Crop productivity and yield are adversely affected by the deficiency of P in agricultural soil. Phosphate fertilizers are used at a large scale to improve crop yields globally. With the rapid increase in human population, food demands are also increasing. To see that crop yields meet demands, farmers have continuously added phosphate fertilizers to their arable fields. As the primary source of inorganic phosphorous, rock phosphate is finite and the risk of its being jeopardized in the foreseeable future is high. Therefore, there is a dire need to improve plant-available P in soil, using feasible, environmentally friendly technologies developed on the basis of further understanding of P dynamics between soil and plants. This study systemically reviews the mechanism of P uptake and P-use efficiency by plants under starvation conditions. The recent advances in various strategies, especially imaging techniques, over the period 2012–2021 for the measurement of plant-available P are identified. The study then examines how plants fulfill P requirements from tissue-stored P during P starvation. Following this understanding, various strategies for increasing plant-available P in agricultural soil are evaluated. Finally, an update on novel carriers used to improve the P content of agricultural soil is provided.
Antibiotic resistance genes (ARGs), prevalent across multiple environmental media, threaten human health worldwide and are considered emerging environmental contaminants. Earthworm gut, a niche for bacteria to survive, represents a potential reservoir for ARGs in soil. However, the compositions of ARGs in the earthworm gut microbiota remain elusive, especially under field conditions. In this study, we applied high-throughput quantitative PCR to profile the ARGs in the gut microbiota of earthworms after chronic exposure to fertilizers. To elucidate the factors that impact the ARGs composition, the bacterial community of gut microbiota, mobile genetic elements (MGEs), soil (nutrients, heavy metals, and antibiotics) and the properties of gut content (pH and nutrients) were analyzed. A total of 98 subtypes among 9 major types of ARGs, and 3 different MGEs were detected in the gut microbiota of earthworms. Organic fertilizer (sewage sludge and chicken manure) application significantly increased the diversity and abundance of ARGs. Of the 1123 identified operational taxonomic units (OTUs) at 97% similarity cutoff, most of them were assigned to Firmicutes (55.5%) and Proteobacteria (33.6%) in earthworm gut microbiota. Long-term organic fertilization slightly changed the microbiota composition, but did not impact the diversity. Partial redundancy analysis (pRDA) revealed that bacterial community, combined with environmental factors (soil and gut content properties) and MGEs, explained 72% of the variations of ARGs in the earthworm gut. Furthermore, the co-occurrence pattern between ARGs and MGEs indicated that horizontal gene transfer via MGEs may occur in the earthworm gut. These findings improve the current understanding of the dynamics of soil fauna-associated ARGs and the gut microbiota of earthworms may be an underappreciated hotspot for ARGs in the environment.
Sustainable municipal solid waste (MSW) management is regarded as one of the key elements for achieving urban sustainability via mitigating global climate change, recycling resources and recovering energy. Landfill is considered as the least preferable disposal method and the EU Landfill Directive (ELD) announced in 1999 requires member countries to reduce the volume of landfilled biodegradable materials. The enforcement of ELD initiated the evolution of MSW management system UK. This study depicted and assessed the transition and performance of MSW management after the millennium in Nottingham via materials flow analysis (MFA), as well as appropriately selected indicators based on the concept of waste management hierarchy and targets set in waste management regulations. We observed improvements in waste reduction, material recycling, energy recovery, and landfill prevention. During the period 2001/02 to 2016/17, annual waste generation reduced from 463 kg/Ca to 361 kg/Ca, the recycling and composting share increased from 4.6% to 44.4%, and the landfill share reduced from 54.7% to 7.3%. These signs of progress are believed to be driven by the ELD and the associated policies and waste management targets established at the national and local levels. An alternative scenario with food waste and textile separation at source and utilizing anaerobic digestion to treat separately collected organic waste is proposed at the end of this paper to fulfil the high targets set by local government and we further suggest that the recycling share may be improved by educating and supporting the public on waste separation at the sources.