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Phosphogypsum-based materials have gained much attention in the field of road infrastructure from the economic and sustainable perspectives. The Three-point bending test, the Four-point bending test and the Semi-circular bending test are three typical test methods applied for fracture energy measurement. However, the optimal test method for fracture energy evaluation has not been determined for phosphogypsum-based materials. To contribute to the gap, this study aims to analyze and compare the three test methods for fracture energy evaluation of phosphogypsum materials based on the peridynamic theory. For this purpose, the load–displacement, vertical displacement–Crack Mouth Opening Displacement (CMOD) and fracture energy of the phosphogypsum-based materials were measured and calculated from the three test methods. The simulated load–displacement and vertical displacement–CMOD by PD numerical models, with different fracture energy as inputs, were compared to the corresponding tested values according to simulation error results. The results showed that the Four-point bending test led to minimized errors lower than 0.189 and indicators lower than 0.124, demonstrating the most optimal test method for the fracture energy measurement of phosphogypsum-based material. The results of this study can provide new methodological references for the selection of material fracture energy measurement tests. [ABSTRACT FROM AUTHOR]

Background and objective Rhizosphere is the interface of soil and plant housing a unique microbial community which not only mediates carbon and nutrient cycles but is also the underlying drivers of soil structure genesis. Soil microorganisms self-restructure following environmental change, which has a consequence for all biogeochemical processes. The purpose of this study is to investigate if and how dripping rate affects the microbial community of the rhizosphere of tomato drip-irrigated using reclaimed water. Method Pot experiment was conducted in an intelligent artificial climate chamber. It compared three dripping rates: 2, 4 and 8 L/h, with traditional flood irrigation taken as the control. After harvesting the plants, microbial community in the different root zone soil layers (0-5, 5-10, and 10-15 cm) of each treatment was analyzed using the 16S rDNA microbial diversity sequencing method. Result Microbial diversity index under drip irrigation was higher than that under the control, regardless of the dripping rate, and their difference was most significant in the 5-10 cm soil layer (P<0.05). Dripping rate did not show a significant impact on dominant flora at phylum and genus level, but the relative abundance of microbial community changed with edaphic factors such as pH, EC, total phosphorus. Dripping at the rate of 2 L/h increased the total phosphorus content in the 10-15 cm soil compared with other treatments, and it also significantly increased the relative abundance of Bacteroidetes. Compared with the control, the drip irrigations increased pH and reduced the relative abundance of Sphingomonas in the 10-15 cm soil. When the dripping rate was 2 L/h, the abundance of each functional microbial pathway was the highest in the top 0-5 cm soil.Conclusion Dripping rate in using reclaimed water to irrigate tomato altered the physical and chemical properties of soil, thereby shifting microbial community and microbial distribution in the rhizosphere. It also reshaped the distribution of the abundance of some functional flora in soil profile. Our finding implicates that selecting an appropriate drip irrigation rate could have a significant consequence for carbon and nutrient cycles in drip-irrigated crops using reclaimed water due to its impact on microbial community and the associated functions. [ABSTRACT FROM AUTHOR]

Biochar is widely used as a promising green and cost-effective alternative for soil amendment, because of its agronomic benefits in soil carbon sequestration and facilitating nutrient cycling, and improvements in water use efficiency and crop growth and yield. The absorption of water and nutrients for plant from soil is directly influenced by root morphology, and root morphology plays a significant role in plant growth and water use efficiency. But there is limited information on the interaction among root morphology and plant growth, water use efficiency under biochar application. Hence, in order to investigate the effects of biochar on winter wheat growth, yield, water use efficiency and root morphology, in this study, a one-year field experiment with different application amounts (0, 20, 30, 40, 50 and 60 t/hm2) of wheat straw biochar (pyrolysis temperature of 600°C) was carried out under subsurface drip irrigation condition. The preliminary results showed that the tiller number, efficient spike number and yield of winter wheat were significantly affected (P<0.05) by biochar, increased by 1.6%-4.9%, 0.7%-1.5%, and 1.0%-5.9%, respectively. Plant height and spike length were not affected by wheat straw biochar. Grain number and 1000-grain weight were significantly increased (P<0.05) only under the treatments of 30, 40, and 50 t/hm2 application of wheat straw biochar. Grain number increased by 4.7%, 8.6% and 2.7%, respectively and 1000-grain weight increased by 5.6%, 8.0% and 5.0%, respectively, which showed biochar application could effectively increase winter wheat yield through the increase of tiller number, efficient spike number, grain number and 1000-grain weight. The water consumption of winter wheat decreased significantly (P<0.05) with the increase of application amount of wheat straw biochar, which decreased by 2.6%, 7.0%, 7.7%, 9.1% and 9.4% respectively under the biochar application amounts of 20, 30, 40, 50 and 60 t/hm2. The water use efficiency increased from 17.06 to 17.69-19.57 kg/hm2·mm with the increase of application amount of wheat straw biochar, and the highest value was obtained under the treatment of 40 t/hm2. The root morphology characteristics of winter wheat were significantly affected by wheat straw biochar. The application of wheat straw biochar increased total root length of 0-20 and ≥20-40 cm for winter wheat by 2.8%-14.6% and 8.4%-21.2%, respectively, increased root surface area by 5.6%-19.5% and 1.9%-13.6%, respectively and increased average root diameter by 0.4%-4.1% and 1.4%-2.0%, respectively. The application of wheat straw biochar had less positive effect on average root diameter of winter wheat, compared with total root length and root surface area. In comparison with other levels of biochar application, the treatment of 40 t/hm2 was more effective in the improvement of winter wheat root growth. The root morphology characteristics were very significantly correlated with the yield of winter wheat (P<0.001). Compared to other application amounts of wheat straw biochar, the treatment of 40 t/hm2 had the most significant impact on the growth, yield, water use efficiency and root morphology characteristics of winter wheat. This study provides references for scientific and rational utilization of biochar in agriculture. [ABSTRACT FROM AUTHOR]