Cadmium (Cd) and lead (Pb) are recognized as the most toxic metal ions due to their detrimental effects not only to plants, but also to humans. The objective of this study was to investigate the effects of Cd and Pb treatments on seed germination, plant growth, and physiological response in tall fescue (Festuca arundinacea Schreb.). We employed six treatments: CK (nutrient solution as control), T1 (1000 mg L-1 Pb), T2 (50 mg L-1 Cd), T3 (150 mg L-1 Cd), T4 (1000 mg L-1 Pb+50 mg L-1 Cd), T5 (1000 mg L-1 Pb+150 mg L-1 Cd). Antagonistic and synergistic actions were observed in tall fescue under Pb and Cd combined treatments. Under low Cd, plants exhibited higher relative germination rate, germ length, VSGR, catalase (CAT) and peroxidase (POD) activities. Additionally, in the shoots, the gene expression level of Cu/Zn SOD, FeSOD, POD, GPX, translocation factors, MDA, EL, and soluble protein contents were reduced under Pb stress. Conversely, under high Cd level, there was a decline in NRT, Pb content in shoots, Pb translocation factors, CAT activity; and an increase in VSGR, Pb content in roots, gene expression level of Cu/ZnSOD and POD in tall fescue exposed to Pb2+ regimes. On the other hand, tall fescue plants treated with low Cd exhibited lower relative germination rate, germination index, germ length, NRT, Cd content in roots. On the other hand there was higher Cd content, Cd translocation factor, CAT and POD activities, and gene expression level of Cu/Zn SOD, FeSOD, POD, GPX under Pb treatment compared with single Cd2+ treatment in the shoots. However, after high Cd exposure, plants displayed lower NRT, Cd content, CAT activity, and exhibited higher Cd contents, Cd translocation factor, MDA content, gene expression level of Cu/ZnSOD and GPX with the presence of Pb2+ relative to single Cd2+ treatment. These findings lead to a conclusion that the presence of low Cd level impacted positively towards tall fescue growth under Pb stress, while high level of Cd impacted negatively. In summary, antioxidant enzymes responded to Cd and Pb interaction at an early stage of exposure, and their gene expression profiles provided more details of the activation of those systems.
Abstract In order to validate whether optimizing irrigation and fertilization can improve degraded saline soil and increase wheat production, a 4‐year wheat field experiment on saline soil in the Yellow River Delta of China was conducted from October 2013 to June 2017. Eight optimizing treatments including two irrigation applcations of 90 (I90) and 135 (I135) mm/time, four irrigation times: at pre‐sowing, wintering, jointing, filling stages, and two fertilizer rates 225 kg N hm −2 ‐75 P 2 O 5 hm −2 ‐150 K 2 O hm −2 (F312), 225 kg N hm −2 ‐150 P 2 O 5 hm −2 ‐75 K 2 O hm −2 (F321) with two basal/topdressing ratios 1:1 (A11) and 1:2 (A12) were designed compared with no‐irrigation and fertilization (CK) and farmer mode (CM). The optimizing treatment combined I135 with F321 and A12 was the optimal practice for wheat production on degraded saline soil in this region. This treatment significantly decreased topsoil salinity on average by 21.97%, increased wheat grain yield, topsoil total N, available P and K, respectively, by an average of 0.74‐, 0.75‐, 1.13‐ and 0.78‐times, improved water utilization efficiency, water productive efficiency, nitrogen utilization efficiency, phosphorus utilization efficiency, respectively, by average of 1.26‐, 8.13‐, 0.32‐, 0.43‐times compared with the CM. These results demonstrate that the optimization of irrigation and fertilization can be extensively applied as a feasible and effective strategy to improve degraded saline soil, maintain soil nutrients, maximize crop yield, and enhance efficiency in other similar degraded saline soil areas of the world.
Abstract Straw returning effectively promotes the soil organic carbon (SOC) pool, but the straw‐induced change in SOC quality (C fraction) remains unclear, particularly in saline soil. Here, we investigated how straw returning and soil salinity (low, medium, and high) affect SOC fractions, including easily oxidized and particulate organic C (EOC and POC) and mineral‐associated organic C (MOC) at aggregate scales, including macroaggregates (MA), microaggregates (MI), and silt + clay particles. The results revealed that SOC fraction contents in the whole soil decreased with increasing soil salinity, and straw returning increased the total organic C (TOC) in both low‐ and medium‐salinity soils. In low‐salinity soil, straw returning induced decreases of 12.1% and 30.6% in MI‐associated EOC and POC, respectively, and promoted significant increases of MI‐associated MOC, indicating that 'hierarchical aggregation' theory (i.e., single soil particles gradually form clusters, MI and MA) dominated during soil aggregate formation. In medium‐salinity soil, straw application increased all SOC fraction contents in MA, and raised the POC/TOC of the whole soil by 56.6%, suggesting that the 'macroaggregate turnover' theory (MI is formed within MA) played a more important role in forming aggregates. Our results demonstrated that low‐ and medium‐salinity soils had different C‐increasing strategies under straw returning: MA contributed more to the increased SOC than MI in low‐salinity soil, whereas the reverse was true in medium‐salinity soil. These findings suggest that higher soil salinity would weaken the C sequestration potential of straw returning, and that targeted measures should be applied to enhance reclamation efficiency.
Abstract A high geological background can increase the ecological and health risks associated with crop production; therefore, it is essential to assess the heavy metals and their impact. In this study, ecological and health risk impacts of heavy metal contamination, in combination with positive matrix factorization was assessed for an area with high geological background with wheat–maize cropping system, to provide a quantitative understanding of the effects of heavy metals, enabling its prevention and control. This study revealed that the comprehensive ecological risk ( RI wheat–maize ) is 56.21 (low), with industries being the biggest contributors (34.22%). Comprehensive health risk (non-carcinogenic) assessment showed that industrial (40.98–49.30%) and natural (23.96–37.64%) factors were the primary (particularly of Cd and Zn) and secondary (particularly of Cr and Ni) contributors, respectively in eastern China. Comprehensive health risk ( HI wheat–maize ) for children and adults were 0.74 and 0.42, respectively, indicating that non-carcinogenic risks were at an acceptable level. Soil ingestion was the primary pathway for health risks (62.23–73.00%), especially for children. Based on soil heavy metal sources and crop systems, source-ecological risk assessment and source-health risk assessment were used to provided valuable insights on making strategies to protect human health in high geological background areas.
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