Impact of soil degradation on crop production in Brazil

A conceptual model is proposed to facilitate understanding of the effects of soil and crop management practices on soil properties, yields, economics and political interference in production from heavy clay oxisols of the Brazilian developed regions. This model was developed for illustrative purposes, and was established by qualitative and quantitative analyses of data and observations on the rates of change of soil structure, the susceptibility of soils to this changes, and its effects on different cropping systems. Rates of production, technological aspects of production, production efficiency and profitability are compared. In general, the model is presented as a hypothetical function for characterizing and facilitating understanding of the impact of soil degradation on several aspects of crop production from oxisols in Brazil.     

Natural degradation of low-level petroleum hydrocarbon contamination under crop management

Journal of Soils and Sediments - Natural degradation of petroleum hydrocarbons (PHC) is a crucial process to consider when managing contaminated soils. However, the degradation rate is dictated by...     

Priming effect and C storage in semi-arid no-till spring crop rotations

Adoption of less invasive management practices, such as no-till (NT) and continuous cropping, could reduce CO₂ emissions from agricultural soils by retaining soil organic matter (SOM). We hypothesized that C storage increases as cropping intensity increases and tillage decreases. We also hypothesized that pulsed addition of C increases the mineralization of native SOM. We evaluated C storage at the 0- to 5-cm depth in soils from four crop rotations: winter wheat-fallow, spring wheat-chemical fallow, continuous hard red spring wheat, and spring wheat-spring barley on a Ritzville silt loam (Calcidic Haploxeroll). In two incubation studies using ¹⁴C-labeled wheat straw, we traced the decomposition of added residue as influenced by (1) cropping frequency, (2) tillage, and (3) pulsed additions of C. Differences in ¹⁴C mineralization did not exist among the four rotations at any time throughout the incubations. However, differences in total CO₂ production between the continuous wheat rotations and the fallow rotations point to a priming of native SOM, the degree of which appears to be related to the relative contributions of fungi and bacteria to the decomposition of added residue. Addition of non-labeled wheat straw to select samples in the second incubation resulted in a flush of ¹⁴C-CO₂ not seen in the controls. This priming effect suggests C inputs have a greater effect on mineralization of residual C compared to disturbance and endogenous metabolism appears to be the source of primed C, with priming becoming more pronounced as the fungal:bacterial ratio in the soil increases.     

Effects of soil storage on the microbial community and degradation of metsulfuron-methyl

The effect storage had on the microbial biomass in two soils (Trevino and Fargo) was compared to the effect storage had on each soil's capacity to degrade metsulfuron-methyl. Soils were collected from the field and used fresh (<3 weeks old) or stored at 20 and 4 degrees C for 3 or 6 months. The phospholipid fatty acid content of the soils was used to monitor changes in the microbial biomass during storage and incubation in a flow-through apparatus. In both soils, [phenyl-U-14C]metsulfuron-methyl was used to monitor changes in the route and rate of degradation along with 14CO2 evolution (mineralization). Total microbial biomasses in both soils were significantly reduced for soils incubated in the flow-through apparatus, whereas only the Trevino soil's microbial biomass was significantly reduced as a result of storage. The microbial communities of both soils were significantly different as a result of storage as shown by discriminant analysis. In both soils, degradation rate, pathway of degradation, and mineralization of metsulfuron-methyl were significantly affected by storage compared to fresh soil. The half-life of metsulfuron-methyl increased significantly (P < 0.05) in the Trevino soil from 45 days (fresh) to 63 days (stored soil), whereas in the Fargo soil half-lives increased significantly (P < 0.05) from 23 days (fresh) to 29 days (soils stored for 6 months). In both soils, mineralization of [14C]metsulfuron-methyl was significantly (P < 0.05) higher in fresh soils compared to stored soils. The degradation pathways of metsulfuron-methyl changed with storage as evidenced by the loss of formation of one biologically derived metabolite (degradate) in stored soils compared to fresh soils.     

