Higher Soil Organic Matter Content Research Articles

若尔盖高原湿地泥炭沼泽土亚硝酸盐还原酶（nirK）反硝化细菌群落结构分析

PDF HTML阅读 XML下载 导出引用 引用提醒 若尔盖高原湿地泥炭沼泽土亚硝酸盐还原酶（nirK）反硝化细菌群落结构分析 DOI: 10.5846/stxb201607151442 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（41201256）。 Analyzing the nitrate reductase gene (nirK) community in the peat soil of the Zoige Wetland of the Tibetan Plateau Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:若尔盖泥炭湿地是世界少有的低纬度永久冻土湿地，具有高海拔、高紫外辐射、高有机质的特点。该区域N2O的排放量对全球气候变暖有重要影响。对若尔盖高原湿地泥炭沼泽土中的亚硝酸盐还原酶（nirK）反硝化细菌群落结构多样性进行分析，以期揭示该区域N2O释放的微生物调控机制。基于若尔盖高原湿地泥炭沼泽土的理化性质和反硝化活性（PDA），结合限制性酶切片段长度多态性（Restriction fragment length polymorphism， RFLP）技术、克隆文库及分子测序对该生态系统中的nirK反硝化细菌群落结构及多样性进行分析。反硝化活性测定结果显示：阿西地区>麦溪地区>分区地区，反硝化活性与土壤有机碳、总氮和丰富度呈显著正相关（P < 0.05）。Shannon-wiener多样性指数以阿西最高、分区最低。3个样品中共测序15条nirK基因代表序列，系统发育表明若尔盖高原湿地优势nirK反硝化菌群为变形门菌群。其中，阿西地区主要为α-变形菌门，麦溪地区主要为β-变形菌门，分区地区无法确定优势种群。冗余分析（Redundancy analysis， RDA）显示：有效钾和有效磷是影响nirK反硝化细菌群落结构的关键环境因子。本论文显示，若尔盖高原湿地存在着明显的反硝化作用，调控这些反硝化作用的nirK反硝化细菌多样性较高，且与土壤有效钾和有效磷密切相关。 Abstract:The Zoige Wetland, which is located in the northeast of the Tibetan Plateau, is a typical low latitude permanent permafrost wetland, with high altitude intensive ultraviolet radiation and high soil organic matter content. The nitrous oxide fluxes in this area are critical to global warming. The main objective of this study was to elucidate the diversity and structure of the nitrate reductase (nirK) gene denitrifier community, and to further explore the microbial mediated mechanism of N2O release in this climatically extreme area. Based on the soil physicochemical properties and denitrifying activity (PDA) analysis, restriction fragment length polymorphism (RFLP), clone library and sequencing were further used to analyze the diversity and structure of the nirK gene in the denitrifier community. The results showed that the highest activity of PDA was detected in the Axi soil, while the lowest activity was in the Fenqu soil. The PDA was significantly and positively correlated with soil organic carbon, total nitrogen and nirK gene richness (P < 0.05). The highest and lowest Shannon-Wiener diversity indices were detected in Axi and Fenqu soils, respectively. Based on the RFLP patterns, 15 different nirK gene clones were selected for sequencing and further phylogenetic analysis. The phylogenetic analysis showed that the majority of the nirK-denitrifiers in the peat soil of the Zoige Wetland belonged to Proteobacteria, and the dominant species in the Axi soil were Alphaproteobacteria, whereas Betaproteobacteria species dominated in the Maixi soil. The dominant nirK denitrifiers remained unidentified in the Fenqu soil. Redundancy analysis (RDA) was used to explore the possible relationship between the nirK denitrifiers community and soil physicochemical parameters, and the results showed that soil available potassium and available phosphorus were the two most important factors in shaping nirK denitrifier communities. In conclusion, the current study revealed obvious denitrifying activities in the Zoige Plateau Wetland. The nirK gene denitrifying community, which plays an important role in mediating the denitrifying process, was relatively diverse and positively influenced by soil available potassium and available phosphorus. 参考文献 相似文献 引证文献

Phosphorus Solubility from Rock Phosphate Mixed Compost with Sulphur Application and Its Effect on Yield and Phosphorus Uptake of Wheat Crop

