Potential effect of conservation tillage on sustainable land use: A review of global long-term studies

Although understood differently in different parts of the world, conservation tillage usually includes leaving crop residues on the soil surface to reduce tillage. Through a global review of long-term conservation tillage research, this paper discusses the long-term effect of conservation tillage on sustainable land use, nutrient availability and crop yield response. Research has shown several potential benefits associated with conservation tillage, such as potential carbon sequestration, nutrient availability, and yield response. This research would provide a better perspective of the role of soil conservation tillage and hold promise in promoting application of practical technologies for dryland farming systems in China.     

A review of plant disease, pathogen interactions and microbial antagonism under conservation tillage in temperate humid agriculture

The advent of conservation tillage presents a need for a greater understanding of plant disease and disease interactions in temperate humid agriculture, where excessive crop residues, continuous moist soil conditions and soil compaction are potential constraints. In this review, biotic and abiotic factors, and aspects of microbial antagonism, which can influence plant disease development in the root zone, are characterized in the context of conservation tillage in humid climates.Soil densification and reduction in macroporosity can aggravate abiotic root disease. Changes in soil aeration and permeability status can alter the quantitative and qualitative differences between soil rhizofloral populations, and survival and distribution of pathogen inoculum. Further-more, anaerobic soil conditions can result in root-pathogen interactions leading to plant disease development. A good quality soil physical environment is an important indicator for root health under conservation tillage in humid climates.Conservation tillage tends to concentrate plant debris and consequently microbial biomass in the top 5 to 15 cm of soil, and thus promotes survival of pathogens. However, disease-causing microbes make up only a proportion of the rhizofloral population. Relatively high soil microbial activity can lead to competition effects that may ameliorate pathogen activity and survival, and counteract a high pathogen inoculum pressure. Microbial antagonism in the root zone can lead to the formation of disease-suppressive soils. This phenomenon, which is important for the adoption of conservation tillage in humid climates, can be influenced by soil and crop management practices, especially crop rotation.     

Denitrification in the rooting zone of cropped soils with regard to methodology and climate: A review

Summary Denitrification N losses can be determined by three methods. The first is by estimating the non-recovery of ¹⁵ N-labelled compounds (¹⁵N-balance method). Using this method, denitrification losses are deduced from the balance of an N budged (¹⁵N-labeled fertilizer), having accounted for transformations in soil, plant uptake, and leaching losses. The evolution of gaseous N from native soil N is not taken into account by this procedure. Studies on arable land with annual crops in the temperate zone have shown that of the fertilizer N applied, about 20–500% (10–70 kg N^* ha^–1) is not recovered at the end of the growth period. The second method of determining denitrification N losses is by in situ field measurement of ¹⁵ N ₂ and ¹⁵ N ₂ O production. Under this procedure, ¹⁵N-enriched N is applied to a plot and the denitrification N losses are determined by covering the soil. The method allows a quantitative estimate of the relative contributions to the emitted gas by both the original enriched source and the native soil N. N-evolution rates measured on arable land under a temperate climate are approximately the same order of magnitude as the N losses estimated by the non-recovery of ¹⁵ N method. The third measuring procedure is based on the acetylene inhibition phenomenon. This principle uses the inhibition of bacterial N₂O reduction to N₂ in the presence of acetylene (C₂H₂). The methoddetermines the denitrification of all NO₃ ^–-N irrespective of its source. Measurements on classical crop production systems show maximum N losses in the temperate climate of about 20–30 kg N^* ha^–1 during the growth period of annual crops. A similar level of denitrification is estimated for grassland sites under the same climate. In the subtropics (mediterranean climate with hot summers and mild winters), from both intensively cultivated arable land and grassland sites, N losses may exceed 200 kg^* ha^–1 year^–1. Without the use of irrigation the denitrification flux is negligible in spite of the high temperatures in this climate.     

A review of the problems associated with applying the terms surface charge and zero point of charge to soils

Abstract

Many soil properties are determined by the surface charge on the soil particles. A range of methods for determining the surface charge properties is available from the literature. However, the interpretation of the results obtained and the theoretical basis of some of the methods is confusing with different terms having different meanings for different authors. Thus, the study of surface charge properties and the theoretical basis is particularly difficult for a newcomer to the field. This paper presents a review of the major concepts as used in the current literature and highlights the problems encountered when applying these concepts to the determination of the surface charge properties.     

