Soil Physicochemical Conditions Research Articles

Maize Lowers the N2O Emissions from Maize/Soybean Intercropping

Interspecific interactions between intercropped maize and soybean are expected to cycle soil nitrogen efficiently and avoid N2O emissions. However, the unique interactions of maize and soybean with nitrogen cycling bacteria makes it hard to predict the crop-specific impact on soil N2O production. We conducted a field microcosm experiment with root separation to simulate monoculture and intercropping with maize and soybean. Intercropped maize reduced the N2O emissions by 16–41%, compared to monoculture maize. This was related to reduced nitrification by ammonia-oxidizing bacteria and denitrification reactions (as indicated by the abundance of nirS and nirK gene copies), as well as drier soil conditions and lower soil NO3--N levels. Soil N2O emissions were the same in monoculture and intercropped soybean, suggesting stable denitrification (based on nirS, nirK and nosZ genes) with constant soil physicochemical conditions. As monoculture maize can stimulate soil N2O emission through denitrification, this work justifies the adoption of maize-soybean intercropping as a low N2O-emitting practice in sustainable agriculture, due to its beneficial effects on soil biology and biochemistry.

The seeds of Plantago lanceolata comprise a stable core microbiome along a plant richness gradient

BackgroundSeed endophytic bacteria are beneficial to plants. They improve seedling growth by enhancing plant nutrient uptake, modulating stress-related phytohormone production, and targeting pests and pathogens with antibiotics. Seed endophyte composition can be influenced by pollination, plant cultivar, and soil physicochemical conditions. However, the effects of plant community richness on seed endophytes are unknown. To investigate the effects of increasing plant species richness on the diversity and composition of the seed microbiome, we made use of a well-established long-term biodiversity experiment in Germany (The Jena Experiment). We sampled seeds from different Plantago lanceolata blossoms in a plant diversity gradient ranging from monoculture to 16 species mixtures. The seeds were surface sterilized to remove seed surface-associated bacteria and subjected to a metabarcoding approach to assess bacterial community structure.ResultsOur data indicate a very stable core microbiome, which accounted for more than 90% of the reads and was present in all seeds independent of the plant richness level the seeds originated from. It consisted mainly of reads linked to Pseudomonas rhizosphaerae, Sphingomonas faeni and Pirellulla spp. 9% of the obtained reads were not part of the core microbiome and were only present in plots of specific diversity levels. The number of unique ASVs was positively correlated with plant richness. Interestingly, most reads described as non-core members belonged to the same genera described as the core microbiome, indicating the presence of different strains or species with possibly different functional properties important for seed performance.ConclusionOur data indicate that Plantago lanceolata maintains a large seeds core microbiome across the plant richness gradient. However, the number of unique ASVs increases alongside the plant community richness, indicating that ecosystem biodiversity also mitigates diversity loss in seed endophytes.

Universal microbial reworking of dissolved organic matter along environmental gradients.

Soils are losing increasing amounts of carbon annually to freshwaters as dissolved organic matter (DOM), which, if degraded, can offset their carbon sink capacity. However, the processes underlying DOM degradation across environments are poorly understood. Here we show DOM changes similarly along soil-aquatic gradients irrespective of environmental differences. Using ultrahigh-resolution mass spectrometry, we track DOM along soil depths and hillslope positions in forest catchments and relate its composition to soil microbiomes and physico-chemical conditions. Along depths and hillslopes, we find carbohydrate-like and unsaturated hydrocarbon-like compounds increase in abundance-weighted mass, and the expression of genes essential for degrading plant-derived carbohydrates explains >50% of the variation in abundance of these compounds. These results suggest that microbes transform plant-derived compounds, leaving DOM to become increasingly dominated by the same (i.e., universal), difficult-to-degrade compounds as degradation proceeds. By synthesising data from the land-to-ocean continuum, we suggest these processes generalise across ecosystems and spatiotemporal scales. Such general degradation patterns can help predict DOM composition and reactivity along environmental gradients to inform management of soil-to-stream carbon losses.

