AGROECOLOGY (بوم شناسی کشاورزی)
Year:2015 | Volume:7 | Issue:4|Papers Count:9

Introduction: Saffron as a food, spicy and medicinal plant has more than 62000 ha under cultivation with about 250 tons annual dry stigma production in Iran, which includes about 90% of its world production. Therefore, this plant has a specific value in agricultural export products of Iran (Fallahi et al., 2014). Due to the important role of saffron in Iran’s agroecosystems, the improvement of its agronomic practices is essential. Nutritional management and mother corms size are two of the main factors affecting growth and yield of saffron. Humic acid is an eco-friendly fertilizer that improves the physical, chemical and biological properties of soil. This nutritional source has hormonal compounds and exerts a positive effect on elements absorption, quality and yield of plants. In addition, in saffron cultivation, it is possible to produce considerable amounts of stigma by using of standard mother corms with a minimum weight of 8 g. Because, large corms have a positive effect on stigma yield especially in the first growth cycle and the weight of replacement corms and consequently saffron flowering in the other growth cycles (Nassiri Mahallati et al., 2008). Therefore, the aim of this research was to investigate the interaction effects of mother corm size and different rates of humic acid on growth and yield of saffron.Materials and methods: This experiment was carried out as factorial based on randomized completely block design with three replications in research farm of Ferdowsi University of Mashhad, Iran, during two growing season (2009-2011).Experimental factors were consisted of mother corm weight (4-5, 6-8 and 9-10 g) and application of humic acid (0, 20, 40, 60, 80 and 100 kg.ha-1). Mother corm planting was in early October, 2009 with 10×20 cm corms distances and planting depth of 10cm. Humic acid (dissolved in water) was used along with the first autumnal irrigation in two season growth. Flower and stigma yield of saffron were measured during autumn of 2009 and 2010. In addition, three corm clones were selected randomly in each plot and then all replacement corms were removed after leaf withering in May, 2011. Corm measured indices were included of number of replacement corms per clone, total corms weight per clone, scale weight per clone, mean replacement corms weight and number of buds per replacement corm. Finally, data analysis was done using SAS 9.1 and means were compared by duncan’s multiple range test at 5% level of probability.Results and discussion Results: showed that planting of larger mother corms improved the growth indices of replacement corms and saffron yield. The total weight of replacement corms per colon (91%), number of flowers per square (84%), flower yield (66%) and stigma dry yield (154%) were higher for the larger mother corm (9-10 g) than small mother corm (4-5 g). This result is similar to findings of Nassiri Mahallati et al. (2008) which concluded that planting of more than 9 g mother corms improved the growth and yield of saffron. Selection of appropriate corms is the main factor in saffron cultivation, because the flowering capacity of the plant depends heavily on the weight of planted corms. Planting of small corms is not affordable because they usually do not produce flower in the first growth season (Kumar et al., 2009; Mohammad-Abadi et al., 2011). Moreover, application of different levels of humic acid had a positive effect on the growth and yield indices in saffron. In the highest level of humic acid application (100 kg.ha-1), the amounts of mean number of bud per corm (10%), mean diameter of corm (19%), mean weight of corm (70%), number of flowers per square (38%), flower yield (39%) and stigmadry yield (183%) were higher than control. The positive effects of humic acid on the growth of plants is related o many factors such as increased water and nutrient absorption, increasing the availability of elements, development of plant root system, higher chlorophyll content and change in enzymes activity in the plant(Sabzevari et al., 2010).Conclusion: Generally, the findings of current study revealed that the use of large mother corms (more than 9 g) incombination with humic acid application had positive effects on replacement corms growth and stigma yield of saffron.

