جستجوی مقالات مرتبط با کلیدواژه « مراحل رشد » در نشریات گروه « کشاورزی »

 The history of using American mesquite (Prosopis juliflora) for desertification control especially sand stabilization in Iran, is long. Considering the non-native nature of this species, attention should be paid to its ecological requirements, especially water needs or evapotranspiration (ET). This can contribute to the sustainability of sand stabilization programs and fine dust control and play an influential role in ecosystem development. Determining plants' evapotranspiration rates through lysimetry is one of the most accurate direct measurement methods. 

 The experiment using weighing and drainage lysimeters began in 2021 by planting seedlings inside lysimeters located at the Yazd Shahid Sadoughi Desert Research Station. It continued for two years. Nine lysimeters with a volume of 1.95 m³ (height: 170 cm, diameter: 121 cm) and a surface area of 1.15 m² were used. The ET rates and the crop coefficient (Kc) of Prosopis juliflora were studied under different soil moisture levels, including field capacity (no stress), 67% of field capacity (mild stress), and 34% of field capacity (severe) for various growth stages. Irrigation was performed by drip irrigation based on a fraction of field capacity with an appropriate number of droppers calculated for each treatment. For field capacity, 67% and 34% of field capacity treatments, 6, 4, and 2 droppers with an 8 liters per hour flow rate were used, respectively. Each treatment was irrigated twice with the appropriate amount of water based on soil moisture levels. 

 The results showed that Prosopis juliflora, under lysimeter conditions and the local climate, had an annual ET rate of 496.5 mm and a Kc 0.21. These values for the 67% and 34% field capacity treatments were 445.4 mm with Kc 0.18 and 275.2 mm with Kc 0.11, respectively. The ET rates of Prosopis juliflora at different growth stages revealed that the highest ET occurred during the development period of 124 days. This corresponds to rapid shoot, branch, and leaf growth. The ET rates in different irrigation regimes for field capacity, 67%, and 34% of soil moisture were 322.1 mm, 281.7 mm, and 158.3 mm, respectively. The lowest ET rate was associated with the final growth stage. The Kc for various growth stages in the field capacity treatment were 0.19, 0.24, and 0.14 for the first, second, and third growth periods, respectively. Under these conditions, a sigmoid growth curve (initial growth, development, and end of growth) can be defined for this plant. 

 It is recommended for afforestation with this species in Iran's southern regions, considering its optimal planting density to reduce competition. It is also recommended to pay attention to its ET rate, especially during the hot months of the year when it can exceed 2.5 mm per day. By examining and calculating the ET rates of mature trees with appropriate efficiency in sand stabilization and dust control, it was found that to create a canopy cover area, as mentioned, it is necessary to have 4846 m3 of water per hectare (equivalent to 484.6 mm per year) available to the plant. In other words, with this amount of ET, the plant can expand its canopy cover area to 19.5 m2 and, with 155 individuals per hectare (8×8 meters), cover 30% of the area, which is suitable for sand stabilization.

Palatability is one of the important characteristics of rangeland plants that is related to their acceptance by animals for grazing (Arzani, 2009). It is also defined as an animal's pleasurable reaction to its food depending on the taste, smell, texture, and appetite of nutrition animal (Church, 1988). Molyneux and Ralphs (1992) reported that while palatability means acceptance, it is not necessarily desirable. In other words, a nutritious food may not have a specific smell or taste in terms of preference, and it may not be attractive or taste bad. In terms of nutritional needs, most of the animal food may be composed of plants that have a moderate degree of palatability.

This research has been done in the rangeland of Deh Sheikh Village of Kohgiluyeh and Boyer-Ahmad provinces. To conduct this study, first two healthy three-year-old goats (females) of Mamasani breed were randomly selected from a herd that belonged to the same area. Then, three important rangeland species including two perennial species including Gundelia tournefortii and Bromus tomentellus and one annual species, Aegilops triuncialis were selected by video method to determine the palatability of species at different stages of growth including vegetative growth, flowering and seeding. For this purpose, the grazing time of goats from any plant was monitored at intervals of 30 minutes in three times including morning, noon and evening and in two repetitions (two days in each growing season) with a suitable distance from the goats. Finally, the palatability percentage of each species was calculated separately.

The results of perennial species in vegetative growth and flowering stages showed that there is no significant difference in palatability between different times of the day (morning, noon and evening). In other words, the consumption of goats from any specie is the same at different times of the day in the stages of vegetative growth and flowering. It was also observed that G. tournefortii has more palatability than B. tomentellus in vegetative growth and flowering stages (Figures 2 and 3). Also, the palatability results of perennial species in the seeding stage indicate that there is no significant difference between different species in terms of palatability at any time of the day. In the case of A. triuncialis, it was found that the palatability of this species at different stages of growth has a significant difference at the level of 1%, but at different times of the day there was no significant difference in palatability (Table 3). Also, according to Figure 7, it was found that the highest and lowest palatability of this species are related to the stages of vegetative growth (27.21%) and seeding (8.09%), respectively.