Taking sides? Aspect has limited influence on soil environment or litter decomposition in pan-European study of roadside verges

In addition to well-known effects on species ecophysiology, phenology, and distributions, climate change is widely predicted to impact essential ecosystem services such as decomposition and nutrient cycling. While temperature and soil moisture are thought to influence litter decomposition, elucidating consistent soil process responses to observed or predicted shifts in climate have proven difficult to evidence. Here we investigated how aspect (i.e., north-south orientation), a natural model for variation in soil temperature, influenced soil physico-chemical conditions and decomposition of two standardised litter types (Green tea and Rooibos teabags) in Pole-facing (PF) and Equator-facing (EF) roadside verges spanning a 3000 km and 27° latitudinal gradient across Europe. Despite average daily temperatures being 1.5 - 3.0 °C warmer on EF than PF slopes, there were only minor region-specific differences in initial soil physico-chemical conditions and short-term variation in litter decomposition (i.e., litter mass loss was higher in EF-verges for the first month of deployment only) associated with aspect. We conclude that previously observed differences in soil environments and the decomposition process associated with slope orientation, is largely litter or environment specific, although medium-term soil-decomposition in semi-natural grassland ecosystems may also be insensitive to the magnitude of temperature variation within the range predicted by the IPCC SSP1–2.6 emissions scenario. Nonetheless, consistent average and extreme temperature differences between adjacent PF- and EF-aspects along roadside verges provides a model system to explore exactly how resilient the soil environment and the micro-organisms responsible for decomposition, are to temperature variation.

Cover crop-mediated soil carbon storage and soil health in semi-arid irrigated cropping systems

Cover cropping is considered a climate-smart strategy to regenerate low-fertility soils in arid and semi-arid regions. However, the mechanisms of soil organic carbon (SOC) storage and soil health improvement in semi-arid irrigated cropping systems are poorly understood. The main goal of this study was to evaluate cover crop effects on various physical, chemical, and biological indicators of soil health in an irrigated silage corn (Zea mays L.)–sorghum [Sorghum bicolor (L.) Moench] rotation and understanding how changes in soil health contribute to SOC storage. We evaluated various SOC and nitrogen (N) pools, and microbial community structure under cover crop mixture of grasses, brassicas, and legumes (GBL), grasses and brassicas (GB), grasses and legumes (GL), and no cover crops (NCC) control for four years. Grasses included annual ryegrass (Lolium multiflorum Lam.) and winter triticale (× Triticosecale Wittmack), brassicas included turnip (Brassica rapa subsp. rapa L.) and daikon radish (Raphanus sativus var. Longipinnatus Bailey), and legumes included pea (Pisum sativum subsp. arvense L.) and berseem clover (Trifolium alexandrinum L.). Soil C pools: SOC, potentially mineralizable C, microbial biomass C, mineral-associated organic C (MAOC), and particulate organic C (POC) were greater with cover crops than without, but the effects were not consistent in all study years. Soil organic N was also greater under cover crops than under NCC. Soil C-to-N (C:N) ratio increased over the years but was similar among treatments. Cover crops used N and soil water to grow, significantly reducing soil inorganic N content and water-filled pore spaces in the first two years. However, fungal and bacterial communities grew better under cover crops with a high fungi-to-bacteria ratio than under NCC. The soil MAOC content was related to microbial community and enzyme activity while POC was affected by soil physicochemical conditions, specifically soil pH and mineral N availability, highlighting two major pathways of SOC sequestration in semi-arid cropping systems. This study showed how cover crops enhance SOC storage and soil health in semi-arid cropping systems.

Location: root architecture structures rhizosphere microbial associations.

Root architectural phenotypes are promising targets for crop breeding, but root architectural effects on microbial associations in agricultural fields are not well understood. Architecture determines the location of microbial associations within root systems, which, when integrated with soil vertical gradients, determines the functions and the metabolic capability of rhizosphere microbial communities. We argue that variation in root architecture in crops has important implications for root exudation, microbial recruitment and function, and the decomposition and fate of root tissues and exudates. Recent research has shown that the root microbiome changes along root axes and among root classes, that root tips have a unique microbiome, and that root exudates change within the root system depending on soil physicochemical conditions. Although fresh exudates are produced in larger amounts in root tips, the rhizosphere of mature root segments also plays a role in influencing soil vertical gradients. We argue that more research is needed to understand specific root phenotypes that structure microbial associations and discuss candidate root phenotypes that may determine the location of microbial hotspots within root systems with relevance to agricultural systems.

