N_2O emissions from agricultural soils in the North China Plain: the effect of chemical nitrogen fertilizer and organic manure

An enclosed chamber technique was used to measure N 2O emissions from intensively agricultural soils of the North China Plain during the periods of 1995—1996 and 1997—1998, to reflect distinct components of winter wheat and summer maize growing seasons. The results showed that the continuous application of fertilizer in agricultural soils increased N\-2O emissions by a factor of 24.1—28.1, the calculated annual chemical N fertilizer\|transformed N\-2O\|N emissions was 0.67%. Our results indicated that the application of organic manure also had a significant influence on soil N 2O emissions, which combined with the use of chemical N increased about 20% in a year. It was calculated that there were about 0.11% N of organic manure transformed as N 2O N. Annual mean N 2O emission from our study area of fertilized soils was estimated to be 57.1 μgN 2O/(m 2·h). A weak correlation was also found between N 2O emissions and soil available nitrogen content NH + 4.

Chemicals,Energy,and Biomaterials from Agricultural Waste Resources in South China

Owing to its subtropical or tropical environment and climate,South China is home to unique agricultural crops such as sugar cane,pineapple,banana,cassava,and rice,which generate a large amount of lignocellulosic agricultural wastes during agricultural as well as associated industrial processing.The efficient utilization of these wastes will have a significant impact on the economy and sustainable development of South China.This paper reviews the research investigations conducted both in China and elsewhere on the conversion of wastes from these subtropical or tropical agricultural crops into useful chemicals,energy,and biomaterials.The goal of this paper is to promote and summarize the extensive investigations on these agricultural wastes for the development of biorefinery.

How United States Agricultural Herbicides Became Military and Environmental Chemical Weapons: Historical and Residual Effects

Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

Experiments were carried out to study the removal of heavy metals from municipal sewage sludge by proper method for land application. The sequential extractions for metal fractionation showed that the non digested sludge from Guangzhou contained Cu and Zn principally bound to carbonate and oxides and the metal sulfides were low. Among H 2SO 4, EDTA and NH 4HCO 3 extractant agents, H 2SO 4 was the most efficient and economic in removing the heavy metals, especially with the addition of the concentrated acid. Plant experiment in pots with Chinese cabbage ( Brassica Chinensis ) showed that the acidified sludges neutralized with alkaline amendments such as phosphate rock could increase significantly the plant yield and decreased the soil and plant contamination by heavy metals originated from sewage sludge.

Environmental Issues Related to Chemical Fertilizer Use in China

The current status of chemical fertilizers production and consumption in China as well as their important roles in Chinese modern agriculture are discussed with special concerns to the environmental issues related to chemical fertilizer use. On the one hand, the total amount of chemical fertilizer produced is insufficient to meet the agricultural needs. On the other hand, the production and consumption of chemical fertilizers in China are obviously not balanced. In some areas over application of nitrogen fertilizers and loss of phosphate fertilizer due to soil erosion have resulted in some undesirable environmental problems such as increase of nitrate in water and eutrophication of water bodies. Maximum scientific uses of organic manures in combination with reasonable use of chemical fertilizers are part of good practices not only in increasing soil productivity and keeping sustainable agriculture development but also in mimimizing their detrimental effects on the environment.

Effect of land-use changes on chemical and physical properties of soil in western Iran(Zagros oak forests)

The consequence of land-use change from forest to agriculture and other uses has become one of the world’s greatest concerns.The soil,one of the most important components of forests and containing all the required plant nutrients as soluble ions,is highly impacted by these changes.Because vast areas of the Zagros forests in western Iran have changed in use during the last few decades,the present study investigated the effects of landuse changes of forest area to agriculture,orchard,and agroforestry on soil chemical and physical properties.Soil was sampled at four land-use areas:less-disturbed forest areas(control)and agricultural,orchard,and agroforestry areas.Among each of the two forest-use areas(agroforestry and orchard),we selected five trees with similar-sized crowns and sampled under each tree crown at 0-15 and>15-30 cm depths.Five soil samples also were taken in agriculture area at each depth.The findings indicated that during land-use changes,soil sand particles decreased,and clay and silt particles of soil increased,resulting in a fine soil texture.Moreover,the amount of nitrogen(N),phosphorus(P),organic carbon(OC),and electrical conductivity(EC)of soil decreased at both depths due to the decrease in organic matter.Soil pH and magnesium(Mg)level rose during land-use change at both depths except at agricultural sites.Soil potassium(K)content decreased during agricultural use due to the elimination of tree cover.The level of K decreased only at the depth of 0-15 cm because of K dependency on parent materials.Generally,most soil nutrients were affected by plant removal in the conversion.Forest and agricultural soil are distinguishable by their properties,while land-uses such as agroforestry-orchard separated from the others.Soil nutrients were severely affected by the decrease and elimination of tree cover,plowing,and continuous harvesting,resulting in a decline in soil quality and fertility.

