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1.
Li -Juan Chen Qi Feng Yong-Ping Wei Chang-Sheng Li Yan Zhao Hui-Ya Li Bao-Gui Zhang 《Journal of Soils and Sediments》2017,17(2):376-383
Purpose
Irrigation and fertilization can change soil environment, which thereby influence soil microbial metabolic activity (MMA). How to alleviate the adverse effects by taking judicious saline water irrigation and fertilization regimes is mainly concerned in this research.Materials and methods
Here, we conducted a field orthogonal designed test under different saline water irrigation amount, water salinity, and nitrogen fertilizer application. The metabolic profiles of soil microbial communities were analyzed by using the Biolog method.Results and discussion
The results demonstrated that irrigation amount and fertilizer application could significantly change MMA while irrigation water salinity had no significant effect on it. Medium irrigation amount (30 mm), least (50 kg ha?1) or medium (350 kg ha?1) N fertilizer application, and whatever irrigation water salinity could obtain the optimal MMA. Different utilization rates of carbohydrates, amino acids, carboxylic acids, and polymers by soil microbial communities caused the differences of the effects, and D-galactonic acid γ-lactone, L-arginine, L-asparagine, D-glucosaminic acid, Tween 80, L-threonine, and D-galacturonic acid were the indicator for distinguishing the effects.Conclusions
The results presented here demonstrated that by regulating irrigation water amount and fertilizer application, the effects of irrigation salinity on MMA could be alleviated, which offered an efficient approach for guiding saline water irrigation.2.
Purpose
The study aimed at comparing the effects of different water managements on soil Cd immobilization using palygorskite, which was significant for the selection of reasonable water condition.Materials and methods
Field experiment was taken to discuss the in situ remediation effects of palygorskite on Cd-polluted paddy soils, under different water managements, using a series of variables, including pH and extractable Cd in soils, plant Cd, enzyme activity, and microorganism number in soils.Results and discussion
In control group, the pH in continuous flooding was the highest under three water conditions, and compared to conventional irrigation, continuous flooding reduced brown rice Cd by 37.9%, and brown rice Cd in wetting irrigation increased by 31.0%. In palygorskite treated soils, at concentrations of 5, 10, and 15 g kg?1, brown rice Cd reduced by 16.7, 44.4, and 55.6%; 13.8, 34.5, and 44.8%; and 13.1, 36.8, and 47.3% under continuous flooding, conventional irrigation, and wetting irrigation (p < 0.05), respectively. The enzyme activity and microbial number increased after applying palygorskite to paddy soils.Conclusions
Continuous flooding was a good candidate as water management for soil Cd stabilization using palygorskite. Rise in soil enzyme activity and microbial number proved that ecological function regained after palygorskite application.3.
Suresh Panta Richard Doyle Marcus Hardie Peter Lane Tim Flowers Gabriel Haros Sergey Shabala 《Journal of Soils and Sediments》2018,18(11):3290-3302
Purpose
The concept of irrigating crops with saline irrigation water is not new, but impacts of this practice on soil properties remain debatable, particularly the use of highly saline water. In this work, key soil chemical properties were assessed to a depth of 300 cm following 2.5 years of application of highly saline irrigation to a sodic texture-contrast soil (Brown Sodosol) in south-eastern Tasmania, Australia.Materials and methods
Control plots (rainfall only) were compared to irrigation treatments of low (0.8 dS/m) and high salinity (16 dS/m) waters at application rates of both 200 and 800 mm/year.Results and discussion
Whilst significant increases in both electrical conductivity and chloride concentration occurred throughout the soil profile in the high salinity treatment, these values were well below those of the irrigation water, indicating effective deep leaching. In the upper soil profile, 0–50 cm, of the high salinity treatments both the exchangeable Na+ and its ratio to total base cations (ESP) were significantly increased whilst the lower soil profile between 50 and 200 cm, was improved via both reduced alkalinity and sodicity. Leaching of the exchangeable base cations Ca2+, Mg2+ and K+ was significant in the upper soil profile (0–50 cm). As expected, the low salinity treatment (0.8 dS/m) had minimal impacts on soil chemical properties. The upper topsoil (0–10 cm) total organic carbon was significantly reduced in the high salinity plots and was negatively correlated with Cl? concentration.Conclusions
The data confirms the general concerns about application of saline irrigation, namely increased whole profile salinisation and upper soil profile (0–50 cm) sodicity, but they also show unexpected and desirable reductions in the lower soil profile (>?50 cm) alkalinity and sodicity. It appears the Na+ ions present in the saline waters led to differential leaching of base cations from the rooting zone, especially Ca2+ which then ameliorate the alkalinity and sodicity deeper in the soil profile (>?50 cm). Thus, surface application of gypsum may help sustain the application of highly saline waters; alternatively, subsurface irrigation above the sodic clayey subsoils could be trailed.4.
