The application of biochar to improve the quality of saline soils has attracted widespread attention. However, the impact of saline soil amendments with biochar prepared at different pyrolysis temperatures remains unclear. Therefore, we conducted a two-year (2022–2023) field experiment in the Hetao Irrigation District, China, to evaluate the effects of the biochar pyrolysis temperature (C1: 300 °C, C2: 500 °C, and C3: 700 °C) and application rate (T1: 10 t/ha and T2: 20 t/ha) on the soil quality and maize yield. The results indicated that (1) all biochar treatments significantly decreased the soil bulk density and increased the soil porosity; (2) treatment C3T1 significantly increased the soil moisture content and decreased soil salinity. The C3T2 treatment significantly increased the soil’s organic carbon content, and the soil’s available phosphorus content was greatest in the C1T2 treatment. (3) The maize yield increased linearly with the soil quality index (SQI), which was attributed mainly to improvements in the soil water–salt conditions and increases in the soil organic carbon content. In summary, biochar produced at high pyrolysis temperatures, when applied at a low application rate (C3T1), can result in high corn yields and improve saline soil quality.

The combined application of manure and mineral fertilizer represents an effective strategy for enhancing crop yield. However, the relationship between soil fertility and crop yield remains unclear in saline-alkaline soil. Here, a 9-year field experiment (2015–2023) was conducted to investigate the effects of manure application and crop rotations on crop yield and economic efficiency as well as potential associated mechanisms in the Hetao Irrigation District. The results showed that in the third cropping rotation cycle, combined application of manure and mineral fertilizers (NPKO) caused a 6.2%, 38.9%, 65.3%, and 132.2% increase in wheat, sunflower, wheat equivalent yield, and the economic income of sunflower, respectively. The average grain yield had a positive correlation with soil organic matter and nutrient supply. This suggested that the soil organic matter had a positive effect on the crop yield due to its impact on nutrient supply. Simultaneously, the sunflower seed setting rate increased by 65.2% under NPKO. The linear regression model revealed that each additional input of 20 Mg ha⁻¹ of manure resulted in an increase of 3.56 kg ha⁻¹ in crop phosphorus harvest and a 0.05 Kg ha⁻¹ increase in wheat equivalent yield compared to NPK. In conclusion, our results highlighted that manure application promotes soil properties and improves crop yield.

A sustainable model of combined organic–inorganic fertilizer application for high maize yields and environmental health is important for food security. The short-term combined application of organic and inorganic fertilizers can improve crop yields; however, the effect of different proportions of organic and inorganic fertilizers on the maize yield and nitrogen gas emissions in a long time series has not been reported. In this study, field experiments and DeNitrification-DeComposition (DNDC) model simulations were used to study the long-term effects of substituting inorganic fertilizers with organic fertilizers on crop yields and nitrogen-containing gas emissions. Six treatments were included: no nitrogen (CK); urea (U1); and 25%, 50%, 75%, and 100% of the urea N substituted by organic fertilizers (U3O1, U1O1, U1O3, and O1, respectively). The DNDC model was calibrated using the field data from the U1 treatment from 2018 to 2020 and was validated for the other treatments. The results showed that this model could effectively simulate crop yields (e.g., nRMSE < 5%), soil NH₃ volatilization, and N₂O emissions (nRMSE < 25%). In addition, long-term (26 years) simulation studies found that the U1O1 treatment could considerably increase maize yields and ensure yield stability, which was 15.69–55.31% higher than that of the U1 treatment. The N₂O, NH₃, and NO emissions were in the descending order of U1 > U3O1 > O1 > U1O3 > U1O1, and the total nitrogen-containing gas emissions from the U1O1 treatment decreased by 53.72% compared with the U1 treatment (26 years). Overall, substituting 50% of inorganic nitrogen with organic nitrogen could maintain the high yield of maize and reduce emissions of nitrogen-containing gases, constituting a good mode for the combined application of organic–inorganic nitrogen in this area.

