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1.
The aim of this study was to determine how the potential to rely on arbuscular mycorrhiza (AM) for plant nutrition differs between a conventional and a low-input cropping system in the long term. The roles of fertilisation rate, composting of recycled plant residues and stage of the rotations in the overall impact of the cropping systems on soil quality and AM were also identified. The conventional cropping system with a non-leguminous crop rotation (barley–barley–rye–oat–potato–oat) was fertilised at either full or half the recommended rate. In the low-input cropping system, one year with barley was replaced by clover, and oat was cultivated mixed with pea. Straw and clover were returned to the soil either with or without composting. In the low-input system, biotite and rock phosphate were used to compensate for K and P in the harvested yield, while animal manure was applied at the start only. After 15 years, crop growth and nutrition, AMF colonisation and soil quality were assessed in the field, while the AM contribution to growth and nutrient uptake were determined in a bioassay in a growth chamber. AM functioning made a higher contribution to soil quality in terms of crop performance and environmental benefits in the low-input cropping system than at either fertilisation rate in the conventional system. Halving fertilisation in the conventional system prevented some costs and enhanced some of the benefits of AM in comparison with full fertilisation. However, only the low-input system with composting conclusively favoured AM in comparison with the conventional system. It resulted in the highest percentage colonisation and, in a bioassay with flax and clover, gave a relative average contribution to growth of 27% and to P uptake of 68% in comparison with 4 and 36%, respectively, for the conventional cropping system with full fertilisation. Rye yield was in the low-input system without composting similar to that in the conventional system with full fertilisation, and with composting 87% of the latter one. Incorporation of clover green manure without composting inhibited AM functioning, leading to a temporary loss of AM contribution to crop performance. This effect draws attention to the impact of the form of recycled organic matter on supporting ecosystem services such as nutrient cycling.  相似文献   

2.
This paper reports on the influence that residue and fertilizer management have on nutrient balances, soil organic matter (SOM) dynamics, and crop yields of a flooded rice system in northeast Thailand (1992–1997) and a wheat–forage legume rotation in eastern Australia (1992–1998). Both soils had been subject to at least 18 years of cultivation and had lost up to 90% of the original labile (CL) and 85% of the total carbon (CT).For the rainfed rice cropping systems of northeast Thailand, a system is described in which small applications of leaf litter from locally grown trees are applied annually to rice paddy soils prior to transplanting. Annual applications of 1500 kg ha−1 of leaf litter from different locally grown shrubs for five seasons resulted in increases in rice grain yield in 1997 of between 20 and 26% above the no-leaf litter control. Nutrient balances, determined by the difference between the inputs (fertilizer and added leaf litters) and outputs (grain and straw), indicated net positive balances of up to 457 kg N ha−1, and 60 kg P ha−1, after five seasons of leaf litter applications. Sulfur and potassium balances resulted in net deficits of up to −13 kg S ha−1 and −52 kg P ha−1, where no leaf litter was applied and rice straw was removed following harvest. Soil carbon (C) concentrations increased significantly only where higher fertilizer rate and rice stubble retention were combined.The poor management of fertilizers and crop residues, and excessive cultivation has also resulted in large soil fertility losses in the grain growing areas of Eastern Australia. After five wheat and two legume/fallow crops, negative N balances of up to −303 kg ha−1 were calculated for the treatments where wheat stubble was not retained and bare fallow leys were used. The balance of nutrients such as K, which are contained in larger proportions in stubble, were found to be up to −362 kg ha−1 on the straw-removed treatments and up to +29 kg ha−1 on the straw-retained treatments. Forage legume leys resulted in short term increases in CL and the carbon management index (CMI).Sustainable farming systems require that crop yields are stable through the maintenance of soil fertility and the balance of nutrients in the system. Increases in soil C levels require sustained periods of balanced fertilization and residue retention.  相似文献   

