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Microplastic effects in terrestrial ecosystems have recently moved into focus, after about a decade of research being limited to aquatic systems. While effects on soil physical properties and soil biota are starting to become apparent, there is not much information on the consequences for plant performance. We here propose and discuss mechanistic pathways through which microplastics could impact plant growth, either positively or negatively. These effects will vary as a function of plant species, and plastic type, and thus are likely to translate to changes in plant community composition and perhaps primary production. Our mechanistic framework serves to guide ongoing and future research on this important topic.

Abstract The physical properties of the soil are studied to understand the influence of soil properties on infiltration rate. The effect of soil physical properties on infiltration rates on logged-over forests was measured with a mini-disk infiltrometer across various levels of soil disturbances. Results of soil analysis suggest are mostly loamy texture and the bulk density has varied from 0.74 - 1.02 g cm −3 , respectively. The basic infiltration rate has varied from a minimum of 0.61 mmhr −1 to a maximum of 45.22 mmhr −1 with an average of 3.81 mmhr −1 . The results of simple regression analyses showed that there was little association between the physical properties of the soil and the infiltration rate. This study suggests that the high variation of infiltration rate in this study site is attributed to the high spatial variability of soil properties.

Soil tillage can affect the stability and formation of soil aggregates by disrupting soil structure. Frequent tillage deteriorates soil structure and weakens soil aggregates, causing them to be susceptible to decay. Different types of tillage systems affect soil physical properties and organic matter content, in turn influencing the formation of aggregates. The objective of this study was to evaluate the effect of long-term tillage on soil aggregates and aggregate-associated carbon in a black soil of Northeast China and to identify the optimal conservation tillage in this system. This research was conducted on a long-term tillage experimental field established in 1983 at the Jilin Academy of Agricultural Sciences, Gongzhuling, China. Plots were treated with four tillage systems including no tillage (NT), spacing tillage (ST), moldboard plowing (MP), and conventional tillage (CT). We took samples every 10cm from 0-60cm depth and demonstrated that water-stable soil aggregates >0.25mm in diameter accounted for over 66.0% of total aggregates for all tillage treatments, and the percentage for the ST treatment was 34.5% higher than in the other treatments. The NT treatment had the highest effect at 0-10cm depth, while the effect for the ST treatment was highest at 0-30cm. SOC storage decreased with soil depth, with a significant accumulation at 0-20cm depth. Across treatments, aggregate-associated C at a depth of 0-10cm was higher in the NT and ST treatments than in the MP and CT treatments. The advantage of the NT treatment weakened with soil depth, while the amount of aggregate-associated C remained higher for the ST treatment. There were more macro-aggregates in the ST and NT treatments than in the MP and CT treatments, while the MP and CT treatments had more micro-aggregates. The sum of macro-aggregate contributing rates for soil organic C (SOC) was significantly superior to that of the micro-aggregates. Water-stable aggregates increased by 34.5% in the ST treatment, effectively improving the soil structure. Furthermore, 0.25-1.00 and 1-2mm aggregates had the highest SOC storage and responded rapidly to the various tillage treatments. Hence, they can serve as indicators for the long-term influence of different tillage treatments on the distribution of aggregates and SOC.

Abstract Microplastic contamination, like other global change factors, can induce effects on ecosystem functions and processes, affecting various soil biophysical properties. However, effects of such contaminants on nutrient cycles in agroecosystems are still poorly understood. We here performed two pot experiments to investigate the effect of polyester microplastic fibers (PMFs) on soil physical properties, nitrogen cycle, and plant performance in a maize-based agroecosystem. Moreover, we followed the N loss via leaching in soil contaminated or not with PMFs by simulating heavy rainfall events that mimic a future scenario of climate change. Our results show that soil contaminated with PMFs (at a concentration of 0.5% w/w) can jeopardize agroecosystem sustainability by affecting soil physical properties and in particular soil macro- and microporosity, the nitrogen cycle, and plant performance. In particular, we found that soil PMF contamination limited crop growth and N uptake by circa 30%, and consequently increased N loss via leaching. Overall, our findings show that soil contamination with PMFs may pose problems to future agricultural challenges like food security and environmental protection.

