Plastic mulching is suspected to be a significant source of microplastics in terrestrial environments owing to its intensive application and improper disposal. However, there has been a comparative lack of studies examining this hypothesis. In this study, the occurrence of macroplastics in agricultural soils was investigated by analysing 384 soil samples collected from 19 provinces across China. Additionally, the abundance of microplastics was investigated in potential hotspots that have carried out plastic mulching for over 30 years. Macroplastic concentrations in the soil samples ranged from 0.1 to 324.5 kg/ha, with an average of 83.6 kg/ha; the concentrations were higher in western China than in eastern China. A highly significant linear correlation (R² = 0.61) was found between the consumption of mulching film and the plastic residue in soils, indicating plastic film mulching may be a major source of macroplastics. The abundances of microplastic particles increased over time in the locations where plastic mulching was continuously employed, with concentrations of 80.3 ± 49.3, 308 ± 138.1, and 1075.6 ± 346.8 pieces/kg soil in fields with 5, 15, and 24 y of continuous mulching, respectively. Fourier transform infrared analyses revealed that the composition of the microplastics matched that of the mulching films, suggesting the microplastic particles originated from the mulching films. These findings confirm that plastic mulching is an important source of macroplastic and microplastic contamination in terrestrial environments. Further studies to investigate the microplastic hazards in soils are thus necessary.

Microplastic pollution is a major global environmental problem in both aquatic and terrestrial environments. Pesticides are frequently applied to agricultural soil to reduce the effects of pests on crops, but may also affect the degradation of plastics. In this study, we generated microplastics from polyethylene (PE) film and biodegradable poly(butylene adipate-co-terephthalate) (PBAT) film and determined (1) the effect of prothioconazole on degradation of the microplastics, and (2) the adsorption and release characteristics of heavy metals (Cr, Cu, As, Pb, Ba, and Sn) by the microplastics during degradation process. Changes of surface functional groups and morphologies were measured by FTIR and SEM, while metal concentrations were determined by ICPMS. Prothioconazole was found to promote plastic degradation. PBAT degraded faster and adsorbed more heavy metals from the soil than PE. Whether the microplastics adsorb or release heavy metals depended on the metal and their concentrations. Prothioconazole inhibited the adsorption of Cr, As, Pb and Ba by microplastics, promoted the adsorption of Cu, and had no significant effect for Sn. These results can help to assess the ecological risk of microplastic pollution from plastic mulch when combined with heavy metals.

Plastic film mulching is a common practice to increase crop yield in dryland, while the wide use of plastic film has resulted in ubiquitous phthalate esters (PAEs) releasing into the soil. PAEs in soil could be taken up and accumulated by dietary intake of food crops such as wheat, thus imposing health risks to residents. In the present study, samples from a long-term location-fixed field experiment were examined to clarify the accumulation of PAEs in soil and wheat, and to assess the human health risks from PAEs via dietary intake of wheat grain under plastic film mulching cultivation in dryland. Results showed that concentrations of PAEs in grains from mulching plots ranged from 4.1 to 12.6 mg kg−1, which were significantly higher than those in the control group. There was a positive correlation for the PAE concentrations between wheat grains and field soils. Concentrations of PAEs in the soil were in the range of 1.8–3.5 mg kg−1 for the mulching treatment, and 0.9–2.7 mg kg−1 for the control group. Di-n-butyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) were detected in all soil and grain samples, and DEHP was found to be the dominant PAE compound in grains. Based on DEHP concentrations in wheat grains, the values of carcinogenic risk for adults were higher than the recommended value 10−4. Results indicated that wheat grains from film mulching plots posed a considerable non-carcinogenic risk to residents, with children being the most sensitive resident group. Findings of this work call the attention to the potential pollution of grain crops growing in the plastic film mulching crop production systems.