A field experiment was conducted to determine the effect of sulphur application with Rock phosphate mixed compost on phosphorus (P) solubility and its effect on yield and P uptake of wheat crop. The experiment was laid out in randomized complete block design (RCBD) with three replications at the research farm of The University of Agriculture Peshawar. The experiment was conducted during rabi 2015-16 with plot size of 3 m × 5 m. Nitrogen, phosphorus and potassium were applied at the rate of 120, 90 and 60 kg&#183ha-1 in the form of urea, compost, or single super phosphate and potassium sulphate, respectively. Elemental sulphur was applied at the rate of 10, 20 and 30 kg&#183ha-1 at the time of sowing. Results showed that sulphur applied with compost significantly improved wheat yield and yield components, soil organic matter, soil total N and AB-DTPA extractable P contents, plant N and P concentrations and their uptake, plant micronutrients concentration and their uptakes. No significant changes were noted in soil pH, ECe and lime contents. Maximum grain yield of 4076 kg&#183ha-1, total dry matter yield 9721 kg&#183ha-1, straw yield 5644 kg&#183ha-1, plant height 98.3 cm, spike length 11.2 cm, grain per spike 61.0, thousand grain weight 50.2 g were recorded on the application of S at the rate 20 kg&#183ha-1 with compost. The highest soil organic matter content of 1.41% was found for the application of S at the rate of 10 kg&#183ha-1 with compost. Maximum soil total N content of 1756 mg&#183kg-1 and P 5.7 mg&#183kg-1 were observed by the application of double recommended S with compost. Plant N uptakes of 125.7 kg&#183ha-1, and P uptake of 17.5 kg&#183ha-1, were maximum with application of compost and S @ 20 kg&#183ha-1. Highest plant uptake of Fe 0.56 kg&#183ha-1, Zn 0.41 kg&#183ha-1, Cu 0.16 kg&#183ha-1 and Mn 0.93 kg&#183ha-1 were found by the application of full recommended S with compost. Results suggested that S at the rate of 20 kg&#183ha-1 application with compost prepared from farm yard manure and rock phosphate proved better combination to enhance wheat yield, yield components and nutrients uptakes of wheat crop.

English

As a sustainable method of agriculture, organic agriculture aims to increase the soil organic matter through the use of crop rotation, legume cover crop, animal green manure, and organic compost. These practices add organic residues with high organic Carbon (C) which results in a higher soil organic matter content over time primarily due to the no-tillage practices. However, different soil tillage systems, such as conventional tillage and reduced tillage are also used in organic agriculture, and therefore the accumulation of organic matter does not follow similar trends. The studies under conventional tillage have shown that soil tillage influences negatively the organic matter accumulation in organic agriculture plots, while the results from different studies on organic agriculture showed the potential benefits of reduced or zero tillage for organic matter accumulation. Key words: Sustainability, soil quality, management systems.

Characterisation of soil organic matter in a semi-arid fluvic Entisol fertilised with cattle manure and/or gliricidia by spectroscopic methods

The stable fraction of soil organic matter (SOM) has received considerable attention due to concerns about the sustainability of agricultural systems. The main structural characteristics of the SOM of an Entisol in the semi-arid region of Paraíba state, Brazil, after 6 years of cultivation of annual crops with different organic fertiliser treatments, were determined. Six different treatments were evaluated, as follows: (1) gliricidia prunings (Gliricidia sepium Jacq. Walp) incorporated into the soil before planting (GI); (2) cattle manure incorporated before planting (MI); (3) gliricidia applied after planting (GS); (4) manure and gliricidia incorporated before planting (MI+GI); (5) manure incorporated before planting and gliricidia applied after planting (MI+GS); and (6) a control treatment. Spectroscopic techniques were used to analyse carbon in whole soil samples (0–20cm), as well as in fulvic acid (FA) and humic acid (HA) extracts. Surface-applied gliricidia resulted in the highest SOM content. Laser-induced fluorescence spectroscopy showed that MI+GS contributed to increases in the degree of humification, whereas for the HA fraction, the highest degree of humification occurred with the GS treatment. The ultraviolet–visible absorbance spectra of FA fractions indicated the presence of fresh soluble SOM in all treatments except GS, and mid-infrared region spectra revealed no differences in the chemical structure of the HA fractions. Application of gliricidia prunings (GI and GS), which are nitrogen rich and highly labile, resulted in low HA transformations compared with the control based on nuclear magnetic resonance analysis. Therefore, gliricidia, whether incorporated before planting or applied after planting, decreases the labile fractions of SOM, probably because of its higher decomposition rates.