3.
Increasing land pressure during the past three to four decades has transformed farming systems in the mid-altitude zone of East Africa. Traditional millet-, cotton-, sugarcane- and/or banana-based farming systems with an important fallow and/or grazing component have evolved into continuously cultivated cassava or cassava/maize-based systems. Within three to four decades, cassava cultivation increased from 1–11 to 16–55% of cropped fields in our six study sites. Declining soil fertility, and not labour or food shortage, was apparently the primary trigger for this transformation. The land use changes have increased nutrient offtakes and reduced nutrient recycling rates. Cassava and maize now account for 50–90% of nutrient removal. Whereas single-season fallows were the most important source of nutrient recycling on cropped fields in the past, currently cassava litterfall and maize stover contribute roughly 70% of nutrient recycling, with 50–70% of N, P and K recycled in cassava litterfall. This may explain why many farmers reason that cassava ‘rests’ the soil. With increasing land use pressure farmers progressively use cassava as an ‘imitation fallow’ throughout their farm. Farmers increasingly target cassava to poor fertility fields characterized by low pH and available P. High cassava intensities are nonetheless maintained on more fertile fields, probably to guarantee regeneration of soil fertility on all fields. Once cassava is targeted to poor fertility soils, farmers have run out of low-input management options and need to intensify management to maintain system productivity. As cassava is now used by more farmers and on a larger acreage than fallowing in the studied farming systems, cassava cropping could perhaps serve as an excellent entry point to strengthen system sustainability.  相似文献   

4.
The main objective of this study was to assess the combined use of chlorine dioxide (ClO2) and chlorine (Cl2) on the speciation and kinetics of disinfection by-product (DBP) formation in swimming pools using synthetic pool waters prepared with a body fluid analog (BFA) and/or fresh natural water. At 1:25 (mass ratio) of ClO2 to Cl2, there was no significant reduction in the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) for both BFA solution and natural water compared to the application of Cl2 alone. When the mass ratio of ClO2 to Cl2 increased to 1:1, substantial decreases in both THMs and HAAs were observed in the natural water, while there was almost no change of DBP formations in the BFA solution. Haloacetonitriles and halonitromethanes levels in both water matrices remained similar. In the presence of bromide, the overall DBP formation increased in both BFA solution and natural water. For the DBP formation kinetics, after 72 hr of contact time, very low formation of THMs and HAAs was observed for the use of ClO2 only. Compared to Cl2 control, however, applying the 1:1 mixture of ClO2/Cl2 reduced THMs by > 60% and HAAs by > 50%. Chlorite was maintained below 1.0 mg/L, while the formation of chlorate significantly increased over the reaction time. Finally, in a bench-scale indoor pool experiment, applying ClO2 and Cl2 simultaneously produced less THMs compared to Cl2 control and kept chlorite at < 0.4 mg/L, while HAAs and chlorate accumulated over 4-week operation period.  相似文献   

5.
Soybean (Glycine max (L.) Merr.) is becoming increasingly important in the cereal-based cropping system of the Nigerian Guinea savanna zone and this justifies research on its effects on soil N. Although soybean can obtain 50% or more of its N requirement from the atmosphere, the N contribution of the crop to the system depends on the amount of N contained in roots, haulms, and fallen leaves after grain harvest. At four sites in the northern Guinea savanna, the effects on N balance of P fertilizer and soybean varieties of different duration were tested. The varieties received P fertilizer at the rates of 0, 30, and 60 kg P ha−1. The total N accumulated aboveground at harvest averaged 104 kg N ha−1 in the early and medium varieties, and 135 kg N ha−1 in the late varieties. Across all varieties and sites, total N content was increased by 40–47% when P was applied. Apparent N harvest index averaged 85% but was not significantly affected by variety or P rate. When only grain was exported, the calculated N balance of the early and the medium varieties was −2.6 to −12.2 kg N ha−1 while the longer duration varieties had positive N balances ranging from 2 to 10.9 kg N ha−1. The N accrual was negative when P was not applied and ranged from 2.4 to 5.2 kg N ha−1 with P application. The interaction of variety and site on the N balance was significant at P<0.05. N balance at the southernmost site was −14.2 kg N ha−1 compared with 2.6–10 kg N ha−1 at the northern sites where N2 fixation was higher. The estimate of N balance is reduced when soybean haulms are exported. A positive N contribution by soybean is, therefore, possible in a soybean–cereal rotation when: (i) P is applied, (ii) the soybean variety is late maturing, and (iii) only grain is exported.  相似文献   

