The plastic mulch films used in agriculture are considered to be a major source of the plastic residues found in soil. Mulching with low-density polyethylene (LDPE) is widely practiced and the resulting macro- and microscopic plastic residues in agricultural soil have aroused concerns for years. Over the past decades, a variety of biodegradable (Bio) plastics have been developed in the hope of reducing plastic contamination of the terrestrial ecosystem. However, the impact of these Bio plastics in agroecosystems have not been sufficiently studied. Therefore, we investigated the impact of macro (around 5 mm) and micro (<1 mm) sized plastic debris from LDPE and one type of starch-based Bio mulch film on soil physicochemical and hydrological properties. We used environmentally relevant concentrations of plastics, ranging from 0 to 2% (w/w), identified by field studies and literature review. We studied the effects of the plastic residue on a sandy soil for one month in a laboratory experiment. The bulk density, porosity, saturated hydraulic conductivity, field capacity and soil water repellency were altered significantly in the presence of the four kinds of plastic debris, while pH, electrical conductivity and aggregate stability were not substantially affected. Overall, our research provides clear experimental evidence that microplastics affect soil properties. The type, size and content of plastic debris as well as the interactions between these three factors played complex roles in the variations of the measured soil parameters. Living in a plastic era, it is crucial to conduct further interdisciplinary studies in order to have a comprehensive understanding of plastic debris in soil and agroecosystems.

Pistacia atlantica Desf. (Beneh) is an important woody species that has been facing significant challenges to its natural regeneration and reforestation in Iran. This study investigates the interaction of soil moisture and shade on growth, chemical contents, and morphological and physiological characteristics of Beneh saplings. One-year-old Beneh saplings were treated with varying amounts of soil moisture (20, 50, and 100% of field capacity) and shade (0, 30, and 50% of full sunlight) in a split-plot experiment of a randomized complete block design in semiarid conditions of the Alborz Research Station of the Research Institute of Forests and Rangelands (RIFR) in Iran. The results indicate that soil moisture significantly affects the water content of the leaf, total chlorophyll, proline content, activity of catalase enzyme, leaf dry biomass, leaflet area, and dry stem biomass in the leaf. Shade significantly affected total chlorophyll, catalase enzyme activity, specific leaflet area, relative water content of the leaf, proline content, dry root biomass, and leaflet area. The interaction of shade and soil moisture significantly affected seedling height, catalase enzyme activity, specific leaflet area, and nitrogen and potassium content of the leaf. Shade moderates the stress of drought on Beneh saplings, but shading of Beneh saplings is not recommended in conditions where there is no concern about soil moisture. These conclusions can be used to improve the production of Beneh saplings in nurseries.

The objective of this work was to test the effect of water limitation on Copaifera langsdorffii Desf. cultivated in mining tailings from the dam rupture in Mariana City, Brazil. Plants were grown in the mining tailing and under two conditions: field capacity (FC) and 50% FC for 60 days. The effects of water restriction on growth, gas exchange, water potential, and leaf anatomy of C. langsdorffii were evaluated. The experimental design was completely randomized with two treatments and 15 replicates, and data was submitted to one-way ANOVA to p < 0.05. Mining tailings showed adequate nutrient levels and the presence of Al, Cd, Pb, and Cr as well as very small particles of 1.19 μm in diameter. The reduction in water availability promoted no changes in the shoot fresh weight, however, increased this parameter for the roots. In addition, water limitation increased plant investment in the root system while reduced biomass allocation to shoots. Lower water levels also increased the root length, number of leaves, and leaf area. However, both water potential and content were not changed by reduced water availability. Lower water levels also increased gas exchange parameters and chlorophyll content. In addition, 50% FC increased the stomatal length/width ratio and their size though no effect in stomatal density was found. Thus, Copaifera langsdorffii grows and thrives in mining tailings even under reduced water availability up to 50% FC showing potential for reforestation systems.

The transformation of poultry litter waste through the pyrolysis process produces a product called biochar which, applied to the soil, improves its characteristics. The objective of this work was to evaluate the effect of biochar produced from poultry litter wastes, submitted to pyrolysis at 350 °C on soil chemical and physical characteristics. For this, an experiment was carried out involving soil incubation treatments during 100 days with six doses of biochar equivalent to 0.0, 2.02, 4.05, 6.07, 8.10, and 10.12 t ha⁻¹, calculated by the base saturation method, with correction levels from 61 to 87%. After the incubation, soil samples were physically and chemically analyzed. Biochar doses promoted significant increase in pH, electrical conductivity, potassium, sodium, carbon, phosphorus, and base saturation, and decrease in potential acidity and in the soil cation exchange capacity contributing to the increase of soil fertility. The application of the biochar to the soil decreased the bulk density and increased porosity, field capacity, wilting point, and available water for plants. In general, the use of the biochar demonstrates great potential of it as a soil amendment.

