The optimum resource level in agro-ecosystems should be determined to decrease production costs، conserve resources and reduce environmental pollution which occurs as a result of excessive use of these resources. In order to determine the optimum use of water، nitrogen and canola density، an experiment was conducted using central composite design in the Research Field of Ferdowsi University in 2011. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m3)، nitrogen (0 and 400 Kg urea ha-1) and canola density (50 and 150 plant m-2). Seed yield، nitrogen losses، nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as independent variables and changes of these variables were calculated by a regression model. Optimum levels of irrigation، nitrogen and canola density، respectively، were proposed to obtain the expected level of traits based on three scenarios: economic، environmental and economic-environmental. Increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses، whereas increasing canola density caused an increase in seed yield but a decrease in nitrogen losses. The optimum level of water، fertilizer and density were 3643 m3، 186 Kg N ha-1 and 149 plant m-2 in economic scenario. In the environmental scenario، the optimum levels of the treatments obtained were 1813، 12 and 150، respectively، and for the economic-environmental scenario were 2639، 105 and 144، respectively. In general، it seems that resource use based on the economic-environmental scenario is preferable to the other scenarios since it takes account not only of economic but also of environmental issues.

Today، the agricultural sector is one of the main energy consumers worldwide. Increasing world population، accompanied by natural resource limitations، reveals the importance of research about energy use efficiency in agriculture that is responsible for supplying food security for this population. This study was performed to evaluate and compare energy efficiency in the rice agroecosystems of Kohgiluye and Bouyerahmad and Guilan Provinces of Iran in the 2010-2011 crop season. Data acquisition was performed using the field study method and completing a questionnaire. Completion of the questionnaire was accomplished by face-to-face interviews on farms. According to the results، the total energy input of Guilan rice agroecosystems was 43496. 33 MJ/ha، of which the greatest share of energy inputs was related to water for irrigation (38. 54 %)، electricity (23. 99 %) and nitrogen fertilizers (18. 98 %). The energy input amount of the Kohgiluye and Bouyerahmad rice agroecosystems was 33668. 16 MJ/Ha، and the geatest share of energy inputs was related to water for irrigation (49. 7 %)، nitrogen fertilizers (27. 99 %) and phosphorous fertilizers (4. 65 %). The combined energy output of Guilan and Kohgiluye and Bouyerahmad Provinces’ rice agroecosystems was obtained at 122913. 16 and 113820. 21 MJ/Ha، respectively. Energy efficiency for the aforementioned fields was calculated as 2. 82 and 3. 38، respectively.

Determination of land suitability for cropping purposes through evaluation of climatic، soil and topographic factors is of great importance for developing a sustainable agricultural system. In this research the land suitability of Tehran and Alborz Provinces for rapeseed cultivation was evaluated using the Geographical Information System (GIS). The results of overlaid maps with application of the maximum limitation method based on climatic variables which are necessary for winter rapeseed (active growth degree days from planting until frost period، active growth degree days from planting to flowering، active growth degree days from planting to harvesting of canola، average maximum and minimum temperatures during growing and number of frosted days in the study area) indicated that the most of the land in the study area (34. 85%) in terms of climate is moderately suitable (S2) for rapeseed cultivation. Approximately 30. 17% of the land in the North and the Southeast of the study area is unsuitable (N) for rapeseed growth and development. This occurs because the temperature reaches as low as -26°C in the Shemiranat and Damavand regions and -32°C in the Firouzkooh region during the rosette growth stage of rapeseed and، therefore، not enough growth degree days in the rosette، flowering and harvesting stages are available. In the Southeast of the study area، with temperatures of 27، 30 and 35°C occurring at the flowering، packing pod and maturity stages، respectively، are harmful and، therefore، rapeseed cultivation is not suitable. The results indicated that 18. 51% of the land in terms of climate is suitable (S1) for growing rapeseed. The results of overlaid maps with application of the maximum limitation method for climate، land use، topography and soil variables also showed that approximately 83. 12% of the land is not suitable (N) for cultivation of rapeseed. However، climatic and soil constraints are important limiting factors for cultivation of rapeseed in these areas. Thus، for rapeseed cultivation، only 7. 9% of the land in the study area is suitable (S1).