6.
不同类型DOM对三峡库区消落带土壤汞甲基化的影响   总被引:1,自引:0,他引:1  
三峡水库特殊的调度方式导致了消落带的形成,在落干期,消落带上会生长大量以狗牙根为主的植物.在淹没期,狗牙根会发生腐解并释放出溶解性有机质(Dissolved Organic Matter,DOM),消落带作为汞的敏感区,狗牙根释放的DOM对汞甲基化的影响值得关注.为此,本文以狗牙根提取液中的DOM(记为DOM_g)为研究对象,同时选取猪粪中的DOM(记为DOM_z)作为比较,利用室内模拟实验,研究这两种不同类型的DOM对土壤汞甲基化影响的差异,并分析两种DOM的光谱特征,探讨其作用机制.结果表明,两种DOM的光谱特征存在明显的差异,DOM_z的有色可溶解性有机物(Chromophpric Dissolved Organic Matter,CDOM)浓度、芳香性及疏水性组分都高于DOM_g.同时,两种DOM均以类蛋白组分为主,但DOM_z的生物可利用性高于DOM_g.并且这两种DOM均能促进土壤的汞甲基化,且在培养后期促进效果更加显著.但两种DOM的促进效果存在差异,DOM_z的促进效果优于DOM_g.  相似文献   

7.
溶解性有机质对芘在土壤中吸附解吸的影响   总被引:3,自引:1,他引:3  
从腐解不同阶段的水稻秸秆提取溶解性有机质(DOM),用DAX-8树脂分组的方法分析了其亲疏水性,并研究了提取到的DOM对芘在土壤中吸附-解吸行为的影响.结果表明,随秸秆腐解时间的延长,产生DOM中亲水性组分减少,疏水性组分增多.在本试验所研究的吸附解吸实验条件下,芘在土壤中的吸附解吸均可用线性方程进行描述.加入DOM后,芘的吸附受到显著抑制(p0.01),并且随腐解时间延长,抑制作用增强;芘在土壤中存在解吸迟滞现象,加入DOM后迟滞现象减弱,促进了芘在土壤中的解吸.随腐解作用的进行,DOM促进芘解吸的作用增强,解吸迟滞系数减小.这是由于随秸秆腐解作用的进行,产生DOM中疏水性组分含量增多,其对芘的增溶作用增强所致.  相似文献   

8.
Atmospheric nitrogen deposition is at a high level in some forests of South China. The effects of addition of exogenous N and P on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0-10 cm) was sampled from monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana...  相似文献   

9.
土壤强还原处理(Reductive Soil Disinfestation,RSD)可以有效地修复设施蔬菜土壤的连作障碍,但实施过程中亦会引起可溶性有机质(Dissolved Organic Matter,DOM)数量和质量的变化.本研究通过培养实验,设置未修复对照(CK)、RSD修复(RSD)、生物炭修复(BC)及R...  相似文献   

10.
土壤溶解性有机质(soil DOM)作为陆地系统天然有机质的重要组成部分,以其活跃的生物地球化学性质,在污染物的环境行为中扮演着极其重要的作用.而了解其来源和结构组成是进一步明确其"结构-反应活性"的关键和前提.本文以三峡库区消落带土壤DOM为研究对象,基于传统氮/碳比值(N/C)及衍生的双端元源负荷模型,讨论该溯源方法在分子水平上的合理性;同时采用光漂白试验,进一步讨论各样本反应活性与其源负荷的相关性.结果表明,N/C值和双端元线性混合模型值均表明土壤DOM具有"陆源"和"内源"的双重特性——这与其他高级分析技术溯源结果基本一致.这种传统溯源分析结果在分子水平上具有合理性,但仅仅反映DOM结构和来源在特定面相上的信息,只能证明库区土壤DOM属于"混合型来源",却无法提供分辨率更高的特定组分来源信息.另外,N/C元素比值及源负荷分别和光漂白动力学过程极显著相关,因此可作为较方便的指标,快速简单判断DOM的光化学反应活性.但在关注DOM本身生物地球化学的研究工作中,仍建议使用多重方法的比较分析,以便于提高单一解析方法的分辨率.  相似文献   