This study was carried out to test ex situ growth and soil nutrient removal efficiency of 1-year-old potted willow and poplar plants. Plants were grown under two different water regimes: low irrigation—around soil field capacity (W)—and high irrigation—five times higher than field capacity (W 5). Results showed that plant productivity and water use efficiency were greater when trees were grown in the appropriate level of soil water content rather than at excessive moisture levels. Nutrient leaching was also affected by the high irrigation treatment. However, the poplar and willow clones used in this experiment showed different nutrient allocation patterns in the plant–soil–water system. The poplar clone accumulated the highest quantities of N and P in the soil. Willow accumulated N and P mainly in the biomass due to better root development under both treatments. This indicates the better performance of the willow clone in removing N and P from contaminated aquaculture wastewaters during the first growing season.

The effects of urea, (NH₄)₂SO₄, KNO₃, and NH₄NO₃ on nitrous oxide (N₂O) emission from soil at field capacity and submerged condition were studied during 120 days in the laboratory. Soils in both moisture regimes gave higher emissions in the beginning, which were reduced later. Total emission of N₂O was higher at submergence as compared to field capacity regardless of fertilizer type. At field capacity soil fertilized with ureaemitted the highest amount of N₂O (1903 μg N₂O-N kg⁻¹ soil) during 120 days while at submerged condition, soil with NH₄NO₃ gave the highest emission (4843 μg N₂O-N kg⁻¹ soil). In another study, the efficacy of seven nitrification inhibitors in reducing the emission of N₂O-N from soil fertilized with urea was tested in the laboratory. Nitrapyrin, 2-amino-4-chloro-6-methylpyrimidine (AM), and dicyandiamide (DCD) reduced the emission to 12, 24, and 63% that of urea, respectively, whereas sodium thiosulphate, sulphur, acetylene,and thiourea had no effect on emission of N₂O. In submerged conditions none of the inhibitors reduced the emission.

Processes contributing to acid release/consumption during weathering of a lignite mine spoil (2.3% w/w S as sulfides) from As Pontes (N.W. Spain) were studied under three moisture conditions (at field capacity or under alternate wetting-drying or forced percolation), which were simulated in laboratory experiments. Oxidation of sulfides to sulfates was favoured under all three moisture conditions, releasing most acid in spoil kept at field capacity. Hydroxysulfates formed in spoil kept at field capacity or under alternate wetting-drying conditions, thereby contributing to acid release. Acid consumption by dissolution of clay minerals, especially micas, was favoured under all three moisture conditions, but was particularly intense in spoil at field capacity. Dissolution of aluminium oxides was also favoured under all the moisture conditions studied.

Natural free estrogens found in animal manures are potent endocrine-disrupting compounds. Environmental detections can be caused by such processes as physical and chemical non-equilibrium and colloidal or conjugate facilitate transport. Antecedent or “legacy” concentrations of estrogens resident in soil may also contribute significantly to environmental detections. The objective of this study was to measure and understand the dominant causes contributing to estrogen detections in the environment from a grazed system. To achieve this objective, the effluent of undisturbed lysimeters constructed from soils of fields grazed by dairy cows (Bos taurus) was monitored for free and conjugated estrogens. Four lysimeters were dosed with urine (Urine) and four only received water (Control). Water transfer for all lysimeters was similar, and all lysimeters were near field capacity for the duration of the experiment. Rapid transport of a conservative bromide tracer suggested that preferential flow was an important physical non-equilibrium transport process. Free estrogens and conjugated estrogens (17β-estradiol (E2), estrone (E1), 17β-estradiol-17-sulfate (E2-17S), 17β-estradiol-3-glucuronide (E2-3G), estrone-sulfate (E1-S)) were detected in the source urine (E2 = 17,248 ng/L, E1 = 1006 ng/L, E2-3G = 967 ng/L, E2-17S = 886,456 ng/L, E1-S = 1730 ng/L). These same free and conjugated estrogens, in addition to estriol (E3), were all detected frequently in both Control and Urine lysimeters (detection concentration ranks: E3 > E2-17S = E2 > E2-3G = E1 = E1-3S). Total potential estrogenicity in the effluent of the Control and Urine was also similar, indicating the presence of antecedent estrogens was the dominant contribution to estrogenic detections. Additionally, the frequent detection of conjugates in the lysimeter effluent was important, because it indicated that conjugates were stable in soil but had greater potential mobility than free estrogens.

