A low amount of organic matter and insufficient irrigation are two main challenges facing successful crop production in arid and semiarid regions. Application of biochar as an organic amendment to soil not only can help increase organic matter in soil, but also may alleviate adverse effects of water deficit on plant growth and yield production. To test this hypothesis, a two-year field experiment was conducted to assess the effect of sugarcane biochar on yield and yield components of cowpea in water-deficient soil. Treatments consisted of two levels of seed treatment with nitroxin, three levels of biochar application (0, 4, and 8 ton/ha), and a threelevel irrigation regime (60, 90, and 120 mm from evaporation pan class A), laid out in a split-factorial design. Results showed that the seed number per plant was significantly higher in cowpea when grown with biochar, possibly due to the relief of water-deficient stress and higher phosphorus and potassium content. Biomass production of cowpea declined under a severe waterdeficit condition (ir3) compared to normal irrigation (ir1) in 2018 and 2019, decreasing by 39% and 42%, respectively. The maximum biomass obtained from application of 8 ton/ha biochar reached 617.43 and 664.92 g/m2 in 2018 and 2019, respectively. Seeds treated with nitroxin exhibited 10% and 8% greater biomass production in 2018 and 2019 as compared with control treatments. Seed yield increased with the addition of biochar to soil under all irrigation regimes; however, the maximum seed yield of 266.46 and 275.36 g/m2 was observed when there was no water-deficient stress condition and application of 8 ton/ha biochar in 2018 and 2019, respectively.

The adverse effects of abiotic stresses have always restricted oilseed crop production, particularly in arid and semi-arid regions. On the other side, global climate change has led us to adapt planting dates and select tolerant cultivars to encounter the new climatic conditions. To evaluate the effect of late-season drought stress under different planting dates on rapeseed cultivars, an experiment was conducted as a factorial split-plot based on randomized complete block design in Karaj region- Iran, during 2015-2017. Planting date and irrigation treatments were considered in the main plots as factorial and cultivars were placed in subplots. Two planting dates were regular date (October 7) (PD1) and late planting date (November 6) (PD2). Irrigation was also carried out at two levels of normal irrigation (NI) and irrigation interruption from flowering stage onwards (II). Experimental cultivars included ES Hydromel, ES Alonso, ES Darko, ES Lauren, and Ahmadi. According to the results, late-season drought stress and delayed planting date reduced leaf relative water content (LRWC), total chlorophyll content (TCC), proline (LPC), and grain yield (GY), and increased stomatal resistance (SR), canopy temperature (CT), and leaf soluble carbohydrates (CLS) in rapeseed cultivars. The highest grain yield (4505.6 kg ha-1) was obtained in NI conditions and PD1. Significant interactions of planting date, irrigation, and cultivar on LRWC, SR, and CLS traits indicated that the ES Hydromel was the most tolerant hybrid cultivar with the highest LRWC and the lowest SR and CLS levels compared to other ones in unfavorable conditions of late-season drought stress and delayed planting. To confirm these results, cluster analysis led to the formation of two clusters, where ES Darko, Ahmadi, and ES Lauren cultivars were placed in the sensitive cluster and ES Hydromel and ES Alonso cultivars were assigned to the tolerant cluster. Therefore, ES Hydromel can be introduced as a superior cultivar to be selected as a genotype that presents acceptable resistance under drought stress and late sowing in arid and semi-arid regions.

