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.
Wheat is the main food for the majority of Iran's population. Precise estimation of wheat yield change in future is essential for any possible revision of management strategies. The main objective of this study was to evaluate the effects of climate change, CO2 concentration, technology development and their integrated effects on wheat production under future climate change. This study was performed under two scenarios of the IPCC Special Report on Emission Scenarios (SRES): regional economic (A2) and global environmental (B1). Crop production was projected for three future time periods (2020, 2050 and 2080) in comparison with a baseline year (2005) for Khorasan province located in the northeast of Iran. Four study locations in the study area included Mashhad, Birjand, Bojnourd and Sabzevar. The effect of technology development was calculated by fitting a regression equation between the observed wheat yields against historical years considering yield potential increase and yield gap reduction as technology development. Yield relative increase per unit change of CO2 concentration (1 ppm(-1)) was considered 0.05 % and was used to implement the effect of elevated CO2. The HadCM3 general circulation model along with the CSM-CERES-Wheat crop model were used to project climate change effects on wheat crop yield. Our results illustrate that, among all the factors considered, technology development provided the highest impact on wheat yield change. Highest wheat yield increase across all locations and time periods was obtained under the A2 scenario. Among study locations, Mashhad showed the highest change in wheat yield. Yield change compared to baseline ranged from -28 % to 56 % when the integration of all factors was considered across all locations. It seems that achieving higher yield of wheat in future may be expected in northeast Iran assuming stable improvements in production technology.
h i g h l i g h t s• About 85% of used water irrigation in agriculture was supplied from groundwater in Iran. • Reduced irrigation system improved the IWEUE and energy use efficiency.• Direct and renewable energies were higher under reduced than full irrigation system. • Reduced irrigation could be reduced irrigation water use up to 95% than full irrigation. • Reduced irrigation system led to save the energy resource. a b s t r a c tResource and energy use efficiency is one of the principal requirements of eco-efficient and sustainable agriculture. Seedy watermelon (Citrullus vulgaris; Joboni population) is irrigated by two methods including full and reduced irrigation systems in Iran. The objective of the present study was to compare seedy watermelon production in full (high input) and reduced (low input) irrigation systems in terms of irrigation water energy use efficiency (IWEUE), energy budget and economic analysis. Data were collected from 116 full irrigated and 93 reduced irrigated farms in northeast of Iran by using a face-toface questionnaire in 2011-2012. The results showed that the total energy consumed under high input systems was 25625.94 MJ ha −1 , whereas under low input was 3129.3 MJ ha −1 . IWEUE and all of the energy indexes were improved in the reduced irrigation system compared to the full condition. The direct and renewable energies in the reduced irrigation system were higher than full irrigation. The economical analysis indicated that higher return was gained by the full irrigation system due to higher yield compared to the reduced irrigation system. Human labor had the highest impact on seedy watermelon among the other inputs based on the Cobb-Douglas production function.
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