Abstract
BackgroundInappropriate disposal of the plastic mulching debris could create macroplastics (MaPs) and microplastics (MiPs) pollution in agricultural soil.MethodsTo study the effects of farming systems on accumulation and distribution of agricultural plastic debris, research was carried out on two farming systems in Northwest China. Farming in Wutong Village (S1) is characterized by small plots and low-intensity machine tillage while farming in Shihezi (S2) is characterized by large plots and high-intensity machine tillage. In September 2017, we selected six fields in S1, three fields with 6–8 years of continuous plastic mulching (CM) as well as three fields with over 30 years of intermittent mulching (IM). In S2, we selected five cotton fields with 6, 7, 8, 15 and 18 years of continuous mulching. In both regions, MaPs and MiPs from soil surface to 30 cm depth (0–30 cm) were sampled.ResultsThe results showed that in S1, MaPs mass in fields with 6–8 years CM (i.e., 97.4kg·ha−1) were significantly higher than in fields with 30 years IM (i.e., 53.7 kg·ha−1). MaPs in size category of 10–50 cm2 accounted for 46.9% in fields of CM and 44.5% in fields of IM of total collected MaPs number. In S2, MaPs mass ranged from 43.5 kg·ha−1 to 148 kg·ha−1. MaPs in size category of 2–10 cm2 account for 41.1% of total collected MaPs number while 0.25–2 cm2 accounted for 40.6%. MiPs in S1 were mainly detected in fields with over 30 years of intermittent mulching (up to 2,200 particles·kg−1 soil), whereas in S2 were detected in all fields (up to 900 particles·kg−1 soil). The results indicated farming systems could substantially affect the accumulation and distribution of agricultural plastic debris. Continuous plastic mulching could accumulate higher amount of MaPs than intermittent plastic mulching. High-intensity machine tillage could lead to higher fragmentation of MaPs and more severe MiPs pollution. These results suggest that agricultural plastic regulations are needed.
Highlights
Plastic mulching is a widespread agricultural practice in arid and semi-arid agricultural areas
Plastic mulching has experienced a rapid growth in China since it was first introduced in the 1980s (Cai et al, 2013; Ma et al, 2018), growing from 6,000 tons used on 117,000 hectares of land in 1982 to about 1.5 million tons used on 18.4 million hectares of land in 2016 (NBSC, 2017)
Accumulation and distribution of macroplastics in selected agricultural fields In S1, across the 6 selected fields, MaPs number varied from 56.7 × 104 p·ha−1 to 264.7 × 104 p·ha−1 and MaPs mass varied from 53.7 kg·ha−1 to 108 kg·ha−1 (Table 1)
Summary
Plastic mulching is a widespread agricultural practice in arid and semi-arid agricultural areas. Macro-size plastics (MaPs) in agricultural fields have been reported could significantly reduced the gravimetric water mass and bulk density of soils, decreases macro-pores and alters soil water distribution (Jiang et al, 2017). Inappropriate disposal of the plastic mulching debris could create macroplastics (MaPs) and microplastics (MiPs) pollution in agricultural soil. In S2, we selected five cotton fields with 6, 7, 8, 15 and 18 years of continuous mulching In both regions, MaPs and MiPs from soil surface to 30 cm depth (0–30 cm) were sampled. High-intensity machine tillage could lead to higher fragmentation of MaPs and more severe MiPs pollution. These results suggest that agricultural plastic regulations are needed
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