Sebastián Meier Gustavo Curaqueo Naser Khan Nanthi Bolan Joaquín Rilling Catalina Vidal Natalia Fernández Jacquelinne Acuña María-Eugenia González Pablo Cornejo Fernando Borie 《Journal of Soils and Sediments》2017,17(5):1237-1250
Purpose
Copper (Cu) contamination has been increasing in land ecosystems. Biochars (BCs) and arbuscular mycorrhizal fungi (AMF) are known to bind metals, and metallophyte can remove metals from soils. Will BC in combination with AMF contain the Cu uptake by a metallophyte growing in a metal-contaminated soil? The objective of this study was to investigate the effects of BCs on the Cu immobilization and over soil microbial communities in a metal-contaminated soil in the presence of AMF and metallophyte.Materials and methods
Two BCs were produced from chicken manure (CMB) and oat hull (OHB). A Cu-contaminated sandy soil (338 mg kg?1) was incubated with CMB and OHB (0, 1, and 5 % w/w) for 2 weeks. Metallophyte Oenothera picensis was grown in pots (500 mL) containing the incubated soils in a controlled greenhouse for 6 months. A number of analyses were conducted after the harvest. These include plant biomass weight, microbial basal respiration, and dehydrogenase activity (DHA), AMF root colonization, spore number, and glomalin production; changes in fungal and bacterial communities, Cu fractions in soil phases, and Cu uptake in plant tissues.Results and discussion
The BCs increased the soil pH, decreased easily exchangeable fraction of Cu, and increased organic matter and residual fraction of Cu. The BCs provided favorable habitat for microorganisms, thereby increasing basal respiration. The CMB increased DHA by ~62 and ~574 %, respectively, for the low and high doses. Similarly, the OHB increased soil microbial activity by ~68 and ~72 %, respectively, for the low and high doses. AMF root colonization, spore number, and total glomalin-related soil protein (GRSP) production increased by ~3, ~2, and ~3 times, respectively, in soils treated with 1 % OHB. Despite being a metalophyte, O. picensis could not uptake Cu efficiently. Root and shoot Cu concentrations decreased or changed insignificantly in most BC treatments.Conclusions
The results show that the BCs decreased bioavailable Cu, decreased Cu uptake by O. picensis, improved habitat for microorganisms, and enhanced plant growth in Cu-contaminated soil. This suggests that biochars may be utilized to remediate Cu-contaminated soils.5.
Manuel Carrillo Christina Siebe Philipp Dalkmann Jan Siemens 《Journal of Soils and Sediments》2016,16(9):2186-2194
Purpose
The increasing reuse of wastewater for irrigation introduces surfactants and antibiotics into the environment. How these two kinds of compounds interact with regard to their sorption processes in soil is not clear.Materials and methods
We performed batch experiments to investigate the sorption of linear alkylbenzene sulfonates (LAS) and its effect on sorption of sulfamethoxazole and ciprofloxacin in irrigated and non-irrigated soils with different organic matter (OM) contents.Results and discussion
LAS sorption was non-linear in the presence of the antibiotics, and as general trend, it increased with rising OM content of soils. Free LAS was also removed from solution by complexation with Ca2+. Dissolved organic compounds released from soils with OM contents ≥18.4 g kg?1 further reduced LAS sorption. Sorption of sulfamethoxazole was reduced by LAS sorption only in one soil with a small OM content of 9.5 g kg?1.Conclusions
The strong sorption of ciprofloxacin is not affected by LAS. Sulfamethoxazole sorption only competes with LAS sorption in organic matter-poor soils. Accumulation of organic matter in soils, for example due to long-term wastewater irrigation, provides extra sorption capacity for LAS and sulfamethoxazole so that competition for sorption sites is reduced.6.