In the vegetative and flowering stages of G. tournefortii, which is a forb species, it has more palatability than B. tomentellus (grass) for goats. In fact, if G. thournefortii thorns are not for livestock, this species will appear in the form of a palatable species and will be selected by goats. In this regard, Shoaib Amjad et al. (2014) stated that the morphological characteristics of plants such as thorns, hairs, bitter taste and unpleasant reduce palatability. The findings of Arzani and Naseri (2007) in relation to the study of goat grazing behavior of G.tournefortii also showed that G.tournefortii is more grazed by goats at the flowering stage when the thorns are soft. The results of some studies also showed that even in the flowering stage, changes in flowering time and flowering and fruiting rates affect the behavior of animal species that are directly or indirectly dependent on plant phenology. On the other hand, the results of the seeding stage of perennial species showed that in the sowing stage of B.tomentellus species has a higher percentage of palatability than G.tournefortii species in all three times of the day (Figure 5). The results of this study on A. triuncialis palatability (annual species) showed that the highest and lowest palatability of this species for goats coincides with the stages of vegetative growth and seeding (Table 3 and Figure 6). It should be noted that the decrease in palatability of most plants with the development of vegetative stages is almost confirmed for most species. So that in the early growth of forage is very green and palatable and with the development of puberty most of its nutrients are reduced (Tan et al., 2003; Rebole et al., 2004; Alikhahasl, 2008). The results of some studies also confirm that forage quality indicators also change as the growth stages progress. In fact, forage quality changes constantly as plants mature, and these changes are so rapid that a significant reduction in forage quality can be detected every two or three days (Twidwell and Wegenhoft, 1999). The results of Heady and Denis (1994) show that in the vegetative growth stage of forage plants, the amounts of crude protein, sugars and vitamins are high; but fiber and lignin levels are low. According to the results of this study, it can be said that future studies can extend these results to vegetation, including a wider range of vegetative forms, because our results emphasize the importance of maintaining the complex structure of plant communities in rangelands (different species, vegetative forms and growth stages). To maintain their nutritional value over time. Although goats are known as browser and are interested to shrubs, but as Arzani and Naseri (2009) reported, in the absence of shrubs, this animal will graze on grass and forb in the rangeland, so most herds Countries A combination of sheep and goats can be seen.

 Plant development is defined as a series of phenological events that are controlled by external factors and determine changes in the shape or function of some organs. Temperature and photoperiod are two of the most important environmental factors affecting phenological development. Papaver rhoeas L. and Papaver dubium L., from the Papaveraceae family, are common annual winter weeds in northern Iran. The life cycle of these species is closely related to winter crops such as wheat (Triticum aestivum L.) and other winter cereals that compete severely with them. The Papaver species are capable of producing a huge amount of small-sized seeds that remain dormant at maturity. The timing of emergence, growth and sexual reproduction is highly important for the success of invasive weeds. Checking the phonological behavior of these plant species along with their seed production would be useful for decision-support systems helping managers select the best management strategies and, thereby, improving P. rhoeas and P. dubium control. Also, the phenology data would allow predicting these species invasibility of new areas. The present study was aimed to quantify the phonological behavior of these weeds.
 In the present study, the phenology of P. rhoeas and P. dubium were studied in the research field at Agricultural Sciences and Natural Resources University of Sari, Iran, with an annual rainfall of 851 mm per year. Seeds of these species were collected from a wheat field located in Mazandaran province, north of Iran during spring 2018. These species seeds were cultivated on 12 November 2018. The phenological stages were recorded from emergence to the end of the seeding stage. The phenology was studied based on the growing degree day. At the end of the experiment, the period of each phenological stage was calculated based on the day and the growing degree day. In order to determine the morphological traits of the plant, eight sampling steps were performed. Morphological traits such as plant height, number of leaves, number of flowers, number of capsules, and dry matter were measured.
 The results showed that P. rhoeas and P. dubium grow from 0 to 1723.56 and 1759.06 growth degrees day, respectively. During this period, seven phenological stages were recorded for these two species. These stages were included emergence, rosette (7-8 leaves), stem elongation and branching, blooming, flowering, fruiting, and seed maturity. The flowering stage period in both species was long, 48 days in P. dubium and 46 days in P. rhoeas. The results showed that the shortest and longest stages of development of these two weeds were emergence and stem elongation, respectively. In this study, the growth period of P. rhoeas and P. dubium took about eight months. It has some variation with regard to height, the number of flower, number of capsule and dry matter between both species under the same environmental conditions but both plants started their developmental stages at the same time and finished at almost the same rate. The trend of changes in height, number of leaves, number of flowers, number of capsules, and dry matter were similar in both species. The life cycle of these two species begins with germination in autumn and ends with seed production in late June. The longest period of growth stage in both species was in spring and this trend decreases in late spring. The flowering stage begins in late March and ends in mid-June. The maturity period of these two species was from mid-June to the end of the first decade of July. One of the characteristics of these two species is high seed production. In P. rhoeas, at the end of the fruiting stage, each plant produced an average of 13 capsules and each plant produced an average of 5000 seeds. Also, in P. dubium, each plant produced an average of 14 capsules, and each plant of this species produces an average of 5922 seeds.
 Based on knowledge of the different phenological stages of the two species, it is possible to plan for proper management. From a managerial point of view, these two species should be controlled before the blooming stage; so that their seeds do not enter the seed bank, because their seeds are considered as causes of contamination in the field.

