Traditional agriculture in transition: examining the impacts of agricultural modernization on smallholder farming in Ghana under the new Green Revolution

Following the renewed effort at achieving a new green revolution for Africa, emphasis has been placed on modernizing smallholder agriculture through the deployment of improved inputs especially mechanized technologies. In Ghana, the government has in the last decade emphasized the provision of subsidized mechanized ploughing services to farmers alongside a rapidly growing private sector tractor service market. While mechanized technology adoption rates have increased rapidly, the deployment of these technologies has been without critical analysis of the impacts on production patterns and local agrarian systems. This paper examines the distributional impacts of agriculture mechanization on cropping patterns and farm sizes of smallholder farmers in northern Ghana using Geographic Information Systems (GIS) techniques, and semi-structured interviews with smallholder farmers (n=60). Specifically, comparative analysis of the field sizes and cropping patterns of participant farmers prior to and after the adoption of mechanized technologies was conducted. In-depth interviews were used to contextualize the experiences of smallholder farmers toward understanding how mechanization may be impacting traditional agriculture. Our findings reveal a mechanization paradox in which farm sizes are expanding, while cropping patterns are shifting away from traditional staple crops (pearl millet and sorghum bicolor) to market-oriented crops (maize, rice and groundnuts). This transition we argue, has adverse implications on the cultural dimension of food security, the organization of social life, and climate change adaptation. We recommend a retooling of the current agricultural policy focus to ensure context sensitivity for a more robust battle against food insecurity.     

我国人口资源与食物问题

人口增多,耕地减少,部分地区供水不足,是我国人口与资源矛盾的基本格局。由于人口的压力,对资源实行超强度的利用,使较大范围的地区生态环境恶化,严重威胁农业生产,并成为许多地区多灾、低产、贫困的根本原因,较低的食物人均占有水平,将继续成为中国国民经济发展和人民生活水平提高的严重限制因素。增加食物,必须挖掘资源的潜力,开源与节流相结合,以内涵挖潜为主。首先是要立足现有的耕地,致力于提高单产;同时,合理开发水域、山地、草地等资源,广辟食物来源,提高非耕地资源的生产力,提高林牧渔业的发展水平。耕地应以深度开发为主,走资源节约型(节地、节水、节时、节能)的集约化道路。     

Performance of different macrophytes in the decontamination of and electricity generation from swine wastewater via an integrated constructed wetland-microbial fuel cell process

Plants constitute a major element of constructed wetlands(CWs).In this study,a coupled system comprising an integrated vertical flow CW(IVCW) and a microbial fuel cell(MFC) for swine wastewater tre atment was developed to research the effects of macrophytes commonly employed in CWs,Canna indica,Acorus calamus,and Ipomoea aquatica,on decontamination and electricity production in the system.Because of the different root types and amounts of oxygen released by the roots,the rates of chemical oxygen demand(COD) and ammonium nitrogen(NH_4~+-N) removal from the swine wastewater differed as well.In the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,the COD removal rates were 80.20%,88.07%,84.70%,and 82.20%,respectively,and the NH_4~+-N removal rates were 49.96%,75.02%,70.25%,and 68.47%,respectively.The decontamination capability of the Canna indica system was better than those of the other systems.The average output voltages were 520±42,715±20,660±27,and 752±26 mV for the unplanted,Canna indica,Acorus calamus,and Ipomoea aquatica systems,respectively,and the maximum power densities were 0.2230,0.4136,0.3614,and0.4964 W/m~3,respectively.Ipomoea aquatica had the largest effect on bioelectricity generation promotion.In addition,electrochemically active bacteria,Geobacter and Desulfuromonas,were detected in the anodic biofilm by high-throughput sequencing analysis,and Comamonas(Proteobacteria),which is widely found in MFCs,was also detected in the anodic biofilm.These results confirmed the important role of plants in IVCW-MFCs.     

Identification of potential electrotrophic microbial community in paddy soils by enrichment of microbial electrolysis cell biocathodes

Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in paddy soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five paddy soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%–45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in paddy soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.     

