e bijanzadeh

In order to investigate the effect of deficit water stress and different combinations of relay intercropping of chickpea with barley on some biochemical traits and grain yield, a field experiment was conducted at College of Agriculture and Natural Resources of Darab, Shiraz University during 2017-2018 cropping season, as split plot based on a randomized complete block design with three replications. Treatments included two irrigation regimes (normal irrigation and cutting off irrigation at milk development stage) as main factor and the 6 combinations of cropping  systems consisted of cultivation of barley on December, barley on January, and different combinations of intercropping consisted of barley in December + chickpea in December, barley in December + chickpea in January, barley in January + chickpea in December, and barley in January + chickpea in January with a ratio of 1:1 as sub factor. Results showed that deficit water stress had significant effects on chlorophyll a, catalase and peroxidase activity, leaf relative water content (RWC) and contribution of current photoassimilates to the grain yield of barley and grain yield of chickpea. Under deficit water stress, barley grain yield had a positive correlation with leaf relative water content (R2=0.47)*. Also, under deficit water stress condition, the highest carotenoid content was obtained from intercropping of barley in December + chickpea in January. Since intercropping of barley in December + chickpea in January had the highest carotenoid content, remobilization efficiency, and contribution of current photoassimilates to the grain yield of barley and hence grain yield of barley (4215.7 kg/ha), it may be a suitable cultural strategy to be taken under late season deficit water stress conditions.

To remain viable in facing with increasing costs, farmers need to increase irrigation Water Productivity (WP) and save Virtual Water (VW). To evaluate the WP and VW for five barley cultivars (Reyhan, Nimrooz, Valfajr, Zehak, and Yusof) under different irrigation regimes [well-watered (100% Field Capacity; FC), mild water stress (75% FC), severe water stress (50% FC), and extremely severe water stress (25% FC)], a two-year field experiment was laid out in Darab, Fars Province, Iran, during 2014 and 2015 growing seasons. Results showed that change in moisture stress from well-watered to extremely severe water stress, was associated with a significant increase in WP and Economic Water Productivity (EWP) for straw and biological yield. A positive linear relationship was found between grain yield and VW, and the lowest VW was found in the range of 3,314 to 3,451 kg ha-1 of grain yield. Interestingly, for all irrigation regimes, Zehak and Yusof cultivars had greater WP for the grain yield. Furthermore, VW for biological yield of Yusof cultivar sharply decreased from 0.410 m3 kg-1 in well-watered treatment to 0.164 m3 kg-1 under extremely water stress conditions in both years. Comparison of Zehak and Yusof cultivars with Reyhan, Nimrooz and Valfajr showed that under water stress conditions, the first two cultivars showed significantly lower VW for the grain yield than the other cultivars. Indeed, Yusof and Zehak cultivars showed the lowest Economic Virtual Water (EVW), which was in the range of 0.054 to 0.091 m3 1,000 Rials-1, under extremely water stress conditions. Thus, to achieve optimum EWP and EVW and attaining stable yields under semi-arid conditions, suitable barley cultivars such as Zehak and Yusof could be irrigated with less water (i.e. 25 to 50% FC).

In the dry climate of southern Iran including Fars province, most precipitation occurs in winter, thus winter cereals such as triticale (Triticosecale Wittmack) experience water shortage at booting, flowering and grain filling stages in spring. The booting, flowering and grain filling periods are the most sensitive stages to water deficit. Nitrogen fertilizer application is a farmer’s common practice to increase yield, but its performance depends mainly on soil water status than the amount and timing of N applications. On the other hand, matching N fertilization with crop water availability is essential for achieving acceptable grain yield. Farmers of southern Iran use N fertilizer beyond the recommended rate. High N fertilizer application in dry areas that water availability limitations frequently occurred during the grain filling stage of cereals increased severity of water stress. Some authors reported that the silicon application reduces the destructive effects of drought stress by physiological, biochemical, and physical mechanisms (Hattori et al., 2005). Therefore, silicon foliar application may decrease water stress severity, especially in high N crops. Therefore, the aims of this study were to investigate the effects of silicon foliar application, different N rates and irrigation regimes on triticale yield in an arid area of southern Iran (Fars province).     

This research was conducted at the experimental farm of the Darab Agricultural Faculty of Shiraz University. A split factorial experiment in a randomized complete block design with three replications was carried out in the 2017-2018 growing season. Treatments included two levels of irrigation as the main plots [normal irrigation; irrigation based on the plant's water requirement up to the physiological maturity (IRN) and deficit irrigation; irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis) (IRDI)]. Also, sub plots were two levels of silicon foliar application [0, and 3 mM] and three N fertilizer levels [N0, no nitrogen fertilizer (control); N100, 100 kg N ha-1; N150, 150 kg N ha-1]. Biological yield, grain yield, yield components, plant height, spike length and chlorophyll index of flag leaf were measured. Then, the harvest index (HI) was calculated. Data were analyzed by using SAS 9.1 software (SAS Institute, 2004) and the means were compared using Duncan’s multiple range test at 5% probability level.