Introduction: The global climate is changing and, despite efforts to reduce greenhouse gas emissions, weather variation is inevitable. Meanwhile, agriculture as a major water consumer will require adaptation to these variations, along with other challenges, to guarantee its persistence and sustainability. Given the arid and semi-arid climate of Iran, water, as a main limiting factor for agricultural production, plays an important role in determining the type of farming activities (Osamu et al., 2005). Crop water requirements and evapotranspiration are the main cause of water consumption in agricultural sector, the both accepted to face a dramatic increase in future under influence of increasing temperatures resulting from climate change (Koocheki et al., 2001). In this regard, the foreknowledge about future changes in climate and its effects on agricultural water use can be helpful for farmers and decision-makers. This study aimed to evaluate the climatic conditions of Birjand plain in the next two decades, and to investigate the effects of climate change on water consumption of wheat and barley as two main crops in this region.Materials and methods In the present survey, the effects of estimated climate change in Birjand plain on water requirement of wheat and barley and wheat yield in the 2010-2039 period were studied. Based on average weather data for the last thirty years from Birjand synoptic stations, climatic parameters of temperature and precipitation for the time period of 2010-2039 were simulated with LARS-WG5 using A1 scenario confirmed by the IPCC. Wind speed and relative humidity also were estimated for the future period. Common planting and harvesting dates were obtained from local farmers and Birjand Agriculture Organization and duration and crop coefficients (Kc) for early, developmental, middle and final crop growth stages in the current period were extracted from FAO Irrigation and Drainage Paper No.56. For the future period, these dates and growth stages duration were estimated by matching the average daily temperature at the current time with the time of their occurrence in the future. The reference and crop evapotranspiration were calculated based on Penman-Monteith equations and effective rainfall was determined with USDA method. Crop water requirement was also calculated using the Crop Wat software and effects of climate change on crop yield was evaluated using DSSAT model. The genetic factors were taken from the study of Mansouri (2012) in Birjand. Other required input data (edaphic and crop data) obtained from Agricultural Organization and local farmers.Results and discussion: The results showed that the minimum and maximum temperatures of the future years will increase, and there would be an approximately 3.5 percent more annual rainfall in the future decades. The largest temperature increase will occur in cold months, with a maximum rise in temperature of 2 °C in February. Overall, the average maximum temperature for 2010-2039 would be up to 0.6 °C higher than current period in Birjand. These higher temperature will result a significant decrease in the length of crop growth period, so that the time of planting to maturity will be reduced from 240 and 219 days (in current terms) to 227 and 193 days (in the future) for wheat and barley, respectively. Koocheki et al. (2001) has estimated 26 days shorter growing season for wheat in Mashhad due to higher temperatures in future. Despite higher reference evapotranspiration, crop water requirement will drop in the future between 19.5 percent (wheat) to 22.5 percent (barley), due to earlier planting of these crops and their shorter growing period. Indeed, due to the shorter duration of crop growth under climate change condition, the wheat yield will be reduced by about 30 percent. It was also previously estimated that despite an increase in carbon dioxide, wheat yield will be lower between 13 and 28 percent towards year 2050, which depends to location and employed general circulation models. Obviously, the agricultural practices and management should improve to comply with the inevitable climate changes. Increasing tolerance of wheat cultivars grown in this area to higher temperatures, especially during flowering time, can be effective in order to adapt to climate change.Conclusion: Climate change is one of the main challenges facing the agricultural sector, especially in arid and semi-arid regions, and simulation of its effects in the future, can be useful for the planning and policy making to ensure food security for the community and welfare for the producers. The models which used in this study have already been successfully used in different studies. Our results showed that the use of these models to predict climate change and its effects on crops water requirements in Birjand plain will be possible with a good accuracy.