The introduction of new genotypes of crop plants is among the most strategic research programmes, especially in arid and semi-arid regions. To study the effect of drought stress on seed yield and some physiological traits of promising lines of rapeseed at different sowing dates, an experiment was conducted for two years (2015-2017) in a semi-arid region of Iran. In this research, two conventional sowing dates were set in October 12 and November 1 (late sowing). Irrigation was carried out at two levels: normal irrigation (control) and irrigation interruption from the silique formation stage to the next stage (late-season drought stress). The genotypes included four promising lines (L1112, L1091, L1093, L1206), and a cultivar (Okapi) as a control. Results showed that delayed sowing and drought stress increased carbohydrate content and decreased seed yield, with the highest carbohydrate content and highest yield loss in L1112 and the lowest carbohydrate and lowest yield loss in the L1206 line. Among the physiological traits measured, stomatal resistance had the highest degree of correlation and the highest direct negative effect on seed yield, which declined with increasing stomatal resistance. L1112 had the highest stomatal resistance (52.76 s cm-1) in delayed sowing and drought stress conditions. Therefore, L1206 and L1112 were revealed to be resistant and sensitive lines, respectively.

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The first risk posed by heavy metal pollution in an ecosystem is metal accumulation in the biomass of growing plants, which has harmful effects on human health. Natural-based nanoparticles are efficient in remediating environmental pollutants because they have a high surface/volume ratio, high chemical activity and produce no harmful side-products. The present study investigates the capacity of natural-based nano-porous adsorbents for reducing the availability of heavy metals to annual alfalfa (Medicago scutellata L.) roots and keeps them in soil. In a factorial experiment based on a randomized design (with four replications), three nano-adsorbents (nano-activated carbon, natural nano-zeolite and modified nano-zeolite) and two heavy metals (lead and cadmium) have been tested. The results demonstrated that applying the highest rate of activated carbon and modified nano-zeolite reduced shoot Pb content by 34% and 33.2%, and shoot Cd content by 35.5% and 46.7%, respectively, compared with the adsorbent-free control.   ********* In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 4, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue. *********

Microelements are inorganic compounds involved in the synthesis of enzymes and biologically active substances. To evaluate the physiological responses of maize to ZnSO4 and FeSO4 under drought stress, a field experiment was conducted on maize plants grown under different soil moistures and treated with foliar ZnSO4 and FeSO4 applications. Drought stress especially at early seed growth stage significantly reduced grain yield and Fv/Fm ratio; however, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione reductase (GR) was enhanced under drought stress. Foliar applied ZnSO4 and FeSO4 boosted the grain yield under non irrigation at vegetative growth stage and at early seed growth stage, respectively.  Between grain yield and MDA concentration (r=­ -0.73), superoxide dismutase (r= -0.57), peroxidase (r= -0.49), H2O2 (r= -0.67) and catalase enzyme (r= -0.42) significant and negative correlation were observed. Combined application of ZnSO4 and FeSO4 resulted in alleviation of maize plant drought stress by Zn and Fe-mediated improvement in photosynthetic attributes. In addition, the foliar application of ZnSO4 and FeSO4 regulated physiological processes in maize plants and alleviated the adverse effects of water stress. According to the results, ZnSO4 and FeSO4 could be used for improving maize growth under drought stress.

Climate change and water scarcity are among the significant limited factors to constrain the production and development of oilseed crops, especially rapeseed (Brassica napus L.), in arid and semi-arid areas. The effects of drought stress and late-sowing on the grain yield and oil quality of rapeseed were studied by conducting a factorial split-plot experiment as a randomized complete block design with three replications for two years (2015-2017) in Karaj, Iran. Irrigation and sowing date treatments were considered in the main plots as factorial, and cultivars were placed in subplots. Two sowing dates were the regular date (October 7th) and the late-sowing date (November 6th). Irrigation was also carried out at two levels of normal irrigation and irrigation interruption from the flowering stage onwards. Experimental cultivars included ES Hydromel, ES Alonso, ES Darko, ES Lauren, and Ahmadi. The highest grain yield (4505.6 kg ha-1) was obtained on the regular date, and the normal irrigation. ES Hydromel had the best quality of oil and grain meal due to the highest percentage of palmitic acid (4.44%) under late cultivation and drought stress and the lowest glucosinolates (23.19 µmol g-1 DW) content under late cultivation. Therefore, the ES Hydromel hybrid cultivar was more successful in optimal use of water resources in the face of water scarcity and late-planting in arid and semi-arid regions.

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