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Optimisation of water and nitrogen use is an effective management tool to conserve resources and reduce environmental pollutions. Response surface methodology (RSM) is defined as a collection of mathematical and statistical methods that are used to develop, to improve or to optimize a product or process. In order to determine optimum levels of water, nitrogen and planting density of canola (Brassica napus L.), a 2-year experiment (2010-2011) was carried out by central composite design as RSM at the research station of Ferdowsi University of Mashhad. The treatments were designed based on low and high levels of irrigation (1500 and 4000 m 3 ha −1 ), nitrogen (0 and 400 kg N ha −1 ) and density (50 and 150 plant m −2 ) as independent variables. Furthermore, seed yield, nitrogen losses, nitrogen use efficiency (NUE) and water use efficiency (WUE) were measured as response variables in a full quadratic polynomial model. Optimum levels of irrigation, nitrogen and planting density were suggested to achieve the target range of dependent variables based on three scenarios: economic, environmental and eco-environmental. The results showed that increasing irrigation and fertilizer led to an increase in seed yield and nitrogen losses, whereas increasing canola density resulted in an increase in seed yield but a decrease in nitrogen losses. The optimum levels of water, fertilizer and density based on environmental scenario were 1802 m 3 ha −1 , 11 kg N ha −1 and 122 plant m −2 , respectively. To achieve optimum conditions under the economic scenario, it is necessary to use 3411 m 3 water ha −1 , 178 kg N ha −1 and 119 plant m −2 . Amounts of 2347 m 3 water ha −1 , 92 kg N ha −1 and 114 plant m −2 were found to be the optimum conditions for the eco-environmental scenario. In general, it seems that resource use based on the eco-environmental scenario may be the most favorable cropping strategy for canola production.

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In order to evaluate the effects of different organic and biological fertilizers on quantity and quality of fennel essential oil, an experiment was conducted in a completely randomized block design with three replications. The experimental treatments included two organic (compost and vermicompost) and two biological (Pseudomonas putida and Azotobacter chroococcum) fertilizers, their all twin combinations (Ps. putida + A. chroococcum, Ps. putida + compost, Ps. putida + vermicompost, A. chroococcum + compost, A. chroococcum + vermicompost and compost + vermicompost) and control (non fertilized). There were significant differences between treatments in terms of seed essential oil percentage, essential oil yield; anethole, fenchone, limonene and estragole content in seed essential oil. Results showed that the highest and the lowest percentages of essential oil were obtained in control (2.9%) and A. chroococcum + vermicompost (2.2%) treatments, respectively. The highest essential oil yield (29.9 L ha -1 ) and anethole content of essential oil (69.7%) and the lowest contents of fenchone (6.14%), limonene (4.84%) and estragole (2.78%) in essential oil were obtained in compost + vermicompost treatment. It seems that compost + vermicompost treatment compared to other treatments supplied the highest equilibrium of nutrients and water in the root zone of sweet fennel which is led to increasing the anethole content, there upon, decreasing other compounds. Essential oil yield and percentage of anethole content in essential oil were significantly higher in all organic and biological treatments compared with control.Additional key words: anethole; Azotobacter chroococcum; compost; Pseudomonas putida; vermicompost. ResumenEfecto del abonado orgánico y biológico sobre el rendimiento de los frutos y los aceites esenciales del hinojo (Foeniculum vulgare var. dulce) Con el fin de evaluar los efectos de diferentes fertilizantes orgánicos y biológicos sobre la cantidad y calidad del aceite esencial de hinojo, se realizó un experimento en un diseño aleatorizado de bloques completos con tres repeticiones. Los tratamientos experimentales incluyeron todas las combinaciones dobles de dos fertilizantes orgánicos y dos biológicos (Pseudomonas putida + Azotobacter chroococcum, Ps. putida + compost, Ps. putida + humus de lombriz, A. chroococcum + compost, A. chroococcum + humus de lombriz, y compost + humus de lombriz) y un control (sin fertilizar). Hubo diferencias significativas entre tratamientos en términos de porcentaje del aceite esencial de las semillas, rendimiento de aceite esencial y contenido en anetol, fenchone, limoneno y estragol en el aceite esencial. Los resultados mostraron que el mayor y el menor porcentaje de aceites esenciales se obtuvieron en los tratamientos control (2,9%) y A. chroococcum + humus de lombriz (2,2%), respectivamente. En el tratamiento compost + humus de lombriz se obtuvo la mayor producción de aceite esencial (29,9 L ha -1 ) y contenido en anetol (69,7%), así como el menor contenido de fenchone...