Introduction: Mites of the Phytoseiidae family have been extensively studied as biological control agents of different mites and insect pests. Some species also feed on nematodes, fungal spores, pollen and exudates from plants and insects. About 2, 300 phytoseiid species belonging to 90 genera have been described in this family (Chant and McMurtry 2007). Considerable efforts have been made in recent years to the collection and identification of the predaceous phytoseiid mites in Iran (Rahmaniet al.2010). Despite some studies on phytoseiid mites in Iran, our knowledge remains limited about their fauna and diversity in Mazandaran province. The data of these studies showed that until recently, only 75 species were reported from Iran. The objective of this study was to evaluate the species diversity of Phytoseiidae and access to effective predatory mites for biological control of injurious mite pests in Sari, the center of Mazandaran province (Southern coast of the Caspian Sea, 35o 47' -36o 35' N, 50o 34' -54o 10' E) Materials and methods Samples were taken from 80 plant species belonging to 46 plant families including forest trees, orchards and farm crops representing three types of ecosystems from September 2011 to October 2012. Harvested samples of each plant were separately collected in plastic bags and labeled with region and date of collection. The bags were transported to the laboratory on the same day and stored in a refrigerator at about 4oC for up to a week, until the materials washed for mite extraction. Samples were composed of leaves, stems and shoots of different ages and the number of leaves per sample varied between plant species. In order to assimilate the samples, a volume nearly equal mass of each sample were put in a two-liter water container. The mites were floated on water by adding 1.5 liters of tap water and a few droplets of detergent. The plant leaves and shoots were shaken for several times until the mites fall from the plants into water. Plant materials then removed from the solution and discarded. Mites in the solution were separated by pouring the solution through sieves of 20, 50, 200 and 400 meshes. Mites transferred into a labeled glass jar for further processing and identification in the laboratory. The mites were cleared in Nesbitt's fluid and mounted in Hoyer’s medium on microscope slides. The slides were dried at 45oC for 1-2 weeks. Then the edge of the coverslip was sealed with colorless nail polish to prevent absorption of the air moisture. All specimens collected were nominally identified to species level by using a Nikon phase contrast microscope (E600) and related identification keys.The scientific names of the plants were adapted from a dictionary of Iranian plant names (Mozaffarian 1998).The ecological indices including Margalef's richness, Simpson, Shannon-Wiener and Pielou's evenness were calculated for species diversity, dominance, richness and evenness of the mites in different ecosystems. Some mite specimens were sent to Dr. E.A. Ueckermann of the ARC-Plant Protection Research Institute, Pretoria, South Africa for identification or species confirmation.Results and discussion: A total number of 946 mites of 19 species belonging to 8 genera of three phytoseiid subfamilies namely Amblyseiinae, Typhlodrominae and Phytoseiinae were identified (Table 1). Most individual mites collected in this study, 698 mites in total (73%), belonged to 12 species of the Amblyseiinae which 68% of them (475 in total) were Transeius caspiansis and 13% (90 mites in total) were Euseius amissibilis. Phytoseius plumifer, the single species of the Phytoseiinae and the species of Typhlodrominae amounted to 16% (152 in total) and 10% (96 in totals) of the collected mites, respectively. In this study Amblyseiinae also had the highest proportion ofspecies (63%), while Typhlodrominae and Phytoseiinae had 31% and 5% of the species, respectively. Most phytoseiids collected in this study were mentioned above species that formed 76% (a total of 717) of the whole collected mites. These species were the most frequently found predators on varieties of plants. They were found on plants associated with tetranychid, tenuipalpid and eriophyid mites and small insect pests such as thrips and whiteflies. They were very common and were examined from 80 plant species, they observed on 59, 22 and 26 plants, respectively. It was interesting to observe these predators on some plants that there were not phytophagous mites. Therefore these species are generalist predators and are known to feed on pollen and exudates of plants and insects. Overall, mean mite's biodiversity indices of Margalef's richness, Simpson, Shannon-Wiener and Pielou's evenness were 1.656, 0.69, 1.546 and 0.525, respectively. Actually, when a community has many about equally abundant species, it is said to have high species diversity. But when a few species are present or like this study only a few species are abundant, then species diversity is low. The low Shannon-Wiener and Pielou's evenness indices also showed relatively low biodiversity in the area.Conclusion: Despite that 19 phytoseiids species were found in Sari, the present study revealed a low diversity of phytoseiid mites in this region. Most phytoseiids collected in this area belonged to Transeius caspiansis, Euseius amissibilis and Phytoseius plumifer (a total of 717) species. However, it was expected that many additional species could be found by similar studies in the same area, especially when other plant species were sampled.The diversity of plants in the forest, orchards and farm crops were far greater than the number of plant species sampled in this study.