In order to investigate the effects of drought stress on grain yield, biological yield, yield components and harvest barley index of Gohar cultivar, an experiment was conducted as a randomized complete block design in the experimental farm of Shushtar Azad University. For this purpose, in field conditions, drought stress treatment at five levels was applied as irrigation interruption in the stages of tillering, stem emergence, flowering, seed filling and no irrigation interruption (control treatment). The amount of water consumed was measured by a volume meter. The results showed that there was a significant difference between drought stress treatments in all studied traits except harvest index. Stress-free treatment produced the highest grain yield by producing the highest biological yield, number of spikes per unit area and number of grains per high spike and suitable 1000-grain weight. In terminal stress conditions or cessation of irrigation in the grain filling stage after non-stress conditions had a higher yield than other stages. The study of correlation coefficients showed that among the yield components, the number of spikes per unit area had the highest correlation (0.63) with grain yield. In this experiment, the lowest grain yield was obtained in the cut-off treatment at the flowering stage, which indicates the sensitivity of this stage of plant growth to dehydration stress

In order to estimate the amount of soil moisture by the Crop Water Stress Index (CWSI), research was performed on the maize (SC 704). The experiment was a factorial and in format of randomized complete block design. In the control, treatment was done full irrigation and in other treatments, was applied water stress in the stages of 6-leaf, 12-leaf, flowering and seeds milking. The meteorological parameters, stomata resistance and leaf surface temperature were measured daily. At different growth stages, the stress low line had a slope of 0.09 to 0.14. The amount of the stress up line was estimated between 3.3 and 4.2 . In the period of stress, the CWSI index was calculated and the amount of soil moisture was measured. According to the results, between soil moisture and CWSI index values, the inverse relationship was established with good correlation. Therefore, regression models with linear, exponential, logarithmic, polynomial and power forms were fitted between the above (two) parameters. The best and worst models for estimating soil moisture were the polynomial ( :0.987) and the power ( :0.65) models, respectively. The results showed that the critical values of CWSI index (at the time of increasing leaf surface temperature compared to air temperature), determined the irrigation time. Also, by indirectly estimating the amount of soil moisture, was calculated the soil moisture deficiency and water requirements for irrigation.

Estimation of evaporation and transpiration components of maize using by experimental models, is useful for management the water consumption in irrigation. In this research, the amounts of evaporation and transpiration components of maize were modeled for growth stages and salinity stress conditions. Salinity treatments were applied by water with EC of 0.5(S0), 2.1(S1), 3.5(S2), and 5.7(S3)dS.m-1, in the mini-lysimeter. Modeling of maize evapotranspiration components was performed by regression functions of linear, exponential, logarithmic, polynomial and power. Parameters of evapotranspiration (ETc), coefficients of evapotranspiration stress (Ks) and crop growth stage sensitivity (Kpi) were considered as the independent variables and transpiration (T) and evaporation (E) parameters (in separate models) were considered as the dependent variables. The equations coefficients were estimated by SPSS software and the multivariate regression models were generated. From S0 to S3 treatments, the values of evapotranspiration, transpiration and evaporation parameters (in the all of growth period) were measured in the range of 420-307.5, 289-150 and 131-157.5 mm, respectively. Under salinity stress conditions, the maize transpiration was decreased to a more value relative to evapotranspiration. But the evaporation was increased to the same extent. In modeling evaluation, exponential and polynomial models were selected as the optimal models for estimation the transpiration and evaporation rates, respectively. The sensitivity coefficient values (Kp) in four growth stages were equal to 0.556, 0.972, 1.315 and 0.432 (in exponential model) and 1.485, 1.238, 0.447 and 0.816 (in polynomial model). The result of this research was that regression models had an acceptable performance for simulation the evaporation and transpiration components of maize, under salinity stress conditions. Therefore, by estimation the transpiration amount, the crop net water requirement is estimated actually and the water use efficiency increases. Also, by estimation the amount of evaporation losses, the water application efficiency is calculated accurately.

Determining the intra-seasonal sensitivity of maize evapotranspiration to environmental stresses has an important effect on modeling of yield. In this research, the effect of drought and salinity stresses were investigated on the relative evapotranspiration (during initial, development, mid, and late stages) and relative yield of maize, in a field with sandy loam soil texture. Salinity treatments were applied by water with EC of 0.5(S0), 2.1(S1), 3.5(S2), and 5.7(S3)   dS.m-1. Drought treatments included four irrigation levels of 100% (I0), 80% (I1), 60% (I2), and 40% (I3) of the crop water requirement. The experiment was performed as factorial in a randomized complete block design, with three replications. The relative evapotranspiration of maize in the initial, development, middle and final stages was estimated between 63.5-100%, 62.6-100%, 55.2-100%, and 66.4-100%, respectively. The relative yield of maize in the I0S0 to I3S3 treatments was calculated between 42.6-100%. The results showed that salinity and drought stresses reduced both the evapotranspiration and maize yield. Also, evapotranspiration decreased with a steeper slope in sensitive growth stages compared to yield. Effect of the mentioned stresses at sensitive growth stages caused disruption in the flowering and fruiting of maize. In this study, the relative yield of maize was modeled by additive models of Blank, Stuart, Singh and multipliable models of Jensen, Rao, and Minhas. According to the results, Stewart model with sensitivity coefficients (in four growth stages) of 0.227, 0.416, 0.604, 0.14 and Jensen model with sensitivity coefficients of 0.301, 0.41, 0.608, and 0.147 were selected as the optimal models. However, Rao, Blank, Singh, and Minhas models were chosen as the next priorities. Therefore, under salinity and drought stress, the relative yield of maize was modeled based on the amount of evapotranspiration in the growth stages.

Adeqiate water use in the agricultural sector requires accurate knowledge of crop sensitivity to environmental stresses (such as water stress). The crop sensitivity to water stress may be different at different growth stages and may have a different effect on the actual amount of crop evapotranspiration compared to the standard conditions. At different levels of water stress, studying the sensitivity of crop evapotranspiration at different growth stages can be provided management strategies for optimal water consumption. In the present research, the intra-seasonal sensitivity coefficients of maize were modeled by using the Jensen model.