Identification of protein degradation during post-mortem storage of pig meat

Eighteen proteins and peptides that were found to change post-mortem in Longissimus dorsi from pig muscle were identified by the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The 18 peptides originate from 9 different proteins including the 3 structural proteins (actin, myosin heavy chain, and troponin T) and the 6 metabolic proteins glycogen phosphorylase, creatine kinase, phosphopyruvate hydratase, myokinase, pyruvate kinase, and dihydrolipoamide succinyltransferase. The molecular weight and estimated sequence length of the identified spots show that these fragments result from proteolytic activity in meat. Identification of the parent proteins and the enhanced post-mortem appearance of the degradation products make these specific peptides good candidates for meat quality markers, and further studies of these specific fragments will lead to a better understanding of the proteolytic activities involved in the post-mortem conversion of muscle to meat.     

Effect of storage temperature on the degradation of dimethoate in fortified orange and peach juices

The effect of storage temperature on dimethoate degradation in fortified orange and peach juices was studied. The insecticide was aseptically injected into packed orange and peach juices and stored at 40, 15, and 0 degrees C. Samples were taken at regular time intervals and were examined for dimethoate residues. The residues were determined with a simple gas chromatographic method; the recoveries of dimethoate from orange and peach juices were found to be from 88 to 114% for both products. The limits of determination were 0.004 and 0.003 mg/kg, respectively. From the experimental data, rate constants, half-lives, and activation energies for the decomposition of dimethoate in orange and peach juices were evaluated. During the storage of fruit juices in refrigerated rooms (0 degrees C) half-lives of dimethoate were found to be largely extended, being 1733 days for orange juice and 2310 days for peach juice. Corresponding times for storage at 15 degrees C were 533 days for both juices and for storage at 40 degrees C 24 days for orange juice and 24.6 days for peach juice. The activation energy for dimethoate in orange juice was 22.3 kcal/mol and for peach juice, 21. 2 kcal/mol.     

Antiplasmodial and antitrypanosomal activity of pyrethrins and pyrethroids

In a screen of 1800 plant and fungal extracts for antiplasmodial, antitrypanosomal, and leishmanicidal activity, the n-hexane extract of Chrysanthemum cinerariifolium (Trevir.) Vis. flowers showed strong activity against Plasmodium falciparum. We isolated the five pyrethrins [i.e., pyrethrin II (1), jasmolin II (2), cinerin II (3), pyrethrin I (4), and jasmolin I (5)] from this extract. These were tested together with 15 synthetic pyrethroids for their activity against P. falciparum and Trypanosoma brucei rhodesiense and for cytotoxicity in rat myoblast L6 cells. The natural pyrethrins showed antiplasmodial activity with IC(50)s between 4 and 12 μM, and antitrypanosomal activity with IC(50)s from 7 to 31 μM. The pyrethroids exhibited weaker antiplasmodial and antitrypanosomal activity than the pyrethrins. Both pyrethrins and pyrethroids showed moderate cytotoxicity against L6 cells. Pyrethrin II (1) was the most selective antiplasmodial compound, with a selectivity index of 24.     

Effects of cover crop in an apple orchard on microbial community composition,networks, and potential genes involved with degradation of crop residues in soil

Changes in the soil microbial communities and networks were monitored after planting the cover crop for 9 years. The field experiment included plots with a cover crop and without a cover crop but with weed control, and two subplots with or without chemical fertilizer (192 kg N ha^?1, 108 kg P₂O₅ ha^?1, and 168 kg K₂O ha^?1 each year). After applying the cover crop and chemical fertilizer for 9 years, the composition and activity of bacterial and fungal communities changed significantly (p?<?0.05), with the cover crop had greater effects than the chemical fertilizer on the composition of the soil microbial community. The relative abundances of 22 selected genera (in Firmicutes and Bacteroidetes) and two selected classes (Ascomycota) related to cover crop residue degradation increased significantly in the presence of the cover crop (p?<?0.05). Network analysis showed that the cover crop decreased the number of positive links between bacterial and fungal taxa by 25.33%, and increased the negative links by 22.89%. The positive links among bacterial taxa increased by 16.63% with the cover crop, mainly among Proteobacteria (increase of 39), Firmicutes (16), Actinobacteria (five), and Bacteroidetes (10). The links among fungal taxa were less than among bacterial taxa and were not significantly affected by cover crop. Taxa such as Thaumarchaeota, unidentified_Nitrospiraceae, unidentified_Nitrosomonadaceae, Faecalibacterium, Coprococcus_3, and Ruminococcaceae_NK4A214_group dominated the network without the cover crop but they were not dominant with the cover crop. The relative abundances of potential genes involved with the degradation of cellulose, hemicellulose, and cello-oligosaccharides increased significantly with the cover crop. Therefore, the SOC and TN contents were enhanced by the cover crop with the increase of the soil enzyme activities. Thus, the apple yield was improved by the cover crop.     