7.
Ana Pérez-Gimeno José Navarro-Pedreño Maria Belen Almendro-Candel Ignacio Gómez Manuel M. Jordán 《Journal of Soils and Sediments》2016,16(4):1345-1351
Purpose
The use of composted sewage sludge and limestone outcrop residue in land rehabilitation, soil improvement, and technosol making can influence the mobility of nitrogen compounds in groundwater.Materials and methods
This experiment analyzed this source of possible pollution under an experimental design based on the use of columns (0–30 cm) formed by both wastes and a heavy irrigation regime. Two waters of different quality (saline and non-saline) were used for irrigation. The presence of nitrate, nitrite, and ammonium in the leachates was checked.Results and discussion
The environmental risk due to the presence of nitrogen species associated with the use of these materials was very low in general, although nitrate was the most important compound affected by the use of sewage sludge compost and saline water.Conclusions
The combination of saline water for irrigation with the compost has to be seriously considered as a source of pollution for surface and ground waters, and the use of both resources may be a key factor to be studied (low-quality water and sewage sludge compost).8.
Ting-Ting Fan Yu-Jun Wang Cheng-Bao Li Juan Gao Dong-Mei Zhou Shmulik P. Friedman 《Journal of Soils and Sediments》2016,16(6):1683-1689
Purpose
For agricultural production and environment protection, it is cations loosely bound to the soil particles that have a great significance in short-term processes of adsorption–desorption, exchange, and transport. It is beneficial to be able to evaluate the fractions of these cations in order to correctly predict potential pollution of soils by heavy metals and availability of plant nutrients.Materials and methods
The homionic suspensions of yellow-brown soil (YB) and black soil I (BI) saturated with Na+ and Ca2+ and three subsamples of black soil II (BII) saturated with Ca2+ and Cd2+ were prepared to determine the electrical conductivity (EC) of the suspensions. On the basis of electrical conductivity vs. field strength (EC-E) curve, the fraction of electrically associated cations on surfaces of soil particles was evaluated by extrapolation of strong-field Wien effect measurements in dilute suspensions.Results and discussion
The maximum dissociation degree (α max) of Na+ adsorbed on surfaces of yellow-brown soil and black soil I was about 0.21, which is approximately twice as much as those of Ca2+ (0.07–0.10) adsorbed on surfaces of two soils. The soil type was not the main factor in evaluating α max, and the valence of the cations was. For divalent cations, α max of Ca2+ and Cd2+ adsorbed on soil particles with different contents of organic matter descended in the order: top black soil II?>?bottom black soil II?>?OM-free bottom black soil II.Conclusions
The relatively small fractions of electrically adsorbed cations—about 0.2 for Na+ and 0.1 for Ca2+ on yellow-brown and black soils particles indicated that even for the more loosely adsorbed Na+ ions, most of the cations in the double layers of soil particles were adsorbed strongly by other, more specific mechanisms and cannot be stripped off into the solution, which would increase its electrical conductivity in a strong applied field.9.