The results showed that the IRDI could cause severe water stress in the grain-filling period of the triticale life cycle and consequently reduction of 1000-grain weight, number of grains per spike and number of fertile tillers per m2. However, this reduction was more severe for 1000- grain weight than the other grain yield components and was not constant in different N fertilizer levels (18%, 21% and 36% reduction for N0, N100 and N150 kg N ha-1). Foliar silicon application decreased severity of late-season water stress and consequently improved 1000-seed weight, chlorophyll index, biological yield and finally HI and grain yield. With respect to grain yield, under IRN conditions, the highest grain yield was achieved by N150. Water stress decreased grain yield as a function of N fertilizer (24%, 26% and 46% reduction for N0, N100 and N150 kg N ha-1). Therefore, application of N100 could be acceptable for IRDI conditions.

According to the results of this study, the highest triticale grain yield (7098 kg ha-1) achieved by N150 in normal irrigation. The IRDI significantly decreased triticale grain yield at all N levels as compared with IRN. However, this reduction was different in N fertilizer rates (24%, 26% and 46% reduction for N0, N100 and N150). Therefore, the highest grain yield under IRDI conditions (4128 kg ha-1) was observed in N100. Therefore, with respect to environmental and economical considerations application of 100 and 150 kg N ha-1 were recommended for late-season water stress and normal irrigation conditions, respectively. Silicon foliar application decreased the severity of water stress and consequently increased grain yield (26%) under IRDI conditions. Therefore, the application of 3 mM of silicon at the anthesis stage is recommended for farms of triticale that expose to late-season water stress in southern Iran (Fars province).

Wheat is the most important crop in the world, which has always been of particular importance since its domestication and has the highest cultivated area among crops. Wheat is the main food of most people in many parts of the world. Among the factors that reduce wheat production, weeds are of particular importance and according to the studies; the average weed damage in wheat fields is 23%. Mixed cropping systems based on carefully designed species mixtures reveal many potential advantages in terms of enhancing crop productivity, reducing pest and weed interference. Recently, mixed cropping of wheat cultivars by different morphological characteristics is a suitable approach in increasing crop productivity especially under biotic stress conditions. This study aimed to investigate the effect of weed control on some biochemical traits, relative leaf water content and grain yield of mixed cropping of wheat cultivars.

In order to study the effect of weed control on biochemical traits and yield in mixed cropping of wheat cultivars, a field experiment was laid out as randomized complete block design with three replications in Research Station of Agriculture College and Natural Resources of Darab, Shiraz University, in 2018-2019 growing season. Experimental treatments consisted of six levels of weed control including weed control at tillering, stem elongation, booting and ear emergence stages, weed-free and weedy check and cropping system consisted of Sirvan monoculture, Setareh monoculture, and  mixed  row intercropping of Sirvan and Setareh which were in a ratio of  row one to one. The sowing date was 4th Dec in 2018 and harvest date was 19th Jun 2019. At late flowering stage, chlorophyll a and b content, carotenoid content, catalase and peroxidase activity, relative water content and weed biomass was measured. In addition, at physiological maturity grain yield were determined by one square meter quadrat.Finally, data were analyzed by SAS ver 9.1 software and the means were compared by LSD test at 5% probability levels.

The results showed that the simple effects of weed control and cropping system had significant effect on chlorophyll a and b, carotenoid content, catalase and peroxidase activity, relative water content, weed biomass and grain yield . The amount of chlorophyll a, carotenoid and relative water content of leaf, catalase and peroxidase in weed control at tillering stage were 64.2, 38.97, 31.4, 93.10 and 88%, respectively, compared to weedy check and these traits in mixed cropping increased by 5.2, 7.2, 12.8, 15.8 and 20.7%, compared to Setareh monoculture, respectively. Also, weed biomass in mixed cropping decreased by 29.6% compared to Setereh monoculture. The highest grain yield was observed in mixed cropping of Sirvan with Setereh which had  29.6% increase compared to Setareh monoculture and the best time to weed control was at the tillering stage because it had the lowest reduction in grain yield compared to weed free treatment.Overall, weed control at late-season especially at ear emergence would be less effective in crop productivity while weed control at early growth stages and before flowering provided the best crop performance in terms of photosynthetic pigments and grain yield.

It seems that mixed cropping of wheat cultivars could be effective in weed competition compared to monoculture, so that weed biomass in mixed cropping decreased especially at tillering and only 11.9% grain yield was reduced compared to weed-free control. Overall, when plants exposed to weed interference up to late growth stages, chlorophyll a and b content and carotenoid content decreased while catalase and peroxidase activity and weed biomass increased, significantly. Also, mixed cropping treatment weed interference increased catalase and peroxidase activities and relative water content and caused grain yield increasing compared to monoculture.

