a b s t r a c tEfficient use of energy in agroecosystems will reduce environmental problems, prevent destruction of natural resources and serve to promote sustainable agriculture as an economical production system. The aim of this study was to investigate the energy use efficiency in four double cropping systems including: wheat-silage corn (W-SC), barely-silage corn (B-SC), barely-grain corn (B-GC) and barely-rice (B-R) in the arid regions of Isfahan province, Iran. Data used in this study were collected from 73, 45, 38, 18, 18 wheat, barley, silage corn, grain corn and rice farms, respectively, personal interview using semistructured questionnaire during 2010. The results indicated that the total energy consumed were 140,422, 128,979, 121,360 and 172,962 MJ ha −1 for the W-SC, the B-GC, the B-SC and the B-R cropping systems, respectively. The share of diesel fuel by 43.36% (W-SC), 43.93% (B-GC), 42.82% (B-SC) and 49.40 % (B-R) was the highest input. This was followed by fertilizer (W-SC: 24.70%, B-GC: 25.12%, B-SC: 27.05 and B-R: 16.11) and water (W-SC: 10.54%, B-GC: 11.76%, B-SC: 10.73 and B-R: 13.85), respectively. The energy use efficiency was found as 1.70 for W-SC, 1.65 for B-GC, 1.64 for B-SC and 1.03 for B-R double cropping systems, respectively. According to the research results the W-SC, B-SC, B-GC and B-R double cropping systems were more efficient in terms of energy, respectively.

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This experiment was conducted to evaluate the effects of two irrigation regimes (control and water stress) and two nitrogen (N) levels (0 and 112.5 kg/ha) on forage yield and silage quality in millet. Bastan (Setaria italica (L.) P. Beauv) and Pishahang (Panicum miliaceum) were sown at two different dates during 2015 and 2016. Both cultivars exhibited reduced dry‐matter (DM) yields (45% and 51% in Bastan and Pishahang respectively) due to drought stress. Proline and phenolic contents increased as a result of drought and were significantly and negatively correlated with DM yield and digestibility. Moreover, Pishahang had a reduced acid detergent fibre (ADF) content but improved leaf/stem ratio, digestible dry matter (DDM), relative feed value (RFV), net energy for lactation (NEL), digestibility and silage quality as a result of drought stress, while no significant effects on these traits were observed in Bastan. Silage quality was greatly cultivar‐dependent. Both cultivars had higher levels of DDM, RFV and NEL at early sowing dates. Nitrogen supply had greater positive effects on increasing ash, crude protein (CP) content and DM yield under normal irrigation than under water‐stress conditions. In summary, given the importance of the energy received per unit of forage from an animal husbandry viewpoint and the significance of DM yield per unit area from an agricultural viewpoint, the obtained results might help farmers in choosing not only the best sowing dates but also proper irrigation and N management practices to achieve their quantitative and qualitative objectives in forage production.

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Drought stress is one of the main limitations to crop growth and yield. Efficient nitrogen (N) nutrition may moderate the negative effects of drought stress on plants through retention of metabolic activities. The present study was conducted to investigate the biochemical responses of two millet species, foxtail millet (Setaria italica (L.) P.Beauv.) and proso millet (Panicum miliaceum L.), under two irrigation regimes (based on 55% and 85% soil-water depletion) and two N fertiliser levels (0 and 112.5 kg N ha–1) at four sowing dates (22 June and 6 July 2015, 14 and 30 June 2016). Drought stress increased hydrogen peroxide (H2O2), malondialdehyde (MDA) and other aldehyde contents of the plants, ultimately leading to 52% and 55% reductions in grain yield in foxtail millet and proso millet, respectively. Antioxidant activities showed significant increases under drought stress. Nitrogen application decreased H2O2, MDA and other aldehyde contents and activities of antioxidant enzymes, whereas it increased chlorophyll, carotenoid, phenolic compound and proline contents as well as grain yield. Higher grain yields were obtained with early planting dates under sufficient water supply, whereas superior yields were obtained with delayed planting dates under water stress owing to lower temperatures and evaporation rates. The results suggest that N application could mitigate the adverse effects of drought stress on millet plants by promoting osmoregulation, alleviating lipid peroxidation, and improving plant physiological traits. Foxtail millet had higher antioxidant potential than proso millet, resulting in greater capacity to inhibit production of free oxygen radicals and making it the more drought-tolerant species.

The effect of different fertilizing systems on the seed yield and phosphorus uptake in annual medic (Medicago scutellata cv. Robinson) was examined at two locations under dry farming conditions in Kermanshah province, Iran, in 2009. Experiments were conducted based on a randomized complete block design with three replications; the treatments consisted of control (no fertilizer), chemical fertilizer, biological fertilizer and different combinations of chemical and biological fertilizing systems. The results showed that application of different fertilizing systems had a highly significant effect on the number of pods per plant. The highest values were obtained in the treatment using the urea chemical fertilizer + phosphorus-solubilizing bacteria + mycorrhiza. The highest soil seed bank was recorded in the nitrogen-fixing bacteria + phosphorus-solubilizing bacteria treatment; it increased the number of seeds by approximately 50 percent compared to the control (only 134 pod containing seeds). The highest pod yield was obtained after applying nitrogen-fixing bacteria + mycorrhiza (445 kg/ha), the lowest yield in the control treatment (266 kg/ha). In general, under the conditions of this experiment, the seed yield of annual medic var. Robinson receiving nitrogen-fixing + phosphorus-solubilizing bacteria out-yielded other fertilizing treatments. This indicates a synergistic interaction between these groups of bacteria that increases seed yield, the soil seed bank as well as the seed phosphorus uptake of this plant species under dry farming conditions.