Assessment of Agricultural and Mining Pollutions of Waterbodies within the NakanbéBasin (Burkina Faso): The Case of the Goinré, Ziga and BagréReservoirs

Agriculture is harming its own future through soil degradation and pollution of the water that it generates. The different chemical analyses carried out on surface waters and the land surveys carried out in the Nakanbé basin have shown that agricultural practices contribute to water pollution. The monitoring of nitrate, orthophosphate and BOD5 levels in the dams of Goinré, Ziga and Bagré during the period from August to December revealed that agricultural practices lead to variation in these parameters. The average values for nitrates are 0.833 mg/L in the Goinré fresh waterbody, 1.372 mg/L in the Ziga reservoir, and 1.267 mg/L in the Bagré fresh waterbody. As for ortho phosphate, mean values are 0.357 mg/L in the Goinré reservoir, 0.157 mg/L in the Ziga reservoir and 0.123 mg/L in the Bagré reservoir. These average values are higher than the norms established by Nisbet and Vernaux (1970) for eutrophication. Nitrates and orthophosphate are the elements that contribute to the eutrophication of water surfaces in the Nakanbé basin, although this eutrophication is of low intensity. Of all pesticides encountered in our study sites, 45% are registered by the Sahelian Pesticides Committee (CSP): 35% are non-accredited and 20% are unknown in the global list authorized by the CSP in 2010.

Evaluating the Effects of Sustainable Chemical and Organic Fertilizers with Water Saving Practice on Corn Production and Soil Characteristics

The rapidly growing world population,water shortage,and food security are promising problems for sustainable agriculture.Farmers adopt higher irrigation and fertilizer applications to increase crop production resulting in environmental pollution.This study aimed to identify the long-term effects of intelligent water and fertilizers used in corn yield and soil nutrient status.A series of field experiments were conducted for six years with treatments as:farmer accustomed to fertilization used as control(CON),fertilizer decrement(KF),fertilizer decrement+watersaving irrigation(BMP1);combined application of organic and inorganic fertilizer+water-saving irrigation(BMP2),and combined application of controlled-release fertilizer(BMP3).A significant improvement was observed in soil organic matter(14.9%),nitrate nitrogen(106.7%),total phosphorus(23.9%),available phosphorus(26.2%),straw yield(44.8%),and grain yield(54.7%)with BMP2 treatment as compared to CON.The study concludes that integrating chemical and organic fertilizers with water-saving irrigation(BMP2)is a good approach to increasing corn productivity,ensuring water safety and improving soil health.The limitations of the current study include the identification of fertilizer type and its optimum dose,irrigation water type,and geographical position.

Soil chemical properties under modern and traditional farming systems at Khagrachari,Chittagong Hill Tracts,Bangladesh

Land degradation in Chittagong hill tracts has been taking place due to shrinkage of forest cover, policy weakness, population explosion, and inappropriate hill farming system. Modem farming system in the Chittagong hill tracts like Sloping Agricultural Land Technology （SALT） is practiced to provide a new strategy for developing lands for economic productivity and bio-diversity conservation through establishment of ecological community rather than traditional shifting cultivation which is no longer sustainable according to the carrying capacity of ecosystem of Chittagong hill tracts. This study is to find out changing trends of soil chemical properties of sites under modem and traditional farming systems at Khagrachari district of Chittagong hill tracts. The result of the research shows that Sloping Agricultural Land Technology has significantly higher capacity of production due to the presence of the highest percentage of organic carbon, organic matter, compared with shifting cultivated site. The study recommends that shifting cultivation may be changed into a relatively stable semi-permanent farming system through developing participatory integrated farming systems to establish stable production environment in the Chittagong Hill Tracts.