Soil Organic Matter Content and Volumetric Water Content Affect Indaziflam–Soil Bioavailability

Indaziflam is a cellulose biosynthesis-inhibiting herbicide for annual weed control in various agricultural systems. Sporadic cases of unacceptable injury to desirable plants have been reported after indaziflam application, which may have been due to conditions favoring increased indaziflam–soil bioavailability. Research was conducted from 2013 to 2015 on a sandy soil to elucidate the effects of soil organic matter content (SOMC) and soil volumetric water content (SVWC) on indaziflam–soil bioavailability. Indaziflam was applied (50 or 100 g ha–1) at fall only, fall plus spring, and spring only timings to plots in a factorial arrangement of SOMC, pre–indaziflam application (PrIA) SVWC, and post–indaziflam application (PoIA) SVWC. After application, field soil cores were collected for a subsequent greenhouse bioassay experiment, where foliage mass reduction of perennial ryegrass seeded from 0 to 15 cm soil depth was used as an indicator of indaziflam–soil bioavailability throughout the profile. Significant edaphic effects were observed at 0 to 2.5, 2.5 to 5, and 5 to 7.5 cm depths, with increased bioavailability at low compared with high SOMC. Pre–indaziflam application SVWC did not affect bioavailability, whereas PoIA high SVWC increased indaziflam–soil bioavailability at 2.5 to 7.5 cm depth compared with PoIA low SVWC. Low SOMC–PoIA high SVWC decreased perennial ryegrass foliage mass 40 and 37% at 5 to 7.5 cm depth from cores collected 10 and 14 wk after treatment, respectively, whereas reductions from all other SOMC–PoIA SVWC combinations were &lt; 12% and did not vary from each other. Pearson's correlation coefficients showed a moderate, positive relationship between perennial ryegrass mass reductions at 0 to 2.5, 2.5 to 5, 0 to 5, and 0 to 10 cm depths and hybrid bermudagrass cover reduction, which suggests conditions favoring increased indaziflam–soil bioavailability can adversely affect plant growth. Data from this research will aid land managers to use indaziflam effectively without adversely affecting growth of desirable species.

Effect of Soil Organic Matter Content and Volumetric Water Content on ‘Tifway 419’ Hybrid Bermudagrass Growth Following Indaziflam Applications

Indaziflam is a cellulose biosynthesis–inhibiting herbicide for PRE annual weed control in turfgrass systems. Since indaziflam's 2010 U.S. registration, sporadic cases of hybrid bermudagrass injury have been reported; however, causes are not well understood. Field research was conducted from 2013 to 2015 on sandy soil to elucidate the effects of soil organic matter content (SOMC) and soil volumetric water content (SVWC) on plant growth following indaziflam application on established or root-compromised (5 cm long) hybrid bermudagrass. The effect of SOMC was evaluated at two levels, 1.4 (low) and 5.5% (high) w/w at the soil surface (0 to 2.5 cm depth), whereas SVWC was evaluated PRE (2 wk before) and POST (6 wk after) indaziflam application at two levels (low or high). Indaziflam was applied (50 or 100 g ai ha−1) at fall-only, fall-plus-spring, and spring-only timings. Regardless of application timing or SVWC, indaziflam applied at 50 g ha−1 to high SOMC did not cause &gt; 10% visual cover reduction on established or root-compromised hybrid bermudagrass. Indaziflam applied to hybrid bermudagrass on low SOMC exacerbated adverse growth effects, most notably when root systems were compromised before application. Overall, PRE indaziflam application SVWC did not affect hybrid bermudagrass growth. Within low SOMC, low POST indaziflam application SVWC caused less visual hybrid bermudagrass cover reduction than did high POST indaziflam application SVWC, whereas both fall-plus-spring and spring-only application timings caused similarly greater reductions than fall-only indaziflam application. Data from this research will aid turfgrass managers to effectively use indaziflam without adversely affecting hybrid bermudagrass growth.

