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Microplastics (MPs) pollution in agroecosystems have aroused great alarm and widespread concern. However, the spatial distribution and temporal variation characteristics of MPs in apple orchards with long-term plastic mulching and organic compost input are still poorly understood. This study investigated MPs accumulation characteristics and vertical distribution after applying plastic mulch and organic compost in apple orchards for 3 (AO-3), 9 (AO-9), 17 (AO-17), and 26 (AO-26) years on the Loess Plateau. The clear tillage (no plastic mulching and organic composts) area was used as a control (CK). At a soil depth of 0–40 cm, AO-3, AO-9, AO-17, and AO-26 treatments increased the abundances of MPs, and the black fibers and fragments of rayon and polypropylene were dominant. In the 0–20 cm soil layer, the abundances of MPs increased with the treatment time; the abundance was 4333 pieces kg−1 after 26 years of treatment, gradually decreasing with soil depth. In different treatments and soil layers, the percentages of MPs <1000 μm were dominant (>50%). The AO-17 and AO-26 treatments significantly increased the MPs with the size of 0–500 μm at 0–40 cm and the abundances of pellets in 0–60 cm soil. In conclusion, the long-term (≥17 years) application of plastic mulching and organic composts increased the abundances of small particles at 0–40 cm, and plastic mulching contributed the most to MPs, while organic composts increased the complexity and diversity of MPs. [Display omitted] • Spatio-temporal variation and distribution of soil microplastics was studied. • The abundances of Microplastics (MPs) at topsoil increased with the treatment time. • Long-term treatments significantly increased the MPs of sizes 0–500 μm and pellets. • MPs distribution in different soil layers were disordered under short-term treatment. [ABSTRACT FROM AUTHOR]

The objective of this present study was to understand the distribution patterns of various forms of soil phosphorus (P) and the biotic and abiotic factors affecting the soil P fractions under long-term cover crops. Here, we investigated the characteristics of soil P forms, community structure of P-solubilizing bacteria (using 16S rRNA) and the related enzyme activity under clean tillage (CT), 14 years of white clover (WC, Trifolium repens L.) and orchard grass (OG, Dactylis glomerata L.) cover crops in a rain-fed apple orchard on the Weibei Loess Plateau, China. Relative to CT treatment, long-term cover crops enhanced the bioavailability of soil P by increasing the contents of total phosphorus (TP), microbial phosphorus (MBP), organic phosphorus (Po) and certain forms of inorganic phosphorus (e.g. Al-P, Ca 2 -P, Ca 8 -P and Fe-P) in the surface soil, in addition, WC treatment also increase the available P (AP) contents in the topsoil. A redundant analysis (RDA) showed that soil organic matter (SOM), NH 4 +-N and pH were the key environmental factors affecting the morphological changes of soil P. In addition, the effects of long-term cover crops on soil P forms were mainly concentrated in the topsoil, and the WC treatment had a greater impact on soil P composition than the OG treatment. Interestingly, long-term cover crops effectively increased the abundances of P-solubilizing bacteria, such as Streptomyces , Sphingomonas , Nocardioides and Haliangium , and enhanced the alkaline phosphatase (ALP) activity. Overall, long-term cover crops were an effective strategy to activate soil P as they improve the soil environment. [Display omitted] • Long-term cover crops increased topsoil TP, MBP, Po, IP, and P bioavailability. • The SOM, NH 4 +-N and pH were key factors affecting the morphological changes of soil P. • Long-term cover crops increased ALP activity and P-solubilizing bacterial abundance. • The effect of legume mulching on soil P forms was greater than that of gramineae mulching. [ABSTRACT FROM AUTHOR]