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Heavy metals are among the major environmental pollutants and the accumulation of these metals in soils is of great concern in agricultural production due to the toxic effects on crop growth and food quality. Phytoremediation is a promising technique which is being considered as an alternative and low-cost technology for the remediation of metal-contaminated soils. Solanum nigrum is widely studied for the remediation of heavy metal-contaminated soils owing to its ability for metal uptake and tolerance. S. nigrum can tolerate excess amount of certain metals through different mechanism including enhancing the activities of antioxidant enzymes and metal deposition in non-active parts of the plant. An overview of heavy metal uptake and tolerance in S. nigrum is given. Both endophytic and soil microorganisms can play a role in enhancing metal tolerance in S. nigrum . Additionally, optimization of soil management practices and exogenous application of amendments can also be used to enhance metal uptake and tolerance in this plant. The main objective of the present review is to highlight and discuss the recent progresses in using S. nigrum for remediation of metal contaminated soils. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutumL.) is a well-known and economically most beneficial crop worldwide while nickel (Ni) toxicity is a widespread problem in crops grown on Ni-contaminated soils. We investigated the response of silicon (Si) in cotton under Ni stress with respect to growth, biomass, gas exchange attributes, enzymatic activities, and Ni uptake and accumulation. For this, plants were grown in hydroponics for 12 weeks with three levels of Ni (0, 50, and 100 µM) in the presence or absence of 1 mM Si. Results showed that Ni significantly reduced the plant growth, biomass, gas exchange attributes, and pigment contents while Si application mitigated these adverse effects under Ni stress. Nickel stress significantly decreased antioxidant enzymes’ activities while increased malondialdehyde (MDA), hydrogen peroxide (H2O2), and electrolyte leakage (EC) in leaves and roots. The application of Si enhanced the activities of antioxidant enzymes and reduced MDA, H2O2, and EC in plants. Nickel application significantly increased Ni concentration and accumulation in leaf, stem, and roots while Si application significantly decreased Ni in these plant parts. The present study indicates that Si could improve cotton growth under Ni stress by lowering Ni uptake and reactive oxygen species (ROS) and by increasing antioxidant enzymes activities. [ABSTRACT FROM AUTHOR]

Silicon (Si) is as an important fertilizer element, which has been found effective in enhancing plant tolerance to variety of biotic and a-biotic stresses. This study investigates the Si potential to alleviate zinc (Zn) toxicity stress in cotton ( Gossypium hirsutum L.). Cotton plants were grown in hydroponics and exposed to different Zn concentration, 0, 25, and 50 μM, alone and/or in combination with 1 mM Si. Incremental Zn concentration in growth media instigated the cellular oxidative damage that was evident from elevated levels of hydrogen peroxide (HO), electrolyte leakage, and malondialdehyde (MDA) and consequently inhibited cotton growth, biomass, chlorophyll pigments, and photosynthetic process. Application of Si significantly suppressed Zn accumulation in various plant parts, i.e., roots, stems, and leaves and thus promoted biomass, photosynthetic, growth parameters, and antioxidant enzymes activity of Zn-stressed as well unstressed plants. In addition, Si reduced the MDA and HO production and electrolyte leakage suggesting its role in protecting cotton plants from Zn toxicity-induced oxidative damage. Thus, the study indicated that exogenous Si application could improve growth and development of cotton crop experiencing Zn toxicity stress by limiting Zn bioavailability and oxidative damage. [ABSTRACT FROM AUTHOR]

Using an alkaline calcareous soil, experiments were conducted to elucidate the effects of nitrification inhibitor dicyandiamide (DCD) on the fate of N-labelled urea applied to cotton, maize, and wheat under greenhouse conditions. Combined effects of DCD and two levels of wheat straw (applied to cotton) and of fertilizer application method (conventional broadcast vs. point injection in maize and wheat) on the recovery of the fertilizer N were also studied. High soil temperatures prevailed under cotton and maize, whereas the soil temperature was relatively moderate during the wheat growing season. The fertilizer N loss under cotton was lowest (44% of the applied) when urea was applied alone; the loss increased due to DCD (54%) or wheat straw (50-54%) and was highest (63-64%) when DCD and wheat straw were applied together. Under maize also, DCD increased the loss of the fertilizer N applied by the conventional method (51% without DCD vs. 66% with DCD) or by point injection (26% without DCD vs. 42% with DCD). With the conventional method under wheat, DCD had no effect on the fertilizer N loss (34-37% of the applied). The fertilizer N loss under wheat was least (16%) when urea solution was point-injected but increased (24-26%) due to DCD or/and when pH of the urea solution was reduced to 2. Besides, DCD significantly reduced the fertilizer N uptake and increased the fertilizer N immobilization in soil under cotton and maize. However, DCD applied in combination with a higher level of wheat straw significantly increased the cotton dry matter and N yields due to increased N availability from sources other than the fertilizer. The results suggested that the use of DCD may not be beneficial in alkaline calcareous soils and that point injection of urea solution without any amendment is more effective in conserving the fertilizer N as compared to the conventional broadcast method. [ABSTRACT FROM AUTHOR]