中国耕地保护与粮食安全研究进展可视化分析

探究情景模拟下耕地进出平衡政策实施绩效与影响,有助于完善该政策机制和促进耕地保护。该研究以广州市为例,通过构建现实情景（政策实施情景）和反现实情景（惯性发展情景）下的农用地内部转换决策效用函数、土地利用需求预测模型和基于元胞自动机（cellular automata,CA）的土地利用转换潜力综合模型,对比分析两种情景下的土地利用时空动态格局变化,对该政策未来实施绩效进行预测。结果表明：1）该政策实施有效减少了广州市耕地的流失,政策实施情景中2020—2030年耕地流向非耕农用地的面积减少了20.40km²;2）该政策实施对耕地和园地的景观格局影响较大,政策实施情景中耕地的聚集程度更高,但园地的破碎程度更大;3）政策实施情景中2020—2030年广州市农用地内部地类数量比例保持平衡,较多园地恢复为耕地,且各地类分布更加均匀。耕地进出平衡政策未来在广州市的实施绩效良好,有效减少了耕地流失,维持了农用地内部结构比例,促进了园地向耕地转换,对保持耕地数量动态平衡、保障国家粮食安全具有重要意义。

     

Contamination of soils and groundwater with new organic micropollutants: A review

The input of organic micro- and nanopollutants to the environment has grown in recent years. This vast class of substances is referred to as emerging micropollutants, and includes organic chemicals of industrial, agricultural, and municipal provenance. There are three main sources of emerging pollutants coming to the environment, i.e., (1) upon soil fertilization with sewage and sewage sludge; (2) soil irrigation with reclaimed wastewater and (3) due to filtration from municipal landfills of solid wastes. These pollutants contaminate soil, affect its inhabitants; they are also consumed by plants and penetrate to the groundwater. The pharmaceuticals most strongly affect the biota (microorganisms, earthworms, etc.). The response of microorganisms in the contaminated soil is controlled not only by the composition and the number of emerging pollutants but also by the geochemical environment.     

Production,oxidation, emission and consumption of methane by soils: A review

Methane emission by soils results from antagonistic but correlated microbial activities. Methane is produced in the anaerobic zones of submerged soils by methanogens and is oxidised into CO₂ by methanotrophs in the aerobic zones of wetland soils and in upland soils. Methanogens and methanotrophs are ubiquitous in soils where they remain viable under unfavourable conditions. Methane transfer from the soil to the atmosphere occurs mostly through the aerenchyma of aquatic plants, but also by diffusion and as bubbles escaping from wetland soils. Methane sources are mainly wetlands. However 60 to more than 90 % of CH₄ produced in the anaerobic zones of wetlands is reoxidised in their aerobic zones (rhizosphere and oxidised soil-water interface). Methane consumption occurs in most soils and exhibits a broad range of values. Highest consumption rates or potentials are observed in soils where methanogenesis is or has been effective and where CH₄ concentration is or has been much higher than in the atmosphere (ricefields, swamps, landfills, etc.). Aerobic soils consume atmospheric CH₄ but their activities are very low and the micro-organisms involved are largely unknown. Methane emissions by cultivated or natural wetlands are expressed in mg CH₄·m^–2·h^–1 with a median lower than 10 mg CH₄·m^–2·h^–1. Methanotrophy in wetlands is most often expressed with the same unit. Methane oxidation by aerobic upland soils is rarely higher than 0.1 mg CH₄·m^–2·h^–1. Forest soils are the most active, followed by grasslands and cultivated soils. Factors that favour CH₄ emission from cultivated wetlands are mostly submersion and organic matter addition. Intermittent drainage and utilisation of the sulphate forms of N-fertilisers reduce CH₄ emission. Methane oxidation potential of upland soils is reduced by cultivation, especially by ammonium N-fertiliser application.     

阿特拉津在土壤, 矿物质及堆肥中的吸附, 运输和转化

Atrazine is a widely used herbicide for controlling weeds on both agricultural and nonagricultural land,which is equally detected in water supplies beyond safe concentrations.Although the presence of atrazine metabolites is an indication of herbicide degradation,some of them still exhibit toxicity,greater water solubility and weaker interaction with soil components than atrazine.Hence,studies with atrazine in the environment are of interest because of its potential to contaminate drinking water sources.Data on atrazine availability for transport,plant uptake,and microbial degradation and mineralization are therefore required to perform more comprehensive and realistic environmental risk assessments of its environmental fate.This review presents an account of the sorption-desorption phenomenon of atrazine on soil and other sorbents by revisiting the several mechanisms of atrazine-sorbent binding reported in the literature.The retention and transport of atrazine in soils;the influence of organic matter on atrazine sorption;the interactions of atrazine with humic substances,atrazine uptake by plants,atrazine bioccumulation and microbial degradation;atrazine transformation in composting environments;and finally atrazine removal by biosorption are discussed.     