Post-fire soil emissions of nitric oxide (NO) and nitrous oxide (N2O) across global ecosystems: a review

AbstractWildfires may increase soil emissions of trace nitrogen (N) gases like nitric oxide (NO) and nitrous oxide (N2O) by changing soil physicochemical conditions and altering microbial processes like nitrification and denitrification. When 34 studies were synthesized, we found a significant increase in both NO and N2O emissions up to 1 year post-fire across studies spanning ecosystems globally. However, when fluxes were separated by ecosystem type, we found that individual ecosystem types responded uniquely to fire. Forest soils tended to emit more N2O after fire, but there was no significant effect on NO. Shrubland soils showed significant increases in both NO and N2O emissions after fires; often with extremely large but short-lived NO pulses occurring immediately after fire. Grassland NO emissions increased after fire, but the size of this effect was small relative to shrublands. N2O emissions from burned grasslands were highly variable with no significant effect. To better understand the variation in responses to fire across global ecosystems, more consistent measurements of variables recognized as important controls on soil fluxes of NO and N2O (e.g., N cycling rates, soil water content, pH, and substrate availability) are needed across studies. We also suggest that fire-specific elements like burn severity, microbial community succession, and the presence of char be considered by future studies. Our synthesis suggests that fires can exacerbate ecosystem N loss long after they burn, increasing soil emissions of NO and N2O with implications for ecosystem N loss, climate, and regional air quality as wildfires increase globally.

Effect of microbial consortia on maize yield in Chiapas, Mexico

The use of microbial consortia as biofertilizers allows improving crop productivity and the quality of agricultural soils, by incorporating microorganisms that facilitate the availability of nutrients for plants and change the soil physicochemical conditions. In order to evaluate the effect of microbial consortia on maize yield, inoculums from different environments were used in the maize crop of Villa Corzo and Villaflores municipalities, Chiapas. Six treatments with different consortia were defined: three from agricultural plots and three from mountains “La Frailescana”, “Cerro Nambiyugua” and Biosphere Reserve “La Sepultura”-, and one control, under a randomized block experimental design with four replications. The application of the microbial consortia was made directly to the soil at 20, 40 and 60 days after sowing of the crop. The effect of the consortia on maize yield was determined using a design with nested effects in which the effects of the origin of the microbial consortia were controlled, and the nested treatments in the environments. The association between the physicochemical components of the consortia and the culture yield was evaluated using Pearson’s correlation (p ≤ 0.05). Only the mountain consortiums from “La Sepultura” were the ones that showed maize yield increase. However, both the mountain and plot consortiums have the potential to be used as biofertilizers in maize cultivation, when combined with another source of organic fertilization, such as poultry manure.

Nitrogen fate during agricultural managed aquifer recharge: Linking plant response, hydrologic, and geochemical processes

Agricultural managed aquifer recharge (Ag-MAR, on-farm recharge), where farmland is flooded with excess surface water to intentionally recharge groundwater, has received increasing attention by policy makers and researchers in recent years. However, there remain concerns about the potential for Ag-MAR to exacerbate nitrate (NO3−) contamination of groundwater, and additional risks, such as greenhouse gas emissions and crop tolerance to prolonged flooding. Here, we conducted a large-scale, replicated winter groundwater recharge experiment to quantify the effect of Ag-MAR on soil N biogeochemical transformations, potential NO3− leaching to groundwater, soil physico-chemical conditions, and crop yield. The field experiment was conducted in two grapevine vineyards in the Central Valley of California, which were each flooded for 2 weeks and 4 weeks, respectively, with 1.31 and 1.32 m3 m−2 of water. Hydrologic, geochemical, and microbial results indicate that NO3− leaching from the first 1 m of the vadose zone was the dominant N loss pathway during flooding. Based on pore water sample and N2O emission data, denitrification played a lesser role in decreasing NO3− in the root zone but prolonged anoxic conditions resulted in a significant 29 % yield decrease in the 4-week flooded vineyard. The results from this research, combined with data from previous studies, are summarized in a new conceptual model for integrated water-N dynamics under Ag-MAR. The proposed model can be used to determine best Ag-MAR management practices.