Sequestration and bioavailability of perfluoroalkyl acids (PFAAs) in soils: Implications for their underestimated risk

Different from typical hydrophobic organic contaminants (HOCs), perfluoroalkyl acids (PFAAs) are more soluble in water and less partitioned to soil than the HOCs. It remains unclear whether and to what extent PFAAs could be sequestrated in soil. In this study, sequential extraction of PFAAs in soil and bioaccumulation of PFAAs in earthworm were carried out to understand the sequestration and bioavailability of PFAAs in soils with different soil organic matter (SOM) and aged for different time periods (7 and 47d). Sequestration occurred in different degrees depending on the amount and compositions of SOM in soil, structural properties of PFAAs and aging time. Surprisingly, in one peat soil with high fraction of organic carbon (foc, 59%), the PFAAs were completely sequestrated in the soil. Aging might lead to further sequestration of PFAAs in soil with relatively lower foc. As a consequence of sequestration, the bioavailability of PFAAs in peat soils was reduced 3–10 times compared to that in the plain farmland soil. However, the sequestrated PFAAs were still bioaccumulative in earthworms to some extent. The results indicated that the risk of PFAAs in field soil with high content of SOM could be underestimated if only free PFAAs using mild solvent extraction were monitored.

Soil Restoration after seven Years of Exclosure Management in Northwestern Ethiopia

AbstractEcological restoration through exclosure establishment has become an increasingly important approach to reversing degraded ecosystems in rangelands worldwide. The present study was conducted in northwestern Ethiopia where policy programs are aiming to restore degraded lands. Changes in soil properties following establishing exclosures on communal grazing lands were investigated. A space‐for‐time substitution approach was used to monitor changes in soil properties after conversion of communal grazing lands to exclosures with ages of establishment ranging from 1 to 7 years. Significant differences in soil pH, exchangeable cations, cation exchange capacity, soil moisture content and bulk density were observed within exclosures and between exclosures and communal grazing land. Communal grazing land displayed significantly higher soil total nitrogen, phosphorus and potassium compared with exclosures. Exclosures did not display significantly higher soil organic matter content when compared with the communal grazing land. The results confirm that more than 7 years after the establishment of exclosures is required to detect significant improvements in most of the investigated soil properties. Prohibition of the practice of grass harvesting during the first 3 to 5 years following the establishment of exclosure, and decreasing the amount of grass harvest with exclosure age could support to increase easily decomposable organic inputs to the soil and improve soil properties in relatively short period of time. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Distribution and geochemical speciation of soil mercury in Wanshan Hg mine: Effects of cultivation

The distribution and speciation of mercury (Hg) were investigated in contaminated soils collected from two adjacent land use systems (arid land and rice paddy) near the Wanshan Mercury mine, SW China. In both sites, fine soil aggregate size fractions (<231μm) showed higher total Hg concentrations and higher soil organic matter contents than in larger aggregate size fractions (231 to 2000μm). Compared to arid land, paddy soils are characterized by higher proportions of fine soil aggregates, higher soil organic matter and higher total Hg content. Soil Hg speciation, based on X-ray absorption spectroscopy (XANES) analysis, indicated that the majority (64–81%) of Hg in soils under both land use systems was associated with metacinnabar (β-HgS), indicating the precipitation of β-HgS in soils. We also observed the presence of bioavailable HgCl2 and Hg(0) in soils at both sites, which may represent a considerable environmental concern. Our study clearly showed that different cultivation practices can largely change the distribution and speciation of Hg in agriculture soils.

Microbial transport of aerated compost tea organisms in clay loam and sandy loam – A soil column study

Soil bioaugmentation is a promising approach with applications in agriculture and in bioremediation of polluted soil. One way of supplying microorganisms to the soil that has received increasing attention during the last decade is by the addition of compost teas. The success of such strategies depends on whether the organisms are capable of migrating through the soil and reaching its target, i.e. the pollutants or soil pathogens. The structural conditions of the soil affect the microbial migration rate and this study aims to determine the migration rates of microorganisms found in aerated compost tea through both a sandy loam and a clay loam in soil columns. A considerably higher proportion of the microorganisms from the aerated compost tea were deposited at 2 cm in the sandy loam compared to the clay loam. Microbial deposition was concentrated to the top 2 cm in the sandy loam and then decreased abruptly at 10 cm whereas the clay loam presented an irregular pattern. Despite a favourable particle size distribution for microbial transport, the sandy loam retained a greater proportion of the microorganisms present in the aerated compost tea in the top 2 cm, presumably because the lower bulk density and higher soil organic matter in the clay loam aided transport and growth of microorganisms. The limited migration of aerated compost tea microorganisms in sandy soil suggests that its efficiency for bioremediation or pathogen control may be limited below 2 cm depth in similar soils. Our results indicate that in less dense soil with higher soil organic matter content the efficiency may be higher.