Heavy metal pollution is a global issue due to health risks associated with metal contamination. Although many metals are essential for life, they can be harmful to man, animal, plant and microorganisms at toxic levels. Occurrence of heavy metals in soil is mainly attributed to natural weathering of metal-rich parent material and anthropogenic activities such as industrial, mining, agricultural activities. Here we review the effect of soil microbes on the biosorption and bioavailability of heavy metals; the mechanisms of heavy metals sequestration by plant and microbes; and the effects of pollution on soil microbial diversity and activities. The major points are: anthropogenic activities constitute the major source of heavy metals in the environment. Soil chemistry is the major determinant of metal solubility, movement and availability in the soil. High levels of heavy metals in living tissues cause severe organ impairment, neurological disorders and eventual death. Elevated levels of heavy metals in soils decrease microbial population, diversity and activities. Nonetheless, certain soil microbes tolerate and use heavy metals in their systems; as such they are used for bioremediation of polluted soils. Soil microbes can be used for remediation of contaminated soils either directly or by making heavy metals bioavailable in the rhizosphere of plants. Such plants can accumulate 100 mg g −1 Cd and As; 1000 mg g −1 Co, Cu, Cr, Ni and 10,000 mg g −1 Pb, Mn and Ni; and translocate metals to harvestable parts. Microbial activity changes soil physical properties such as soil structure and biochemical properties such as pH, soil redox state, soil enzymes that influence the solubility and bioavailability of heavy metals. The concept of ecological dose (ED 50 ) and lethal concentration (LC 50 ) was developed in response to the need to easily quantify the influence of pollutants on microbial-mediated ecological processes in various ecosystems.

The aim of this work was to evaluate the physical and mechanical properties of cement-wood composites with the addition of biomass ashes at different levels (0, 5, 10, 15, 20, and 25%). The composites were produced using Portland cement CPII, Eucalyptus grandis particles, and ashes from eucalyptus wood. The tests followed the NBR 7215 (2019) and ASTM E1876 (2022) standards, density, 24-hour thickness swelling, 24-hour water absorption, dynamic modulus of elasticity from non-destructive testing, static modulus of elasticity, and compressive strength at 28 days tests were carried out. After the tests, statistical analysis was performed to verify if there were statistically differences between the means at a 5% level of significance. The partial replacement of cement with ashes shows potential, especially with a 5% replacement, due to better physical and mechanical properties. El objetivo del presente estudio fue evaluar las propiedades físico-mecánicas de compuestos cemento-madera con la incorporación de cenizas de biomasa en diferentes proporciones (0, 5, 10, 15, 20 y 25%). Estos compuestos se fabricaron utilizando cemento Portland CPII, partículas de Eucalyptus grandis y cenizas procedentes de la combustión de madera de eucalipto, siguiendo las normativas NBR 7215 (2019) y ASTM E1876 (2022). Se realizaron pruebas de densidad, expansión en espesor a las 24 horas, absorción de agua a las 24 horas, módulo de elasticidad dinámico mediante ensayos no destructivos, módulo de elasticidad estático y resistencia a la compresión a los 28 días. Posteriormente, se efectuó un análisis estadístico para determinar si existían diferencias entre las medias con un nivel de significancia del 5%. La sustitución parcial del cemento por cenizas demostró tener potencial, destacándose especialmente el tratamiento con una sustitución del 5% debido a sus mejores propiedades físico-mecánicas.

Heavy clay soils are globally widespread but their poor drainage and poor aeration limit their use for agriculture. This study was designed to test the effect of the amendment of biochar (BC) from woody shrubs on drainage/saturated hydraulic conductivity (Ksat), soil aeration/air capacity, available water capacity and biomass and grain yields of maize. In a field experiment, BC from Gliricidia sepium was applied in planting basins or rip lines at 2.5% and 5% w/w in addition to a control without BC. The maize biomass and grain yields were higher in BC treated plots compared to control (p<0.05) during the 2012 and 2013 seasons. There was no significant difference in the yields between 2.5% and 5% BC treatments (e.g. grain yield were 6.6 and 8.1 t ha-1 in 2012 and 9.3 and 10.3 t ha-1 in 2013 compared to control with 4.2 and 6.7 t ha-1 in 2012 and 2013, respectively). Soil from the same field site was also mixed with a similar woody shrub BC from Eupatorium adenophorum in the laboratory at rates of 2.5%, 5% and 10% BC w/w and a control without BC. The mixtures were then incubated and subjected to two wet-dry cycles for two weeks. Core samples were taken from the incubated soil and tested for bulk density, Ksat and pF measurements. Total porosity and moisture at field capacity and wilting point were 72.3%, 43.7% and 23.7%, respectively, and not affected by BC amendment (p>0.05). In contrast, bulk density decreased linearly by 0.011±0.002 g cm-3 per percent BC added (p<0.001). Ksat and air capacity of the soil were 288 cm day-1 and 30.9%, respectively falling within the generally accepted optimal range. Both Ksat and air capacity followed a significant quadratic relation (p<0.05) upon BC addition, decreasing at low BC doses, reaching a minimum at 3-5% BC and increasing at higher doses. Results allowed a partial attribution of the yield increases to changes in soil physical properties such as changes in bulk density and not clearly to Ksat and air capacity.