Weiying Wang Jingjing Sun Cuiling Dong Bin Lian 《Journal of Soils and Sediments》2016,16(7):1901-1910
Purpose
Biotite, as a type of associated mineral, is normally applied as a filling material for buildings, or is discarded as tailings. However, as a potassium-bearing phyllosilicate mineral, biotite can be easily weathered by fungi, which leads to its internal potassium being released for agricultural production (1), and the mineral residues being weathered by the fungus may be applied for adsorption of heavy metal ions (2).Materials and methods
This work investigates the weathering of biotite by Aspergillus niger through the analysis of the differences in ion dissolution from biotite, producing of organic acids, the change of mineral morphology and composition by inductively coupled plasma optical emission spectrometry (ICP-OES), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Besides, the mineral residues were applied for adsorption of heavy metal ions.Results and discussion
Results showed that the mycelia envelope the mineral and form fungal–mineral aggregates. The fungus can secrete a variety of organic acids including citric acid and oxalic acid; these attacked the surface and cleavage of biotite to release ions (Al3+, Fe3+, Mg2+, and K+). During incubation with A. niger, biotite weathered as shown by the relative decrease in biotite content and increase in interlayer spacing. Moreover, a certain concentration of phytic acid and tween-80 could promote the release of K+, and the fermentation liquid of rice bran has the same effect. Biotite residues showed a good adsorption for Cd2+, Pb2+, Zn2+, and Cu2+.Conclusions
The results indicate that biotite can be biotransformed and release K+, of which the production can be acted as heavy metal ion adsorbent. It provides a reference for application of biotite in agriculture and control of heavy metal ion pollution in soil.10.
Jiangpei Han Jiachun Shi Lingzao Zeng Jianming Xu Laosheng Wu 《Journal of Soils and Sediments》2017,17(2):471-480
Purpose
Sampling and analysis of greenhouse soils were conducted in Shouguang, China, to study continuous excessive fertilization effect on nitrifying microbial community dynamics in greenhouse environment.Materials and methods
Potential nitrification activity (PNA), abundance, and structure of nitrifying microbial communities as well as the correlations with soil properties were investigated.Results and discussion
Short-term excessive fertilization increased soil nutrient contents and the diversity of nitrifying microbial communities under greenhouse cultivation. However, the abundance and diversity of nitrifying communities decreased greatly due to the increase of soil acidity and salinity after 14 years of high fertilization in greenhouse. There was a significant positive correlation between soil PNA and the abundance of ammonia-oxidizing bacteria (AOB) but not that of ammonia-oxidizing archaea (AOA) in topsoil (0–20 cm) when pH ≥7. Soil PNA and AOB were strongly influenced by soil pH. The groups of Nitrososphaeraceae, Nitrosomonadaceae, and Nitrospiraceae were predominant in the AOA, AOB, and nitrite-oxidizing bacteria (NOB) communities, respectively. Nitrifying community structure was significantly correlated with soil electrical salinity (EC), organic carbon (OC), and nitrate nitrogen (NO3 ?–N) content by redundancy analysis (RDA).Conclusions
Nitrification was predominated by AOB in greenhouse topsoil with high fertilizer loads. Soil salinity, OC, NO3 ?–N content, and pH affected by continuous excessive fertilization were the major edaphic factors in shaping nitrifying community structure in greenhouse soils.11.
Zhiyuan Yao Jiajia Xing Haiping Gu Haizhen Wang Jianjun Wu Jianming Xu Philip C. Brookes 《Journal of Soils and Sediments》2016,16(8):2041-2049
Purpose
The objectives of this study were to investigate (i) how the changes in cultivation pattern of vegetable affect soil microbial communities and (ii) the relationships between soil physico-chemical properties and microbial community structure.Materials and methods
Soil samples were collected from fields growing vegetable crops with various times of plastic-greenhouse cultivation (0, 1, 4, 7 and 15 years, respectively). Phospholipid fatty acid (PLFA) analysis was conducted to reveal the soil microbial community of the test soils.Results and discussion
The open-field soil had the highest total PLFAs amount. Although the Shannon-Weaver index was also highest in the open-field soil, the difference was not significant. Plastic-greenhouse cultivation decreased PLFAs species diversity and richness. Cluster analysis and principal component analysis (PCA) of the PLFA profiles revealed distinct groupings at different times during plastic-greenhouse cultivation.Conclusions
Ultimately, PLFA analyses showed that long-term plastic-greenhouse cultivation make the physiological status of soil microbial community worse and increased stress level of microorganisms. And soil microbial community was significantly affected by field water capacity and water-soluble organic carbon. The study highlights the potential risk of long-term plastic-greenhouse cultivation to soil microbial community.12.