The Role of Trees and Pastures in Organic Agriculture

&lt;p&gt;Environmental concerns associated with annual row crop grain production – including soil erosion, soil carbon loss, intensive use of chemicals and petroleum, limited arable land, among others – could be addressed by converting conventional livestock production to an organic pasture based system. The inclusion of tree crops would further enhance the opportunity for feeding pasture- raised livestock by providing shelter and alternative feed sources. Biodiversity is an essential aspect of an organic farm plan. The idea of including tree crops and other perennials into the vision of an organic farm as a “living system” is very much compatible with the goals and philosophy of organic farming. Before modern no-till farming systems were developed, tree crops and pasture systems were found to provide similar benefits for controlling soil erosion and conserving soil carbon. For example, J. Russell Smith’s &lt;em&gt;Tree Crops: A Permanent Agriculture&lt;/em&gt; (Smith, 1950) and pioneered tree crop agriculture as the alternative to annual row crops for protecting soils from erosion while producing livestock feed such as acorns, nuts, and fodder. A survey of Mid-Atlantic USA soils under pasture found 60% higher soil organic matter content than cultivated fields. Because United States Department of Agriculture’s National Organic Program (USDA-NOP) standards require dairy cattle consume pasture forage and limited grain (7 C.F.R. pt. 206), organic milk contains higher concentrations of omega-3 and fewer omega-6 fatty acids than conventional milk. Organic standards also state “the producer must not use lumber treated with arsenate or other prohibited materials for new [fence posts] installations or replacement purposes in contact with soil or livestock.” Black locust (&lt;em&gt;Robinia pseudoacacia&lt;/em&gt;) is a fast growing renewable alternative to treated lumber with many attributes compatible with organic farming. This versatile tree fixes nitrogen (N), provides flowers for honey bees and other pollinators, and produces a highly durable dense wood ideal for fence posts useable for up to 50 year.&lt;/p&gt;

Subaqueous Soils and Coastal Acidification: A Hydropedology Perspective with Implications for Calcifying Organisms

In the coastal zone, biological and biogeochemical processes, influenced by anthropogenic inputs, drive pH variability and contribute to coastal acidification. Spatial patterns of these processes across coastal estuaries are unknown. In this study, we used a hydropedological approach to assess the spatial variability of coastal acidification within two coastal lagoons and embayments in Rhode Island by measuring oyster shell dissolution, pH within the water column, and pore water pH within the upper 5 cm of the underlying subaqueous soils. Sampling and monitoring sites were stratified based on submerged soil-landscape types mapped at the Great Group level as Haplowassents, Sulfiwassents, and Psammowassents. We found that pore water pH varied significantly among soils and with depth. Median pore water pH was significantly greater in sandy, low organic matter content Psammowassents (7.97) than the finer textured, higher soil organic matter content Sulfiwassents (7.35), and the Haplowassents (6.57) that receive groundwater discharge from the surrounding subaerial soils. Juvenile calcifying organisms can experience acidic stress at pH values below 7.6; thus, current pH values within the upper few centimeters of Sulfiwassents and Haplowassents may be low enough to impact recently set juvenile calcifying organisms inhabiting these soils. Consequently, mean shell loss during a 4-wk period was significantly greater in the Sulfiwassents (1.54) than the Psammowassents (0.96%), with the greatest shell loss (18.62%) in one of our Haplowassent sites with groundwater discharge. Our research suggests that measures of pore water pH and shell dissolution may be helpful in developing soil interpretations regarding the effects of coastal acidification on calcifying organisms.