Introduction: Evaluating yield in intercropping systems is based on selecting compatible plants with appropriate characteristics to establish minimum competition and maximum cooperation, and the application of suitable agricultural practices (crop density and intercropping ratio). The use of plant species with different morphological characteristics in terms of nutrient uptake and utilization of growth environment, and the least competitive species in ecological and environmental factors in a fixed nest causes possibility of presence of two plants in the same ecological niche and better use of resources (Banik et al, 2006; Mushagalusa et al., 2008).Competitive ability of species in the intercropping is estimated using the relative interference parameters and determining the dominant species (Dhima et al., 2007). One of the indicators to evaluate intercropping is competitive ratio which is the competitive ability of the crop in the form of a better expression (Dhima et al., 2007). In general, the intercropping is one of the ways that increases the stability of agroecosystems.Materials and methods: In order to study the effects of density, weedy and various proportion of corn (704 Variety) and peanut (Goli Variety) intercropping an experiment was conducted in 2012 in the Agriculture Research Station (Chah Nimeh) of Zabol University. The experiment design was factorial in randomized complete block design with three replications. Experiment factors consisted of planting proportions in 4 levels (sole crop of corn, 50% corn+50% peanut, 100% corn+100% peanut and sole crop of peanut), weedy in 3 levels (non-weedy, once-weedy and twice-weedy) and the space between rows in 2 levels (40 and 50 centimeter). For appointment of dominant treatment, Relative Crowding Coefficient (RCC), Competitive Ratio (RC), Aggressivity and Land equivalent ratio (LER) were calculated. All treatments were planted in a row of peanut and a row of corn. In intercropping alternative treatments and increasing sowing ratio with bush density change (the distance change between two bushes on a row) and variable distance between two rows (40 and 50 cm) were carried out. In monoculture and alternative intercropping systems, the distance between bushes for both plants was identical, but alternative intercropping, a row of corn and a row peanut were planted and there were 30 plants of corn and 40 plants of peanut per unit area on each row. To intensify the intercropping, the distance between plants on the rows decreased and due to variable spacing between rows, number of plants per unit area increased and there were 60 corn plants and 80 peanuts plants per unit area on each row.Results and discussion: The highest yield for corn (3.18 t.ha-1) was obtained in a intercropping of 100% corn+100% peanut and peanut (9.43 t.ha-1) in 50% corn+50% intercropping of peanut respectively. This means that the proximity of the legumes and grasses can be more productive in terms of intercropping than mono cropping system. The reason could be due to biological nitrogen fixation and increases in light absorption by roots of peanuts. Results indicated that various factors had significant effects on valuated index. The highest and least LER was in 100% corn+100% peanut and 50% corn+50% peanut. The highest RCC was for peanut, treatment non-weedy at higher population (7.41) and least was in the corn, treatment once-weedy at lower population (0.4). Corncompetitive ratio on peanut in all treatments was less than one, which indicated peanut had advantage over corn.Based on this scale treatment with less density and twice-weedy was more dominate. The Aggressivity index for corn in all the treatments were negative but increased. Therefore in the all indices peanut was the dominant species, this was referred to better use of resources and weed control.Conclusion: The results showed that both morphology and structure of the components of a intercropping, in dominant and recessive forms are effective. Row spacing and weed control are factors affecting the competitiveness and profitability indicators in intercropping. Peanut was the dominant species and a top competitor in corn and peanut intercropping with higher Aggressivity index, relative interference and higher competition and to the effective use of environmental resources and weed control, which makes it the most serious rival for corn.

Introduction: Intercropping is a multiple cropping practices involve growing two or more crops together. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop. Intercropping is one of the ways that causes more stability and increases protection and security in ecological farming systems. Intercropping is an agronomic practice that lubricity movement towards ecological agronomic system, increases the efficiency of resources (Mushagalusa et al., 2008) and yield stability. Intercropping is a sustainable practice used in many developed and developing countries and an essential element of agricultural sustainability. Many intercropping systems have proved to be better than sole crops in terms of yield because intercropping makes better use of agricultural resources and reduces interference of weeds. Muhammad et al. (2008) reported that intercropping of millet (Pennisetum glaucum) and cowpea (Vigna unguiculata) is the most predominant cropping system in the Sudan and Sahelian zones of West Africa. Millet is the staple diet while cowpea serves as a source of vegetable protein. Considering the importance of intercropping towards sustainable agriculture this study aimed to determine the best combination of soybean and millet in mixed cropping to optimal use of available resources with minimum crops competing with each other.Materials and methods: In order to study the effects of soybean (Glycine max L.) and millet (Panicum miliaceum L.) replacement intercropping on agronomic traits and weed species diversity, an experiment was conducted at the Research Station of Agricultural Faculty, of Bu-Ali Sina University, in 2014. The experiment was carried out as a randomized complete block design with three replications. The replacement intercropping series consisted of monoculture of soybean, monoculture of millet, 75% soybean+25% millet, 50% soybean+50% millet and 25% soybean+75% millet.Weed diversity was calculated using Shannon- Weiner diversity index (Equation 1).