Tahir Abbas Khan

Arsenic (As) contamination has significantly increased in recent decades due to anthropogenic activities. This is a serious challenge for human health, environmental quality, and crop productivity. Biochar (BC) is an important practice used globally to remediate polluted soils. Likewise, melatonin (MT) has also shown tremendous results in mitigating metal toxicity and improving crop productivity. Nevertheless, the mechanism of combined BC and MT in alleviating As toxicity in rice (Oryza sativa L.) remains unexplored. In this study, we investigated how As affected rice and how the combined BC and MT facilitated As tolerance. The study comprised a control, As stress (100 mg kg⁻¹), As stress (100 mg kg⁻¹) + BC (2%), As stress (100 mg kg⁻¹) + MT (100 µM) and As stress (100 mg kg⁻¹) + BC (2%) + MT (100 µM). Arsenic significantly decreased rice growth and yield by increasing electrolyte leakage (EL), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂). Co-applying BC and MT substantially enhanced rice growth and yield by increasing chlorophyll synthesis (48.12–92.42%) leaf water contents (40%), antioxidant activities (ascorbate peroxide: 56.43%, catalase: 55.14%, peroxidase: 57.77% and superoxide dismutase: 57.52%), proline synthesis (41.35%), MT synthesis (91.53%), and phytochelatins synthesis (125%) nutrient accumulation in rice seedlings and soil nutrient availability. The increased rice yield with BC + MT was also linked with reduced H₂O₂ production, As accumulation, soil As availability, and an increase in OsAPx6, OsCAT, OsPOD, OsSOD OsASMT1, and OsASMT2 and a decrease in expression of OsABCC1. Biochar + MT enhanced residual OM- and Fe, ((Fe₂As) and Mn (Mn₃(AsO₄)₂) bound forms of As leading to a substantial increase in rice growth and yield. Thus, the combination of BC and MT is an eco-friendly approach to mitigate As toxicity and improve rice productivity.

Salinity is a serious abiotic stress that limits crop production and food security. Micronutrient application has shown promising results in mitigating the toxic impacts of salinity. This study assessed the impacts of zinc seed priming (ZSP) on the germination, growth, physiological and biochemical functioning of sorghum cultivars. The study comprised sorghum cultivars (JS-2002 and JS-263), salinity stress (control (0 mM) and 120 mM)), and control and ZSP (4 mM). Salinity stress reduced germination and seedling growth by increasing electrolyte leakage (EL: 60.65%), hydrogen peroxide (H₂O₂: 109.50%), malondialdehyde (MDA; 115.30%), sodium (Na), and chloride (Cl) accumulation and decreasing chlorophyll synthesis, relative water contents (RWC), total soluble proteins (TSPs), and potassium (K) uptake and accumulation. Nonetheless, ZSP mitigated the deleterious impacts of salinity and led to faster germination and better seedling growth. Zinc seed priming improved the chlorophyll synthesis, leaf water contents, antioxidant activities (ascorbate peroxide: APX, catalase: CAT, peroxidase: POD, superoxide dismutase: SOD), TSPs, proline, K uptake and accumulation, and reduced EL, MDA, and H₂O₂ production, as well as the accumulation of toxic ions (Na and Cl), thereby promoting better germination and growth. Thus, these findings suggested that ZSP can mitigate the toxicity of salinity by favoring nutrient homeostasis, antioxidant activities, chlorophyll synthesis, osmolyte accumulation, and maintaining leaf water status.

Agriculture is a major source of greenhouse gas (GHG) emissions. Biochar has been recommended as a potential strategy to mitigate GHG emissions and improve soil fertility and crop productivity. However, few studies have investigated the potential of biochar co-compost (BCC) in relation to soil properties, rice productivity, and GHG emissions. Therefore, we examined the potential of BC, compost (CP), and BCC in terms of environmental and agronomic benefits. The study comprised four different treatments: control, biochar, compost, and biochar co-compost. The application of all of the treatments increased the soil pH; however, BC and BCC remained the top performers. The addition of BC and BBC also limited the ammonium nitrogen (NH₄⁺-N) availability and increased soil organic carbon (SOC), which limited the GHG emissions. Biochar co-compost resulted in fewer carbon dioxide (CO₂) emissions, while BC resulted in fewer methane (CH₄) emissions, which was comparable with BCC. Moreover, BC caused a marked reduction in nitrous oxide (N₂O) emissions that was comparable to BCC. This reduction was attributed to increased soil pH, nosZ, and nirK abundance and a reduction in ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) abundance. The application of different amendments, particularly BCC, favored rice growth and productivity by increasing nutrient availability, soil carbon, and enzymatic activities. Lastly, BCC and BC also increased the abundance and diversity of soil bacteria, which favored plant growth and caused a reduction in GHG emissions. Our results suggest that BCC could be an important practice to recycle organic sources while optimizing climate change and crop productivity.