Widespread use of herbicides throughout the world plays an important role in water and soil pollution. Hence، knowledge of the behavior of herbicides is necessary to reduce their adverse effects on the environment. An experiment was conducted in RCBD with a factorial arrangement of treatments and 3 replications to study the effect of manure and herbicide application rates on trifluralin dissipation in soil. The factors were two amounts of animal manure (0 and 25 ton ha-1) and three application rates of trifluralin (0. 48، 0. 96 and 1. 92 kg ai ha-1). Sampling from the soil was carried out immediately and 7، 14، 28، 48، 90 and 120 days after applying the trifluralin and the herbicide residues were measured using HPLC. Dissipation of trifluralin followed first-order kinetics in the soil and its rate was higher in the amended soil independent of the application doses or cover state. A maximum dissipation rate of 0. 032 mg kg-1 ha-1 was observed in no manure and of 0. 48 and 0. 96 kg ai ha-1 of herbicide; a minimum dissipation rate of 0. 012 mg kg-1 ha-1 was observed in the manure treatment and of 1. 92 kg ai ha-1 for trifluralin. A maximum half-life (57. 75 days) was related to the manure treatment and 1. 92 kg ai ha-1 for trifluralin، and a minimum half-life (21. 38 days) was related to the no manure treatment and 0. 48 kg ai ha-1 for trifluralin. According to the findings of this experiment، the persistence of trifluralin in soil is increased by increasing the application rate of the herbicide and applying manure. It is likely that manure utilization increases trifluralin absorption into the soil which probably results in a reduction in herbicide evaporation.

In order to evaluate the effects of corm density، weight and planting method on the vegetative and reproductive characteristics of saffron (Crocus sativus L.)، a factorial field experiment was carried out based on a randomized complete block design with three replications at the Agricultural Research Station، College of Agriculture، Ferdowsi University of Mashhad، during two growing seasons of 2009-2010 and 2010-2011. The treatments were three corm weights (<5 g، 5-8 g and >8 g)، two corm densities in 40 cm (5 and 10 corms) and two planting methods (row and mass). Criteria such as leaf dry weight، tunic dry weight، leaf length، corm diameter، number of daughter corms، corm number and corm weight in three groups of weight (2-4، 4-8 and 8-16 g)، flower number، flower fresh weight and stigma weight of saffron per area unit were measured. The results indicated that the simple effects of corm weight and density and planting method were significant on all characteristics of saffron during the two years of the experiment. By increasing corm density and weight، growth characteristics and stigma yield of saffron were enhanced. By increasing corm density from 5 to 10 corms in 40 cm، stigma yield was enhanced up to 12 and 10% for the first and the second years، respectively. By enhancing corm weight form <5 g to >8 g stigma yield was increased up to 100% for two years of experiment. In the first and the second years، mass planting method increased stigma yield up to 23 and 25% compared to row planting method for the first and the second years، respectively. Interaction effects of the different treatments were not significant on saffron traits.

Today، higher yield and a decrease in the costs of production are important objectives in agriculture. The aim of this investigation was to compare sugar beet and potato production systems in terms of energy efficiency، energy intensiveness، energy productivity، benefit-to-cost ratio and amount of renewable and non-renewable energy use. Data were collected from 153 and 54 sugar beet and potato fields using a face-to-face questionnaire in 2010. The results showed that the total energy requirement for sugar beet and potato fields was 42232 and 59611 MJ ha-1، respectively. Total energy input consumed in sugar beat and potato fields could be classified as direct، indirect، renewable and non-renewable energies that were، in sugar beet field، 57%، 43%، 31% and 69%، and in potato farms were 54%، 46%، 43% and 57%، respectively. Energy use efficiency of 13. 35 in sugar beat and 1. 55 in potato was achieved. The benefit-to-cost ratios in sugar beet and potato fields were 1. 26 and 2. 33، respectively. Based on the results of the present study، sugar beet fields had higher energy efficiency in comparison with potato fields، while potato fields yielded a higher economic benefit in comparison with sugar beet fields.