In this research, the effect of water stress levels and growth stage sensitivity on the amount of maize (S.C 704) evapotranspiration was investigated. The experiment was performed as factorial based on randomized complete block design. The treatments included four irrigation levels of 100 (I0), 80 (I1), 60 (I2), and 40 (I3) percent of the crop water requirement and four growth stages of initial, development, middle and final. In between two irrigations, the amount of daily soil moisture was measured in the center of each plot and the depth of the crop root zone. Therefore, the amount of evapotranspiration of crops per unit area was estimated according to the soil water balance. Analysis of variance and mean data comparison of evapotranspiration and dry biomass yield were performed by SPSS software and using Duncan's multiple tests. By actual evapotranspiration and yield data, intra-seasonal sensitivity coefficients of maize to water stress (λ1 to λ4) were determined by SPSS software.

Evapotranspiration The effect of irrigation water amount and growth stage on the maize evapotranspiration amount was significant at the probability level of 1%. Evapotranspiration amounts at the initial, developmental, middle, and final of maize growth stages were estimated equal to 79, 201.8, 123.8 and 14.6 mm (in I0 treatment), 78.3, 196, 126.6 and 14.6 mm (in I1 treatment), 72, 173.6, 99 and 11.7 mm (in I2 treatment), 62.8, 147.5, 81.5 and 8.4 mm (in I3 treatment), respectively. Reduction of evapotranspiration compared to control treatment (I0) in the initial, developmental, middle, and final growth stages were estimated equal to 0.9, 2.8, 9, and 0 (in I1 treatment), 8.8, 14, 20, and 19.8 (in I2 treatment), 20.5, 26.9, 34.2 and 42.4 (in I3 treatment) percent, respectively. The results showed that the slope of evapotranspiration reduction was not the same at different irrigation levels. Also, the relative evapotranspiration of maize (in all growth seasons) at irrigation levels of I1, I2, and I3 were estimated equal to 95.6, 85, and 71.6 percent, respectively. Therefore, when applying water stress, the optimal evapotranspiration rate can be adjusted by selecting the suitable growth stage. Yield The effect of irrigation levels on the dry biomass yield of maize was significant at the level of 1% probability. The dry yield of maize in treatments of I0, I1, I2, and I3 were equal to 17.1, 15.8, 12.6, and 8.7 (tons per hectare), respectively. The relative yield of maize at irrigation levels of I1, I2, and I3 were estimated to be 92.4, 73.7, and 50.9 percent, respectively, in the Qazvin region. The reduction of soil available water affected the water uptake by the crop and reduced the yield of maize. Modeling of intra-seasonal sensitivity coefficients of water stress At the initial, developmental, middle, and final growth stages of maize, stress sensitivity coefficients of λ1, λ2, λ3, and λ4 were estimated in water stress treatments. The mean of mentioned coefficients in stress treatments was calculated to be 0.421, 1.37, 0.274, and 0.133, respectively. The results showed that during the development stage of maize growth, the effect of water stress on yield reduction was more. The model efficiency for estimating the amount of relative yield was evaluated. Evaluation statistics of R2, EF, RMSE, ME and CRM were estimated to be 0.998, 0.986, 2.753, 0.026 and 0.021, respectively. The results showed that the Jensen model efficiency was good, and it can be used in planning the low irrigation for different growth stages of maize. Yield-Evapotranspiration Function of Maize in all of the growth stages Across different irrigation levels, a simple linear relationship of Y=69.935ET-12281 (with a correlation coefficient of 0.999) was fitted between two parameters of evapotranspiration and dry biomass yield of maize. Therefore, using the above equation in low irrigation management, the amount of maize yield can be estimated based on the evapotranspiration amount. In this research, 175 mm evapotranspiration was needed for the production of the initial unit of maize biomass. That is, the transpiration portion in the above amount was negligible, and it was mostly allocated to the soil evaporation portion.

The crop sensitivity to water stress and different needs to transpiration at different growth stages were the reasons for the different reduction of maize evapotranspiration. Reduction of soil available water reduced the water uptake and transpiration, and crop biomass. The results showed that reducing the water stress was effective in increase of maize evapotranspiration efficiency. In order to produce the maximum crop biomass, the sensitivity of the maize growth stage and the water stress level must be considered.

The present study was carried out to compare the phenology of annual ground cherry (Physalis divdricata L.) and its effect on maize yield ‎ ‎.

A field experiment was conducted in the Research Station of Mahidasht in Kermanshah Agricultural and Natural ‎Resources Research and Education Center, in 2017.‎ Different densities of annual ground cherry, including 0, 8 and 16 plants m-2 and corn were planted.  The competition‎ and their phenological stages ‎were recorded based on GDD (growing degree days) for each growing stage. ‎

The results of this study showed that ‎annual ground cherry ends its phenological stages later than corn. In order to complete its life cycle, ‎‎1262.7 growing degree days and 159 days were needed. Thus, complete life cycle of corn required ‎‎1890.7 GDD and 139 days.Both plants passes the early stages of growth and ‎germination concurrently, Maize, however, ‎comleted Vegetative growth and seed ‎ripening more earlier than annual ground cherry. ‎Also, the results of studying the effect of different densities of ‎annual ground cherry on yield and yield components of corn including 1000-seed weight, number of seeds per ear row, corn harvest index and leaf area index showed that all these traits decreased by increasing density of annual ground cherry. However, the number of seed rows per ear, which is genetically-control trait, was not affected by competition with annual ground cherry. In contrary to the above traits, the density of this weed increased with the effect of increasing the height of corn and as a result, increasing the biomass of corn compared to control. In general, weed densities of the 8 and 16 plants m-2 decreased maize yield by 10 and 14 percentages, respectively.