离子溅射Pt对光催化降解冷藏环境中乙烯的影响

为了了解纳米铂（Pt）对以活性碳纤维（ACF）为载体所负载TiO₂的复合材料（TiO₂/ACF）光催化降解冷藏环境中乙烯的影响。该文采用真空离子溅射仪制备纳米Pt沉积的TiO₂/ACF光催化材料（TiO₂/ACF-Pt）,在模拟园艺产品冷藏环境中,进行了两种不同溅射方案制备TiO₂/ACF-Pt的光催化降解乙烯反应速率影响研究,并利用环境扫描电镜（ESEM）、场发射扫描电镜（FESEM）、X射线光电子能谱仪（XPS）对制备材料进行观察与分析。结果表明：在模拟园艺产品冷藏环境中,TiO₂ /ACF-Pt光催化降解乙烯的动力学可用表观一级速率方程来描述;ACF表面先溅射沉积Pt,再进行TiO₂附着方案,能提高降解乙烯的能力,当溅射时间为60 s（Pt/Ti原子浓度比为0.112）时,表观一级速率常数是未溅射Pt的1.16倍;TiO₂/ACF-Pt的制备方法,对ACF形貌结构没有破坏,并能得到有利于对微量乙烯的吸附的多孔结构。     

热管技术在自然冷源蓄冷中的应用

为实现无能耗、无噪音、方便快捷有效地贮存冬季自然冷源,基于热管技术,开发建成了一套热管模组自然冷源蓄冷系统,建立了单管制冰过程的一维传热模型,并对理论进行了试验验证。结果表明：单管制冰半径与制冰时间呈幂函数关系,修正后的解析解能够可靠预测实际制冰情况。研究成果为热管模组间管间距的设计和蓄冷制冰量的预测提供了有效的理论依据。     

The function of the pericarp in fruits of crop legumes

Summary Legume fruits consist of the seeds and the pericarp that develops from the carpel. Anatomical as well as physiological functions of the pericarp on the one hand resemble those of leaves, on the other hand similarities exist to storage organs. This double function is closely related to the maintainance of a continuous ontogenetic development of the embryo and contributes to the survival of the species. The fleshy and reserve accumulating pericarps of most of the agronomically used grain legumes may have been accidentally selected by breeders in former times. A well developed system of relations between pericarp and developing seeds may have an evolutionary advantage, too. Consequently, the optimally coordinated development of pericarp and seeds in fruits of grain legumes should also be of interest in breeding for increased yields.Pericarps represent a protection against damage of the developing embryo and maintain a favourable micro-climate. All transport streams supplying nutrients to the developing embryo have to pass through the pericarp tissues; pericarp vascular tissue mediates the transport between vegetative parts and the developing young plant organism. Like leaves pericarp assimilates carbon dioxide as well as nitrate autotrophically. During stage 1 of embryogenesis, when the seeds are only small and slowly growing organs, the pericarp represents the centre of anabolism in the fruits and accumulates starch and amides that are degraded and transferred into the seeds during stage 2 of ontogenesis when the cotyledons are growing rapidly. Pericarp metabolism seems to be controlled by the seeds. Temporarily physiological processes in the pericarp can buffer seed development against damages by environmental and nutrient stress.The present knowledge on the structures and functions of the pericarp in grain legume fruits is summarized on the basis of available literature as well as on the basis of own investigations.

