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.

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 effect of plantain peel biochar on the uptake of six heavy metals (Cd, Cr, Cu, Fe, Pb and Zn) in spinach (Spinacia oleracea L.) irrigated with untreated wastewater was investigated in nine outdoor lysimeters (0.45 m diameter × 1.0 m height) arranged in a completely randomised design with three replicates. The lysimeters were packed with sandy soil (bulk density 1.35 Mg m⁻³) and brought to field capacity 1 day before starting the experiment. Biochar (1% w/w) was mixed in the top 0.10 m of soil under biochar amendment. Spinach were planted in each lysimeter, irrigated (every 10 days for 4 times in total), harvested (harvest 1 and harvest 2) and analysed for the heavy metals. Spinach leaves accumulated more heavy metals than the roots and stems. Biochar amendment did not affect the translocation of heavy metals (Cd, Cu, Cr, Fe and Pb) to spinach leaves, possibly due to competition with other compounds in the soil solution. However, the biochar amendment improved CEC and increased the pH of soils which resulted in a 42% reduction of translocation of Zn in spinach leaves. Assuming daily spinach consumption of 200 g per person, Zn in spinach grown in soil amended with biochar would be below the provisional maximum tolerable daily intake limit for adults (20 mg) as prescribed by WHO/FAO/IAEA. Consumption of spinach grown with wastewater in soil without biochar amendment may not be safe because of Zn toxicity. Likewise, the concentration of Cd, above CODEX permissible levels in the spinach leaves and eleven times higher in wastewater than freshwater irrigation, raises a concern for consumers in developing countries where untreated wastewater is often used for irrigation.

Potassium silicate drilling fluid (PSDF) is a relatively new type of drilling waste generated by the oil and gas industry. PSDF effects on soil, vegetation, and ground water must be determined before its land disposal and use in reclamation can be regulated. A laboratory column leachate study was conducted to quantify the response of select soil and leachate properties to PSDF at various depths in soil column profiles. A spent PSDF was applied to two soils (sand and loam textures) at four rates (20, 40, 60, 120 m³ ha⁻¹) with two application methods (incorporated, sprayed). Changes to soil and leachate properties were at values that would not be detrimental to most plant species when PSDF was applied at ≤60 m³ ha⁻¹. Applying PSDF at 120 m³ ha⁻¹had significant effects on soil properties and leachate quality. Hydraulic conductivity and field capacity were significantly reduced, and soil available potassium and sulfate concentrations, pH, and salinity increased with PSDF. Incorporated PSDF in the upper 10 cm of soil accelerated PSDF element transport through soil columns to leachate and increased organic carbon and salinity in leachate. PSDF application rate significantly reduced soil field capacity, available nitrogen, and increased salinity at the highest rates in loam soil, suggesting a threshold beyond which conditions will not be suitable for land spraying PSDF. This research demonstrates that PSDF has potential to improve soil short term water availability, macronutrient potassium and sulfur for disposal on cultivated and uncultivated lands. This potential should be field tested.

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.

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.

In today’s agriculture, the use of pesticides has become a necessity for higher yield of crops. Out of the total pesticides applied, only a small fraction reaches the target pest and the rest pollute different environmental segments. The present study signifies the effect of soil moisture and enhanced sunlight intensity on the degradation of dimethoate, a commonly used organophosphate pesticide in soil. The study was conducted in dry, field capacity, and submerged soils under enhanced sunlight conditions (3 intensity levels) obtained by using a solar collector. Higher degradation was observed in submerged soil followed by dry and field capacity soils under all the light conditions and might have occurred through radical mediated mechanism. When sunlight intensity was almost doubled, the pesticide residue was 17.2% less but 9% higher as compared to UV light in submerged soil after 30 days of experimentation, mainly due to the increase in UV component of enhanced sunlight intensity. Therefore, although artificial UV light is still most effective in pesticide degradation, enhanced sunlight can also play an important role and be used as a viable, economical, and greener technique. Statistically, sunlight intensity and the degradation rate were correlated positively. Moreover, the degradation of the pesticide in soil followed first order kinetic model. The half-life of the pesticide varied widely from 7.96 to 41.11 days under different soil moisture and sunlight conditions. This study can help in understanding and modeling the degradation behavior of dimethoate under varying soil and environmental conditions.

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.

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.