Plastic is an indispensable material essential for modern human life. With highly increasing demand for plastic use, however, environmental contamination by plastic litters has become an emerging issue. Globally, large quantity of used plastics is landfilled or emitted directly to the aquatic and terrestrial environments, albeit a part of the plastics is recycled or incinerated as energy source. In particular, microplastic debris that are smaller than 5 mm are considered to be emerging contaminants of global concern. In the past decade, however, most of the researches on impacts of microplastic contamination have been focused on the marine ecosystem, whereas very limited ones on the terrestrial ecosystem. Soil can be considered as a major sink and a carrier of microplastic contaminants to the aquatic environment. Most sources of microplastics in the soil environment are entered via a variety of routes and subsequent fragmented and spread to the surrounding environments, vertically and horizontally. In addition, there are negative impacts on soil biota, which in turn would cause concerns of human health by affecting the food web. Here, we provide an overview of characteristics, research trend, analytical methods, migration and degradation processes, effects on soil biogeochemistry, and interaction with soil organisms of microplastics suggesting the importance of ongoing research impacts of microplastics on the terrestrial ecosystem.

Some intensive farmers tend to expect short-term beneficial effects by applying soil amendments, but inconsistent fertilization practices are often conducted, causing economic losses and environmental problems. This study aimed at investigating the short-term application effects of different soil amendments on soil organic carbon (SOC) fractions, biogeochemical properties, and crop performance for finding the best land management approach using one-year field trial growing Chinese cabbages. This filed experiment was conducted in 2020 and included eight fertilizer treatments: control (w/o fertilizers), chemical fertilizer (CF), manure compost (MC), double MC amount (2MC), CF + MC, CF + rice husk (RH), MC + RH, and CF + MC + RH. As a result, the concentrations of recalcitrant to labile C forms, including Loss-On-Ignition C (LOIC), Walkley-Black C, permanganate oxidizable C (POXC), and microbial biomass C, were the highest in a mixture of MC and RH and 2MC. Additionally, the treatment with the largest difference from the control in key soil parameters was 2MC: bulk density (10%), total N (30%), available P (186%), and CO₂ (433%) and N₂O (825%) emissions, followed by MC + RH. Moreover, more than 20% higher fresh weight (FW) of cabbage was found in 2MC and MC + RH than in the control. Therefore, these two organic amendments appeared to benefit SOC storage and overall soil biogeochemical processes, contributing to higher biomass crop production. Moreover, LOIC significantly correlated to bulk density, available P and K, and FW, while POXC significantly correlated to N concentration in plants, indicating the short-term fertilization effects on the status of SOC fractions and the qualities of soil and plant by applying soil amendments. Overall, our findings suggest that applying MC + RH would be an alternative to replace the conventional farming practices for promoting soil quality and crop performance, but further studies to sustain the application effects of this amendment should be monitored for longer durations.