Advances in Measures of Reducing Chemical Pesticides to Control Plant Diseases

In order to provide the technological support for further implementing measures of reducing chemical pesticide to control plant diseases,the research progress on non-chemical pesticide measures to control plant diseases are reviewed from the aspects of agricultural control,botanical pesticide control and microbial pesticide control,and the development prospects are proposed,including accelerating innovative research on botani-cal pesticide control such as Chinese herb extracts,and screening microbial pesticides from valuable bio-control bacteria or plant endophyte metabolites for commercial production and utilization.

Influence of Cooperatives’Socialized Services on Agricultural Households’Chemical Fertilizer and Pesticide Use Intensity-Based on the Evidence from Two Counties,Hubei,China

Abuse of chemical fertilizer and pesticide will not only impair the quality of agricultural products,but also damage the agricultural ecological environment.From the perspective of cooperatives’socialized services,this paper studies agricultural households’chemical fertilizer and pesticide use behavior,attempting to provide references for the government’s formulation of relevant policies and cooperatives’adjustment of their operation strategies.The survey data of 518 agricultural households in Zigui County and Badong County,Hubei Province,China are used to examine the influence of cooperatives and their socialized services on agricultural households’chemical fertilizer and pesticide use intensity via propensity score matching.Research reveals that:(1)Joining cooperatives has a significantly negative influence on agricultural households’chemical fertilizer and pesticide use intensity,and the average treatment effect is-341.505 yuan mu^(-1).(2)Agricultural materials supply services and technical support services can significantly bring down agricultural households’chemical fertilizer and pesticide use intensity,and the average treatment effect is-225.966 yuan mu^(-1)and-163.580 yuan mu^(-1),respectively.While the influence of agricultural products sale services on chemical fertilizer and pesticide use intensity is not significant.(3)Grouped investigation is carried out by age,education years and planting scale,and the influence of socialized services on agricultural householders’chemical fertilizer and pesticide use intensity is obviously varied among different groups.The influence of agricultural materials supply services on agricultural households who are elder,with smaller education years and small planting scale is significant;the influence of technical support services on agricultural households who are younger,with higher education years and small planting scale is significant;the influence of agricultural products sale services on agricultural households who are elder is significant.It is necessary to improve the percentage of agricultural households joining cooperatives,increase the supply level of cooperatives’socialized services,and make socialized services of cooperatives more targeted.All this can contribute to further reduction of agricultural households’chemical fertilizer and pesticide use intensity.

Performance evaluation of a multi-rotor unmanned agricultural aircraft system for chemical application

Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has attracted considerable attention from manufacturers and researchers.The objective of this research was to design a UAAS equippingwith a data acquisition system,to characterize its chemical application performance based on droplet deposition data and optimize the operating parameters.Each test was repeated three times to assess the reliability of the spraying system.Various flight parameters were also evaluated.The optimal spray pressure for the XR8001 and XR8002(TeeJet,Wheaton,IL,USA)nozzles was found to be 300 kPa,and the latter nozzle had a higher droplet deposition rate and spray volume.Spray volume was not significantly affected by the flight speed or droplet density and was negatively correlated with the nozzle pressure.The results of this study provide a basis for improving the efficiency of UAAS chemicalapplication systems in terms of large-scale application.

On-Station and On-Farm Assessment of the Effects of Soil Cover on Conservation Agriculture Performances in Western Burkina Faso