The study of biological activity of transformation products of diclofenac and its interaction with chlorogenic acid

In the present work we compared the biological activity of DCF, 4′-OHDCF and 5-OHDCF as molecules of most biodegradation pathways of DCF and selected transformation products (2-hydroxyphenylacetic acid; 2,5-dihydroxyphenylacetic acid and 2,6-dichloroaniline) which are produced during AOPs, such as ozonation and UV/H₂O₂. We also examined the interaction of DCF with chlorogenic acid (CGA). CGA is commonly used in human diet and entering the environment along with waste mainly from the processing and brewing of coffee and it can be toxic for microorganisms included in activated sludge. In the present experiment the evaluation of following parameters was performed: E. coli K-12 cells viability, growth inhibition of E. coli K-12 culture, LC₅₀ and mortality of Chironomus aprilinus, genotoxicity, sodA promoter induction and ROS generation. In addition the reactivity of E. coli SM recA:luxCDABE biosensor strain in wastewater matrices was measured. The results showed the influence of DCF, 4′-OHDCF and 5-OHDCF on E. coli K-12 cells viability and bacteria growth, comparable to AOPs by-products. The highest toxicity was observed for selected, tested AOPs by-products, in comparison to the DCF, 4′-OHDCF and 5-OHDCF. Genotoxicity assay indicated that 2,6-dichloroaniline (AOPs by-product) had the highest toxic effect. The oxidative stress assays revealed that the highest level of ROS generation and sodA promoter induction were obtained for DCF, 4′-OHDCF and 5-OHDCF, compared to other tested compounds. We have also found that there is an interaction between chlorogenic acid and DCF, which resulted in increased toxicity of the mixture of the both compounds to E. coli K-12, comparable to parent chemicals. The strongest response of E. coli SM biosensor strain with recA:luxCDABE genetic construct in filtered treated wastewaters, comparable to control sample was noticed. It indicates, that E. coli SM recA:luxCDABE biosensor strains is a good tool for bacteria monitoring in wastewater environment. Due to toxicity and biological activity of tested DCF transformation products, there is a need to use additional wastewater treatment systems for wastewater contaminated with pharmaceutical residues.     

Responses of nitrification performance, triclosan resistome and diversity of microbes to continuous triclosan stress in activated sludge system

Triclosan(TCS) is commonly found in wastewater treatment plants,which often affects biological treatment processes.The responses of nitrification,antibiotic resistome and microbial community under different TCS concentrations in activated sludge system were evaluated in this study.The experiment was conducted in a sequencing batch reactor(SBR)for 240 days.Quantitative PCR results demonstrated that the abundance of ammonium oxidizing bacteria could be temporarily inhibited by 1 mg/L TCS and then gradually recovered.And the abundances of nitrite oxidizing bacteria(NOB) under 2.5 and 4 mg/L TCS were three orders of magnitude lower than that of seed sludge,which accounted for partial nitrification.When the addition of TCS was stopped,the abundance of NOB increased.The mass balance experiments of TCS demonstrated that the primary removal pathway of TCS changed from adsorption to biodegradation as TCS was continuously added into the SBR system.Moreover,TCS increased the abundance of mexB,indicating the efflux pump might be the main TCS-resistance mechanism.As a response to TCS,bacteria could secrete more protein(PN) than polysaccharide.Three-dimensional excitation-emission matrix revealed that tryptophan PN-like substances might be the main component in PN to resist TCS.High-throughput sequencing found that the relative abundances of Paracoccus,Pseudoxanthomonas and Thauera increased,which could secrete extracellular polymeric substances(EPS).And Sphingopyxis might be the main TCS-degrading bacteria.Overall,TCS could cause partial nitrification and increase the relative abundances of EPS-secreting bacteria and TCS-degrading bacteria.     