“FORMULA”Where N is the number of individuals, ni is the number of individuals related species i and S is number of species.Biological and grain yield were determined at the end of growing season. Before harvesting, plant height, LAI max, total chlorophyll, number of pods per plants, number of soybean seeds per plant, number of millet panicles per plant and 100 seed weights were measured in 5 randomly selected plants. Analysis of variance (ANOVA) and Duncan’s multiple range test (DMRT) were performed.Land Equivalent Ratio (LER), Aggressiveness and Actual Yield Loss (AYL) were calculated as follows (Dhima et al., 2007).“FORMULA”Where Ysm and Yss are the grain yields of intercropped and sole soybean, and Yms and Ymm are the grain yields of intercropped and sole millet, respectively. Zsm and Zms are the mixing ratio of soybean and millet, respectively.Results and discussion: The results showed that the highest seed yield of 219.8 and 171.9 g.m-2 belonged to monoculture of soybean and monoculture of millet, respectively. Intercropping reduced maximum leaf area index of soybean and millet but leaf chlorophyll content of soybean and millet were increased. The highest number of pods per plant, number of seeds per plant of soybean and panicle number per plant of millet were obtained in 50S: 50M ratio. Mean soilrespiration rate in intercropping treatments was 4% and 8 % higher than that of monoculture of soybean and millet, respectively. Tavassoli et al. (2010) in a millet and common bean intercropping system, showed that grain yields of intercropped millet and common bean were significantly higher than those of millet and common bean in the corresponding sole cropping.Intercropping patterns of 50S: 50M and 25S: 75M were successful in reducing weed plant density and diversity in comparison with soybean sole cropping.For all intercropping treatments, land equivalent ratio (LER) was more than one. Maximum value of LER(2.20) was achieved in 50S: 50M intercropping. Soybean and millet intercropping at different levels of replacement did not have actual yield loss. Calculating the aggressiveness showed that millet was more dominate than soybean. The maximum relative crowding coefficient of soybean was observed in 75S: 25M, however that of millet was obtained in 25S: 75M and 50S: 50M intercropping indicating that millet is more competitor than soybean.Conclusion: Land utilization indices such as land equivalent ratio, relative crowding coefficient and aggressiveness indicated that intercropping of soybean and millet in comparison to sole cropping, increased economic usage of land in different mixed proportions. According to above mentioned indices the best proportion of soybean and millet intercropping was 50: 50. Aggressiveness index of components showed that millet was more dominant than soybean.

Introduction: Due to the development of sustainable agriculture and the reduction of utilizing chemical fertilizers, it is essential to use organic fertilizer. Organic matter is vital to soil fertility and its productivity. To maintain the level of fertility and the strength of soil, organic matter levels should be maintained at an appropriate level.Unfortunately, the level of organic matter in soil is generally less than 1%. One solution to increase the soil’s organic matter content is to use organic fertilizers such as animal manure, green manure, and vermicompost (Nuralvandy, 2011). As a correction factor, green manure can increase water supply and nutrient soil conservation (Tajbakhsh et al., 2005).Materials and methods In order to assess the effects of fertilizer sources (green manure, cow manure, and chemical fertilizer) on maize yield and yield components (KSC 704) under tillage management, a field experiment was carried out at Zahak Agricultural and Natural Resource Research Station in two years (from 2013 to 2014). Before corn planting, barley was planted as green manure in the fall of each year. The experiment was conducted as a split plot arranged in a completely randomized block design with three replications. The main plots were tillage and no tillage, whereas the sub plots were: 1-barley green manure (without application of fertilizer), 2-barley green manure with applying 100% chemical fertilizer (NPK) to the barley during cultivation, tillering and stemming stages, 3- green manure with 2.3 of chemical fertilizer to the barley and 1.3 to the maize, 4- green manure with 1.3 of chemical fertilizer to the barley and 2.3 to the maize, 5- barley green manure with 50% animal and chemical manures, 6- barley green manure with 40 t ha-1 of animal manure, 7-control (non-fertilizer application).Corn was planted on 15 March each year. Phosphorus, potassium fertilizer, and animal manure were added to the soil as the base fertilizers. At full maturity, 10 plants were randomly selected and the plant height, the number of kernels per row, the number of rows per ear, the seed weight, the harvest index, and the ear length were measured, separately.Results and discussion: The results showed that in comparison with the