Soil Quality Index for the Two Agricultural Areas along the Naboc River in Davao de Oro, Philippines Contaminated with Mercury

The study aimed to determine the soil physicochemical conditions, soil quality index (SQI), its relationship to soil total mercury (THg), and their spatial autocorrelation of the two mercury- contaminated agricultural areas in Monkayo, Davao de Oro, Philippines. Soil physicochemical parameters and THg were assessed, and the data underwent principal component analysis (PCA). The minimum data set (MDS) revealed that percent sand, pH, THg, phosphorus (P), and organic carbon (OC) significantly contributed to the SQI expression. The two agricultural areas (Diwata and Naboc) had comparable (P > 0.05) soil quality indices (0.46 ± 0.073 and 0.46 ± 0.11), which were categorized as Grade 3 (moderate SQI). THg was negatively associated with the SQI, with the regression coefficient (R) equal to –0.419 (p = 0.021); however, this association did not mean a causal effect. Hence, mercury (Hg) contamination could not be singled out as the sole factor in soil quality deterioration but rather the synergistic effects of the agricultural practices and the Hg contamination. Spatial autocorrelation analysis revealed that THg spatial distribution in both areas and the SQI of Diwata were clustered; however, the spatial distribution of SQI in Naboc was random. An in-depth study of soil microbiological function and the ecotoxicological effect of mercury on soil quality is deemed important to be studied.

The Interaction of Organic Fertilizer and Pitting on Nutrient Content, Phenolic Compounds, and Root and Shoot Lengths in Vetiver Grass (Chrysopogon zizanioides L.)

ABSTRACT The shortage of elements in the soil and water available to the plant are some of the most common environmental stresses in Iran which faces drought every year. The purpose of this study was to study the effect of pitting and organic fertilizers on the growth and physiological characteristics of vetiver grass in drought stress conditions. After cultivating the seedlings in the pots in the greenhouse and their growth for three months, the seedlings were transformed to the field and the treatments were applied to them for six months. This experiment was conducted as a factorial experiment based on randomized complete block design in the field. The treatments applied to the seedlings were cultivation with pitting and without pitting, three levels of fertilizer (0, 150, and 300 kg fertilizer per hectare), and two levels of irrigation determined based on field capacity (FC) (FC and 1/4FC). After harvest, the plants were transferred to the laboratory for measurements. The results showed that by applying pitting and fertilizers, shoot height changed from 9.8 cm to 16.68 cm, root length from 18.81 cm to 25.55 cm, potassium (K) from 25.95 mg/kg to 34.30 mg/kg, calcium (Ca) from 1.20 mg/kg in pitting treatment to 2.27 mg/kg in non-pitting treatment, phenol from 0.22 mg/g DW to 0.83 mg/g DW and phosphorus (P) from 2.99 mg/kg to 11.95 mg/kg. The results indicated the interactive effects of organic fertilizer and pitting due to improvement in soil physicochemical conditions and increase in growth and nutrient uptake of vetiver grass.