Soil–water relationships in the upper soil layer in a Mediterranean Palexerult as affected by no-tillage under excess water conditions – Influence on crop yield

In Mediterranean regions, the performance of conservation tillage under water-deficit conditions has been widely reported, but conversely there exists a lack of studies investigating its effects during periods of water excess, which are common in these regions between fall and spring. Our experiment was established in 2005 on a degraded Palexerult from a raña, a continental detritic formation, of western Spain to study the influence of soil tillage and Ca amendments on soil quality. During high precipitation periods, perched water tables can be formed in very flat raña surfaces with the upper limit close to soil surface due to the presence of Bt horizons with low permeability. In the 2010–2011 and 2012–2013 campaigns, when perched water tables developed very close to the soil surface between November and March, we studied the effects of no tillage (NT) vs. tillage (T) on selected soil hydraulic properties in the 0–5cm soil layer and on crop yield. We observed the lowest bulk density and the highest soil organic matter content (SOM) for this soil layer under NT. As a result of the higher SOM content and higher total porosity as well as the potential to preserve soil biopores under NT, water content at saturation (SAT), plant-available water capacity (AWC), water infiltration and saturated hydraulic conductivity were also higher in the NT plots compared with those under T. During wet periods, the degree of water saturation (Sr) under T was higher, and sometimes close to saturation. Crop development and yield were strongly affected by near-saturation conditions in the 0–5cm surface layer, resulting in substantial yield losses under T.

Anthropogenic Dark Earth in Northern Germany — The Nordic Analogue to terra preta de Índio in Amazonia

During an archaeological excavation of a Slavic settlement (10th/11th C. A.D.) in Brünkendorf (Wendland region in Northern Germany), a thick black soil (Nordic Dark Earth) was discovered that resembled the famous terra preta phenomenon. For the humid tropics, terra preta could act as model for sustainable agricultural practices and for long-term CO2-sequestration into terrestrial ecosystems. The question was whether this Nordic Dark Earth had similar properties and genesis as the famous Amazonian Dark Earth in order to find a model for sustainable agricultural practices and long term CO2-sequestration in temperate zones. For this purpose, a multi-analytical approach was used to characterise the sandy-textured Nordic Dark Earth in comparison to less anthropogenically influenced soils in the adjacent area in respect of ecological conditions (pH, electric conductivity, cation exchange capacity, amino sugar) and input materials. Total element contents (C, N, P, Ca, Mg, K, Na, Fe, Cu, K, Zn, Mn and Ba) were highly enriched in the Nordic Dark Earth compared to the reference soil. Faecal biomarkers such as stanols and bile acids indicated animal manure from omnivores and herbivores but also human excrements. Amino sugar analyses showed that Nordic Dark Earth contained higher amounts of microbial residues being dominated by soil fungi. Black carbon content of about 30Mgha−1 in the Nordic Dark Earth was about four times higher compared to the adjacent soil and in the same order of magnitude compared to terra preta.The input materials and resulting soil chemical characteristics of the Nordic Dark Earth were comparable to those of Amazonian Dark Earth suggesting that their genesis was also comparable. Amazonian Dark Earth and Nordic Dark Earth were created by surface deposition and/or shallow soil incorporation of waste materials including human and animal excrements together with charred organic matter. Over time, soil organisms degraded and metabolized these materials leaving behind deep black stable soil organic matter. The existence of the Nordic Dark Earth in the temperature zone of Europe demonstrates the capability of sandy-textured soils to maintain high soil organic matter contents and nutrient retention over hundreds of years. Deeper insights are needed urgently to understand soil organic matter stabilization mechanisms in this sandy soil to promote conceptual models for sustainable land use and long-term C sequestration.It is argued that the knowledge of Nordic Dark Earth probably was an important part of the Viking–Slavic subsistence agriculture system, which could have had a great impact on the development of the Viking age emporia in the 9th/10th C. A.D.

Tensile and erosive strength of soil macro-aggregates from soils under different management system

Abstract Reduced soil tillage practices are claimed to improve soil health, fertility and productivity through improved soil structure and higher soil organic matter contents. This study compares soil structure stability of soil aggregates under three different tillage practices: conventional, reduced and no tillage. The erosive strength of soil aggregates has been determined using the abrasion technique with the soil aggregate erosion chambers (SAE). During abrasion soil aggregates have been separated into the exterior, transitional and interior regions. The forces needed to remove the material from the aggregate were calculated as erosive strength and compared with the tensile strength of the aggregates derived from crushing tests. The relationship between aggregate strength and other soil properties such as organic carbon and hydrophobic groups’ content has also been identified. The results show that erosive and tensile strength of soil aggregates is very low in topsoil under conventional and reduced tillage comparing with the subsoil horizons. Negative correlation was found between the content of organic carbon, hydrophobic compounds and erosive aggregate strength which suggests that the stabilising effect of soils organic carbon may be lost with drying. The positive relationship between the tensile strength and erosive strength for aggregates of 8-5 mm size suggests that the total strength of these aggregates is controlled by the sum of strength of all concentric layers