first year, in the second year a significant increase was observed in plant height, ear length, number of kernel per row, weight of 100 seed weight, harvest index, and seed yield. The highest grain yield was obtained from the conventional tillage systems (mixing the fertilizer with the soil) with the mean of 4494.85 kg.ha-1. Other characteristics, except the number of row per ear, increased more in the conventional tillage than in the no tillage. Fertilizer sources were significant for plant height, ear length, number of kernel per row, weight of 100 kernels, harvest index, and seed yield. The highest grain yield was obtained from the sixth treatment (mix of animal, chemical and green manures) with the mean of 7018.5 kg.ha-1. The interaction of year, tillage and fertilizer sources indicated that the highest grain yield and 100 seed weight were obtained from the conventional tillage systems and from the 6th treatment (mix of animal, chemical and green manures) with the means of 9400.33 kg.ha-1 and 246 g, respectively. In the conventional tillage, microbial decomposition occurs faster than in the no tillage. Nutrients are released in vicinity of the plant roots and it can be placed conveniently at the disposal plant. In this way, the sixth treatment will achieve higher yield and better quality, because it can create diverse sources of essential nutrients for the plant; moreover, it canincrease absorption capacity in corn.Conclusion: In conventional tillage systems, where the sources of fertilizer are mixed with soil, the plant is placed indirect contact with the soil degrading bacteria, accelerating the fertilizers’ mineralization, and ultimately, improving the plant growth. Due to high soil density, the root growth limited during the first year of no tillage.Organic Food Systems (green manure and animal manure) provide the mineral food for plants. However, the low rate of mineralization in the early stages of root development can limit the nutrient availability. Nevertheless, these limits are removed over time. Integration of green manure, animal manure, and chemical fertilizer with conventional tillage not only strengthens the initial growth but it also accelerates the mineralization. In general, itcan be concluded that application of green, animal, and chemical manures and conventional tillage for corn production can both reduce chemical fertilizer and environmental pollution and play a positive role in increasing the yield of maize.

Introduction: Reduced availability of water resources in many arid countries including Iran, particularly in response to the indiscriminate harvesting of water reservoirs and climate change, has created concerns. Therefore, the sustainable use of water resources especially in agriculture is a necessity for these countries. Strategies such as deficit irrigation and superabsorbent application are two important ways for improving water use efficiency in agricultural lands. In deficit irrigation the crop must be irrigated less than its required water. Therefore, some reduction may occur in crop yield, but the savings in water will improve the water use efficiency (Akbari Nodehi, 2011). Superabsorbent polymers also increase the nutrients and water holding capacity of soil for a long time and thereby reduce crop water requirement. However, the effectiveness of these materials could be affected by dehydration frequencies, temperature and irrigation water quality (Karimi et al., 2009). Due to the limitation of water resources in many parts of Iran, the aim of this study was to investigate the possibility of cotton production under deficit irrigation along with application of different rates of superabsorbent. In addition, simulation of superabsorbent efficiency at different levels of salinity, temperature and dehydration frequencies (swelling and de-swelling) were the other objectives in this study.Materials and methods: 1. Laboratory experiments In these experiments the effects of temperature (4, 10, 20, 30 and 40oC), salinity (0, 0.25, 0.5, 0.75 and 1% NaCl solutions at two temperatures of 10 and 25oC) and frequency of partial dehydration (from 1 to 5 stages watering and 70% dewatering) were simulated on water absorption capacity of superabsorbent polymer at laboratory of environmental stresses, Sarayan Faculty of Agriculture, Birjand University.2- Field experiment This experiment was designed at Research Station of Sarayan Faculty of Agriculture, Birjand University, Iran, during 2014. The experiment was carried out as factorial arrangement based on randomized complete block design with three replications. Study factors were consisted of different levels of superabsorbent (0, 30, 60 and 90 kg.ha-1) and deficit irrigation [irrigation intervals of 12 (control), 15 and 18 days equal to  ~120, 155 and 190 mm evaporation from pan, respectively]. Seeds of cotton (Khordad cultivar) were sown in 20 June, with 60×25 cm distances in 3×4 m plots. The harvesting of cotton was performed at three times on 27 Oct, 10 Nov and 17 Nov. At the end of experimental period the yield and quality indices of produced fibers including fiber length, uniformity index, strength, elasticity, fineness (micronaire), brightness, yellowing, ripening ratio and short fibers percentages were measured. Finally, statistical analysis was employed by using the Duncan’s multiple range test at the 5% level of probability.Results and discussion: Results of laboratory experiments showed that salinity had considerable negative effects on water absorption capacity of superabsorbent in both 10 and 25oC temperatures. The amount of water absorbed by superabsorbent reduced by 73% and 85% by increasing salinity from 0 to 0.25% and to 1%, respectively. In