In this study، different characteristics of 38 Rosa damascena accessions were evaluated based on flower yield، yield components and certain other traits. The experiment was conducted during 2006-2008 using a randomized complete block design with three replicates in Dezful، Iran. Correlation analysis showed significant relations between the traits. Flower yield correlated positively with flower number، flower fresh weight، flower dry weight and petal weight. Essential oil content showed a significant positive correlation with flowering duration but a negative correlation with flower number. Also، the correlation between plant canopy diameter and plant height was positively significant. Based on factor analysis results، for the first factor، flower dry matter percentage، flower fresh weight، flower dry weight، petal fresh weight and petal weight/flower weight were considered as the key selection factors and the most important traits. In the second factor، flower yield، plant canopy diameter and oil content had the most variation while، in the third factor، flower number and flowering duration had the highest values. In the fourth and fifth factors، plant height and petal number also showed the highest variation، respectively. Results of stepwise regression analysis showed a significant association between flower yield and flower number، flower weight، flower dry matter percentage، plant canopy diameter، and a good fit was obtained for this association by linear regression model. According to the path analysis، the greatest direct positive effect on flower yield was related to flower number and flower weight. Also، the effect of flower dry matter percentage shown on flower yield was direct and positive. Plant canopy diameter via flower number showed a positive indirect effect on flower yield. It could be concluded from this study that flower yield and flower number are appropriate criteria for selecting superior Rosa damascena cultivars for Khuzistan and similar ecological conditions.

Insecticides are one of the most important pesticides applied in Iran and، during the last two decades، have accounted for about 50 percent of pesticide usage. However، the negative impacts of insecticide have resulted in several environmental problems and placed human health in danger. In this study، the environmental impacts of registered insecticides in Iran were evaluated using the environmental impact quotient (EIQ). EIQ has three major variables، namely the farm worker، consumer and ecology for which the final score is the average of these variables. Following this، insecticides were classified according to the International Resistance Action Committee (IRAC) classification and the results for each class were analyzed. Results show that، potentially، classes 2 and 6 (based on EIQ scores) are the most hazardous and Imidacloprid، which is classified in group 4، received the highest EIQ score. Considering the active ingredients of registered insecticide، EIQ scores، and their rates of application in Iran during 2000-05، the EIQfield which demonstrates practical hazards was calculated. According to this، classes 2، 1 and 4 are، respectively، the most hazardous insecticides. Therefore، it seems that it is vital to find an alternative for Imidacloprid. Considering the environmental impacts of pesticides and their mode of action simultaneously could be a valuable approach in order to achieve sustainable pest management in sustainable agriculture.

In order to study the effects of mixed and row intercropped sesame and bean on the species growth indices، a split-plot experiment based on randomized complete blocks design with three replicates was performed at the Research Farm of Ferdowsi University of Mashhad during the growing season of 2011-2012. A cropping pattern (mixed and row intercropping) was allocated to the main plots and different planting ratios (25% bean +75% sesame، 25% sesame +75% bean، 50% sesame +50%bean، pure sesame، pure bean) were assigned to the sub-plots. Results indicated that sole sesame treatment showed superiority (Total Dry Matter (TDM)، Leaf Area Index (LAI) and Relative Growth Rate (RGR)) in most cases compared to the other treatments. This is the result of the lack of competition between sesame and bean in this treatment and taking great advantage of nutritional sources and light. The highest rate of growth indices were achieved in mixed intercropping. The highest total dry matter amount of sesame was obtained in sole sesame treatment. The highest crop growth rate amount of sesame in row intercropping pattern was 21 g m-2 day-1 while the highest crop growth rate amount of sesame in the mixed intercropping pattern was 24 g m-2 day-1. The effects of row and mixed intercropping on the relative growth rate were not same: The highest level of growth indices was observed in the sole treatment of sesame while intercropping had no positive effect on growth indices of sesame.