Studies on N losses from ornamental plantings - other than turf - are scant despite the ubiquity of these landscaping elements. We compared pore water NO₃ and extractable soil NO₃ and NH₄ in areas with turf, areas with seven different types of ornamental landscape plantings, and a native woodland. Turf areas received annual N inputs of ~48 kg ha-¹ and annual flowers received ~24 kg N ha-¹ at the time of planting. None of the other areas were fertilized during the course of the study. Data were collected on 23 occasions between June 2002 and November 2003. Pore water NO₃ concentrations at a 60-cm depth - based on pooled data - were highest (1.4 to 7.8 mg NO₃-N l-¹) under ground covers, unplanted-mulched areas, turf, deciduous trees, and evergreen trees, with no differences among these vegetation types. Lower values were observed under woodlands, annual and perennial flowers, and evergreen and deciduous shrubs. Pore water NO₃ concentrations exceeded the drinking water regulatory limit of 10 mg NO₃-N l-¹ under ground covers, turf and unplanted-mulched areas in 39, 20 and 10% of samples, respectively. Leaching losses of NO₃-N over 18 months ranged from 0.17 kg N ha-¹ in the woodlands to 34.97 kg N ha-¹ under ground covers. Annual NO₃ losses under unplanted-mulched areas and ground covers were approximately twice the average N input (10 kg N ha-¹ year-¹) from atmospheric deposition. Extractable NO₃ in woodland soils (0.5 μg NO₃-N g-¹) was lower than for all other vegetation types (3.1-7.8 μg NO₃-N g-¹). Extractable NH₄ levels were highest in woodlands, deciduous trees, and annual flowers (6.7-10.1 μg NH₄-N g-¹). Most vegetation types appear to act as net N sinks relative to atmospheric inputs, whereas unplanted-mulched areas and areas planted with ground covers act as net sources of NO₃ to groundwater.

Water-saving cultivation techniques have been attracting increased attention worldwide. Ridge-furrow mulching system (RFMS), as a prospective rainwater harvesting system, has been widely adopted in arid and semi-arid areas. Field experiments were conducted in 2014 and 2015 to compare soil water storage, soil temperature, maize yield, and water use efficiency (WUE) among different ridge/furrow width arrangements in RFMS comprised of three different ridge/furrow ratios, i.e., 40:70 cm (RFMS40), 55:55 cm (RFMS55), and 70:40 cm (RFMS70) and conventional flat planting (CK, without mulching). All these four planting patterns had the same planting density. The RFMS technique not only increased soil temperature of the ridge but also improved soil moisture of the furrow when compared with CK. These positive effects were intensified with increasing ridge/furrow ratio in RFMS. This improvement in RFMS resulted in more stable and earlier seedling establishment. Maize yields were increased by 26.1, 36.4, and 50.3% under RFMS40, RFMS55, and RFMS70 treatments, respectively, when compared with CK across both years. RFMS did not decrease the evapotranspiration significantly, compared with CK. Eventually, WUE were enhanced by 25.7, 38.7, and 53.9% in RFMS40, RFMS55, and RFMS70, respectively, compared with CK. Taken together, our results suggest that increasing ratio of ridge to furrow in the case of RFMS70, can be recommended as high-yielding cultivation pattern for promoting precipitation use efficiency in the rain-fed semi-arid areas.

Weed management is one of the prime concerns for sustainable crop production. Conyza bonariensis and Conyza canadensis are two of the most problematic, noxious, invasive and widespread weeds in modern-day agriculture. The biology, ecology and interference of C. bonariensis and C. canadensis have been reviewed here to highlight pragmatic management options. Both these species share a unique set of biological features, which enables them to invade and adapt a wide range of environmental conditions. Distinct reproductive biology and an efficient seed dispersal mechanism help these species to spread rapidly. Ability to interfere strongly and to host crop pests makes these two species worst weeds of cropping systems. These weed species cause 28–68 % yield loss in important field crops such as soybean and cotton every year. These weeds are more prevalent in no-till systems and, thus, becoming a major issue in conservation agriculture. Cultural practices such as crop rotations, seed rate manipulation, mulching, inter-row tillage and narrow row spacing may provide an effective control of these species. However, such methods are not feasible and applicable under all types of conditions. Different herbicides also provide a varying degree of control depending on crop, agronomic practices, herbicide dose, application time and season. However, both these species have evolved resistance against multiple herbicides, including glyphosate and paraquat. The use of alternative herbicides and integrated management strategies may provide better control of herbicide-resistant C. bonariensis and C. canadensis. Management plans based on the eco-biological interactions of these species may prove sustainable in the future.