The effects of land use and landscape on soil nitrate availability in Southern Italy (Molise region)

The aim of this study was to verify the significance of land use on nitrate availability (NO3–N) at landscape scale in two different sites by using multivariate geostatistical methods. NO3–N and several other soil properties of Nitrate Vulnerable Zone (NVZ) monitoring network of 71 and 63 top-soils, respectively were measured in Venafro and Campomarino areas of Southern Italy (Molise region). Data analysis was performed firstly with classical descriptive statistics assuming spatial independence of samples; secondly, geostatistical analysis was performed in order to investigate spatial dependence and estimate map soil indices. The result of the distribution of NO3–N contents indicates the existence of many hot spots (high kurtosis) with high NO3–N concentration in both the study areas. Higher NO3–N levels in Venafro were distributed in the central zone that appeared to be correlated with animal manure applied to the fields in the summer strongly associated to high values of soil organic matter (SOM) and total nitrogen (Ntot). In Campomarino, the highest NO3–N concentrations occurred in random spots that appeared lesser correlated with high SOM content and low C/N ratio. Factor co-kriging analysis was applied separately to the two data sets to synthesize the complex multivariate variation of the two areas in a restricted number of zones so they could be ranked as at different risks of NO3–N leaching. The loading values of the factors indicate that Venafro SOM and clay and, to a lesser extent, Ntot and C/N are the variables that mainly affect the first factor at shorter range. On the other hand, cation exchangeable capacity (CEC) and, to a less extent, silt, SOM, C/N and fine sand content weighed more, but negatively, on the first factor at longer range. For Campomarino, clay content and available water capacity (AWC) and, to a lesser extent, NO3–N, weighed more and positively on the first factor at shorter range. The first factor at longer range was quite exclusively dominated by elevation and partially and negatively by pH and CaCO3. Soil factor map appears more variable in both the NVZ areas, characterized by many spots indicative of intensive land use and management. The highest NO3–N levels were found in intensive land use and in dairy farming located for the most part in Venafro catchment. The maps of the two factors at small scale for Campomarino appear to be quite erratic owing to the small size of the farms with different cropping systems differently managed. The results, of the present research, provide data useful to support land use planning and soil management, to mitigate soil nitrate leaching. Reduction in soil NO3–N could be achieved by enhancing useful recommendations in N fertilization and animal manure application to farmers.

Organic Matter Fractions Controlling Soil Water Repellency in Sandy Soils From the Doñana National Park (Southwestern Spain)

AbstractThe relationship between soil organic matter (SOM) content and organic molecular assemblages (n‐alkane/alkenes pairs andn‐fatty acids) with soil water repellency (WR) in different sieve fractions (1–2, 0·25–1, 0·05–0·5 and &lt;0·05 mm) was studied in sandy soils from the Doñana National Park (SW Spain) under four vegetation species:Quercus suber(QS),Pteridium aquilinum(PA),Pinus pinea(PP) andHalimium halimifolium(HH). The severity of soil WR [assessed according to the water drop penetration time (WDPT) test] was ordered according to the sequence QS &gt; PA &gt; PP &gt; HH. A positive correlation was found between soil WR from each sieve fraction and SOM content. Most severe soil WR was detected in QS for all sieve fractions, followed by the finer fractions (&lt;0·05 mm) from PA, PP and HH samples. The finer fraction had the highest SOM content, ranging between 20·9% (PP) and 46·9% (QS). Coarser PA, PP and HH soil fractions (1–2 mm) showed the highest long‐chain‐even C numbered fatty acids in the order PP &gt; PA &gt; HH. A significant correlation was observed between SOM content and the severity of soil WR in QS samples and finer fractions of soil under other vegetation (PA, PP and HH). Coarser fractions (1–2 mm) from PP, PA and HH 1–2 mm sieve fractions showed high severity of WR and relatively low SOM contents that could be explained by a low degree of evolution of the organic residues as seen by analytical pyrolysis, that is, higher alkane/alkene carbon preference index values and the presence of a higher diversity of fatty acid structures. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Stability of soil aggregates and their ability of carbon sequestration