Physicochemical variability of agricultural soils in the bulb onion (Allium Cepa L.) crop of the irrigation and drainage district Usochicamocha in Boyacá, Colombia

The bulb onion crop, besides being one of the main vegetable crops worldwide for Boyacá, is considered one of the pillars of the regional agricultural economy. Despite being so important from the economic aspect, at the agricultural level this crop has several problems among which stand out the nutritional requirements of the crop and poor practices in terms of soil management and conservation. That is why it is important to understand the physicochemical variability of the soil associated with the crop and how these can be related to intrinsic processes at a local geographic scale. To determine the variability of soil physicochemical conditions in the bulb onion crop, a total of 15 zones of 50m x 50m within the Usochicamocha irrigation district were analyzed. Soil samples were collected and subsequently analyzed in the laboratory. Information was obtained on parameters such as pH, OM%, ED, bulk density, soil texture, Ca, Mg, K, Na and P. The soil data obtained allowed us to observe the grouping patterns of study zones which have no geographical incidence, suggesting that intrinsic characteristics of the crops such as agricultural practices would play a more important role in the physicochemical variability than extrinsic factors such as the ecogeographic range of the zone. Our results support efforts to continue exploring the variability of soil physicochemical conditions within a crop and how these may relate to local soil management and conservation practices after each harvest season.

Floristic study of perennial flora and ethnomedicinal uses in annual ground fire affected part of dry deciduous forest, Godapiyasal Paschim Medinipur, West Bengal, India

The lateritic belt of south West Bengal is characterized by dry deciduous forest mainly dominated by Sal. The Godapiyasal forest range, near to Midnapore sadar town and beside NH14 is Sal dominated mixed forest with five to six subdominants of similar life form. The forest area scattered in a vast area with intermittent villages and a major portion of it is affected by ground fire annually. This study was conducted to record the present vegetation status of perennial plants of this forest with their actual habit observed along some soil physico-chemical conditions. Survey and sampling were done randomly up to fourteen km along the road through the forest in second and third week of February, 2019. Along the road, from 10 different roadside points up to one km within the forest both sides were surveyed throughout accessible zones by walking without hampering the vegetation. Photographs were taken also. Plants were identified following local, regional and continental Flora and with the help of expert persons. Soil samples were collected from those zones from up to 20 cm depth and mixed well to form composite soil sample and studied in triplicate. Soil pH, moisture content, organic carbon contents were studied. The survey revealed forest was with 32% trees, 15% small trees, 22% shrubs and climbers or lianas, 8%, herbs and 1% fern. Soil analysis revealed pH 5.5-5.6, moisture content 0.86%, and organic corbon0.004%.

Bridging Microbial Functional Traits With Localized Process Rates at Soil Interfaces.

In this review, we introduce microbially-mediated soil processes, players, their functional traits, and their links to processes at biogeochemical interfaces [e.g., rhizosphere, detritusphere, (bio)-pores, and aggregate surfaces]. A conceptual view emphasizes the central role of the rhizosphere in interactions with other biogeochemical interfaces, considering biotic and abiotic dynamic drivers. We discuss the applicability of three groups of traits based on microbial physiology, activity state, and genomic functional traits to reflect microbial growth in soil. The sensitivity and credibility of modern molecular approaches to estimate microbial-specific growth rates require further development. A link between functional traits determined by physiological (e.g., respiration, biomarkers) and genomic (e.g., genome size, number of ribosomal gene copies per genome, expression of catabolic versus biosynthetic genes) approaches is strongly affected by environmental conditions such as carbon, nutrient availability, and ecosystem type. Therefore, we address the role of soil physico-chemical conditions and trophic interactions as drivers of microbially-mediated soil processes at relevant scales for process localization. The strengths and weaknesses of current approaches (destructive, non-destructive, and predictive) for assessing process localization and the corresponding estimates of process rates are linked to the challenges for modeling microbially-mediated processes in heterogeneous soil microhabitats. Finally, we introduce a conceptual self-regulatory mechanism based on the flexible structure of active microbial communities. Microbial taxa best suited to each successional stage of substrate decomposition become dominant and alter the community structure. The rates of decomposition of organic compounds, therefore, are dependent on the functional traits of dominant taxa and microbial strategies, which are selected and driven by the local environment.