Year-round film mulching in winter wheat field facilitates rainwater storage in summer fallow period and reduces water evaporation in growing reason, and then increases water use efficiency in the dryland of the Loess Plateau, China. Optimized fertilization further promotes fertilizer utilization efficiencies. In this study, plastic film mulching was extended from plant growth season to summer fallow, and fertilizers were applied by monitoring soil nutrient availability. Field trials were conducted in the dryland of the Loess Plateau over 4 years by using four types of cultivation to investigate the effects of year-round plastic film mulching with monitored fertilization on utilization efficiencies of rainwater and nitrogen (N), and winter wheat yield. The four types of cultivation were farmer practice (FP), ridge-furrow with plastic film mulching system plus conventional fertilization(RPCF), ridge-furrow with plastic film mulching system plus monitored fertilization (RPFM), and flat soil surface with plastic film mulching system plus monitored fertilization (FPFM). Our results indicate that the average yield of winter wheat in RPFM and FPFM treatments was 4491 kg ha⁻¹. Compared with FP treatment, the combined effects of monitored fertilization and film mulching(RPFM and FPFM treatments) could increase grain yield in the range of 24.7 to 42.1%. The film mulching extended to the fallow season increased the water storage in 2 m depth of soil profile, and the amount of soil water storage in the summer fallow period increased by 27 to 30% in FPFM treatment than FP treatment. After 4-year consecutive planting of wheat, the accumulation of nitrate-N in 2 m soil reached 277 kg·ha⁻¹ in the FP treatment, which is 87.7% higher than of the level at the beginning of the experiment. Seventy-five percent of nitrate-N was distributed in the soil layer of 0–120 cm. In addition, the residual nitrate-N showed downward leaching with rainfall during the experiment. The RPFM and FPFM treatments reduced the apparent loss and residual levels of soil N, whereas increased its apparent mineralization compared with FP treatment. The FPFM treatment exhibited a greater utilization of residual nitrate-N from previous years and showed a higher amount of the mineralized N from soil organic matter, therefore leading to a relatively high apparent utilization rate of N (56.7%). Considering both grain yield production and utilization efficiencies of water and N, FPFM with year-round mulching was the most effective cultivation measure for winter wheat in the Loess Plateau.

The purpose of this study is to determine whether the allelopathy of living Myriophyllum aquaticum and its straw has the same effects; two pot experiments were conducted to study the effects of intercropping using M. aquaticum and its straw on the growth and cadmium (Cd) accumulation of Nasturtium officinale. Different planting ratios (1:3, 2:2 and 3:1) of N. officinale and M. aquaticum led to an increase in the biomass of both plant species and increased the Cd content in roots and shoots of N. officinale, but led to a reduction in the Cd content in roots and shoots of M. aquaticum. When the intercropping ratio of N. officinale and M. aquaticum was 3:1, the Cd amount in whole plants reached the maximum of 293.96 μg pot⁻¹. Mulching the straw of M. aquaticum roots on the soil surface increased the biomass of N. officinale, but mulching the straw of M. aquaticum stems and leaves led to a decrease. Mulching the straw of roots, stems and leaves of M. aquaticum reduced Cd content and amounts in roots and shoots of N. officinale. Intercropping with M. aquaticum can improve the Cd uptake ability of N. officinale, but mulching M. aquaticum straw can reduce its Cd uptake ability.