One of the most important binding agents for forming stable aggregates is a soil organic matter (SOM), which can be retained in various size fractions of aggregates. If aggregates are water-resistant, they retain more carbon. Therefore, the aim of this study was to evaluate the stability of aggregates and their ability of carbon sequestration in different soil types and soil management systems in Slovakian vineyards. The highest content of water-stable macro-aggregates (WSA&lt;sub&gt;ma&lt;/sub&gt;) was determined in Cambisols, and the lowest in Fluvisols. The highest content of WSA&lt;sub&gt;ma&lt;/sub&gt; (size fraction 0.5&amp;ndash;3 mm) was determined in Chernozems, decreasing within the following sequence: Fluvisols &amp;gt; Leptosols &amp;gt; Cambisols &amp;gt; Luvisols. The soil type had a statistically significant influence on the re-distribution of soil organic matter in size fractions of water-stable aggregates. The highest content of SOM in water-stable aggregates of the vineyards was determined in grassy strips in-between the vineyard rows in comparison to intensively cultivated rows of vineyard. The highest values of carbon sequestration capacity (CSC) in WSA&lt;sub&gt;ma&lt;/sub&gt; were found in Cambisols &amp;gt; Leptosols and the lowest values of CSC were in Fluvisols. The micro-aggregates represented a significant carbon reservoir for the intensively cultivated soils (rows of vineyard). On the other hand, increasing of macro-aggregates (size fraction 0.5&amp;ndash;3 mm) was characteristic for grassland soils (between the rows of vineyard).

Soil and crop management and biomass removal effects on soil organic matter content in Hungary

Greater use of biomass for bioenergy has increased the need to evaluate above ground biomass removal (BR) effects on soil quality components, especially soil organic matter (SOM). A multifactor, 40 year fi eld experiment was conducted in Kompolt, Hungary on a carbonate-free, slightly acidic chernozem brown forest soil (USDA: Ustolls) with the objective of determining the effect of different management systems with concurrent removal of the above ground biomass on the SOM content of the 0-320 mm layer. A multifactor experiment composed of treatments involving different crop rotation (CR), beef manure application, mineral fertiliser application, above ground BR (vs. biomass incorporation, BI) and lucerne management options for different rotations are the basis of this study. CR had no signifi cant effect on SOM content. Management options that included a four year lucerne stand produced signifi cantly higher SOM content in fi ve out of six fertiliser and biomass management combinations. Continuous manure applications and manure + NPK fertiliser resulted in a signifi cantly greater SOM content than management options that minimised or eliminated fertiliser or manure additions. SOM content for different soil amendments and biomass treatments ranked: BR < NPK + BR < BI < manure + BR = NPK + manure + BR with SOM contents of 2.75 < 2.82 < 2.87 < 2.92 per cent (w/w) respectively. Manure had the most profound effect because its signifi cance was most consistent across a range of management combinations and years. The results suggest that agricultural management systems that include lucerne and manure application have the potential to sustain SOM content with concurrent above ground BR in continental climates on Ustolls with near level topography.

Soil and crop management and biomass removal effects on soil organic matter content in Hungary

Greater use of biomass for bioenergy has increased the need to evaluate above ground biomass removal (BR) effects on soil quality components, especially soil organic matter (SOM). A multifactor, 40 year fi eld experiment was conducted in Kompolt, Hungary on a carbonate-free, slightly acidic chernozem brown forest soil (USDA: Ustolls) with the objective of determining the effect of different management systems with concurrent removal of the above ground biomass on the SOM content of the 0-320 mm layer. A multifactor experiment composed of treatments involving different crop rotation (CR), beef manure application, mineral fertiliser application, above ground BR (vs. biomass incorporation, BI) and lucerne management options for different rotations are the basis of this study. CR had no signifi cant effect on SOM content. Management options that included a four year lucerne stand produced signifi cantly higher SOM content in fi ve out of six fertiliser and biomass management combinations. Continuous manure applications and manure + NPK fertiliser resulted in a signifi cantly greater SOM content than management options that minimised or eliminated fertiliser or manure additions. SOM content for different soil amendments and biomass treatments ranked: BR < NPK + BR < BI < manure + BR = NPK + manure + BR with SOM contents of 2.75 < 2.82 < 2.87 < 2.92 per cent (w/w) respectively. Manure had the most profound effect because its signifi cance was most consistent across a range of management combinations and years. The results suggest that agricultural management systems that include lucerne and manure application have the potential to sustain SOM content with concurrent above ground BR in continental climates on Ustolls with near level topography.