11.
塬地农田作为黄土高原地区发展种植业的最佳区域,近年来由于人类对农业种植类型的不合理选择,使得该区域土壤保肥持水的水平降低,且已对作物生长及农业经济发展产生严重威胁,故本文旨在研究该区域不同种植类型下耕地土壤肥力和经济效益耦合关系,从而选取合适的种植类型。本研究选取晋西南塬地四种典型样地类型(玉米、棉花、马铃薯、荒地)为研究对象,对2019年、2020年全生育期(3—10月)土壤肥力及产值产量进行测定,基于实验数据采用耦合协调度模型综合分析各作物种植下肥力、经济效益状况及耦合协调度。结果表明:(1)不同种植类型下土壤肥力有显著差异,其中马铃薯种植下土壤肥力最高;(2)不同生育期土壤肥力变化有异,除土壤含水量外各肥力指标在快速发育期含量最高而生长中期显著降低,土壤含水量在快速发育期含量最低;(3)各土壤肥力指标含量在20—40 cm土层较高,土壤含水量在0—20 cm土层含量较低;(4)各种植类型下经济效益排序为棉花>马铃薯>玉米>荒地,其中棉花经济效益分别为马铃薯、玉米和荒地的1.17倍、1.36倍和3.40倍;(5)马铃薯种植下耦合协调度最高,棉花和玉米次之,荒地最低...  相似文献   

12.
土壤冻融对溶解性有机质与菲结合的影响   总被引:1,自引:0,他引:1  
薛爽  刘红  程志辉  孙吉俊 《环境科学学报》2018,38(10):4165-4175
以沈阳市公园土壤和道路边土壤中的溶解性有机质(DOM)为研究对象,利用荧光淬灭法测定DOM与菲的结合常数(K),考察了冷冻温度、融化温度、冷冻时间和冻融次数对其光谱学特性及其与菲的结合常数(K)的影响,并结合相关性矩阵分析K与其他参数的关系.结果表明:冻融处理条件下,K值与溶解性有机碳含量(DOC)显著负相关(p0.01),与254 nm处的紫外吸光系数(a_(254))和单位浓度DOC的254 nm的紫外吸光值(SUVA)显著正相关(p0.01).城市公园土壤DOM和城市道路边土壤DOM的K值都是3.5×10~4L·kg~(-1),经过冷冻温度、冷冻时间和冻融次数相同的冻融处理后,城市公园土壤DOM的K值始终高于城市道路边土壤DOM,这是由于冻融导致城市土壤DOM的芳香性高于城市道路边土壤DOM,而分子量小于城市道路边土壤DOM.经过冻融作用二者的K值变化范围分别为1.6×10~5~8.4×10~5L·kg~(-1)和1.5×10~5~3.7×10~5L·kg~(-1),冻融作用使二者的K值都增大一个数量级.这一方面会增强固相土壤中多环芳烃的溶出和迁移,另一方面也会降低多环芳烃的生物可利用性.  相似文献   

13.
了解农田土壤有机质的时空动态变化对促进农田生态系统绿色发展具有重大意义。本研究对陕西省耕地土壤有机质含量进行测定,以期探讨长期耕种下陕西省农田土壤有机质时空变化特征及其影响因素。于2017年采集耕层土样705份,采用重铬酸钾氧化—外加热法测定其有机质含量,并运用ArcGIS 10.5和GS+9.0软件进行了数据分析。结果表明:陕西省耕地土壤有机质平均含量为15.90 g·kg?1,4级水平占比最大;不同行政区有机质含量排序为:汉中>西安>安康>咸阳>宝鸡>商洛>渭南>铜川>延安>榆林;陕西省各市有机质含量较20世纪80年代均有不同程度的提升,其中汉中市提升幅度最大;陕西省农田土壤有机质具有强烈的空间自相关性,最优拟合模型为高斯模型,呈现南高北低的空间分布特征;结构性因素(坡度、海拔、经度、纬度)和随机性因素(施肥、耕作、秸秆还田等)共同作用导致了陕西省农田土壤有机质的空间分布差异,不同类型土壤有机质含量差异显著(P<0.05)。本研究为指导陕西省低碳农业的发展及实现碳达峰与碳中和提供了一定的科学依据。  相似文献   

14.
以SBR系统反硝化除磷污泥为对象,利用氧化还原电位、溶解氧和磷酸盐微电极定量研究了污泥聚集体内除磷菌的原位除磷活性及有机物浓度的影响.结果发现,厌氧初期污泥聚集体内最大净体积释磷速率为3.29 mg·(cm3? h)-1,是缺氧初期最大净体积吸磷速率的3倍左右;厌氧末期释磷速率明显降低,最大净体积释磷速率仅为厌氧初期的...  相似文献   

15.

