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To ensure national food and ecological security in China, it is essential to develop various reserve resources for cultivated land based on existing farmland advantages. Owing to abundant saline-alkali land reserves, the Yellow River Delta has enormous potentials for agriculture development. However, water scarcity and imbalance between water and land resources allocation have significantly limited the efficient utilization of saline-alkali land in this region. According to the development status regarding salinealkali soil amelioration and crop production, this study analyzes water and land resource conditions, clarifies major challenges for the sustainable development of local agriculture from the perspectives of water resource supply, groundwater table regulation, management and utilization system of saline-alkali land, technological innovation, and follow-up engineering maintenance, and proposes strategies for efficient use and coordinated allocation of water and land resources in the region. The strategies include: (1) increasing water supply from the Yellow River and connecting the coastal hydrographic net to make optimal allocation of regional water resources; (2) improving irrigation and drainage systems and auxiliary projects to enhance the quality of arable lands; and (3) accelerating demonstration and promotion of key technologies for saline-alkali soil amelioration to fully leverage the supporting function of sciences and technologies. The research results can provide a reference for comprehensive governance and utilization of saline-alkali land and agricultural sustainable development.

Dynamics of vegetation in arid areas have drawn worldwide attention. The expansion of irrigated cropland (ICE) in arid regions contributes to increased food security and impacts on the extent and development of regional vegetation. However, the quantitative attribution of vegetation growth variation from ICE and biogeochemical factors (e.g., atmospheric CO2 concentration, climatic factors) is still lacking. Here, we assessed key drivers of vegetation growth in the inland arid region of Northwest China (IANC) from 1982 to 2018, including ICE, increased nitrogen rates, elevated atmospheric CO2 concentration (eCO2) and climate drivers, using normalized difference vegetation index (NDVI) and ecosystem gross primary productivity (GPP) as measures. These variables were quantified through trend decomposition, machine learning algorithms, and a satellite-based model. The results show that vegetation growth was increased in IANC mainly due to eCO2 and ICE. After 1995, as the regional climatic aridity intensified, the CO2 fertilization effect on vegetation growth decreased, as the atmospheric CO2 concentration continued to increase. Meanwhile, irrigated cropland area increased sharply, and ICE-driven GPP variation exceeded that driven by eCO2 in the whole region, while the ICE-driven NDVI variation exceeded that due to eCO2 when the ICE reached 6.38%. The ICE effect on regional vegetation growth rather than the CO2 fertilization effect has mitigated the slowdown of the rate of vegetation growth caused by climate changes. Although the ICE is conducive to food security and continuous greening of arid areas, further reclamation will exacerbate water scarcity. Our results provide research base for identifying the scale of sustainable agricultural development. Highlights: Vegetation growth was enhanced in Northwest China mainly due to the CO2 fertilization effect and irrigation expansion during 1982–2018. The effect of irrigation on vegetation growth approached or even outweighed that of elevated atmospheric CO2 concentration after 1995. The effect of irrigation expansion mitigates the slowdown of vegetation growth trend, instead of the CO2 fertilization effect. [ABSTRACT FROM AUTHOR]

BACKGROUND: Biochar addition strongly alters net carbon (C) balance in agroecosystems. However, the effects of biochar addition on net C balance of maize field under various irrigation water quantities and qualities remains unclear. Thus, a field experiment combining two irrigation levels of full (W1) and deficit irrigation (W2 = 1/2 W1), two water salinity levels of fresh (S0, 0.71 g L−1) and brackish water (S1, 4 g L−1), and two biochar addition rates of 0 t ha−1 (B0) and 60 t ha−1 (B1) was conducted to investigate soil carbon dioxide (CO2) emissions, maize C sequestration and C budget. RESULTS: Compared with W1, W2 reduced average cumulative CO2 emissions by 6.5% and 19.9% for 2020 and 2021, respectively. The average cumulative CO2 emissions under W1S1 treatments were 5.4% and 22.3% lower than W1S0 for 2020 and 2021, respectively, whereas W2S0 and W2S1 had similar cumulative CO2 emissions in both years. Biochar addition significantly increased cumulative CO2 emissions by 17.8–23.5% for all water and salt treatments in 2020, and reduced average cumulative CO2 emissions by 11.9% for W1 but enhanced it by 8.0% for W2 in 2021. Except for W2S1, biochar addition effectively increased total maize C sequestration by 6.9–14.8% for the other three treatments through ameliorating water and salt stress over the 2 years. Compared with W1S0, W1S1 did not affect net C sequestration, but W2 treatments significantly decreased it. Biochar addition increased net C sequestration by 39.47–43.65 t C ha−1 for four water and salt treatments for the 2 years. CONCLUSION: These findings demonstrate that biochar addition is an effective strategy to increase both crop C sequestration and soil C storage under suitable water‐saving irrigation methods in arid regions with limited freshwater resources. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Climate change presents a challenge for plants to acclimate their water relations under changing environmental conditions, and may increase the risks of hydraulic failure under stress. In this study, maize plants were acclimated to two different CO2 concentrations ([CO2]; 400 ppm and 700 ppm) while under either water stress (WS) or soil salinity (SS) treatments, and their growth and hydraulic traits were examined in detail. Both WS and SS inhibited growth and had significant impacts on hydraulic traits. In particular, the water potential at 50% loss of stem hydraulic conductance (P 50) decreased by 1 MPa in both treatments at 400 ppm. When subjected to elevated [CO2], the plants under both WS and SS showed improved growth by 7–23%. Elevated [CO2] also significantly increased xylem vulnerability (measured as loss of conductivity with decreasing xylem pressure), resulting in smaller hydraulic safety margins. According to the plant desiccation model, the critical desiccation degree (time×vapor pressure deficit) that the plants could tolerate under drought was reduced by 43–64% under elevated [CO2]. In addition, sensitivity analysis showed that P 50 was the most important trait in determining the critical desiccation degree. Thus, our results demonstrated that whilst elevated [CO2] benefited plant growth under WS or SS, it also interfered with hydraulic acclimation, thereby potentially placing the plants at a higher risk of hydraulic failure and increased mortality. [ABSTRACT FROM AUTHOR]