Under conditions of continuous global warming, research into the future change trends of regional dry-wet climates is key for coping with and adapting to climate change, and is also an important topic in the field of climate change prediction. In this study, daily precipitation and mean temperature datasets under four representative concentrative pathway (RCP) scenarios in the geophysical fluid dynamics laboratory Earth system model with modular ocean model (GFDL-ESM2M) version 4 were used to calculate the standardized precipitation-evapotranspiration index of the Tibetan Plateau (TP) at different time scales. Using a multi-analytical approach including the Mann–Kendall trend test and run theory, the spatiotemporal variation characteristics of drought in the TP from 2016 to 2099 were studied. The results show that the overall future climate of the TP will develop towards warm and humid, and that the monthly-scale wet–dry changes will develop non-uniformly. As the concentration of carbon dioxide emissions increases in the future, the proportion of extremely significant aridification and humidification areas in the TP will significantly increase, and the possibility of extreme disasters will also increase. Moreover, influenced by the increase of annual TP precipitation, the annual scale of future drought in the region will tend to decrease slightly, and the spatial distributions of the frequency and intensity of droughts at all levels will develop uniformly. Under all four RCP scenarios, the drought duration of the TP was mainly less than 3 months, and the drought cycle in the southern region was longer than that in the northern region. The results of this study provide a new basis for the development of adaptive measures for the TP to cope with climate change.

The numerical simulation of the optimal design of gravity dams is computationally expensive. Therefore, a new optimization procedure is presented in this study to reduce the computational cost for determining the optimal shape of a gravity dam. Optimization was performed using a combination of the genetic algorithm (GA) and an updated Kriging surrogate model (UKSM). First, a Kriging surrogate model (KSM) was constructed with a small sample set. Second, the minimizing the predictor strategy was used to add samples in the region of interest to update the KSM in each updating cycle until the optimization process converged. Third, an existing gravity dam was used to demonstrate the effectiveness of the GA–UKSM. The solution obtained with the GA–UKSM was compared with that obtained using the GA–KSM. The results revealed that the GA–UKSM required only 7.53% of the total number of numerical simulations required by the GA–KSM to achieve similar optimization results. Thus, the GA–UKSM can significantly improve the computational efficiency. The method adopted in this study can be used as a reference for the optimization of the design of gravity dams.

Exploring the biological potential of maize root architecture is one of the most important ways to improve nitrogen use efficiency (NUE). The NUE and its heterosis in maize hybrids have improved remarkably over decades. Yet, there is little research on maize hybrid heterosis for root architecture and its possible physiological relationship to heterosis for NUE. A field study lasting two years was carried out on four typical maize hybrids from old and new eras, including their parental inbred lines with two levels of nitrogen (0, 150 kg N ha⁻¹). Compared to old-era maize hybrids, the brace root angle (BA) and crown root angle (CA) of new-era maize hybrids increased by 19.3% and 8.0% under 0 N, and by 18.8% and 7.9% under 150 N, which exhibited a steeper root architecture; the crown root number (CN) of new-era maize hybrids increased by 30.5% and 21.4% under 0 N and 150 N, respectively, which showed a denser root system; meanwhile, the depth of 95% cumulative root weight (D₉₅) of new-era maize hybrids separately increased by 10.5% and 8.5% under 0 N and 150 N, which exhibited a deeper root distribution. This steeper-denser-deeper root architecture enhanced pre-anthesis N uptake and provided a premise of greater post-anthesis N remobilization. All maize hybrids displayed significant heterosis for root architecture compared to their parental inbred lines. The brace root branching (BB) and crown root branching (CB) of new-era maize hybrids and D₉₅ have positive heterosis, while the BA, CA, and CB of old-era maize hybrids, brace root number (BN), and CN have negative heterosis. Regardless of whether root architecture heterosis was positive or negative, new-era maize hybrids showed an overall elevated trend compared to old-era maize hybrids. Structural equation modeling (SEM) showed that heterosis for nitrogen internal efficiency (NIE) was the primary reason for NUE heterosis in maize, influenced by heterosis for root architecture, which was steeper, denser, and deeper. Our results indicated that, compared with old-era maize hybrids, new-era maize hybrids had stronger heterosis for root architecture, which was beneficial to pre-silking nitrogen absorption and is an important physiological basis for the higher NIE heterosis and NUE heterosis in new-era maize hybrids.