Biochar and biogas slurry have been proved to improve the quality of some soil types, but the long-term effects on fluvo-aquic soil are not fully understood. This study aimed to compare the continuity effects of peanut-shell biochar and biogas slurry on the physicochemical properties, microbial population size, and enzyme activities of fluvo-aquic soil. We conducted a four-year field experiment of winter wheat-summer maize rotation in the North China Plain. Along with equal nitrogen inputs, three treatments were applied—conventional fertilizers, peanut-shell biochar, and hoggery biogas slurry—after which various soil quality indicators were compared. Compared with those of control, both biochar and biogas slurry increased the soil total nitrogen and organic matter content, and improved soil aggregation, microbial biomass, and actinomycetes. Biogas slurry decreased soil pH and improved urease and protease activities. With biochar and biogas slurry treatments, wheat yield increased by 8.46% and 23.47%, and maize yield by 18% and 15.46%, respectively. Biogas slurry increased the content of crude protein and starch in the grains. Both biogas slurry and peanut-shell biochar improved fluvo-aquic soil nutrient content, water-stable macroaggregates, and microbial population, which might be related to their high nutrient content, large specific surface area, adsorption capacity, and functional groups. Biogas slurry generally exhibited stronger effects than biochar probably because of its richness in nutrients and bioactive substances.

Plants are exposed to various abiotic stressors in agricultural systems, especially cadmium (Cd) stress, which hinders plant growth and development. The current study was conducted to assess the protective role of silicon (Si) application in two methods and to identify the optimum method of Si application for wheat plants grown hydroponically under the same levels of Cd stress. For this purpose, we used two different silicon (Si; 1 mmol L −1 Na 2 SiO 3) application methods (i.e., root application and foliar spray) on growth, chlorophyll contents, cell membrane injury contents, enzymatic and non-enzymatic antioxidants, and membrane permeability contents of winter wheat (Triticum aestivum L.) against four levels of cadmium (Cd), normal, 50 μmol L −1 , 100 μmol L −1 , and 200 μmol L −1 , in 2-repeated greenhouse experiments. Results showed that Cd stress markedly affects growth, chlorophyll contents, and physiological traits and boosted up anti-oxidative defense system activity, osmoprotectants, and Cd contents. However, Si application as foliar or root induced reversibility of Cd toxic effects by significantly increasing growth, chlorophyll contents, membrane stability index, and Si contents and significantly reducing membrane injury contents measured as electrolytic leakage (EL) contents, lipid peroxidation measured as malondialdehyde (MDA) contents, and osmotic pressure measured as hydrogen peroxide (H 2 O 2) contents and increased in enzymatic and non-enzymatic anti-oxidative defense system's activity. Being an effective beneficial element, Si with the preference of root application improved leaf area, plant biomass, membrane characteristic, photosynthetic rate, and anti-oxidative defense system of wheat plants by alleviating Cd toxicity.

Livestock wastewater is rich in nutrients but may contain antibiotics and antibiotic resistance genes (ARGs). Their discharge to watercourses or soil may result in proliferation of ARGs. Irrigation with wastewater appears to be the most feasible option of disposing of it. One efficient irrigation technology used in arid regions is alternate-furrow irrigation (AFI) by alternately drying part of the plant roots for a prolonged period to physiologically reduce transpiration without compromising yield. However, the extent to which AFI with wastewater influences the concentration of antibiotics and spread of ARGs in soil is poorly understood. The purpose of this paper is to investigate how AFI using swine wastewater alters antibiotic kinetics and ARGs abundance under different irrigation rates, using pepper as the model plant. We examined three AFI treatments using 50%, 65% and 80% of the amount of water employed in sufficient conventional furrow irrigation. Each treatment had a groundwater irrigation control. The results showed that antibiotic concentrations and relative ARGs abundance in the top 20 cm of soil did not increase with the irrigation amount, although they were higher than those in the groundwater-irrigated soils. The relative ARGs abundance in the soil was modulated by irrigation amount and reducing the irrigation amount in AFI reduced ARGs dispersion only in rhizosphere. When the soil moisture was close to field capacity, ARGs were more abundant in rhizosphere than in non-rhizosphere, possibly because the rhizosphere is rich in microbes and increasing antibiotic concentrations due to an increase in irrigation rate favors antibiotic-resistant microbiome in competing for substrates. These, however, were not mirrored in the relative ARGs abundance in the roots. These results have important implications as it revealed that reducing the input of antibiotics and ARGs into soil with AFI does not necessarily reduce ARGs proliferation.