Ferrihydrite: A review of structure,properties and occurrence in relation to soils

Ferrihydrite occurs in soils undergoing rapid weathering, and in soils containing soluble silicate or organic anions which inhibit the formation of more crystalline iron oxides. Because of its very high specific surface area and adsorptive capacity (analogous to allophane), ferrihydrite can profoundly influence soil properties, even if present in only low concentrations. Ferrihydrite was recognised as a mineral by the International Mineralogical Association in 1975. Its structure and chemical formula, however, are not yet clearly understood. Most evidence to date indicates hexagonal-close-packed layers of O²′, OH, and H₂O with Fe(III) occupying octahedral positions and giving a trigonal unit cell (a=0.508 nm; c=0.94 nm). Some samples appear to have only a partially ordered structure and uncertainty exists as to how to name such material. Natural ferrihydrites commonly contain up to about 9% Si and the role and location of silicate are subjects of active research. At concentrations greater than 5-10%, ferrihydrite in soils can usually be identified by X-ray diffraction. At lower concentrations, a combination of methods can be indicative. Acid-oxalate-extractable iron is a convenient and often useful indicator of the presence and quantity of ferrihydrite in a soil, though it cannot be regarded as a means of positive identification.     

Effects of alternative tillage systems on soil quality and yield of spring cereals on silty clay loam and sandy loam soils in the cool, wet climate of central Norway

Tillage trials were established on a poorly drained silty loam overlying silty clay loam and on a freely drained sandy loam overlying medium sand, in 1988 and 1989, respectively. Autumn and spring ploughing and two ploughless systems were compared for 12–13 years, with three replications at each site. The ploughless treatments comprised deep versus shallow spring harrowing until 1999, and thereafter autumn plus spring harrowing versus spring harrowing only. In 6 years, treatments with and without fungal spraying of the cereal crops were included. In other years, fungicides were not used. Perennial weeds were controlled by herbicides as necessary, on nine occasions up until 2001. Average spring barley (Hordeum vulgare L.) and spring oat (Avena sativa L.) yields were similar with spring ploughing as with autumn ploughing at both sites. In treatments without ploughing, average yields on the silty loam over clay were 93% of those obtained with ploughing, and on the sandy loam over sand they were 81%. Smaller and non-significant yield differences were found between spring harrowing versus deep spring harrowing, and between autumn plus spring harrowing versus spring harrowing only. Fungal spraying increased yields markedly at both sites (25%), but there was no significant interaction between this treatment and tillage system. Oat was compared with barley in 2 years, with oat performing better under ploughless tillage. At both sites increases in penetrometer resistance occurred in the topsoil of unploughed treatments. These were considered particularly limiting on the sandy loam. On the silty loam there was an increase in surface horizon porosity in the absence of ploughing, which was associated with an increase in topsoil organic matter content. On this soil there was also a tendency toward lower penetrometer resistance at >30 cm depth on autumn plus spring harrowed soil than on ploughed soil, indicating that the plough pan may have diminished. This was supported by observations of greater earthworm activity on unploughed soil. Soil chemical analyses revealed that mineral N and plant-available P and K accumulated in the upper horizon under ploughless tillage. The percentage yields obtained in individual years with autumn as opposed to spring ploughing, were positively correlated with air temperature during 0–4 weeks after planting on the silty loam, and with precipitation during 0–12 weeks after planting on the sandy loam. In the case of yields obtained with spring harrowing only, relative to spring ploughing, positive correlations were found with 0–4 week temperature on both soil types, suggesting that low early season temperatures may limit yields under ploughless tillage.     

CITES, sustainable use of wild species and incentive-driven conservation in developing countries, with an emphasis on southern Africa

Over 30,000 species of animals and plants that are, or may be, detrimentally affected by international trade are listed on the Appendices of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES). The Convention aims to regulate transboundary trade in species and their derivatives through a system of permits and certificates, and to ensure that such trade conforms to the principle of sustainability. In the developing world, a considerable component of its biodiversity lives outside protected areas where governments have limited potential to manage wildlife. Based on selected vertebrate and plant species, this paper concludes that: (1) use of wildlife in developing countries is more likely to be an imperative rather than a choice; (2) the legal instruments of CITES have limited capacities to ensure that international trade is sustainable; (3) sustainable use of species is best achieved by gaining the support of affected local communities; (4) community support can be maximized by the devolution of ownership or user rights of species from the state to, e.g., the communal level, and the development of effective economic incentive structures to prevent alternative land-use strategies; (5) countries in southern Africa have pioneered devolution of ownership/user rights to the district/communal level; (6) in combination with effective CITES trade controls, trade opportunities, rather than trade restrictions, are most likely to assist in the development of incentive-driven conservation strategies; (7) to avoid negative incentives and to increase awareness of livelihoods, the international CITES community may need to consider whether CITES Appendices I and II listing decisions should be based not only on biological/trade criteria but also on socio-economic considerations, if it is in the conservation interest of the species concerned; (8) a strategic cooperation with the Convention for Biological Diversity (CBD) could improve strategies for sustainable trade; (9) while incentive-driven conservation can provide significant longer-term potential for the protection of animal and plant species, it may be most difficult to achieve for species whose high-value products have a long tradition in medicinal use and (10) the conditions under which incentive-driven conservation is most likely to promote sustainable use need to be clearly identified.     

