s. n. mosavian

This research, conducted in Gotvand, southwest Iran, evaluated the energy balance of a field system which watermelon produced in it. In the current research, energy inputs of watermelon planting were measured. To reach this goal, questionnaires were given to the farmers to record the amount of energy input to their watermelon planting field. Statistical analysis of the data revealed that nitrogen was the input with the highest consumption of energy (4175 MJ.ha-1) followed by diesel fuel. About 90% of the consumed energy of watermelon planting system was seen for energies which cannot be renewed. The results showed that the efficiency of energy consumption was positive, indicating that the amount of output energy was higher than that of input energy. With each unit of energy was consumed, 4.86 units of energy were produced, which indicates high energy efficiency. For improving the efficiency of energy usage in the watermelon planting system, nitrogen application to the system should be reduced and it can be reached by suitable rotation which diminish the nitrogen needs.

Heat stress during grain filling period can lead to the reduction of grain yield of wheat. Therefore, in order to evaluate the probable mitigative effect of nitrogen and zinc application of heat stress on physiological properties, grain yield and protein content of wheat (Chamran cultivar), a split-split plot experiment based on RCBD in four replications was carried out in an experimental field of Khuzestan Agriculture and Natural Resources University, Ahvaz, Iran during autumn of 2018-19 growing season. Experimental factors were three planting date (22 November, 11 December and 31 December) as main plot, four nitrogen levels (0 as a control, 75, 150 and 225 kg ha-1 N from urea 46%) as subplot and zinc levels (0 as a control, 10 and 20 kg ha-1 from zinc sulfate) in subplots. The results showed that the delay in planting significantly (P≤0.01) reduced grain protein, leaf chlorophyll index, cell membrane stability index, grain yield, biological yield, and harvest index. Nitrogen application reduced the effects of heat stress on wheat grain yield so that by consuming 75, 150 and 225 kg N ha-1 in cultivation, wheat grain yield was improved by 43%, 59% and 64% for 11 December cultivation date and 50%, 70% and 55% for 31 December cultivation date, respectively, compared to control fertilizer. Zinc application also reduced the effects of heat stress on wheat grain yield, where at late and very late cultivation dates, with the application of 10 and 20 kg ha-1 zinc, wheat grain yield was improved by 5%, 6%, 35% and 40%, respectively. Consumption of zinc also reduced the effects of heat stress on wheat grain yield by increasing grain weight and caused a 24% increase in grain weight. Wheat harvest index decreased by about 18% due to heat stress. Meanwhile, application of nitrogen and zinc at 150 and 10 kg ha-1, respectively, showed the greatest effect in reducing the adverse effects of terminal heat stress on the agronomical and physiological properties of wheat. In general, in case of delayed cultivation, the use of zinc (at least 10 kg ha-1) and nitrogen (at least 150 kg ha-1) can reduce the harmful effects of terminal heat stress in Ahvaz climate and improve physiological (chlorophyll content and cell membrane stability), agronomic and protein content of bread wheat.

This research, conducted in Gotvand, southwest of Iran, compared the energy consumption of two cucumber production systems: field and greenhouse production systems. In this study, energy inputs of two production systems of cucumber (including seed, pesticide, human labor, machinery, diesel fuel, electricity, organic manure, chemical fertilizer) were determined from questionnaires completed by farmers. The results of the experiment indicated that the energy input of the two cultivation systems was not significantly different in input energies. In both cucumber production systems, the most input energy was allocated to nitrogen fertilizer (57% and 53% for field and greenhouse, respectively) followed by diesel fuel (21% in both production systems). Non-renewable energies accounted for 90 and 88% of the total energy input to the farm and greenhouse systems, respectively. Total output energy of field and greenhouse cucumber production system was 33000 and 34000 MJ, respectively. Reducing the consumption of nitrogen fertilizer through the use of appropriate crop rotation is a suitable solution to improve energy efficiency in the cucumber production system.

Rapeseed needs a sufficient amount of nitrogen for optimal seed yield, but the efficiency of this plant in using nitrogenous (N) fertilizers is low, which causes an increase in N consumption in the cultivation of this plant. The need to maintain a high grain yield necessitates the use of a suitable timely program and manage the consumption of N fertilizers. Thus, a field experiment was conducted at the Research Station of Agriculture and Natural Resources of Khuzestan University during 2020-2021 growing season to evaluate the effect of preceding crop and N fertilizer on grain yield of rapeseed. The experiment was carried out as split plots based on a RCBD with three replications. Preceding crops (clover-barley mixture, rapeseed, corn, fallow, mung bean, rice and wheat) were allocated to the main plots and N levels (0.0, 100, 160 and 220 kg ha-1 N from the source of urea fertilizer) were assigned to the sub plots. Results indicated that the grain yield of rapeseed depends mostly on grain number, but the grain yield components (including pods number per plant, grain number per plant, grain number per pods) were mainly affected by the main effect of preceding crop and nitrogen. With the application of 100, 160 and 220 kg ha-1 N the number of grains per pod increased by 34%, 39% and 33%, respectively. The number of grains per plant was also increased by the application of nitrogen fertilizer, where all three levels of nitrogen fertilizer resulted in more than 200% increases in this grain yield attribute. The highest grain yield of rapeseed (3877 kg ha-1) was observed when mung bean was used as preceding crop and 220 kg ha-1 N fertilizer was applied, though it was not significantly different from the treatments of mung bean preceding crop and application of 160 kg ha-1 nitrogen fertilizer (with the production of 3105 kg ha-1 grain) and fallow preceding and 160 kg ha-1 N fertilizer. The lowest grain yield of rapeseed was obtained when corn and rapeseed were used as preceding crops and no N fertilizer was applied, as these preceding crops resulted in only 488 and 497 kg ha-1 grain of rapeseed, respectively. Rapeseed had the highest oil yield (1645 kg ha-1) with mung bean being the preceding crop and 220 kg ha-1 N application. It seems that for achieving the highest oil yield of rapeseed, mung bean preceding crop and 220 kg ha-1 N can be focused on for the next researches.