How soil abiotic factors affect the population fluctuation of Leitneria pugio (Acari: Mesostigmata: Halolaelapidae)

Abiotic factors, such as temperature, humidity, soil elements, along with biotic factors affect terrestrial arthropod communities. Since the application of agricultural fertilizers with the entrance of different elements causes changes in the soil physicochemical conditions, fertilizers may cause fluctuation in the population density of edaphic arthropods. Given this opinion, in this research, the effect of common fertilizers on the population fluctuation and distribution pattern of the predatory mite Leitneria pugio (Karg) was investigated. The experimental treatments were granular urea fertilizer with two doses (200 and 400 kg per ha), poultry manure, zinc sludge (to simulate the accumulation of zinc sulfate fertilizer in the soil), and control in five blocks. Humidity, pH, temperature, NO3– and NO2–, and elements (organic Carbon, K, Na, P, Fe, Cu, Pb, Cr, Cd, Ni, Zn, and As) of soil were measured, and their relationship with the predatory mite population was determined by Pearson correlation coefficient. Iwao's patchiness, Taylor's power law, and Morisita's coefficient of dispersion were used for determining the spatial distribution pattern of L. pugio. The spatial pattern of L. pugio was aggregated, and the highest population density of the predator was observed in December in zinc sludge and control treatments, and in May, in zinc sludge treatment, on the average 60, 35, and 110 per m2, respectively. The relationship between mite's population and Cu and Pb was significantly positive, and L. pugio had a significantly negative relationship with P, NO3– and soil temperature. Nevertheless, the application of different fertilizers did not affect the spatial distribution pattern of the predator.

Composition and abundance of weed-species in relation to physicochemical variables in soil for peach Prunus persica L. var. Rubidoux

Weeds are the main biological constraint for production and sustainability in agricultural systems. This is due to the ability of weeds to modify soil physicochemical conditions (i.e., nutrients, pH, organic matter). It is for this reason that having information on the physicochemical characteristics of the soil within the crop allows observing ecological aspects and the distribution of weed species. The objective of this study was to determine the composition and frequency of weed species and their relationship with soil physicochemical variables in peach Prunus persica L. var. Rubidoux. This study determined the composition and frequency of weed species in relation to physicochemical variables in soil for apeach crop with a total of twenty 10×10 m quadrats within a 2 ha peach crop. Weed species were identified taxonomically. A physicochemical characterization of the soil was performed in each quadrat. A total of 13 weed species were recorded, distributed in 10 families and 8 orders, with the Asteraceae family being the most representative. Additionally, physicochemical variations were found in the soil samples in the peach crop. The soil data were contrasted with the distribution patterns and frequency of weed species. Some weed species were not individually related to the soil physicochemical variables. Our results support efforts to explore how variations in soil physicochemical conditions in a crop can modulate weed species distribution patterns.

Mineralogical and physico-chemical characterization of gypsiferous semi-arid soils in the north of Urmia, Iran

Gypsiferous soils contain sufficient gypsum to influence soil physico-chemical, mineralogical, mechanical properties and geotechnical conditions and as a consequence, affect plant growth and crop production. So physico-chemical and mineralogical properties of 6 soil profiles located on the gypsiferous parent material with semi-arid climate in north of Urmia, West Azerbaijan province, Iran, were investigated. Based on standard methods, morphological, physico-chemical and mineralogical properties of these soils were determined. Soils with higher gypsum content had lighter color, lighter texture, lower values of organic carbon and cation exchange capacity and higher values of electrical conductivity. These parameters were reversely changed with decreasing gypsum content of soils. Semi-quantitative analysis of clay minerals indicated the presence of smectite, illite, chlorite, kaolinite and palygorskite were as major clay minerals with decreasing order from smectite to palygorskite. The origin of illite, chlorite and kaolinite were related to the inheritance from parent material. Smectite group of clay minerals has been resulted from three origins of inheritance from parent material, transformation of illite and palygorskite and neoformation, but the transformation and neoformation are the main pathways for its formation. Palygorskite has pedogenic origin and has been formed via neoformation. The comparison of clay mineralogy of soils with different gypsum values revealed the presence of higher smectites in soils with higher gypsum. Palygorskite was identified just in soils with higher gypsum. In soils with lower values of gypsum, illite and chlorite were the predominant clay minerals and palygorskite did not identified.