Organic city wastes are recycled to prepare composts with improved physical properties and enriched with nutrients for their better utilization. Combined application of composts along with inorganic fertilizers may sustain crop productivity and soil fertility. Present study was conducted to assess the impact of 3 city waste composts (2 nonenriched and 1 enriched with 25% N requirement of crop) on the economical utilization of urea in wheat. Generally, fertilizer application along with compost increased the yield, N and P uptake by wheat compared to the fertilizer alone. Performance of the treatments was found in the order: NEC (nitrogen enriched compost) + fertilizer > nonenriched compost + fertilizer > fertilizer. The NEC along with lower fertilizer-N rate (75 mg kg-1 soil) was found at par with that of the highest fertilizer rate (175 mg N kg-1 soil) alone. The results showed that the use of NEC (200 mg kg-1 soil) for wheat production could be a useful tool to improve the efficiency of commercial N-fertilizer. [ABSTRACT FROM AUTHOR]

Wheat production in rainfed cropping systems is highly vulnerable to climate change, particularly in developing countries. Therefore, assessing the climate change impacts on rainfed wheat production is needed for ensuring global food security. Nitrogen (N) application has been reported to mitigate the impact of climate change on crop production, but its impact in rainfed cropping systems remains uncertain and/or rarely explored. Crop models have been commonly used for projecting the impacts of climate change on crop production. However, uncertainties from single-model simulation analyses call for multi-model simulation capabilities. Here, three models (APSIM-Wheat, CERES-Wheat, and Nwheat) were calibrated and evaluated for simulating phenology, agronomic traits, rainwater use efficiency (RWUE), and N use efficiencies under rainfed conditions in Pakistan. Five Global Circulation Models examined from 2041 to 2070 (RCP8.5) indicated an increase in mean growing temperature and changes in growing season rainfall between 1.6 and 4.9 ℃ and − 34 and + 39 %, respectively. Therefore, cool and dry, cool and wet, middle, hot and dry, and hot and wet projections were selected. All crop models successfully simulated the investigated parameters for different wheat cultivars and N application rates. APSIM-Wheat showed the best performance for validating the RWUE, plant N uptake, N utilization efficiency, and N uptake efficiency (NRMSE = 11.2–14.5 %), while CERES-Wheat performed well for grain yield and N use efficiency (NRMSE = 5.1–6.1 %). Nwheat showed a minimum average NRMSE for plant dry mass and harvest index (3.8–7.8%). All crop models predicted the maximum reduction in grain yield under hot and dry conditions. Compared to baseline, future climate change caused minimum and maximum grain yield reductions for Faisalabad-2008 (6 %) and AUR-809 (11 %), respectively, whereas, for N application rates, the minimum and maximum grain yield reductions were observed for N 0 (7 %), and N 140 (10 %), respectively. There were no significant differences in grain yield and RUWE across N application rates under future climate change. However, applying N from N 0 to N 70 significantly increases grain yield (82 %) and RWUE (77 %) across cultivars under future climate change. The findings would have valuable implications in tackling the negative impacts of future climate change on wheat production through the selection of suitable cultivars and formulating crop N management strategies for rainfed areas. • Performance of various crop-climate models was evaluated under rainfed conditions. • Future climate change jeopardizes wheat growth and development of rainfed wheat. • Selection of suitable cultivar can optimize wheat productivity under climate change. • Application of N can improve wheat productivity under future climate change. • Adaptation strategies are required to mitigate the negative effects of climate change. [ABSTRACT FROM AUTHOR]