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Die Funktion des Pericarps in Früchten von Körnerleguminosen

Zusammenfassung Leguminosenfrüchte bestehen aus dem Pericarp, das sich aus dem Fruchtblatt entwickelt, und den davon umschlossenen Samen. Anatomische und physiologische Funktionen des Pericarps entsprechen einerseits denen eines Blattes, andererseits bestehen Ähnlichkeiten zu Speicherorganen. Diese Doppelfunktion ist eng mit der Erhaltung einer kontinuierlichen ontogenetischen Entwicklung der Embryonen verknüpft und trägt zur Erhaltung der Art bei. Die fleischigen und Reserve-Stoffe akkumulierenden Pericarpien der meisten landwirtschaftlich genutzten Körnerleguminosen könnten in vergangenen Zeiten unbewußt durch Pflanzenzüchter herausgebildet worden sein. Ein gut entwickeltes System von Beziehungen zwischen Pericarp und sich entwickelnden Samen könnte einen Evolutionsvorteil darstellen. Infolgedessen sollte die Herausbildung eines solchen Systems mit optimal koordinierter Entwicklung von Pericarp und Samen für die Ertragszüchtung bei Körnerleguminosen von Interesse sein.Pericarpien bilden einen Schutz gegen die Schädigung der sich entwickelnden Samen und erhalten ein günstiges Mikroklima. Alle Transportströme, mit denen Nährstoffe für den herangewachsenen Embryo bereitgestellt werden, passieren das Pericarp; die Leitgewebe des Pericarps bilden die Transportverbindungen zwischen vegetativen Teilen und den sich entwickelnden jungen pflanzlichen Organismen. Ebenso wie Blätter können Pericarpien autotroph Kohlendioxyd und Nitrat assimilieren. Während der 1. Phase der Embryogenese, wenn die Samen noch klein sind und nur langsam wachsen, liegt das anabolische Stoffwechselzentrum der Leguminosenfrüchte im Pericarp, das zu dieser Zeit Stärke und Amide akkumuliert, die während des 2. ontogenetischen Stadiums reaktiviert und in die nun rasch wachsenden Samen verlagert werden. Der Stoffwechsel des Pericarps scheint unter Kontrolle durch die Samen zu stehen. Physiologische Prozesse im Pericarp können zeitweilig die sich entwickelnden Samen gegen Schädigungen infolge Umwelt- und Ernährungsbelastungen abpuffern.Der gegenwärtige Stand unserer Kenntnisse über Funktion und Struktur des Pericarps der Früchte von Körnerleguminosen wird auf der Grundlage von Literaturinformationen und eigener Untersuchungen zusammenfassend dargestellt.

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介质阻挡放电降解果蔬贮藏环境中的乙烯

为了去除园艺产品贮运环境中的乙烯以达到保鲜效果,该研究采用一种介质阻挡放电（DBD）反应器对乙烯进行降解,对影响乙烯降解的各主要因素进行了考察。结果表明,放电间隙1 mm、放电功率大于15 W、气体流量1.5 L/min时乙烯的降解效果较好,30 min内乙烯被完全降解;产生的臭氧能够更好促进乙烯的降解,但也存在随功率增加臭氧含量突增的缺陷。低温等离子体技术在果蔬保鲜领域是有应用前景的。     

草莓浑浊汁维生素C降解动力学模型

为了弄清贮藏温度对草莓浑浊汁内维生素C降解的影响,建立其降解动力学模型,为选择草莓浑浊汁的贮藏温度提供依据。该文通过研究草莓浑浊汁贮藏过程中还原型维生素C和氧化型维生素C的降解与贮藏温度、贮藏时间的关系,建立了还原型维生素C和氧化型维生素C降解动力学模型。结果表明：草莓浑浊汁在贮藏过程中还原型维生素C和氧化型维生素C对热不稳定,还原型维生素C和氧化型维生素C降解符合一级反应动力学。经过验证表明该降解动力学模型有效,可用于草莓浑浊汁贮藏温度的选择和预测不同温度下的贮藏期。     