The results of this study suggest that if corn fields are infected with this weed and we do not ‎succeed in combating it in the early stages, earlier harvest of corn in the fall will allow it to be ‎harvested by cultivation methods or using a general herbicide of this weed before its seeds are fully ‎ripen.

Sugar beet, scientifically known as Beta vulgaris L, is allogamous, diploid, biennial plant of the spinach genus that is cultivated to produce storage roots. The growth period of sugar beet, depending on environmental conditions and genotype, varies from 5 to 9 months and is known as a late maturing plant. Therefore, estimating the yield reduction due to leaf fall plays an important role in farm management. In addition to the effects of stressors, some farmers may use sugar beet leaves to raise livestock during the growing season. In this case, too, the leaves are damaged. In the experiment of complete removal of leaves in three sugar beet cultivars, it was observed that complete removal of leaves in Antek and Vico cultivars led to reduced root yield and subsequently white sugar yield was significantly reduced, but In Sharif cultivar, leaf removal had no significant effect on root yield and sugar yield. They also reported that leaf removal increased the percentage of root sugar in Sharif cultivar. Effect of leaf removal time on quantitative and qualitative characteristics of autumn sugar beet cultivars in Gorgan region.

This experiment was carried out in factorial design during the 2019-2020 crop year in Varsen of Gorgan based on randomized complete block design with three replications. The first factor includes 6 autumn sugar beet cultivars including Monotana, Jerra-kws, Rosagold, Chimneh, Veles and Sharif and the second factor includes three levels, pruning in May (leaf development), pruning in June (reducing leaf development) and no pruning (control). Pruning was done using a sickle and the entire aerial part (petiole and leaves) was cut from a height of 5 cm above the crown. Seed bed preparation operations including plowing, retorting, leveling and farrowing were performed before planting. According to the planting plan, they were planted by hand on top of the ridges on November 2019. At the end of the growing season of each harvested plant, root yield and qualitative traits were calculated. The most common method of measuring sugar percentage by polarimetry method was calculated using saccharimeter, sodium and potassium by flame photometry method, harmful nitrogen by aqueous number method and other qualitative characteristics. The analyzed traits were analyzed using SAS software and the means were compared by LSD method at a statistical level of 5%.

Sugar beet cultivars showed significant differences in sugar content (grade), sodium, potassium, extractable sugar content, sugar and molasses extraction coefficient; However, no significant differences were observed between cultivars in terms of harmful nitrogen, alkalinity and root dry matter. Leaf pruning treatments except sodium and molasses were significant in other studied traits. The interaction between cultivars and pruning has also been significant in potassium and molasses traits. Significant differences were observed between the treatments by applying pruning treatment; So that the highest percentage of sugar (14.7%) was observed in the control treatment and the lowest percentage of sugar was observed in the June treatment (12%). The highest root yield was related to Chamineh cultivar with an average of 98 tons per hectare and the lowest root yield was related to Rosagold cultivar with an average of 80 tons per hectare. Due to the decrease in leaf production at the end of the sugar beet growing season, the amount of damage caused by root yield in leaf removal treatment in the final stages of growth (June pruning) is much less than the effect of leaf removal in the middle stage of growth.

Removal of sugar beet leaves in the final stages of growth had an effect on root quality properties such as sugar content, extractable sugar percentage and sugar extraction coefficient and root yield and reduced the mentioned traits. Root impurities also increased due to defoliation. Most yield losses were obtained when sugar beet leaves were removed or eliminated in the middle stages of growth (May pruning).

In the recent years, the study of genotypic variation in terms of efficiency of mineral nutrient has attracted the attention of researchers worldwide. Hence, to investigate the variation in the nitrogen (N), phosphorus (P) and potassium (K) use efficiency in 6 important crop and weed species (durum wheat, common barley, naked barley, triticale, wild oat and canary grass), a pot experiment was conducted as a factorial arrangement in a completely randomized design with three replications in Gorgan University of Agricultural Sciences during 2016-17 growing season. This experiment was carried out under unfertilized and fertilized at optimum rate conditions. Concentrations of elements and dry matter were measured in stem elongation, anthesis and physiological maturity. The results of variance analysis showed a significant effect of experimental factors on efficiency (dry matter to nutrient content ratio), nutrient efficiency ratio (dry matter in control to fertilized treatment ratio) and nutrient harvest index (nutrient content in grain to total dry matter ratio). There was no significant interaction between experimental factors for the traits studied in three stages. The results also showed a significant decrease in traits as a result of fertilizer application. According to the results, evaluation of nutrients efficiency in early stages of growth is not sufficient for comparison or screening of genotypes and should be done in more advanced stages, especially maturity. Also, considering the substantial variation among studied genotypes in terms of nutrient efficiency, more detailed studies on genotypic variation seems to be useful for identifying traits related to mineral nutrient efficiency.