To identify the important features of triticale that contribute to improving grain and biomass Water Use Efficiency (WUEg and WUEb, respectively), grain yield, and Nitrogen (N) remobilization, a 2-year side-by-side experiment was carried out on triticale with different nitrogen sources and water regimes, in a typical Mediterranean environment of Iran. There were two levels of water regimes: Normal Irrigation (IRN) and irrigation cut off after anthesis stage (IRMD). Rain-fed treatment (IR0) was included in the second year. Four N sources including Azospirillum brasilense (Bio), Azospirillum brasilense+75 kg N ha-1 as urea (Bio+N75), 150 kg N ha-1 as urea (N150), and control unfertilized (N0) plots were used. This study showed that the highest grain yield (6,258 kg ha-1) was achieved by chemical N fertilizer application (N150) under IRN. In contrast, the application of Bio+N75 resulted in the highest grain yield as compared with the other N sources under IRMD (4,409 kg ha-1) and IR0 (2,960 kg ha-1) conditions. Water stress significantly increased WUEb at all N sources. However, WUEg slightly increased by IRMD and then sharply decreased by IR0 in all N sources, except N150 plots, where WUEg drastically decreased by water stress imposed by IRMD and IR0. The Bio+N75 treatment had the highest N remobilization. Although N remobilization was not affected by IRMD in dryer year, it increased by IRMD (8.4%) in the relatively wet year. Totally, for a more sustainable farming system in arid Mediterranean conditions, integration of biofertilizer and chemical N fertilizer could be successfully used for increasing grain yield, WUE, and N remobilization of triticale, especially under deficit irrigation regimes.

Inappropriate use of chemical inputs damages soil beneficial microorganisms and consumer health. In order to reduce or eventually eliminate chemical inputs, bio-agroecosystems was founded. Azospirillum is one of the most studied genera as nitrogen fixing bacteria in agroecosystems. About 70 percent of the experiments have demonstrated the Azospirilum ability for increasing crop yield. Furthermore, some studies have shown that Azospirilum has a stress-reduction mechanism. Therefore, it seems that the Azospirilum is a suitable microorganism for low yielding conditions (water and N) of southern Iran. On the contrary, with respect to the importance of soil organic matter for microorganisms survival, its deficiency in soils of southern Iran is the biggest challenge for using the microorganisms as biofertilizers. Also, experiments on the interactive effects of crop residue, water deficiency and N sources (biological or chemical) on barley yield are quite scarce in southern Iran. Therefore, the aims of this study were to investigate the effects of crop residue management, different N sources (such as biological and chemical) and water stress conditions on barley yield in arid conditions of southern Iran (Fars province).

This research was conducted at the experimental farm of the Darab Agricultural College of Shiraz University during the 2017-2018 growing season. A split factorial layout based on a randomized complete block design with three replications was used. Treatments included: two irrigation levels as the main plots [1. Normal (IRN): irrigation based on the plant's water requirement up to the physiological maturity and 2. Deficit irrigation (IRDI): irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis)]. Also, subplots were two levels of plant residues [1. without residue, 2. returning 30% of wheat residues to soil] and four fertilizer sources [N0, no nitrogen fertilizer (control) ;N100, 100 kg N ha-1; Bio + N50, Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1 and Bio, Biofertilizer (Azospirillum brasilense)]. Biological yield and grain yield, yield components, plant height, spike length and chlorophyll content of flag leaf were measured. Then, the harvest index was calculated. Data were analyzed by using SAS 9.1 software and the means were separated using Duncan’s multiple range test at 5% probability level.

The results showed that the cutting of irrigation after anthesis could cause severe water stress in the grain-filling period of the barley life cycle and consequently reduction of 1000-seed weight, the number of seeds per spike and the number of fertile tillers per m2. The interaction effect of irrigation regime × N fertilizer source on grain yield was significant at 1% probability level. The highest grain yield was achieved in IRN and Bio + N50 (4049 kg ha-1). Water stress reduced grain yield at all N fertilizer sources as compared with IRN. However, this reduction was different in N fertilizer sources (24.1%, 46.8%, 44.3% and 22.1% in N0, N100, Bio + N50 and Bio, respectively). With respect to the lowest amount of grain yield reduction due to water stress in Bio and then in N0 treatments and economic considerations, N0 treatment can be recommended for use in the cutting of irrigation after anthesis (IRDI) strategy.

According to the results of this study, the highest barley grain yield achieved by the integrated N fertilizer [Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1] in normal irrigation. Deficit irrigation after anthesis significantly decreased barley grain yield at all N sources. Therefore, this irrigation regime was not recommended for barley farms of southern Iran. But if farmers intend to the cutting of irrigation after anthesis because of water resources deficiency, with respect to the lack of significant difference among N sources in this condition, it is recommended that no N fertilizer is applied.