Determining the effect of ridge-furrow cultivation mode on ¹³C carbon isotope discrimination, photosynthetic capacity, and leaf gas exchange characteristics of winter wheat leaves will help to increase wheat production. To verify these effects of cultivation modes with deficit irrigation will provide scientific basis for determining water-saving strategy. Therefore, a mobile rainproof shelter was used to explore the potential benefit of two cultivation modes: (1) the ridge-furrow (RF) precipitation system and (2) traditional flat planting (TF) with two deficit irrigation levels (150, 75 mm) and three precipitation levels (275 mm, 200 mm, 125 mm) were tested in this study. Plastic film mulching on ridges had significant effects on rainwater collection and improved soil water retention. Analysis of the light-response curve showed that RF2₁₅₀ treatment significantly increased flag leaf net photosynthetic rate (Pₙ), stomatal conductance (Gₛ), intercellular CO₂ concentration (Cᵢ), transpiration rate (Tᵣ), leaf WUE, and total contents of chlorophyll ab of wheat at flowering stage than that of TF planting. The RF system significantly increases maximum net photosynthetic rate (Pₙₘₐₓ) (16.2%), light saturation points (LSP) (6.7%), and Pₙ under CO₂-response curves compared to the TF cultivation across the two irrigation and three simulated rainfall levels. The RF system significantly increased Δ¹³C (0.7%) and caused a notable increase in the intercellular to ambient CO₂ concentration ratio (7.6%), dry matter translocation (54.9%), and grain yield plant⁻¹ (19%) compared to the TF planting. Furthermore, Δ¹³C was significantly positively correlated with Pₙ, Gₛ, Cᵢ/Cₐ, Cᵢ, Tᵣ, Pₙₘₐₓ, LSP, and grain yield. This study suggested that the RF2₁₅₀ treatment was the best water-saving technique because it increased soil water content, Δ¹³C, biomass, grain yield, and leaf WUE.

Rice fallow, a rainfed lowland agro-ecology, is presently gaining particular attention for sustainable cropping intensification in the South Asia. Nevertheless, cropping intensification of rice-fallow areas is largely challenged by non-availability of irrigation, the poor financial status of farmers and soil constraints. Indeed, fast depletion of the soil residual moisture remains the primary obstacle for growing a crop in succession in rice fallows. A field investigation was carried out to identify the most adaptable rice-winter crop rotation and to customize appropriate crop establishment practice for a winter crop that could conserve the soil moisture. Treatments comprised of three crop establishment practices for winter crops [utera (relay cropping, i.e. broadcasting of seeds in standing rice crop 15 days before harvesting), zero tillage (ZT) and ZT with mulching (ZTM)], and five post-rainy-season crops (lentil, chickpea, lathyrus, mustard and linseed). Results showed that lathyrus and lentil could be the potential winter crop in the rice-fallow condition of Eastern India. Except for mustard crop, the productivity of all the winter crops was higher in utera cropping, which was primarily attributed to early crop growth and higher soil moisture content over ZT and ZTM treatments. The higher water use efficiency was recorded under utera cropping over ZT and ZTM treatments. Higher system productivity (system rice equivalent yield) in rice–utera lathyrus (9.3 t ha⁻¹) and rice–utera lentil (8.1 t ha⁻¹) led to higher net returns and production efficiency over other treatments (winter crop × crop establishment practice). Benefits of rice residue mulching were prominent in lentil, mustard and linseed crop productivity. Energy use efficiency of different crop establishment practices follows the trend of utera > ZT > ZTM (p < 0.05), being highest in rice–utera lathyrus (5.3) followed by rice–utera lentil (4.8) crop rotations. The simulated data shows that winter crops grown under utera led to less emission of greenhouse gas (GHG) and low global warming potential (GWP) as compared to ZT and ZTM treatments. Rice–lathyrus, rice–lentil and rice–chickpea systems had lower N₂O emission than rice–mustard and rice–linseed rotations. Hence, lathyrus and lentil could be included in rice fallows ideally with utera for sustainable cropping intensification and improving the farmers’ income in Eastern India.