Habitat and edaphic preference of Rafflesia R. Br. plant communities in Royal Belum State Park, Perak, Peninsular Malaysia

Aim: To investigate the relationship between the microhabitat conditions and soil physico-chemical characters of Rafflesia plant communities and to determine similarities across Rafflesia habitats in Royal Belum State Park, Perak, Peninsular Malaysia. Methodology: The site of Rafflesia population and its microhabitat condition was collected by referring to the previous studies, in addition to interviewing the related parties. A plot study was constructed in each Rafflesia habitat in Royal Belum State Park, Perak and the soil sample was collected for estimating their characteristics. Results: Rafflesia population is distributed between 207 - 386 m asl, with the surface slope of 8 to 58° and located 1.0-450.0 m from nearby water sources. The percentage of clay has a strong influence in X-Ray and distance to water source affected the habitat in Sg. Ruok-Papan. Ca2+ was an important soil component in Sg. Kooi while in Sg. Gadong 2 and Sg. Selantan, nitrogen was the most important soil attribute. The dendrogram reveals Sg. Kooi and Sg. Gadong 1 were the most similar habitats while Sg. Ruok differed significantly in terms of the microhabitat and soil physicochemical conditions tested. Interpretation: This study shows that different plant communities favoured different conditions in terms of microhabitat condition and the physico-chemical characteristics of soil, despite being located within the same forest range. Since this study covered only small forest range, large sampling size which cover different forest area is needed to come to a conclusion regarding preference of Rafflesia plant communities towards its habitat.

Is the Polylactic Acid Fiber in Green Compost a Risk for Lumbricus terrestris and Triticum aestivum?

Polylactic acid (PLA) bioplastic was introduced to the market as an environmentally friendly potential solution for plastic pollution. However, the effects of bioplastic debris mixed with composts on soil macroinvertebrates, plant growth and soil conditions are still unknown. Soil macroinvertebrates are soil health indicators. A reduction in their abundance is a sign of soil degradation. The objectives of this study were (i) to assess PLA debris in greenhouse composts, and (ii) to test the ecotoxicological effects of PLA debris mixed with compost on Lumbricus terrestris, a soil organism model, and on Triticum aestevium, a plant growth model. The study was comprised of three stages: (1) determine the PLA debris size distribution in composts; (2) assess the ecotoxicological effects of real-world concentrations (0% to 5%) of PLA mixed with compost on earthworm mortality and reproduction; and (3) assess the influence of compost mixed with real-world PLA concentrations on plant growth and physicochemical soil conditions. One percent of PLA debris was found in green composts, 40% of composted PLA debris measured between 1–10 mm, with a concentration of 82.8 ± 17.4 microplastics.gram−1 compost. A concentration of 1% PLA in composts resulted in significant mortality in earthworms. No significant effects of PLA mixed with composts were observed on plant growth or soil physicochemical conditions. Further studies are required in order to test the effect of this biopolymer on different earthworm and plant’ species.

Role of land set-up systems on soil (physicochemical) conditions

Land reclamation and drainage networks represent one of the most ancient human modifications of the Italian soilscape, where tailored land set-up systems were developed in agro- and forestecosystems in three millennia of man’s activity. Most of once manually maintained land settings are currently scarcely working or even disappeared because of the cost needed for their maintenance and the advent of mechanization that have simplified the field organization. The scarce attention to the soil experienced in the last decades, has accelerated soil erosion and flooding events, which entailed high costs in terms of money and human lives, but also caused reduction of soil thickness, water holding capacity, and fertility. In view of a sustainable agriculture, it is mandatory to assess the role of land set-up systems, which for centuries have been key in protecting soil from erosion, but also in increasing soil fertility. Such an effort cannot be made without considering the different pedo-climatic conditions and land uses of the Italian territory, which is different with respect to the past because of the multiple transformations made to favour the mechanization of agriculture. In this review we discuss the main effect of Italian land settings on the soilscape and on soil physicochemical conditions. Since land settings were developed centuries ago, detailed information about their effect on specific soil parameters is scarce in the scientific literature; thus, in some case, we provide information gathered in places where land set-up systems are still present.