A risk analysis methodology for assessing natural resources degradation

Risk analysis has been employed, amongst other things, both to estimate the probability of future water demand emergencies in reservoir systems (using simulation modelling), and to estimate environmental and public health risks (using empirical data). We assert that this framework, when coupled with simulation modelling, can be applied to examine and compare the impacts of resource exploitation, land use and production strategies which may cause land degradation. Our representation of risk analysis relies on the assumption that each land use strategy is associated with a risk of the system (i.e., social system, production system, ecosystem) attaining a subjectively unacceptable environmental condition (e.g. poor human nutrition, crop failure, degradation of a natural resource) sometime during a management planning period. The research methodology entails: (1) the identification of critical variables in the social and biological environment that are affected by exploitation and management of resources; (2) the identification through interviews, surveys, and research of regions of unacceptability in these variables that determine the dynamics of local environmental degradation; (3) the translation of resource policy and practice into a computer model of impact on the resource system; (4) many iterations of simulation of the system to determine the ‘risk of failing’ in each of the critical variables. The presentation of risk probabilities to decision-makers represents a reduction of many simulations into an understandable estimate of environmental impact. More importantly, risk analysis is potentially a learning tool for human system studies, and an interface for applied social science and ecological research.     

Soil processes as affected by replacement of natural mesquite ecosystem with maize crop

 In the central highlands of Mexico, the vegetation is dominated by mesquite (Prosopis spp.), a leguminous tree or shrub. An experiment was carried out to investigate how cultivating the land and the disappearance of the natural ecosystem affected the biological functioning of the soil. Soil was sampled from under the canopy of isolated (MESQ treatment) and densely growing mesquite trees (DENS treatment), from the surrounding soil not covered by the canopies of the trees (BARE treatment) and from adjacent land cultivated with maize (ARABLE treatment). Soil was characterized and then incubated aerobically for 39 days at 22±1  °C and CO₂, N₂O production, microbial biomass C and inorganic N concentrations were monitored. The organic C content was 2.3 times and 1.1 times greater in the MESQ and the BARE treatments, respectively, than in the ARABLE treatment, while microbial biomass C was 3.5 times and 1.3 times greater. The microbial biomass activity as expressed by CO₂ production was 5.9 times and 3.9 times greater in the MESQ and the BARE treatments, respectively, than in the ARABLE treatment, while N mineralization, as witnessed by the increase in NO₃ ^– concentrations, was 3.4 times and 1.7 times greater. No significant amounts of N₂O were produced in any of the treatments. It was found that cultivating land characterized by the presence of mesquite changed its characteristics profoundly, and even soil not covered by tree canopies had higher microbial biomass C, and C and N mineralization than soil cultivated with maize and beans. Received: 1 December 1997     

不同贮藏条件下荷花粉脂质氧化与色泽降解动力学模型

为了减少干燥后荷花粉贮藏过程中品质的劣变,该研究选用可真空和避光的包装材料,分别研究了30 d贮藏过程中温度(4、20、30℃)、光照(避光、非避光)和氧气(真空、常压)对荷花粉黄色度值(b*值)、过氧化氢值(peroxide value,POV)和硫代苯巴比妥酸反应底物值(thiobarbituric acid reactive substances,TBArs)变化动力学的影响;同时,采用零阶和一阶数学模型对试验数据进行模拟。结果表明:贮藏温度对荷花粉贮藏过程中品质劣变具有显著影响。在避光真空包装条件下,温度为20和30℃贮藏30 d,与4℃贮藏条件相比,荷花粉黄色度值显著降低(P0.05),POV值和TBArs值显著上升(P0.05);贮藏温度为4℃,真空包装贮藏发现,光照对荷花粉POV值的影响不显著(P0.05),但明显加快了脂质氧化的传播速度,非避光条件下贮藏30 d,TBArs值上升了7.42 mg/kg;零阶模型可较好的预测荷花粉贮藏过程中脂质TBArs值的变化,一阶模型可较好的预测荷花粉贮藏过程中黄色度和脂质POV值的变化规律。研究结果为脱水后荷花粉贮藏过程中品质劣变规律的探索及贮藏条件的选择提供了一定的基础。     

Soil profile distribution of total C content and natural abundance of 13C in two volcanic soils subjected to crop residue burning versus crop residue retention