addition, the effect of temperature changes was significant on the water absorption capacity of superabsorbent. The highest value of water absorbed by the superabsorbent was obtained at 20oC treatment. The amounts of water absorbed at 20oC, were 8% and 13% higher than 4oC and 40oC, respectively. In similar study it has been concluded that swelling of polyaspartic acid hydrogels decreased when the temperature of the aqueous media increased from 25oC to 60oC (Zhao et al., 2005). The amounts of water absorption ability of superabsorbent during 1 to 5 watering and dewatering cycles were 266, 311, 334, 340 and 355 g g-1, respectively. Results of field experiment showed that cotton yield was significantly affected by irrigation management and superabsorbent application. Application of 60 kg ha-1 superabsorbent along with irrigation intervals of 15 days was the best combined treatment in terms of fiber production. Moreover, experimental factors had no negative effect on the quality indices of produced fibers.Conclusion: Results of this experiment showed that superabsorbent application and deficit irrigation are the two potential strategies for cotton production in semi-arid regions, especially if low saline water sources are used.

Introduction: Today, Climate change issue is one of the main challenges for scientists and due to the critical role of water in human life, the study of climate change impacts on severity and frequency of drought in each region seems to be indispensable (Hulme et al., 1999). Drought is usually occurred over a period of water shortage owing to less rainfall, high evapotranspiration and pumping a huge amount of water from water tables. This issue could have extensive consequences on agriculture, ecosystems and communities. The objectives of this study were to predict meteorological parameters, calculation of drought index and its zoning under the changing climate in Fars province.Materials and methods: In order to predict the future climate in nine districts of Fars province (including Shiraz, Eghlid, Fasa, Lar, Lamerd, Darab, Zarghan, Neiriz and Abadeh), two climate models (HadCM3 and IPCM4) was applied under three scenarios (B1, A1B and A2). LARS-WG software was applied to downscale climate parameters (Semenov and Barrow, 2002). To predict incident probability of drought in the all study locations, a drought index (Standardize Precipitation Index, SPI) was calculated at a time scale of 12 months. SPI is the most commonly used drought index. SPI is calculated based upon the differences between monthly rainfall and average rainfall for a certain period of time according to the time scale (Mckee et al., 1995). In this study the SPI time series have been estimated for the historical base period 1980-1990 and for three future periods (2011-2030, 2046-2065, 2080-2099). Finally, drought maps and zoning were conducted in the whole province using GIS and based on IDW interpolation method.Results and discussion: Results of climate models evaluation indicated that LARS-GW well predicted radiation, and maximum and minimum temperatures (RMSE of 0.51, 0.46 and 1.02%, respectively). However, the accuracy in prediction of rainfall was not as good as the other climatic variables (RMSE of 11.48%). This is mainly due to the fact that there is a high variability in rainfall under arid and semi-arid conditions. Other studies also showed that LARSWG often over- or underestimate rainfall compared with other climatic variables. According to the simulated aridity index in the baseline period, Abadeh and Lar classified into extreme drought class (-2.48 and -2.09) while under future climate change Lamerd categorized in the extreme drought class. The most severe drought occurred in Neyriz (1.33) using HadCM3 model under A2 scenario in 2080-2099. While, the lowest drought severity obtained in Lamerd (-2.58) using IPCM4 model under A1B scenario in 2046-2065. According to the zoning maps, a vast majority of Fars province had normal climate in the baseline which, are mainly located in southern part of Fars including Neyriz, Darab, Fasa, Lamerd and Eghlid. In contrast, only a limited part of the study locations classified as drought included Abadeh, Zarghan and Lar. Results of t-test also showed that there is no difference between HadCM3 and IPCM4 climate models in terms of future climate prediction (p≥0.05). Results also revealed that for most of study locations, SPI would be in normal class for the all three periods compared with the baseline.Drought zoning in the baseline in 12 month time scale indicated that the lowest drought was occurred in southern part of Fars while the most severe was observed in both northern areas and some limited part of the south. It was generally concluded that the major part of the Fars province was in normal (the southern half of the province) and moderate class (the northern half of the province) for baseline period according to SPI. However, for projected period, major part of regions would be in normal class. As the Fars province is one of the major producers of cereals in the country, it is estimated the area will benefit from climate change in the future particularly under rainfed conditions.Conclusion: The results of the current study showed that drought would be intensified under climate change in Fars province and most of the area will benefit from changing climate in the future. However, it is necessary for the authorities to take the results into account, and have applicable water resources management strategies to be able to deal with possible problems in the future decades. Decision makings also should be accomplished with especial considerations to the uncertainties that almost appear in the results.