Background and aims In recent decades, an increasing proportion of alpine shrub meadow has become severely degraded owing to the combined effects of global climate warming and rodent infestation, with significant impacts on soil water retention. The present paper investigates the patterns and controlling factors of soil water retention of alpine shrub meadow under different degrees of degradation, to help inform decisions on the management of degraded alpine shrub meadow. Methods Four degradation stages were defined: non-degradation (ND); light degradation (LD); moderate degradation (MD) and higher degradation (HD). Pearson correlation and redundancy analysis were used to examine the relationships between soil physical properties and soil hydraulic properties. Results Sand content increased while clay content decreased with increasing degree of degradation. In HD treatment, the available nitrogen and soil bulk density of surface soil layer was significantly lower than that in the other three stages, whereas the soil organic matter content and soil total porosity of surface soil layer was increased significantly, the soil compaction of 0–10 cm soil depth in HD was reduced significantly. The soil water retention of 0–60 cm soil depth first decreased and then increased with increasing degradation, with the maximum values occurring in HD, and the soil organic matter has an overwhelming effect on soil water retention than soil texture. Conclusions As the degree of degradation increased, the surface soil structure deteriorated, and available nitrogen reduced while soil organic matter increased sharply in higher degradation, which leads to the highest soil water retention in higher degradation. Our results suggested that the soil water retention in degraded alpine grassland was largely determined by soil organic matter, and the soil organic matter parameters should be incorporated in hydrological models of degraded alpine ecosystem.

Saturated hydraulic conductivity (Ksat) is an important soil parameter that highly depends on soil's particle size distribution (PSD). The nature of this dependency is explored in this work in two ways, (1) by using the information entropy as a heterogeneity parameter of the PSD and (2) using descriptions of PSD in forms of textural triplets, different than the usual description in terms of the triplet of sand, silt, and clay contents. The power of this parameter, as a descriptor of ln⁡Ksat, was tested on a database larger than 19 000 soils. Bootstrap analysis yielded coefficients of determination of up to 0.977 for ln⁡Ksat using a triplet that combines very coarse, coarse, medium, and fine sand as coarse particles; very fine sand, and silt as intermediate particles; and clay as fine particles. The power of the correlation was analysed for different textural classes and different triplets using a bootstrap approach. Also, it is noteworthy that soils with finer textures had worse correlations, as their hydraulic properties are not solely dependent on soil PSD. This heterogeneity parameter can lead to new descriptions of soil PSD, other than the usual clay, silt, and sand, that can describe better different soil physical properties, that are texture-dependent.

Aims To assess the effects of potato-legume intercropping on selected soil physical and chemical properties after four consecutive growing seasons (from the short rains in 2014 to long rains 2016). Methods The experiment was laid out in a randomised complete block design with four replicates. The treatments were potato-dolichos (PD); potato-garden pea (PG); potato-bean (PB) intercropping systems, and a pure stand of potato (PS). After every harvest, crop residues were ploughed back and selected soil physico-chemical properties were assessed after two years of cultivation. Results Potato-legume intercropping resulted in a significant increase down the slope for clay and silt under PS, PG and PB whereas, an opposite observation was made for sand and bulk density. Nonetheless, under PD, slope position had no significant effect on soil physical properties. In all cropping systems, a significant increase was observed down the slope for pH and cation exchange capacity. Similar observations were made for phosphorous, nitrogen and organic carbon under all the cropping systems except PD. Conclusions This study has established PD as a viable intercropping system, which could be adopted by farmers for improved soil fertility.