Abstract

Soil organic carbon (SOC) plays a key role in crop productivity and soil quality. Conservation agriculture has a positive effect on SOC accumulation in the surface soil horizons, but little information is available regarding the effect of the removal of crop residues by burning. This study aimed to assess the impact of different types of crop residue management practices on the total C distribution and natural abundance of ¹³C (‰, δ¹³C). Two volcanic soils, located in the Mediterranean temperate zone of Southern Chile, were studied: an Ultisol (Collipulli Series, CPL) and an Andisol (Santa Bárbara Series, SBA). Both soils had been cultivated under direct-drilling and a typical annual crop rotation system for a long period of time. Two different types of crop residue management practices were imposed in both soils: (i) crop residue burning (CPL-B; SBA-B) and (ii) crop residue retention over the soil (CPL-R; SBA-R), corresponding to treatments B and R, respectively. Soil profile distribution of the C content and natural abundance of ¹³C were analysed for bulk soils (down to 100 cm depth) and three particle-size fractions of the soils (down to 20 cm of soil depth): (a) ≤ 53 µm, (b) 53-212 µm and (c) ≥ 212 µm. It was found that the effect of crop residue management can be observed in the variations of C content and δ¹³C in the soil profile in both volcanic soils. Crop residue burning (B treatment) increased the C content in bulk soil and the particle-size fractions. On the other hand, soil organic matter of crop residue retention (R treatment) showed higher natural abundance of ¹³C (δ¹³C) compared with residue burning (B treatment) in the two volcanic soils. R treatment enriched the particle-size fractions (except ≥ 212 µm fraction of CPL soil) with ¹³C. Factors that could account for these findings are also discussed here.     

嘧霉胺替代多菌灵在柑橘贮藏过程中的降解及防效研究

多菌灵残留超标已成为影响我国农产品出口的一大制约因素,积极开展多菌灵安全用药研究,寻找多菌灵替代用药方案尤为必要.本研究针对柑橘罐头原料加工果分别开展了以多菌灵、嘧霉胺浸果后的农药残留动态和保鲜防效研究.研究结果显示,柑橘浸药处理后30d内的保鲜效果,嘧霉胺1 000倍液处理略好于多菌灵600倍液处理;嘧霉胺处理后快速...     

Soil physical quality of Luvisols under agroforestry,natural vegetation and conventional crop management systems in the Brazilian semi-arid region

The imposition of agricultural systems changes the natural equilibrium of the soil to an extent that it becomes dependant on management practices and soil resilience. Agroforestry systems (AFs) mimic characteristics of natural ecosystems such as multistrata canopy and deep rooting and may minimize the consequences of these changes by providing soil protection and maintenance of conditions similar to those under natural vegetation. This study evaluates the physical properties of a Luvisol at a site where since 1997 alternative agroforestry systems (AFs) (agrosilvipasture—AGP and silvipasture—SILV), conventional crop management (CCM) and natural vegetation (NV) have been maintained. Undisturbed soil cores were collected in 2005 and submitted to a range of matric suction for which soil bulk density (BD), soil penetration resistance (Q) and soil water content (θ) were determined. Water retention and penetration resistance were used to determine the least limiting water range (LLWR) and the slope of the soil water retention curve at its inflection point (S-value). Particle size, total organic carbon (TOC) and particle density were determined using the disturbed soil samples. Water retention and porosity followed the sequence NV > SILV > CCM > AGP. The AFs studied (AGP and SILV) improved or maintained soil physical quality when compared to NV with no significant differences between the S-values of 0.044, 0.042 and 0.050, respectively. However, the S-value of 0.035 for CCM indicates that this management was unable to maintain soil physical quality on the same levels as AFs and NV. The decrease of LLWR with BD occurred for all treatments, and the BD at a maximum effect (LLWR = 0) which is called the critical BD (BD_c), was, respectively, 1.69, 1.62, 1.56 and 1.56 Mg m^?3 for AGP, SILV, NV and CCM. The larger values of LLWR for AFs (AGP and SILV) are similar to the value for NV, with associated superior aeration, matric suction and reduced resistance to penetration by roots. Indices such as LLWR and S-value were suitably sensitive and could be used in future research, but it is important to identify other potential indices for these situations that can show how quickly changes in soil quality may occur.