Because of evaluating and measurement of different irrigation management and identifying soil salinity consumes more time with high cost, so applying models can overcome these problems and could be used in different irrigation scenarios. Variation Crop models are an appropriate tool for investigating irrigation management and their effect on plant production. The purpose of this study was to evaluate the efficiency of two models including AquaCrop and Saltmed for simulation of yield and soil salinity variation. The accuracy of the results of the simulation models depends on the accuracy of the required data of the model and if the measurement and determination of the input data is accurate, then the applicability model will be in different conditions after calibration and validation. For applying Aquacrop and Saltmed models, having crop growth stages, root effective depth, sowing and havest date, harvest index, crop coefficients in different growth stages, duration of wheat phonological growth stages, initial soil salinity in different layers and some irrigation data including depth and time of water application are necessary. In this regard, the two models including AquaCrop and Saltmed are among the functional models that have high ability and efficiency to simulate plant yield and soil salinity performance have been investigated.

This research was conducted in the Ramseh region of Hamidieh, Khuzestan, in latitude and longitude 47 degrees 41 minutes and 33 degrees and 4 minutes, respectively. In this regard, three pilots of 10 hectares were selected and in each of these parts three pilot trials with an area of 2000 square meters were considered for evaluation and measurement. In the first year, using traditional irrigation management of farmers and using the initial salinity levels, soil physical and chemical characteristics compared to the simulation using two models including Aquacrop and Saltmed model. Saltmed and Aquacrop Models can simulate crop yield, Biomass and soil moisture variation in saline and non saline condition. In this investigation Aquacrop version No. 4(2012) and Saltmed No. 3-04-02(2015) has been used for crop production and soil salinity simulation. During irrigation season reference evapotranspiration has been determined using climatic data of Ahvaz Synoptic station. Data gathering including minimum and maximum temperature, minimum and maximum relative humidity, precipitation, sunshine hours and wind speed. Also, during the growing season, the volume of irrigation water, irrigation hours, water use efficiency and root depth were determined. At the end of the growing season, direct measurement of selected farms in three replications was carried out to determine the wheat grain yield and biomass along with soil moisture changes in soil profile. According to the measured data, two models of Saltmed and Aquacrop were calibrated for the first year of cultivation. Results of calibration of the first year were evaluated for verifying the results of the two models in the second year. The standard error (SE), Root mean square error (RMSE), Normalized root mean square error (NRMSE), correlation coefficient (R2), mean bias error (MBE), and model efficiency (EF) were used to determine the accuracy of the models.

The results of the first year showed that the normalized error of root mean square index for grain yield and biomass values in the AquaCrop model were 4 and 5%, respectively, and these values for the Saltmed model, were 8 and 9%, respectively. This statistical index for simulation of soil salinity with Saltmed model was about 18% and in AquaCrop model was 53%. Therefore, the Saltmed model is more consistent with the measured data of soil salinity. Also, the results of the second year that were used for validation showed that, the normalized error of root mean square index for yield and biomass in the AquaCrop model was 4% and 4% respectively, and these corresponding values for Saltmed model were 22 and 14% respectively. Also, simulated of soil salinity results in the second year with Saltmed model showed that this model with normalized error of mean square error(26%) was more accurate for soil salinity simulation than AquaCrop model with normalized error of mean square error equal to 47%; therefore, the AquaCrop model has a better performance than Saltmed model for yield simulation. Also the performance of Saltmed model has high efficiency and accuracy in simulating soil salinity than AquaCrop model.So based on the goal of projects and precision of simulation data, these individual models can be applied.

Due to the lack of water in different regions of Iran, the introduction and use of indigenous species with valuable ornamental features such as mullein (Verbascum thapsus) is very important. V. thapsus is a perennial and evergreen herb belonging to the Scrophulariaceae family, which like other ornamental plants, can be affected by drought stress in the green space. Drought is an environmental stress that induces adverse effects on most stages of growth, structure and activities of plants. The response of plants to environmental stresses is different in morphological, cellular and molecular levels. Therefore, the present study was conducted to investigate the effect of drought stress on morphological, physiological and biochemical characteristics of V. thapsus during two stages of vegetative and reproductive growth.

In the present study, the reaction of V. thapsus to drought stress and its effect on vegetative and reproductive stages were investigated. The experiment was carried out as factorial in a completely randomized design with two factors as drought stress in 5 levels (control (0.3), 2, 5, 10 and 15 bar) and plant growth stages at two levels (vegetative and reproductive). For this purpose, shoot and root fresh weight, burn and wilt condition, leaf chlorophyll, activity of antioxidant enzymes and proline were measured.

The highest and lowest irrigation interval in both vegetative and reproductive stages was respectively found in 15 bar and control. The water volume used in vegetative stage was higher than reproductive stage. Shoot and root fresh weight in was reproductive stage was more than vegetative stage. The highest fresh weight of shoots was reported under drought stress in control and 2 bar and the lowest amount was observed in 15 bar, but the highest root fresh weight was observed in 5 bar. The highest percentage of leaf burns and wilt was observed in treatment of 15 bar × reproductive stage and its lowest in the treatments of control × vegetative stage and control × reproductive stage. Total chlorophyll in reproductive stage was more than vegetative stage. Also, the highest total chlorophyll was observed under drought stress in control and 2 bar and the lowest was found in 15 bar. The highest activity of superoxide dismutase and catalase was observed in 15 bar × reproductive stage and its lowest value was recorded in control × vegetative stage. Proline in reproductive stage was greater than the vegetative stage. The highest and lowest amount of peoline was observed in 15 bar and control, respectively.

The results of the research showed that the drought stress up to 5 bar did not cause significant changes in the plant, but increasing the intensity of drought stress from 5 bar to 10 bar induces the significant change of most traits in the plant. Therefore, with applying an appropriate plan, we can reduce the water use from 570 m3 (control) to 130 m3 (5 bar) during the vegetative stage and 500 m3 to 140 m3 for reproductive stage.