Conservation agriculture (CA) is one option for dealing with such a challenge, but its main difficulty in West Africa is in maintaining permanent soil cover, particularly with crop residues, due to their preferential use for livestock fodder. The aim of our study was to determine the effect of crop residue mulching on the efficiency of cropping systems based on the principles of conservation agriculture. The experimental design was based on on-station experiments, intended to assess the specific effect of different levels of crop residue mulching on the biological and chemical soil fertility parameters, while in on-farm experiments we mainly assessed the ability of farmers to actually collect crop residues for soil cover and the associated effects on weeds and yields. The on-station experimental design was in fully randomized factorial blocks comprising five treatments and three replicates. The treatments compared the conventional system, tillage and cropping without mulching, and CA systems with 1 ton, 2 tons, and 4 tons of straw per hectare in plots of 10 m2. The effects of CA on the macrofauna, respiratory activity, and soil chemical parameters were evaluated in the 2014 and 2015 growing seasons. For the on-farm experiments, the conventional and CA practices of 15 farmers were compared to conventional practices in 2013 and 2014 in plots of 626 m2. The on-station results showed that the presence of crop residue mulching induced an increase in the density of termites. A significant release of carbon dioxide (CO2) in the CA treatments compared to the conventional treatment was also observed. For the chemical parameters (pH, N, P and K) were significantly and positively affected by mulch in the top 5 centimeters of soil. The on-farm experiments confirmed the difficulty of farmers in collecting enough biomass, with negative effects on grass cover leading to generally lower yields than conventional treatments. Other practices also affected the results, such as the maize sowing date, the gap between sowing and weeding, the gap between sowing and urea supply, the number of years of CA practices in the plot and, the gap between maize sowing and cowpea sowing. For the farmers having the human resources to collect enough crop residues for soil cover and follow the steps of the crop management sequences, it was possible to maintain yields compared to the conventional practice.

农地流转的碳减排效应研究

农地流转可以促进农地的集中使用和规模化经营,会降低农业生产经营过程中的化学品和机械等生产性投入强度,并促进农作物种植结构“趋粮化”,进而降低农业碳排放强度。采用2011—2021年30个省份的数据检验农地流转率对农业碳排放强度的影响,结果表明:农地流转率提高对农业碳排放强度具有显著的负向影响;农地流转能够通过减少农业化学品和机械投入强度、提高粮食种植面积占比来降低农业碳排放强度。进一步分析发现,因流转对象和形式的不同,农地流转的碳减排效应存在异质性,表现为:相比流入农户、企业的农地流转,流入合作社的农地流转具有更为显著的碳减排效应;相比采用出租转包、互换转让形式的农地流转,采用股份合作形式的农地流转具有更为显著的碳减排效应。因此,应积极推动农地有序流转,不断完善农地流转机制,合理引导农地流转方向,并鼓励农地流转与农业碳减排项目相结合,以有效减少农业碳排放。

“双碳”目标下农业废弃物资源化实施新路径

“碳达峰”和“碳中和”是我国的重大国家战略,作为第一产业的农业在这一战略目标的实现过程中发挥着至关重要的作用。而农业领域“双碳”目标的推进中农业废弃物的资源化又是重要的一环。本文阐述了农业废弃物除传统的“五料化”利用技术之外的几种资源化新路径,包括将农业废弃物定向转化为高附加值化学品和液体燃料、农业废弃物制备生物炭及其他功能化碳材料、农业废弃物制备可燃气以及农业废弃物制备生物质基可降解塑料等,并简要提出了这些农业废弃物资源化新路径需要进一步提升的问题及在实施过程中如何实现最大程度的碳减排,从而最大程度地促进农业领域“双碳”战略目标的实现。

现代林产化学加工技术的现状与发展趋势

生物质资源来源广泛,具有可再生性、结构多样性和碳中性等特点。目前,以生物质为原料的林产化工已成为继煤和石油化工之后最重要的化工产业之一。在对中国的林产化学工业发展历史概览的基础上,梳理总结了现代林产化学工业的发展,创新地提出了林产化学加工工程学科发展的能源化、材料化、食药化、饲料化、肥料化和基料化6个方向。其中,能源化中的生物质气/液/固体燃料的有效开发是实现碳达峰和碳中和的重要途径之一,而我国林产化工的传统研究领域制浆造纸、木本油脂、松脂化学等则从材料化找到新的突破和发展,相比前两者,食药化、饲料化、肥料化和基料化还有很大的发展空间。林产化学工业已迈入质量和效益持续提升发展新阶段,今后将在生物质资源高值化利用、全质利用技术创新、精深加工与应用、绿色低碳与生物技术融合、生物基材料与化学品创新应用,以及多学科交叉融合等方面实现突破,推动产业转型升级,构建绿色低碳循环发展新模式。

