45ʹ E, and 37° 26ʹ N), Iran in the 2015-2018 cropping seasons. The main plots included rainfed (as stress conditions), and supplemental irrigation (two times: 50 mm irrigation in the sowing time and 30 mm irrigation in the booting stage) as non-water stress conditions. The sub-plots included 15 barley genotypes (GaraArpa, 71411, Abidar, Ansar, ARM-ICB, ChiCm/An57//Albert, Dobrynya, Kuban-06, Makooei, Redical, Sahand, Sahand/C-25041, Sararood1, Ste/Antares//YEA762 and Valfajr). The barley genotypes were planted by Wintersteiger planter in six-row plots with 8 m long and 1.20 m wide (20 cm row spacing). The sowing rate was 380 seeds per m2 based on the thousand kernel weight (TKW) of each genotype. Seeds were treated by Penconazole fungicide. The planting dates were October 4, 2015, and October 7, 2017. In each plot, two canopy temperatures (Tc) were measured using infrared thermometer Model A-1 in six crop reproductive stages from the half of ear emerged above flag leaf ligule stage (GS55) to the soft dough stage (GS85). Measuring time was between 1:00 to 2:00 pm.

 The results indicated that the upper baseline for non–transpiring of dryland barley genotypes (Tc-Ta = 0.0008VPD + 5.89; VPD: vapor pressure deficit) was 5.9 °C (ranged from 5.5 to 6.9) which is equal to 32.4 °C green canopy and 9.0 to 11.1 mm/day evapotranspiration. Non-stressed baseline or lower baseline (Tc-Ta = -2.4662VPD + 9.15; R2 = 0.97**) showed that CWSI threshold value was 0.75 which is equal to 24.3 °C (23.7 to 26.1 °C) Tc under supplemental irrigation and 23.3 to 24.7 °C under water stress conditions. Additionally, CWSI threshold was equal to 7.3 mm/day evapotranspiration and 5.02 kPa VPD. On the other hand, results revealed that when Tc exceeded 25 °C, biological yield, thousand kernel weight (TKW) decreased significantly, followed by grain yield in different barley genotypes. The slope of the CWSI calibration equation (Tc-Ta = -2.4662VPD + 9.15) is often more negative in hot and dry areas, and tends to zero in cold and humid areas. Therefore, its negativity indicates the conditions of moisture stress for barley genotypes in the dryland phase. The CWSI threshold for barley genotypes growth stages happened at 248 (6th June) days from sowing time (4th – 7th October) which is equal to flowering stage (ZGS60). According to CWSI quantity, Ansar, ChiCm/An57//Albert, Sahand/C-25041and Ste/Antares//YEA762 were grouped in the tolerance class under stress (dryland) conditions. However, Abidar, Sahand/C-25041, GaraArpa, ChiCm/An57//Albert and Makooei were placed in the tolerance class under non-stress (supplemental irrigation) conditions.

The CWSI could estimate the intensity of heat and water stresses in the grain filling stage for barley genotypes in cold and semi-arid areas. The average of canopy temperature threshold values were 24.8 and 24.0 °C for dryland barley genotypes in supplemental irrigation and dryland conditions, respectively. In addition, these indices could be used to estimate heat and water stress tolerance levels for barley genotypes.

Empirical and theoretical methods (energy balance) are widely used to calculate the Crop Water Stress Index (CWSI) and irrigation scheduling to describe crop water status. In this study, irrigation scheduling was performed at the research farm of College of Agriculture, Urmia University, using a manual infrared thermometer and the empirical method of Idso et al. (1981) for the black gram under different irrigation regimes using drip irrigation in 2017. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 which were 50, 75 and 100 percent water requirement in three replications, respectively. Using the baselines obtained for each treatment, the average CWSI values during the growth season of black gram for I1, I2 and I3 treatments were calculated to be 0.37, 0.23 and 0.15 respectively. The relationship between CWSI and total irrigation depth (mm) was determined as CWSI = -0.0008 (I) + 0.58, and the relationship between black gram grain yield (ton/hec) and CWSI was determined as Yield = -1.8237 (CWSI) + 2.1435 which their correlation coefficients (R2) were 0.98 and 0.99 respectively, which shows the high accuracy of regression models. In general, if the amount of water decreases with stress during the plant growth, the CWSI value increases, and as a result of increasing CWSI, the crop grain yield decreases. Finally, the no stress treatment (I3) with CWSI=0.15 was the basis for irrigation scheduling and then some relationships were established for determining the irrigation time using CWSI in Urmia climate for four stages of black gram growth; flowral induction-flowering, pod formation, seed and pod filling, and physiological maturity as (Tc  ̶ Ta)C = 1.9498  ̶ 0.1579(AVPD), (Tc  ̶ Ta)C = 4.4395 ̶ 0.1585(AVPD), (Tc  ̶ Ta)C = 2.4676  ̶ 0.0578(AVPD) and (Tc  ̶ Ta)C = 5.7532  ̶  0.1462(AVPD), respectively.