Influence of tillage and rotation systems on distribution of organic carbon associated with particle-size fractions in Chernozemic soils of Saskatchewan, Canada

The effects of several dominant tillage and rotation systems on soil organic C content of different particle-size fractions were studied in Chernozemic soils from southwestern and east-central Saskatchewan, Canada. In an Orthic Brown Chernozem in southwestern Saskatchewan, 7 years of no-till cereal–fallow, imposed on a long-term tillage fallow–wheat rotation soil, resulted in 0.1 Mg C ha⁻¹ more organic C mass in the sand + organic matter (OM) fraction of the 0- to 5-cm layer, whereas organic C associated with coarse silt (CS), fine silt (FS), coarse clay, and fine clay of 0- to 5- and 5- to 10-cm layers was less than that of the comparable tilled cereal–fallow system. Conversion of tilled fallow–wheat rotation soil to continuous cropping had a slight effect, whereas the organic C mass in all the size fractions was significantly increased in both 0- to 5- and 5- to 10-cm layers after alfalfa was introduced on tilled fallow–wheat as perennial forage for 10 years. In an Orthic Black Chernozem in east-central Saskatchewan that was cultivated and tilled using a cereal–fallow rotation for 62 years, organic C mass decreased in sand + OM, CS, and FS of 0- to 10-cm depth. Conversion of the tilled cereal–fallow cropland soil back to seeded grassland resulted in significantly more soil organic C in sand + OM fraction after 12 years of grass seed-down. The sand + OM fraction appears to be the size fraction pool initially most sensitive to adoption of management practices that are liable to sequester carbon in the soil.     

Organic residues and their impact on soil health,crop production and sustainable agriculture: A review including bibliographic analysis

Despite their potential as a sustainable source of soil nutrients and organic matter, waste organic residues are often discarded rather than utilized in agriculture. This review examines the current state-of-the-art in the application of organic residues in agricultural production systems by analysing trends and results in published research conducted on their use for soil health and crop production purposes. For this, a bibliographic analysis was conducted on 81 papers collected from the Web of Science database. Our research shows a growing trend in the field, particularly in recent years, with articles from India, China and the United States at the forefront. The most commonly evaluated organic residues were compost, animal manure, crop residues, municipal solid waste and biochar. Soil pH, bulk density and especially organic matter/total organic carbon (TOC) were the chemical, physical and biological attributes most frequently evaluated, respectively. This review indicates that the application of organic residues improves soil health, positively affecting crop productivity in crops such as maize, wheat and rice. However, further research is needed to address the potential risk of soil contamination from potentially toxic metals (PTMs) associated with organic residues, as well as to identify best practices to guarantee food safety and environmental preservation.     

A comparison of microarthropod assemblages with emphasis on oribatid mites in canopy suspended soils and forest floors associated with ancient western redcedar trees

Microarthropod abundance, oribatid mite species richness and community composition were assessed in the high canopy (ca. 35 m) of an ancient temperate rainforest and compared with microarthropod communities of the forest floor. Microarthropods were extracted from 72 core samples of suspended soils and 72 core samples from forest floors associated with six western redcedar trees in the Walbran Valley on the southwest coast of Vancouver Island, Canada. Total microarthropod abundances, mesostigmatid and astigmatid mites, Collembola and other microarthropod abundances were significantly greater in forest floors compared to canopy habitats. Oribatid and prostigmatid mite abundance were not significantly different between habitats. The relative abundances of all microarthropod groups considered in this study differed significantly between habitats. Eighty-eight species of oribatid mites were identified from the study area. Eighteen of the 53 species observed in suspended soils were unique to the canopy. Cluster analysis indicates that the arboreal oribatid mite community is distinct and not a taxonomic subset of the forest floor assemblage, however, canopy oribatid mite communities are more heterogeneous in species composition than in the forest floor.     

