Despite evidence from previous case studies showing that agronomic traits partially determine the resulting yield of different rice (Oryza sativa L.) varieties, it remains unclear whether this is true at the ecotype level. Here, an extensive dataset of the traits of 7686 rice varieties, released in China from 1978 to 2017, was used to study the relationship between yield and other agronomic traits. We assessed the association between yield and other agronomic traits for four different rice ecotypes, i.e., indica inbred, indica hybrid, japonica inbred, and japonica hybrid. We found that associations between agronomic traits and yield were ecotype-dependent. For both the indica inbred and indica hybrid ecotypes, we found that greater values of certain traits, including the filled grain number per panicle, 1000-grain-weight, plant height, panicle length, grains per panicle, seed setting rate, long growth period, low panicle number per unit area, and low seed length/width ratio, have accounted for high grain yield. In the japonica inbred and japonica hybrid ecotypes, we found that only high panicle number per unit area and long growth period led to high grain yield. Indirectly, growth period consistently had a positive effect on yield in all ecotypes, and plant height had a positive effect on yield for the indicas and japonica inbred only. Plant height had a negative effect for the japonica hybrid. Altogether, our findings potentially have valuable implications for improving the breeds of rice ecotypes.

Although pervasive microplastics (MPs) pollution in terrestrial ecosystems invites increasing global concern, impact of MPs on soil microbial community assembly and ecosystem multifunctionality received relatively little attention. Here, we manipulated a mesocosm experiment to investigate how polyethylene MPs (PE MPs; 0, 1%, and 5%, w/w) influence ecosystem functions including plant production, soil quality, microbial community diversity and assembly, enzyme activities in carbon (C), nitrogen (N) and phosphorus (P) cycling, and multifunctionality in the maize-soil continuum. Results showed that PE MPs exerted negligible effect on plant biomass (dry weight). The treatment of 5% PE MPs caused declines in the availability of soil water, C and P, whereas enhanced soil pH and C storage. The activity of C-cycling enzymes (α/β-1, 4-glucosidase and β-D-cellobiohydrolase) was promoted by 1% PE MPs, while that of β-1, 4-glucosidase was inhibited by 5% PE MPs. The 5% PE MPs reduced the activity of N-cycling enzymes (protease and urease), whereas increased that of the P-cycling enzyme (alkaline phosphatase). The 5% PE MPs shifted soil microbial community composition, and increased the number of specialist species, microbial community stability and networks resistance. Moreover, PE MPs altered microbial community assembly, with 5% treatment decreasing dispersal limitation proportion (from 13.66% to 9.96%). Overall, ecosystem multifunctionality was improved by 1% concentration, while reduced by 5% concentration of PE MPs. The activity of α/β-1, 4-glucosidase, urease and protease, and ammonium-N content were the most important predictors of ecosystem multifunctionality. These results underscore that PE MPs can alter soil microbial community assembly and ecosystem multifunctionality, and thus development and implementation of practicable solutions to control soil MPs pollution become increasingly imperative in sustainable agricultural production.

Contamination of microplastics (MPs) is a global environmental issue that has received much attention from the scientific and public communities due to ecological concerns in recent decades. Comparing with aquatic ecosystems, soil systems, regardless of the high importance and complexity, have been less studied under widely existing and increasing MP contamination. This review, combined with data assimilation and meta-analysis methods, has summarized current contamination conditions of soil MPs across different sites reported in earlier studies. While performing this meta-analysis, we investigated the effects of MPs on soil biota including their numbers, biomass, diversity, and physiological properties. The results showed that abundance of soil MPs ranged from 0.34 to 410958.9 items kg^-1 and concentration ranged from 0.002 to 67500 mg kg^-1 across sites, with agricultural soils containing significantly lower abundance and concentration of MPs than others. Presence of MPs significantly decreased the individual number of soil biota, operational taxonomic unit, diversity index (Simpson), movement index and reproduction rate, whereas the mortality rate was significantly increased by the soil MPs. Despite these significant effects, MPs did not significantly alter the biomass of soil biota, which could be due to a counteraction of their negative and positive effects on different groups of soil organisms. Moreover, we observed that soil MPs could significantly increase the Chao1 index, suggesting that MPs may act as a food resource for the soil rare biosphere. Based on the existing knowledge, we suggest that future studies should focus on research areas that include but are not limited to methodological improvements, intensive field investigations, risk assessment from the perspective of soil food web and bioaccumulation, MPs induced antibiotic resistance, and restoration strategies to reduce their concentrations in soil.