In order to evaluate the Crop Water Stress Index (CWSI) of potato crop, a split- plot design was carried out in a randomized complete block design in Shahrekord Agricultural and Natural Resources Research Center in the growing season of 2018. This experiment consists of two methods of irrigation (surface and subsurface drip irrigation) in the main plots and four irrigation levels (Full Iirrigation, FI; Regulated Deficit Irrigation, RDI-80; Regulated Deficit Irrigation, RDI-65; and Partial Root-zone Drying PRD-75) in subplots, in three replications for potato (Bourren cultivar) with a period of growth of 120 days. Based on the results, the trend of changes in the CWSI of the crop in irrigation treatments for surface and subsurface drip irrigation was between 0.16 and 0.56 and 0.15-0.49, respectively.The relationship between CWSI and yield (Y) for surface and subsurface drip irrigation was Y = -122.28 CWSI + 82.38 and Y = -101.61 CWSI + 70.97, respectively. The yield of crop for treatments FI، RDI_80، PRD_75 and RDI_65 in surface drip irrigation was 52.1, 48, 31.6, and 23.4 Ton.ha-1, respectively and for subsurface drip irrigation 48.6, 44.3, 29.6 and 21.8 Ton.ha-1, respectively.The maximum amount of water consumed for treatment FI was 4590.2 m3.ha-1. The results showed that in order to achieve the highest yield in subsurface drip irrigation, the potato crop should be irrigated in the range of 0.16 to 0.2 of the CWSI.

According to the amount of wheat production in Fars Province and occurrence of drought, application of crop’s residual on agricultural land in form of biochar may improve soil fertility and increase crops yield. Therefore, the current research was conducted to study the effect of different levels of wheat straw biochar and deficit irrigation on wheat growth and yield. The treatments included four levels of biochar (0, 1.25, 2.5 and 3.75 % w/w) and three levels of irrigation (100, 75 and 50 % crop water requirement). Under full irrigation treatment, increasing in biochar to 1.25%w/w was increased crop height by 11.5% in comparison with that obtained in no biochar application. Biochar levels of 1.25, 2.5 and 3.75% w/w increased (decreased) stomatal conductance (green canopy temperature) by 26.8, 31.2 and 37.9% (15.2, 21.4 and 23.4%), respectively, in comparison with that obtained in no biochar application, under full irrigation treatment. Also, the maximum number of tillers per wheat plant (3.7), number of seed per tillers (36.1), 1000 seeds weight (54.1 g) and above ground dry matter (65 g) were observed in 1.25 % w/w biochar treatment, and further increase in biochar declined these parameters in comparison with control as the soil become more saline. It can be concluded that deficit irrigation of 75% crop water requirement and application of 1.25% w/w biochar is recommended due to positive effect of these treatments on yield and yield components.

Infrared thermometer is one of the proper irrigation scheduling tools that can be used in fields or gardens with different soil texture. In order to schedule irrigation of maize (SC704) in Urmia climate conditions, using a difference in temperature of canopy cover of plant and air in 2017, a research was conducted at research farm of Urmia University college of agriculture under drip irrigation. In this research, the effects of various irrigation water treatments were investigated. The experimental design was carried out in a randomized complete block design with three levels of irrigation I1, I2 and I3 of 50, 75 and 100 percent of water requirement in three replications, respectively. Based on the results, the average values of CWSI for maize during the growth period for treatments of I1, I2 and I3 were calculated to be 0.53, 0.44 and 0.28, respectively. The results showed that the CWSI index increased with decreasing water requirement. The threshold of water stress index (0.28) of I3 treatment (no stress treatment) was the basis for irrigation scheduling. Then, some relationships were presented to determine the irrigation time of maize, using the CWSI index in Urmia climate for July, August and September as ,and  respectively.