耕作措施对温带半干旱地区土壤温室气体(CO2、CH4、N2O)通量的影响

通过设置在甘肃省定西市李家堡镇的不同耕作措施试验, 利用CO₂分析仪、静态箱-气相色谱法对双序列轮作次序下春小麦地、豌豆地生育期内CO₂、CH₄和N₂O通量进行了测定。试验结果表明: 4种耕作措施下春小麦地和豌豆地在生育期内均表现为CO₂源、N₂O源和CH₄汇的功能。传统耕作不覆盖、免耕不覆盖、免耕秸秆覆盖和传统耕作结合秸秆还田下, 春小麦生育期内平均土壤CO₂通量(μmol·m^-2·s^-1)分别为0.203 6、0.221 2、0.241 8、0.224 9, CH₄通量(mg·m^-2·h^-1)分别为-0.041 6、-0.078 0、-0.081 8、-0.053 7, N₂O通量(mg·m^-2·h^-1)分别为0.089 1、0.069 2、0.046 1、0.065 6; 豌豆生育期内平均土壤CO₂通量(μmol·m^-2·s^-1)分别为0.273 6、0.261 6、0.218 1、0.236 0, CH₄通量(mg·m^-2·h^-1)分别为-0.055 0、-0.073 7、-0.066 2、-0.054 5, N₂O通量(mg·m^-2·h^-1)分别为0.123 4、0.084 7、0.080 6、0.035 0。少免耕及小麦秸秆覆盖有利于减少土壤CO₂排放通量, 免耕不覆盖、免耕秸秆覆盖及传统耕作结合秸秆还田均能不同程度地增加CH₄吸收通量、减少N₂O排放通量。综合来看, 免耕不覆盖、免耕秸秆覆盖和传统耕作结合秸秆还田3种保护性耕作措施有助于减少土壤温室气体的排放量。春小麦地CO₂通量随着土壤温度、土壤含水量的逐渐升高而增大; CH₄吸收通量随着土壤含水量的逐渐升高而增大, 而随着土壤温度的逐渐升高而减小。豌豆地CO₂通量的变化与土壤含水量存在极显著正相关关系; 而春小麦地N₂O通量则与平均土壤温度呈显著正相关, 豌豆地则为极显著正相关。     

Interactions of organic phosphorus with soil minerals and the associated environmental impacts: A review

As an important part of the soil phosphorus(P) pool, organic P(OP) is widely found in terrestrial and aquatic environments(e.g., soils and sediments).The interfacial behavior of OP on natural minerals affects the transport, transformation, and bioavailability of P in the environment. This paper reviews the processes involving adsorption-desorption, dissolution-precipitation, and enzymatic/mineral-mediated hydrolysis of OP at the mineral-water interface, and their subsequent effects on OP speciat...     

Regional variability of volcanic ash soils in south Ecuador: The relation with parent material,climate and land use

The high Andes region of south Ecuador is characterised by intense land use changes. These changes affect particularly the páramo, which is a collection of high altitudinal grassland ecosystems. In this region, the interaction between airborne volcanic ashes and the cold and wet climate results in very typical soils, with an elevated organic C contents. The physical soil properties are closely related to the high and reliable base flow in rivers descending from the páramo, which makes them important for the socio-economic development of the region. In this study, we analyse the regional variability of the soils in the south Ecuadorian rio Paute basin. In a first part of the study, data from soil profiles along north–south transects are used to determine the soil properties, and to relate the spatial variability of these properties to the major trends in parent material, volcanic ash deposits and climate. The profiles are Histic Andosols and Dystric Histosols devoid of allophane, with very high amounts of organic matter. Significant differences between the western and central mountain range are observed, as well as a general decrease in Andic properties from north to south, coinciding with the decrease in volcanic influence. Finally, the impact of human activities on the soil properties is assessed in a case study in the Machangara valley. Data from 5 profiles, located in an area with natural grass vegetation and a low degree of human impact are compared with 4 profiles in a heavily disturbed, intensively drained cultivated area. Despite the intensity of the land use, very few significant differences are found.     

Acidic deposition — Extent and impact on forest soils,nutrition, growth and disease phenomena in Central Europe: A review

The paper reviews the present knowledge: (1) about the extent of acidic deposition in Central Europe with special emphasis on the situation in the FRG, (2) about the relationships between soils and soil-mediated effects of acidic deposition on the one hand and forest diseases on the other and (3) the temporal changes of relevant soil properties during the past decades. It is concluded, that infertile soils and acidic deposition are more likely to act as regional or local than as widespread general stressors in forest ecosystems of the FRG. The more or less simultaneous outbreak of natural and of pollutant-determined diseases during the early eighties is assumed to be triggered by largescale weather stress.