Jianqing Tian Chi Shu Huai Chen Yuchen Qiao Gang Yang Wan Xiong Lin Wang Jingzu Sun Xingzhong Liu 《Journal of Soils and Sediments》2015,15(1):179-188
Purpose
Understanding how archaeal communities are affected by water-table drawdown is essential for predicting soil functional responses to future climate change and the consequences of the responses on the soil carbon cycle.Material and methods
We investigated the effect of water-table drawdown, warming, drought, and combinations thereof on archaeal communities using terminal restriction fragment length polymorphism (T-RFLP) and quantitative PCR.Results and discussion
Methanosarcinales, Methanosaeta, Methanomicrobiales, Methanobacteriales, uncultured Rice Cluster II (RC-II), and uncultured Crenarchaeota were detected. Water-table drawdown and drought exhibited significant effects on the archaeal communities. When the water table was at or above 10 cm, the archaeal abundance at 10 cm remained high (approximately 109 cells per gram dry soil), whereas the archaeal abundance at 10 cm was reduced to approximately 108 cells per gram dry soil where the water table was lowered to 20 cm or below. When the water table kept constant, warming caused a significant reduction in the archaeal abundance, whereas drought only caused a decrease in archaeal abundance when the water table was higher than ?20 cm.Conclusions
Results suggest that changes in water table may directly impact archaeal community abundance and assemblage which can in turn influence methane emissions, potentially on a large scale. Our results also indicate that archaeal communities response to water-table drawdowns that are dependent on the initial ecohydrology.13.
Xi-En Long Ju-Pei Shen Jun-Tao Wang Li-Mei Zhang Hongjie Di Ji-Zheng He 《Journal of Soils and Sediments》2017,17(2):384-392
Purpose
Nitrification and denitrification processes dominate nitrous oxide (N2O) emission in grassland ecosystems, but their relative contribution as well as the abiotic factors are still not well understood.Materials and methods
Two grassland soils from Duolun in Inner Mongolia, China, and Canterbury in New Zealand were used to quantitatively compare N2O production and the abundance of bacterial and archaeal amoA, denitrifying nirK and nirS genes in response to N additions (0 and 100 μg NH4 +–N g?1 dry soil) and two soil moisture levels (40 and 80 % water holding capacity) using microcosms.Results and discussion
Soil moisture rather than N availability significantly increased the nitrification rate in the Duolun soil but not in the Canterbury soil. Moreover, N addition promoted denitrification enzyme activities in the Canterbury soil but not in the Duolun soil. The abundance of bacterial and archaeal amoA genes significantly increased as soil moisture increased in the Duolun soil, whereas in the Canterbury soil, only the abundance of bacterial amoA gene increased. The increase in N2O flux induced by N addition was significantly greater in the Duolun soil than in the Canterbury soil, suggesting that nitrification may have a dominant role in N2O emission for the Duolun soil, while denitrification for the Canterbury soil.Conclusions
Microbial processes controlling N2O emission differed in grassland soils, thus providing important baseline data in terms of global change.14.