Wheat is the second most important food crop worldwide, and thus, it is important to protect both its yield and quality. Cadmium (Cd) is a heavy metal with strong soil-plant mobility and biological toxicity. Thus, screening low-Cd-accumulating genotypes to elucidate the underlying molecular regulatory mechanisms and gene networks related to Cd stress may be useful to reduce dietary exposure to this heavy metal. Here, the root transcriptomes of the low-Cd-accumulating genotype YM16 treated (YT) or not treated (YC) with Cd were analyzed using the Illumina Hiseq4000 data. The gene expression analysis of YT and YC revealed 1427 differentially expressed genes (DEGs; 429 upregulated and 998 downregulated). Of these, 298 upregulated DEGs were assigned to 41 gene ontology (GO) terms, whereas 537 downregulated DEGs were assigned to 61 GO terms. The pathway enrichment analysis showed that phenylpropanoid biosynthesis, glutathione metabolism, sulfur metabolism, and nitrogen metabolism were significantly enriched in upregulated DEGs, which are involved in defense and detoxification in response to Cd stress. The expression pattern of eight selected DEGs was also analyzed by quantitative real-time polymerase chain reaction, and the results were consistent with those obtained by RNA-sequencing, confirming data reliability. Overall, our study might increase the understanding of complex molecular mechanisms that regulate the responses of plants to Cd stress, and help develop new improved wheat varieties with low Cd content in the grain.

Reclaimed water (RW) is an alternative water resource that has been utilized all over the world, but its environmental effects are not fully understood. Soil biodiversity is an important indicator of soil tolerance and resilience. In the present study, the impact of RW irrigation on the microbial community diversity and chemical properties of topsoil was investigated by monitoring nitrogen (N) rates. Tomato plants were grown on plots which had been irrigated with reclaimed water for 5 years with varying levels of N fertilization (N270, 270 kg ha −1 ; N216, 216 kg ha −1 ; N189, 189 kg ha −1 ; and N135, 135 kg ha −1 ). Soil bacterial community composition was analyzed by PCR amplification of the 16S rDNA gene and Illumina MiSeq high-throughput sequencing technology of a total of 770,066 quality sequences. The results showed that long-term RW irrigation altered the bacterial composition of soil in an N-dependent manner. RW irrigation increased the abundances of Gemmatimonadetes, Actinobacteria, Firmicutes, and Nitrospirae in soils. The Chao, ACE, and H indices revealed no significant difference under RW irrigation with varying levels of N fertilization. The tomato yield and partial factor productivity from applied N for RN216 increased significantly under RW irrigation with reducing N fertilization. RW irrigation increased the yield of tomato and the abundance of functional microorganisms, which eventually improved the practice of irrigating with reclaimed municipal wastewater. Meanwhile, the potential environmental and health risks of long-term RW irrigation warrant further investigation.

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To investigate the research hotspots and development trends of subsurface drip irrigation (SDI) over the past 20 years, this study analyzed relevant literature from the Web of Science Core Collection spanning from 2002 to 2022. The data were visualized using CiteSpace, showcasing the publication volume trends, countries, keywords, cited references, authors, and affiliated institutions. Based on 1079 articles, the annual publication volume showed an overall upward trend. The United States had the most extensive research coverage and highest publication volume, whereas China had the fastest growing publication rate in recent years. However, relatively little cooperation occurred among research teams and institutions. Over time, research topics became increasingly diverse, with water conservation and yield increases being the primary research objectives. In addition to improving irrigation and fertilizer use efficiency, SDI has also been applied in research on the safe utilization of unconventional water resources (wastewater and salt water) and the optimization of soil conditions. Among these, aerated irrigation technology—aimed at improving root growth in the rhizosphere—may become a new branch of SDI research. Currently, the main research focus in the field of SDI is the diffusion and distribution of water in the crop root zone, for which Hydrus model simulation is a particularly important method.