Introduction: Soybean (Glycine max L.) is one of the major sources to produce oil. Suitable sowing date makes optimum use of climate factors such as temperature, moisture and during the day. Soybean is not easily adaptable with soil and climate change, because its flowering and ripping depends on duration of daylight. Long days delays flowering process and short days causes acceleration of plant maturity. Temperature is one of the most important effective factors on the growth of any kind of plant (Caliskan et al., 2008). Related to the radiation effect on the plant growth, excessive studies have been done in the world. One of the necessary pre-conditions to get upper yield is making necessary conditions for optimal use of radiation (Muchow et al., 1990). Awareness of the effective factors on the yield of soybean can help us to get better management of the plant. Therefore, the goal of this research was to study the effect of sowing date, temperature and sunshine hours on the length of growth period, yield and yield components of soybean.Materials and methods: This research was performed to study the effect of sowing date, temperature, and sunshine hours on yield and yield components of soybean in the area of Aliabad-Katoul in Golestan province, during 2011-2012 cropping year. In this order, different soybean fields with different sowing date had been remarked in vast area of soybeanfields of Aliabad-Katoul area. In this study 30 soybean fields with Katoul (D.P.X) cultivar and 30 soybean fieldswith Sari (J.K) cultivar werte chosen. To assess the study traits (the length of different phenological periods, yield, and yield components) into each of field, 5 plots in zigzag pattern (S) had been chosen and in each plot, the study traits had been measured and the average of them was recorded for each field. The important soybeangrowth stages, including the start of flowering (R1), the start of pods of the plants (R3), the start of seedformation (R5), the start of physiological ripping (R7) and complete ripping (R8) was recorded (Fehr & Caviness, 1980).Results and discussion: In this study, phenological developments during growing period were influenced by the sowing date. There was a negative linear correlation between delaying of sowing date and growth duration as the 86% and 90% of the variation in the Katoul and Sari cultivars justified, respectively. Delaying of sowing date of both cultivars, reduced the yield. This negative significant linear relation explained 79% and 53% of changes in Katoul and Saricultivars, respectively. The slope of the regression equation indicated that delaying of sowing date (days from20th June) reduced seed yield in Katoul and Sari cultivars equal to 50.6 kg.ha-1 and 37.4 kg.ha-1 per day, respectively. The result showed that response of soybean yield components to the average of temperature during flowering and grain filling in both cultivars was positive and significant, except for seed number per squaremeter in Sari cultivar. Between mean temperature during starting flowering to starting grain filling and soybeanpod number per plant was a positive linear correlation as the 77 and 68% of the variation in the Katoul and Sari cultivars justified, respectively. In addition, in this research it was observed that there was a significant relation between the total sunshine hours during flowering and grain filling and the components of soybean yield.Conclusion: The results of this study showed that sowing date had significant effect on plant traits such as seed yield. The majority of the study traits decreased due to delay of sowing date. Thus, in the study area sowing date is one of the most important effective factors on the growth and yield of soybean.