Purpose
The Al forms on maize and soybean roots were investigated to determine the main factors affecting the distribution of Al forms and its relationship with Al plant toxicity.Materials and methods
Solution culture experiments were conducted to obtain the fresh roots of maize and soybean. KNO3, citric acid, and HCl were used to extract the exchangeable, complexed, and precipitated forms of Al on the roots.Results and discussion
The complexed Al was higher than the exchangeable and precipitated Al. Root CECs of soybean and maize were 77 and 55 cmol kg?1, and functional groups on the soybean roots (262.4 cmol kg?1) were greater than on maize roots (210.8 cmol kg?1), which resulted in more exchangeable and complexed Al on soybean roots than on maize roots, and was one of the reasons for the increased Al toxicity to soybean. The total and exchangeable Al were the highest on the plant root tips and decreased gradually with increasing distance from the tips. Ca2+, Mg2+, and NH4 + cations reduced the exchangeable Al on the roots. Oxalate and malate also reduced the adsorption and absorption of Al by roots, and the effect of oxalate was greater than malate.Conclusions
Higher exchangeable and complexed Al on plant roots led to increased Al plant toxicity. Ca2+, Mg2+, and NH4 + and oxalate and malate can effectively alleviate Al plant toxicity.15.
Purpose
Air supply and soil moisture have significant impact on the decay time necessary for complete decomposition of an interred body. Concerning the general structure and hydraulic as well as pneumatic conditions, in many cases, a permeable refilled soil material surrounded by the undisturbed and less permeable soil outside the grave results in water ponding, less aerated conditions, and lower redox potential values within the grave. This reduces the decomposition speed or even leads to preservation of the entire body.Materials and methods
In order to ascertain soil structural processes and hydraulic properties in an earth grave within the first year after burial, a monitoring of soil redox and matric potentials was realized in newly refilled artificial (empty) graves. We surveyed four variations: undisturbed reference soil, soil backfill in artificial grave, soil backfill in artificial grave amended with 20 kg CaO m?3, and grave base and walls strewed with CaO. In the fourth artificial grave (soil backfill only), irrigation experiments were conducted in order to simulate the effects of grave maintenance on soil water budget. Pore size distribution, air conductivity, and saturated hydraulic conductivity were measured on soil core samples from the variations. The monitoring was realized with redox sensors and tensiometers in 50- and 130-cm depth in all four variations.Results and discussion
Soil structure disruption increased soil porosity but also favored saturation of the soil in context with precipitation events. Compared with the graves without amendment, the addition of quicklime resulted in higher air capacity and air permeability, saturated hydraulic conductivity, and a better-aerated (higher redox potentials) and less water-saturated soil. Non-recurring irrigation with 2.2, 4.4, and 8.9 mm did not affect the soil moisture in the 50- and 130-cm depth. Repeated irrigation with 8.9 mm on consecutive days led to persistent water saturation in the soil, especially in the 130-cm depth.Conclusions
The disturbed soil structure in the cover layer of an earth grave is sensitive to settlement and, together with a tendency to the development of stagnic conditions, this can have negative impact on soil aeration in the grave. Addition of quicklime to the soil enhances crack development in the base and walls of the grave, stabilizes the soil fragments in the backfill, and prevents intensive settlement processes. This reduces water ponding and leads to a better aeration of the soil. Irrigation of earth graves should be reduced to a minimum.16.
Yi-Ping Tai Zhi-An Li Murray B. McBride Yang Yang 《Journal of Soils and Sediments》2017,17(12):2822-2830
Purpose
Water management has a strong influence on Cd solubility in agricultural soils, affecting Cd uptake in crops. In the process, sulfur interaction with other metals such as zinc may play an important role. A pot experiment was carried out to investigate the effects of water management coupled with zinc and sulfate amendment on Cd uptake by the leafy vegetable amaranth with a strong Cd accumulation tendency in its edible parts.Materials and methods
The soils were amended with Cd, Cd+SO4 and Cd+SO4+Zn with no amendment as control. Then, the soils were flooded for 1 month, after which amaranth was grown with soil kept saturated (wet cultivation). In the succeeding planting, soils were tilled to aeration condition under which amaranth was grown again (dry cultivation). Soil and crop samples were collected and analysed for various parameters.Results and discussion
The readily exchangeable quantities of Cd and Zn in the soil decreased under wet cultivation, increasing again under dry cultivation but to levels lower than those in the initial soil. Wet cultivation enhanced plant Cd concentration but reduced Zn accumulation compared to dry cultivation. Zn bioavailability was strongly affected by soil water status but failed to reduce Cd uptake by amaranth. Irreversible or slowly reversible changes occurred in Cd and Zn solubility and phytoavailability as soil water-saturated status was altered by periodic flooding events.Conclusions
Dry cultivation with lower soil water content ensured high production with low Cd in the edible part of this leaf vegetable and so remains the recommended irrigation regime.17.
