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In order to evaluate the effect of sowing date and planting pattern on yield and qualitative parameters of rapeseed (Brassica napus L.) and chickpea (Cicer arietinum L.) in intercropping, a split plot experiment was conducted based on randomized complete block design with four replications, in Hamedan, Iran, during 2014-15. The rapeseed seeds were sown on 21st September. Chickpea was sown on four sowing dates as the main factor (21 September, 10 October, 30 October and 20 November) with 20 days interval. The sub-factor was the planting pattern by replacement series including 100:0, 75:25, 50:50, 25:75 and 0:100 chickpea-rapeseed mixtures, respectively. Based on the results obtained, among chickpea sowing dates, the first and the last dates had the lowest and highest above-ground biomass and grain yield, respectively. During the late sowing date of chickpea (20 November) the field temperature was colder than the earlier dates, and therefore the freezing temperatures did not allow the seeds to germinate. However, no damage happened to seedlings with the earlier sowing dates. The highest yield was observed in sole cropping for both crops. In contrast, the highest values of land equivalent ratio were obtained in intercropping system. The highest value for land equivalent ratio was calculated as 1.23 in intercropping of 50% chickpea + 50% rapeseed.

To determine the possible protective and enhancer role of selenium foliar application on oil yield, fatty acid composition and glucosinolate content of rapeseed cultivars under late-season thermal stress, a factorial split-plot experiment based on randomized complete block design with three replications was carried out in Karaj, Iran during the two growing seasons 2014–2015 and 2015–2016. Three sowing dates (Oct. 7 as normal planting date), (Oct. 17 as semi-late planting date), (Oct. 27 as late planting date) and two selenium foliar application (non-application as control and sodium selenate as foliar application) were factorially randomized to main plots, and rapeseed cultivars were allocated to sub-plots. Plant materials were six cultivars including three hybrids and three Iranian open pollinated varieties. Late-season thermal stress caused by late planting date reduced oil yield, oil content, oleic acid, linoleic acid, palmitic acid and increased linolenic acid, erucic acid and glucosinolate content of investigated cultivars. The results of this study demonstrated that the highest amount of oil yield, oil content, oleic acid, linoleic acid, palmitic acid and the lowest amount of erucic acid and glucosinolate content were observed in L72 cultivar in both control and selenium application treatments. This study provided new important findings about the supportive and enhancer role of selenium in the form of sodium selenate on quantity and quality of oil in rapeseed plant.

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The high vulnerability of sweet corn (Zea mays L. var. saccharata) to weed competition and the urgent reduction of the dependence on chemical herbicides are major challenges facing the agricultural community. To investigate the effects of plastic mulches on weed control and yields in sweet corn under different sowing dates, a 2-year experiment was conducted at Varamin, Iran, in 2010 and 2011. The mulch treatments included black plastic mulch, semitransparent biodegradable mulch, an unmulched weeded control, and an unmulched unweeded control. The sowing dates were 5 June, 20 June, and 6 July. Results revealed that delayed sowing (6 July) reduced weed dry weight by 51% and 41% compared with the 5 June sowing date in 2010 and 2011, respectively, without reducing crop yield. The black plastic mulch treatment had the lowest weed biomass. The sowing date × mulch interactions on kernel number per ear, length of ear, percentage of unfilled ear tip, and yield of sweet corn were statistically significant (P < 0.01) in both years. The maximum kernel number per ear (535) and the highest fresh ear yield (24,684 kg·ha−1) in 2010 were obtained on the 6 July sowing date under biodegradable mulch. The plants sown on 6 July produced the highest fresh kernel yield with the black plastic mulch (12,893 kg·ha−1) and unmulched weeded control (11,777 kg·ha−1) in 2010 and 2011, respectively. The highest percentage of unfilled ear tips in both years was observed in the unmulched unweeded plots sown on 5 June. According to our findings, to suppress the weeds and avoid the sweet corn yield loss in such a hot summer that we had, using the black plastic mulch and delayed sowing are recommended.