This study was carried out to compare growth characteristics of three species of Alyssum minus, A. szwitsianum and A. desertorum over two years, 2017 and 2018, in a randomized complete block design with three replication at Isfahan Agricultural and Natural Resources Research and Education Center. Measured traits were yield characteristic including total dry weight, leaf, stem, root and seed dry weight; morphological characteristics including plant height, maximum and minimum plant diameter, plant cover and stem number; and phenolological characteristics including day to flowering, day to seeding and day to seed ripening. The highest biological and seed yield were achieved in A. minus, 1003 and 375 kg/ha respectively, while A. desertorum showed the lowest rates, 559 and 207 kg/ha respectively. Morphological traits analysis represented that A. minus had the highest rates of plant height, stem number, plant diameter and cover. A. minus and A. desertorum with 101 and 95 days to seed ripening were the longest and shortest lifelong species. The highest correlation rates between seed yield with other characteristics were including biological yield (0.90), plant height (0.79), stem number (0.76) and cover (0.75). On the whole, results of this study showed that A. minus showed the highest yield potential among the studied species.

Studying phytochemical changes of fruits is very important for plant physiologists and pomologists. Date is an important horticultural fruit in Iran mainly produced in southern regions. Barhee is considered one of the most important date palm cultivars. The fruit of cv. Barhee can be harvested and consumed at different maturation stages including Khalal, Rutab and Tamar. In the present study, the biochemical alterations of date fruit cv. Barhee during development and ripening stages were studied.

The experiment was carried out in a randomized complete block design with three replications. Sampling was done at Date Palm Research Institute Collection Orchard located in Ahvaz. First, fruits were harvested in five different developmental stages including late Kimri, Khalal, mainly Khalal, mainly Rutab, fully Rutab and Tamar. The fruits were then transferred to Quality Analysis Lab of Department of Horticultural Science at Shahid Chamran University of Ahvaz. Selected uniform fruits were used for the analysis of different phytochemical compounds. Chlorophyll, carotenoid, starch, soluble sugars, phenolic compounds, flavonoids and antioxidant capacity were analysed using spectrophotometric methods. The type and concentration of sugars, organic acids, and phenolics were assessed using HPLC. Also, vitamin C content was determined by titration againt DCIP dye.

The results showed that soluble sugars increased significantly during ripening stages, and glucose and fructose were the main detected sugars for Barhee cultivar. The amount of sucrose was negligible. The acidity of the fruit increased at initial growth stages and then decreased gradually till Rutab stage. At the end of ripening process and at Tamar stage, the amount of organic acid content increased to 2.45 mg/g FW. Among the detected organic acids, acetic acid was dominant in Tamar stage, while in the earlier stages malic acid was considered the main organic acid. Other major investigated compounds, including flavonoids, chlorophylls, carotenoids, starch and vitamin C decreased during the development. Different compounds including p-cinamic, gintistic, gallic, chlorogenic, vanilic, caffeic, syringic and p-cumaric acids were detected by HPLC evaluation of phenolic acids. Among them, gallic acid was the dominant, and the trend was incremental during the development of fruit.

Comparing the current results with published data for other date cultivars shows that there are considerable differences in biochemical compounds among different cultivars. In this cultivar, the increasing trend of accumulation of soluble sugars, organic acids, phenolic compounds and antioxidant capacity during ripening stages from late Kimri to Rutab and Tamar stage makes the fruit an important source of essential nutrients.