Purpose
The aim of this study was to evaluate the role of phosphine in the mobilization of phosphorus in the rhizosphere soil of rice seedlings and to determine the relative efficiency of phosphine in plant P acquisition.Materials and methods
An indoor simulation experiment was conducted and the matrix-bound phosphine (MBP), phosphorus fractions, and phosphatase activity in the rhizosphere soil samples from rice cultivation, biomass, the plant P, and the root system activity were measured under different phosphine concentrations (0, 1.4, 4.2, and 7.0 mg m?3) for a period of 30 days.Results and discussion
The results indicated that phosphine treatments enhanced MBP, inorganic P (resin–Pi, NaHCO3–Pi, and NaOH–Pi), and phosphatase activity, as well as the root system activity, and the content of P in the rice seedlings was stimulated with increasing phosphine concentrations. However, organic P (NaHCO3–Po and NaOH–Po) accumulation occurred in the rhizosphere of the rice seedlings. In addition, the content of organic P in the soil samples decreased with increased phosphine concentration.Conclusions
Therefore, relatively high concentrations of phosphine in paddy field could have a positive impact on the effectiveness of phosphorus in rice plants via influencing the rhizosphere properties.18.
Purpose
The validity of soil erosion data is often questioned because of the variation between replicates. This paper aims to evaluate the relevance of interreplicate variability to soil and soil organic carbon (SOC) erosion over prolonged rainfall.Materials and methods
Two silty loams were subjected to simulated rainfall of 30 mm h?1 for 360 min. The entire rainfall event was repeated ten times to enable statistical analysis of the variability of the runoff and soil erosion rates.Results and discussion
The results show that, as selective removal of depositional particles and crust formation progressively stabilized the soil surface, the interreplicate variability of runoff and soil erosion rates declined considerably over rainfall time. Yet, even after the maximum runoff and erosion rates were reached, the interreplicate variability still remained between 15 and 39 %, indicating the existence of significant inherent variability in soil erosion experiments.Conclusions
Great caution must be paid when applying soil and SOC erosion data after averaging from a small number of replicates. While not readily applicable to other soil types or rainfall conditions, the great interreplicate variability observed in this study suggests that a large number of replicates is highly recommended to ensure the validity of average values, especially when extrapolating them to assess soil and SOC erosion risk in the field.19.
Purpose
Application of olive mill wastewater (OMW) to soil may cause positive or negative effects. The present study aims at a better understanding of the fate of organic matter brought into soil by OMW application under different environmental conditions.Materials and methods
Single OMW application to soil was conducted in spring, dry summer, summer with irrigation, and in winter. Two days and 18–24 months after the application, soil samples from two depths were analyzed for thermal soil organic matter (SOM) properties, total organic carbon, water-extractable dissolved soil organic carbon, and its specific ultraviolet absorbance at 254 nm.Results and discussion
After winter and irrigated summer treatments, OMW was largely leached from the upper horizon within 2 days. Application in spring and summer dry initially increased the thermolabile fraction and the calorific value of SOM, however, in a different degree due to different transport, transformation, and immobilization mechanisms. At the long term, SOM content was still elevated after summer dry treatment. The reduction of the thermostable fraction in spring treatment indicates a priming effect of the labile OMW constituents.Conclusions
Application in winter or with irrigation cannot be recommended for the investigated site. Under hot and dry conditions, SOM content increased most persistently due to stronger mineral-organic interactions. Favorable conditions for biodegradation during OMW application in spring reduced the effects on SOM quantity in the long term. However, a possible priming effect and the persistence of changes in thermal properties need to be further investigated for repeated applications.20.