Background, aim, and scope Diffusive gradients in thin films (DGT) have been recognized as a suitable tool to assess in situ metal bioavailability in soils. Mine tailings have some singular characteristics such as high heavy-metal concentrations, low pH, or absence of water retention capacity that may compromise the correct application of this technique whose applicability is known to be pH dependent. The goal of this study was to determine the response of DGT devices in heavy-metal-polluted mine tailings with different pH. In addition some experiments were performed in order to determine the effect of acidic pH and dissolved ions on the binding properties of the chelating resin. Materials and methods We tested DGT devices on three different mine tailings: acid pH 3, acid tailing limed to pH 5.5, and neutral pH 7.2. The tailings showed high metal concentrations, e.g., 7,000 mg kg⁻¹ Pb, 9,000 mg kg⁻¹ Zn, and 380 mg kg⁻¹ Cu. Diffusive and Chelex resin gels were prepared according to previously published methods. Two chelating resins and diffusive gels thicknesses (0.4 and 0.7 mm) were tested. Four DGT devices of each type were placed during 24 h in pots (one device per pot) containing 1 kg mine tailings in a climate chamber with humidity (50-90%) and controlled temperature conditions (night 16°C and day 23°C). Pots were irrigated with deionized water to field capacity, and then two different experiments were performed: (a) allowing free drainage and (b) maintaining the water saturation. In addition, we tested DGT devices in solutions at pH 3 with similar properties to the soil solution measured in the acid tailing. Eluted Zn, Cd, Pb, and Cu from the chelating resins were measured using inductively coupled plasma-optical emission spectrometer (ICP-OES; Vista-MPX Varian). Results and discussion The metal concentrations taken up by the DGT devices were affected by the different pH values of the tailings. The highest metal concentrations measured with DGT (C DGT) were obtained in the pH 3 treatments (both saturated and free drainage). Significant differences for C DGT were observed between water-saturated and free drainage treatments in the acid pH 3 tailing. When limed pH 5.5 tailing and neutral pH 7 tailing were considered, these differences were lower and not significant. In pH 3 tailings low values for C DGT/C soil solution were obtained (<0.06), indicating that these soils have a low capacity to resupply depleted metals to the solution. The limed acid tailing and the neutral tailing showed values between 0.05 and 0.94 indicating a much more rapid resupply from the solid phase. Deployment under water-saturated conditions yielded much higher C DGT values than under free drainage, indicating the importance to adequately control the moisture content in these soils with poor water retention capacity. In solutions with pH 3 mimicking the soil solution composition of the tailings, a loss of the binding capacity of the resin of 50-60% and 60-80% for Zn in 0.7-mm DGT and 0.4-mm DGT devices, respectively, was observed. As a consequence, 0.7-mm DGT devices had better reliability to carry out in situ determinations in solutions with high metal concentrations and low pH. Conclusions The use of DGT in mining soils can be a promising tool to study bioavailable metals concentrations in mine tailings but it has to be used carefully under acidic pH. Competition with other cations that are present at very high concentrations may hinder the accumulation of metals by the chelating resins, which should be tested under the conditions of the particular mine tailing.

Due to the repeated applications of pesticides, the amount of the pesticides and their products by decomposition may accumulate in the soil ecosystems which are affected by abiotic and biotic factors. Soil microorganisms are the important players that are able to decompose and utilize these chemical waste materials as energy sources and regulate them in the cycling in the soil environment. One of the important insecticides for the control of insect pests including aphids is spirotetramat which can provide protection to plant roots from the attack of insects when it was sprayed on the crops. However, effects of high concentrations of spirotetramat on soil microbial respiration under different soil water contents are unknown. Recommended field dose (RFD) and its 5 (RFD × 5) and 10 (RFD × 10) folds of spirotetramat were mixed with a clay soil; these mixtures were humidified at 50% (50FC), 75% (75FC), and 100% (100FC) of field capacity and then incubated at 28 °C for 21 days. At the end of the incubation period, (1) in general, soil microbial respiration was significantly increased as soil moisture increased in all treatments (50FC < 75FC < 100FC, P < 0.05); (2) all concentrations of spirotetramat significantly decreased the microbial respiration under 100FC (P < 0.05); (3) only RFD × 5 significantly reduced this activity under 75FC (P < 0.05); (4) no significant differences between control and treatments were found under 50FC. In conclusion, high concentrations of spirotetramat insecticide had low toxic effects on soil microbial respiration while the soil moisture regulated the toxicity effects of this insecticide.