Nitrogen is the most important limiting factor, after water deficit for biomass production in natural ecosystems. Efficient use of nitrogen fertilizer is important to economical dryland wheat production and to the quality of ground and surface waters. Researchers have been looking for ways to increase the efficiency of N fertilizer use. Soil and in-season plant tissue testing for nitrogen status are a time consuming and expensive process. Chlorophyll concentration in a leaf is closely correlated with leaf N concentration so the Soil Plant Analysis Development (SPAD) chlorophyll meter is one of the most commonly used diagnostic tools to measure crop nitrogen status. The SPAD chlorophyll meter is a simple, portable, diagnostic and nondestructive light weight device used to estimate leaf chlorophyll content. Chlorophyll meter techniques provide a substantial saving in time and resources and offer a new strategy for synchronizing nitrogen application with actual crop demand. The objective of this study was to establish and analyze the relationships between measurements from a SPAD instrument and the leaf pigments, as extracted at different stages. The study also seeks to evaluate the utility of a chlorophyll meter to inform nitrogen fertilization rates of wheat (Triticum aestivum L.) genotypes in dryland condition. This experiment was carried out in split split plot based on RCBD design with three replications. Treatment included: N application time (whole fertilization of N in fall, and its split fertilization as 2/3 in fall and 1/3 in spring), N rates (0, 30, 60 and 90 kg N ha-1) as urea and 7 genotypes (Azar2, Rasad, Ohadi, HN7/OROFEN//BGN8/3/SERI/4/.., SARA-BW-F6-06-85-86-29-1, TEVEE'S'//CROW/VEE'S' and DH-2049-3. A chlorophyll meter (SPAD-Hansatech Cl-01) was used to read leaf chlorophyll content (SPAD value) at tillering (GS22), shooting (29), stem elongation (GS32), flag leaf (GS39) and anthesis stages. Fresh plant leaf samples were collected from each plot for the estimation of chlorophyll a (Chla), chlorophyll b (Chlb), carotenoids (Ct), total chlorophyll (Chlt) and concentrations. The chlorophylls and carotenoids were determined by spectrophotometric analysis of chemically extracted pigments. To examine the relationship between pigments chlorophyll and SPAD values, 30 wheat leaves were sampled. Average Chla, Chlb, Chlt, carotenoids and SPAD values were computed, and linear regression analysis was performed by least-squares method with Excel. The results showed a strong positive and statistically significant (p<0.01) relationship between SPAD values and total chlorophyll (R2 = 0.93), chlorophyll a (R2 = 0.95), chlorophyll b (R2 = 0.78) and carotenoids content (R2 = 0.79). We demonstrated that the SPAD readings and plant photosynthetic pigment content per-leaf are profoundly affected by nitrogen rate and timing of application. Nitrogen split application increased significantly (p<0.01) the SPAD values (8.3%), Chla (11.1%), Chlb (10.9%), Chlc (27%), Chlt (15%), (exception of carotenoids) and seed protein content (8.5%). Nitrogen application could affect significantly (p <0.01) all chlorophyll indices in plant. The ideal conditions for the chlorophyll indices in the plant were obtained using 72 kg N ha-1. Nitrogen requirement for maximum and optimum economical dryland wheat production is about 20 and 10 kg ha-1 less than nitrogen requirement for creation the ideal conditions for chlorophyll status and its components in dryland wheat. Using chlorophyll meter, chlorophyll a (16.6 mg g-1), chlorophyll b (5.9 mg g-1), chlorophyll c (0.077 mg g-1), total chlorophyll (23.9 mg g-1) and chlorophyll a per Chlorophyll b ratio (2.78), chlorophyll index (9.4) and chlorophyll relative index (1.0) were determined in economical optimum N rate (NRD = 0). Genotype1 was most suitable and Azar2 was the most inappropriate condition in terms of chlorophyll index and total chlorophyll ratio per carotenoids (optimum range 40-70) in the plant as a stress resistance index. It can be concluded that, the actual chlorophyll content and its components can be estimated using chlorophyll meter (SPAD) in dryland wheat genotypes at different growth stages. Chlorophyll components and seed protein can be improved by nitrogen fertilizer application time and rates in dryland wheat.

Dry farming is an important method of crop production, particularly in semi-arid regions, where crop yield strongly depends on precipitation amount and its temporal variation during the growing season. Supplemental irrigation is a suitable practice for mitigating moisture stress and, consequently, improving crop yield in rainfed agriculture. This study was conducted to estimate the proper time of supplemental irrigation in rainfed land by measuring soil water content during growth period, in 2016-2017. A field experiment was conducted using two plowing directions (along the slope and on contour lines) in plots with 2 m × 5 m dimensions, in a rainfed farm with 10 % slope. Volumetric soil water content (SWC) was measured in root zone by a TDR set at 10-day interval during growth period, from November 2016 to June 2017. Based on the results, SWC in the plots plowed on contour lines was about 6 % higher than the plots plowed along slope, and this difference was statistically different (P< 0.05). The mean readily available water (RAW) during growth period in the plots plowed on contour lines (6.07 mm) was about 2.5 times higher than the plots plowed along slope (2.25 mm) and showed significant difference with it (P< 0.05). The highest RAW was observed at stem elongation and the lowest value was found at grain germination, at which stage, about 6.7 mm water deficit was observed in rainfed wheat. Thus, application of supplemental irrigation at this stage can efficiently prevent water stress and improve wheat grain yield in this semi-arid region.

This study aimed to investigate the relationship between morphophysiological and phenology traits with grain yield to determine the best indices of direct and indirect selection in the field of genetic improvement of aerobic rice grain yield in Khuzestan province with 12 aerobic rice genotypes. The traits such as include the grain yield as the dependent variable and total dry matter, panicle weight, stem weight, LAI, CGR, NAR, LAR, SLA, ALW, LWR, L/S, SWR, PWR, LAD and BMD as independent variables, which were analyzed by stepwise regression at different growth stages to determine their effect on grain yield. The results showed that on 25 days after planting traits of L/S, SLA, LAI and leaf weight, on 50 days after planting traits of NAR, L/S, SWR, stem weight and BMD, on 75 days after planting traits of NAR, SLA, stem and LAR, on 100 days after planting traits of CGR, stem, L/S, LAR and PWR and on 125 days after planting traits of CGR, NAR, SLA, L/S and leaf affected the grain yield. In order from the beginning to the end of the growth, traits of L/S, NAR, panicle weight, CGR and CGR had caused the greatest changes in the grain yield. According to the critical period of growth, CGR was the most effective trait on the grain yield because of allocation of more assimilates in the reproductive growth instead of vegetative growth during grain filling period, thus it can be an important objective in the breeding researches.

A study was conducted in order to compare the nutritive value, fermentation and degradability parameters of mountainous and plain alfalfa areas at different growth stages (before flowering, flowering and after flowering) at secondary harvest in four experiments.Alfalfa samples were randomly taken from a second species of the mountainous region (Mountain alfalfa meadows of Barfchal in Minoodasht) and plain (alfalfa plain around the Gonbad Kavous) collected and then transferred to the laboratory. The samples were dried for 48 h at 65°C and with a two-millimeter sieve were milled. Results showed that mountainous alfalfa compared with mountainous alfalfa had higher ether extract, organic matter and crude protein. Extent and rate of gas production were highest at before flowering stage in both mountainous and plain Alfalfa (P