Cadmium (Cd), as the most prevalent heavy metal contaminant poses serious risks to plants, humans, and the environment. The ubiquity of this toxic metal is continuously increasing due to the rapid discharge of industrial and mining effluents and the excessive use of chemical fertilizers. Nanoparticles (NPs) have emerged as a novel strategy to alleviate Cd toxicity. Zinc oxide nanoparticles (ZnO-NPs) have become the most important NPs used to mitigate the toxicity of abiotic stresses and improve crop productivity. The plants quickly absorb Cd, which subsequently disrupts plant physiological and biochemical processes and increases the production of reactive oxygen species (ROS), which causes the oxidation of cellular structures and significant growth losses. Besides this, Cd toxicity also disrupts leaf osmotic pressure, nutrient uptake, membrane stability, chlorophyll synthesis, and enzyme activities, leading to a serious reduction in growth and biomass productivity. Though plants possess an excellent defense mechanism to counteract Cd toxicity, this is not enough to counter higher concentrations of Cd toxicity. Applying Zn-NPs has proven to have significant potential in mitigating the toxic effects of Cd. ZnO-NPs improve chlorophyll synthesis, photosynthetic efficiency, membrane stability, nutrient uptake, and gene expression, which can help to counter toxic effects of Cd stress. Additionally, ZnO-NPs also help to reduce Cd absorption and accumulation in plants, and the complex relationship between ZnO-NPs, osmolytes, hormones, and secondary metabolites plays an important role in Cd tolerance. Thus, this review concentrates on exploring the diverse mechanisms by which ZnO nanoparticles can alleviate Cd toxicity in plants. In the end, this review has identified various research gaps that need addressing to ensure the promising future of ZnO-NPs in mitigating Cd toxicity. The findings of this review contribute to gaining a deeper understanding of the role of ZnO-NPs in combating Cd toxicity to promote safer and sustainable crop production by remediating Cd-polluted soils. This also allows for the development of eco-friendly approaches to remediate Cd-polluted soils to improve soil fertility and environmental quality.

Winter cropping is widely considered as an effective way to increase rice yield. Therefore, this study was performed to find optimal winter cropping patterns in middle and lower reaches of the Yangtze River, China. Five experimental treatments were set up based on the long-term field experiment including winter fallow (CK), Chinese milk vetch winter cropping pattern (CRR), rapeseed winter cropping pattern (RRR), garlic winter cropping pattern (GRR), and winter multiple cropping rotation (ROT). The effects of different winter cropping patterns on the yield, dry matter accumulation and translocation, and plant nitrogen uptake were explored in double-cropping rice. The results showed that compared with CK, winter cropping increased the early and late rice yield by 7.91-10.70% and 3.57-6.89%, respectively. Similarly, compared with CK, winter cropping patterns also increased the number of spikes in early rice by 19.36-25.81% and CRR and ROT increased the effective number of spikes in late rice by 25.58% and 23.26% respectively. The dry matter (DM) translocation by stem and leaf of early rice under CRR was highest, with a 36.2% increase compared with CK, however, DM accumulation after heading in early rice under CRR was lowest. GRR decreased the dry matter translocation by stem and leaf in early rice but increased DM accumulation after heading in early and late rice by 65.28% and 13.44% as compared to CK. Moreover, ROT increased the dry matter translocation by stem and leaf in late rice by 112.63%. Additionally, GRR and ROT treatments increased the stem nitrogen uptake in early rice by 61.76% and 58.61% as compared to control, while CRR increased the nitrogen uptake by stem, leave and spike in late rice by 40.76%, 49.51% and 42.92%. In conclusion, CRR is more beneficial to increase DM accumulation and translocation by stem and leaf in double-cropping rice, and nitrogen uptake by rice plants.

| Phosphorus (P) is an imperious nutrient necessary for plants growth and development. Similarly, cultivars also differed significantly in terms of growth, yield and P utilization. Therefore, present study was performed to assess P efficient maize genotypes on the basis of growth and yield. The study was comprised different maize genotypes; CS-2Y10, KSC-SB 9663, FH-949, 30Y87, NT-6621 and DK-6789 and of diverse P levels; control (No P), 40 and 80 kg P ha -1 . The maximum root length (RL), shoot length (SL) and root and shoot biomass was noted with 80 kg P ha -1 and lowest RL, SL and root and shoot biomass was recorded in control. In case of cultivars FH-949 performed well with maximum RL and SL and root and shoot biomass while NT-6621 performed poorly with minimum RL and SL and root and shoot biomass. Similarly, maximum plant height (199.83 cm), leaves per plant (LPP) (12.15), cob weight (0.209 kg), cob length (17.27 cm), grains/cob (441.06), thousand grain weight (TGW) (279.33 g) and grain yield (GY) (6.49 t ha -1 ) was noted with application of 80 kg/ha P and lowest plant height (174.39 cm), LPP (10.09), cob weight (0.187 kg), cob length (11.99 cm), grains/cob (300), TGW (181.67 g) and GY (4.31 t ha -1 ) was recorded in control. Similarly, among cultivars maximum plant height (201.11 cm), LPP (12.86), cob weight (0.217 kg), cob length (17.32 cm), grains/cob (417.67), TGW (263.33 g) and GY (6.17 t ha -1 ) and minimum plant height (172.11 cm), LPP (10.50), cob length (12.30 cm), grains/cob (347.89), TGW (195.11 g) and GY (4.37 t ha -1 ) was recorded in NT-6621. In conclusion application of 80 kg/ha P is recommended to significantly increase the growth and productivity of maize crop. Moreover, cultivars FH-949 was emerged as a most efficient uses of P and it can also be used in breeding programs to develop the P efficient cultivars.