基于土壤重金属特征的绿色食品产地环境评价——以重庆(江津)现代农业园区为例

以重庆市江津区现代农业园区内4种农用地类型的653个表层土样为研究对象,测定土壤重金属元素含量.依据绿色食品产地环境相关标准,采用重金属污染指数法对标准中所涉及的Cu、Cr、Cd、Hg、As和Pb共6种重金属元素开展土壤环境质量评价和潜在生态风险评价,并结合用地类型确定绿色农产品生产的适宜性土壤分区.结果表明：除元素Cu、Cr和As外,其他元素的平均含量均高于重庆市土壤背景值;除元素As和Hg外,其他元素的平均含量均高于我国土壤背景值.土壤重金属元素Cu、Cr、Cd、Hg、As和Pb的平均浓度均达到《绿色食品产地环境质量》标准要求,但Cd污染已处于安全警戒线内,应高度警惕和严格监管园区内该元素的污染.水田、旱地和果园的土壤环境均以尚清洁为主,其他园地的土壤环境以轻度污染水平为主.部分水田存在一定程度的Pb污染（轻度）、Hg污染（中度）和Cd污染（中度）,旱地存在一定程度的Hg污染（中度）和Cd污染（中度）,果园和其他园地的土壤存在一定程度的Cd的轻、中度污染.全区符合《绿色食品产地环境质量》标准要求的土壤面积为12.47km²,占农用地总面积的63.64%,旱地、果园、水田和其他园地中符合该标准的面积分别占各自总面积的84.83%、68.07%、56.51%和42.09%.4种用地类型的土壤环境生态风险水平均以低等为主,共占研究区总面积的74.70%.Cd和Hg在园区表层土壤重金属生态风险评估中占有较大的贡献率,应列为优先控制污染元素并对其生态效应开展进一步研究.     

不同基质生物炭对厌氧处理餐厨垃圾效能及微生态的影响

探究了剩余污泥（SS）、餐厨垃圾（FW）、玉米芯（CC）、甘蔗渣（BG）4种不同基质生物炭对厌氧生物处理餐厨垃圾效能的影响,对厌氧污泥的关键酶活性、微生物群落分布以及代谢途径等微生态进行了分析.结果表明,厌氧反应器分别加入4种生物炭后,COD平均去除率分别提高了29.49%、23.16%、29.42%、40.32%;傅里叶红外分析表明,投加SS生物炭组出水中羟基、酰胺基以及C-O-C伸缩振动峰减弱.4个厌氧反应器中厌氧污泥的乙酸激酶活性分别为0.40,0.42,0.96,0.98 μmol/g,表明投加CC与BG生物炭促进了餐厨垃圾的厌氧水解酸化过程;厌氧污泥胞外聚合物的蛋白质/多糖之比分别为0.415、0.56、1.89、2.8,投加CC、BG生物炭提高了污泥的稳定性.4个厌氧反应器中拟杆菌门、变形菌门、厚壁菌门为主要菌群,投加BG生物炭促进了变形菌门与厚壁菌门的生长;对于古细菌而言,甲烷杆菌属与甲烷丝菌属为优势种群,SS组的甲烷杆菌属丰度最高（53.48%）,而BG组中甲烷丝菌属丰度最高（42.72%）.KEGG功能分析表明古菌及细菌均以碳水化合物代谢、氨基酸代谢为主;而投加BG与SS生物炭后,微生物膜运输水平得到了提高.     

Extractive Spectrofluorometric Determination of Quinalphos Using Fluorescein in Environmental Samples

A simple, sensitive, convenient and low cost spectrofluorometric technique for determination of quinalphos is described. Quinalphos is decomposed with sodium ethoxide. Resultant sodium diethyl thiophosphate (Na-DETP) is extracted with a cationic fluorescein as ion pair complex into 1-chloro-2-nitrobenzene. The fluorescence of the ion pair, fluorescein-DETP is measured at 530 nm after excitation at 490 nm. This technique is applicable for the determination of quinalphos in water, food grains and vegetable samples up to ng level with Amberlite XAD-4.     

Mulberry-silkworm food chain--a templet to assess heavy metal mobility in terrestrial ecosystems

Assessment of the food chain mobility of heavy metals inthe natural ecosystem receives more attention nowadays. Inthe present study, mulberry-silkworm food chain has beenfocused as a templet to assess the biomobility of heavymetals in soil-higher plant-insect hierarchy. Both in thecase of Cd and Cu treatments, higher mobility wasobserved in the level-1 (soil–root) followed by level-3(leaf–larva), level-4 (larvae–faecal) and level-2(root–leaf). Consequently, roots accumulated more amountsof Cd and Cu, with a limited transport to the leaves.Among the two metals (Cd and Cu) tested, in the plant,the transfer potential of Cd exceeds that of Cu. Whereasin the case of leaf–larval transfer, Cu precedes overCd. Accumulation of Cd and Cu in all the levels (1–4)tested showed a concentration dependent increase, except inthe level 4 (larva–faecal) of Cd treatment where adeclining trend was noticed.