中国农业减污降碳协同效应及其影响机制研究

农业面源污染与农业碳排放是中国农业面临的重要环境问题。现有研究忽视了农业面源污染治理与农业碳减排之间的协同关系,未探索农业减污降碳协同效应及其影响机制,影响农业可持续发展。为此,本文借鉴现有成果,提出农业减污降碳协同效应概念,基于2007—2021年中国30省份面板数据,利用双固定效应回归模型、调节效应模型对农业减污降碳协同效应及其影响机制进行实证分析,并讨论地区异质性。结果表明:1)农业减污降碳协同效应存在,农业面源污染与农业碳排放存在显著的协同关系,当农业面源污染减少时农业碳排放也将显著减少,该结果进行稳健性检验和处置内生性后依然成立;2)农业化学物资消费结构对农业减污降碳协同效应产生显著负向调节作用,农业化学物资使用效率与农业种植结构产生显著正向调节作用,农业投资规模产生负向调节作用但不显著;3)北方地区农业减污降碳协同效应比南方地区更为显著,农业化学物资消费结构与农业化学物资使用效率对北方地区农业减污降碳协同效应产生显著负向调节作用,农业种植结构对北方地区和南方地区农业减污降碳协同效应产生显著正向调节作用。因此,农业降污减碳协同效应存在。

新农科背景下植物化学保护课程“一优二转三创”改革研究与实践

对新农科背景下植物保护专业核心课程——植物化学保护开展“一优二转三创”教学改革的实例和成果进行了总结。通过优化课程内容、转变考核体系和评价机制、创新教学模式与手段,补齐了传统植物化学保护课程的授课短板。通过以上措施提高了学生的学习能力和实践能力,培养了学生“尚德崇学、稼穑厚生”的情怀,实现了价值引领、知识传授、能力培养的有机统一,为新农科背景下农科高等院校课程改革提供了借鉴。

农业要素市场化对农业面源污染的影响效应——兼议环境规制的调节作用

本文探讨了农业市场化改革背景下,农业要素市场化对农业面源污染的影响效应、作用机制以及环境规制在其中的调节作用。基于2004—2020年中国省级(不含港澳台、西藏)面板数据,构建了动态面板模型,并运用差分广义矩阵及调节效应模型进行分析。研究结果表明:1)农业要素市场化对面源污染呈现倒“U”型的动态演化特征;2)机制分析表明,农业要素市场化通过种植结构效应、化学品投入效应和经营规模效应间接影响面源污染,具体而言,农业要素市场化对“非粮化率”和化肥投入强度存在倒“U”型影响,对人均经营规模的影响在市场化程度较高的后期显著为正;3)环境规制在“非粮化率”和化肥投入强度的传导机制中具有显著的负向调节作用,对经营规模与面源污染之间的传导关系不存在显著调节效应。因此,本文提出要进一步发挥市场化改革对农业污染治理的长效机制,立足农业面源污染治理“规模效应”“结构效应”和“投入品效应”的路径依赖,构建“政府-市场”双轨运行机制,以实现农业生态环境的改善和农业可持续发展。

羟基磷灰石与秸秆生物炭对青菜镉积累的钝化效应

农田重金属污染通过食物链危害人体健康,对土壤改良实现安全利用和保障农产品质量安全成为重要现实需求。本研究实地采集苏北Cd污染农田土壤分别进行模拟培养和温室蔬菜盆栽试验,探讨施加不同用量的羟基磷灰石(HAP,1%、2%)、水稻秸秆生物炭(BC,1%、2%)及其组合施用(0.5%HAP+0.5%BC、1%HAP+1%BC)对土壤Cd活性的钝化效率和降低青菜Cd吸收的效果并分析其作用机制。青菜盆栽试验表明,不同钝化剂处理均提高了叶片的净光合速率,生物量增加3.78%~124%,青菜Cd含量与土壤有效态Cd浓度分别降低16.1%~81.7%、15.8%~69.9%;40 d土壤培养试验后,各钝化剂对有效态Cd的降幅达28.9%~87.6%,主要机理是土壤pH显著提高了0.38~0.98个单位、Cd残渣态含量增加19.5%~37.0%、酸溶态含量减少21.1%~25.6%。可见,2种类型的钝化剂均主要通过降低土壤中Cd的化学活性和植物有效性来阻控其被蔬菜吸收积累,而在同等用量下的酸性污染土壤中,无机型材料HAP对提高蔬菜生物量和降低Cd吸收效果最佳且起效更快,其次则是HAP+BC复配的无机-有机复合型改良剂,但有机型材料BC则效果偏弱且起效慢,需要协同施用HAP提升钝化效率。