This study was conducted to study scheduling of single irrigation for rain-fed wheat using crop water stress index (CWSI) for arid and semiarid regions of Honam plain located in upstream of Karkheh River Basin of Iran during 2004-2005. Three cultivated rain-fed wheat were selected to conduct the treatments. Each farm separated to 2 part: (1) rain-fed (2) single irrigation in spring by depth of 60 cm. Application of single irrigation was different in 3 farms which were in heading, flowering, and milk stages accordingly. Soil water content in 60 cm soil depth and canopy temperature in flowering and milk development stages was measured in different times. CWSI was evaluated when upper and lower base line for non-transpiring were determined. Lower and upper baseline for non-transpiring was Tc –Ta = -2.089 VPD 2.28 and 6.2oC accordingly and CWSI and canopy temperature was 0.36 and 26.4. CWSI and yield variation were in 83% agreement. Moreover, wheat canopy temperature and soil water content showed a high agreement (R2) of 0.78.

Irrigation scheduling under water and salinity stress, is much more difficult than full irrigation scheduling. To investigate the effect of plant water stress, there are many indicators. One of them is crop water stress index (Idso method). To evaluate the ability of this index for irrigation scheduling of summer Maize (SC704 variety) and winter Maize (Mobin variety)- in conditions of using saline water, a research was designed at the research station of Shahid Chamran University in 2013-2014 . This research consisted of five quality treatments of irrigation water, including S0: Water Caron, S1: EC= 3.5dS / m, S2: EC=4.5dS / m, S3: EC=5.5dS / m and S4: EC=6.5 dS / m. In the both of the growing seasons, result showed, The upper and lower base lines were affected by salinity stress. The amount of upper and lower base lines for summer Maize were higher than the winter Maize. The lower and upper baseline's equation for summer Maize were (Tc-Ta)l.l=1.641-0.178VPD and h=2.52 0c and for winter Maize were (Tc-Ta)l.l=2.161-0.221VPD and h=3.69 0c. CWSI, which is the base of irrigation scheduling, was calculated 0.23 for summer Maize and 0.17 for winter Maize. By increasing water salinity from 2.2 to 6.5 ds/m, the temperature difference between canopy cover and air was 30C for summer maize and 20C for winter Maize. At this research CWSI was calculated on the days, before irrigation for all treatments and result showed that in the both of seasons, CWSI was increased about three times when water salinity increased from 2.2 to 6.5 dS/m. The effect of salinity stress was calculated separately according to the days, after irrigation (at These days, the effect of salinity is sensible). results showed that CWSI increased about 3.5 times for summer Maize and around 3 times for winter Maize when water salinity increased from 2.2 to 6.5 dS/m. Comparing the results of the two seasons showed that CWSI is affected by irrigation water salinity and it's trend was nearly the same in both of the growing seasons.

Canopy temperature is an important factor for irrigation scheduling. This is because canopy temperature is depend plant water status. This research evaluated usefulness of Modis sensor for estimating wheat canopy temperature. Relationship between temperature and values of digital satellite images were determined on different levels of plant height and then models were evaluated. Based on the results, the best correlation between the temperature of the green cover were with band 34&25, band 3 and band 2 in the special resolution of 1000 m, 500m and 250m respectively, and RMSE was equal to 3.6, 3.6 and 5.3 in the special resolution of 1000 m, 500m and 250m respectively. Lowest error was observed at the top of canopy and maximum error was at the bottom of plant. Result showed that measuring canopy temperature by using remote sensing is possible but magnitude of error showed that models need some modification.

Oil seed rape (Brasica napus) is an important crop, which is cultivated in Iran for oil production. As a management practice deficit irrigation strategy is applied to cope with water shortages, especially during drought periods. This research was conducted to study the effect of water stress on physiological parameter of oil seed rape in the experimental research field of Collage of Agriculture (of shiraz university) during 2004- 2005 and 2005- 2006. Licord cultivar of oil seed rape was planted and experimental design was random block with five treatments and four replications. Treatments were full irrigation in all growth stages, water stress in vegetative stage in early spring, water stress in flowering and podding stages, water stress in grain filling stage and dry land treatment with supplemental irrigation in time of planting. Water stress caused decrease in water potential of plant, an increase in canopy temperature, and decrease in plant height especially in dry land treatment. Leaf area index decreased as water stress increased. The decrease in leaf area index was more severe in vegetative stage water stress treatment. At the end of water stress period leaf area index increased again. Rate of decrease in leaf area index at the end of the growing season was higher in grain filling stage of water stress treatment.