为探究半干旱区湖泊湖滨带土壤养分与盐碱化特征,以典型盐化湖泊岱海为例,分析其湖滨带的草地、浅滩和盐碱地3种土地类型的土壤剖面4种养分〔有机质(OM)、碱解氮(AN)、有效磷(AP)、速效钾(AK)〕浓度、土壤钙(Ca2+)、镁(Mg2+)、交换性钾(K+)、交换性钠(Na+)、碳酸根(CO3 2−)、重碳酸根(HCO3 )、氯(Cl)和硫酸根(SO4 2−)离子浓度分布,结合主成分分析和冗余分析等统计学方法,研究湖滨带土壤盐碱化特征及其影响因素。结果表明:1)岱海湖滨带不同类型土壤剖面盐分空间分布差异明显,其中草地和浅滩呈明显盐分表聚现象,表层全盐量均值分别达1.99、15.27 g/kg,而盐碱地土壤10~20 cm全盐量最高(17.30 g/kg)。2)湖滨带土壤pH为8.24~8.86,在浅滩和盐碱地深层较高,而在草地的浅层较高。盐碱地与浅滩土壤均属于碱土,而草地表层土壤多属于中度碱化土,其碱化度沿深度方向降低。3种土地类型的主要盐碱化因子为Cl、Mg2+、SO4 2−、Na+、全盐量、HCO3 、pH、CO3 2−。3)3种土地类型的4种养分浓度基本呈随土壤深度增加而减少的趋势,其中浅滩营养元素最丰富。根据冗余分析结果,3种土地类型中大部分离子间都具有很强的相关性,AP、Mg2+与pH均具有负相关性,其他盐分与养分在不同土地类型中相关性差异较大。

  相似文献   

16.
通过选择性去除土壤组分的方法,探讨了三峡库区消落带落干期3种典型土壤中有机质、铁氧化物组分对磷形态和磷吸附-解吸的影响.结果发现,三峡库区消落带落干期3种典型土壤去除的有机质以易氧化组分为主,去除有机质后,土壤中各种磷形态的含量变化较小.然而,去除游离铁氧化物后,土壤中各种磷形态的含量均发生明显降低.同时,去除有机质、游离铁氧化物组分后并未改变土壤中各种磷形态的相对大小顺序,均为:钙结合磷(Ca-P) > 有机磷(OP) > 铁/铝结合磷(Fe/Al-P).此外,黄壤(FJ)、紫色潮土(KX)和灰棕紫泥(FL)去除有机质后对磷的吸附能力较原始土壤仅分别降低0.5%、2.3%、6.5%(P=0.017<0.05,显著性差异),表明3种土壤中有机质组分对磷吸附的影响较小;而去除游离铁氧化物后对磷的吸附能力分别降低45.6%、51.7%、43.9%(P=0.004<0.05,显著性差异),表明土壤中游离铁氧化物组分是决定磷吸附大小的重要因素.另外,3种土壤去除游离铁氧化物后较原始土壤吸附磷的解吸能力明显增加,表明游离铁氧化物组分是控制3种土壤吸附磷的解吸的重要因素.FL土壤去除有机质组分后较原始土壤吸附磷的解吸能力略有降低,而KX和FJ土壤去除有机质组分后较原始土壤吸附磷的解吸能力无明显差异,表明有机质组分对土壤吸附磷的解吸的影响与土壤类型有关.  相似文献   

17.
Soil organic carbon (SOC) and total nitrogen (TN) contents as well as their relationships with site characteristics are of profound importance in assessing current regional, continental and global soil C and N stocks and potentials for C sequestration and N conservation to offset anthropogenic emissions of greenhouse gases. This study investigated contents and distribution of SOC and TN under different land uses, and the quantitative relationships between SOC or TN and site characteristics in the Upstream Watershed of Miyun Reservoir, North China. Overall, both SOC and TN contents in natural secondary forests and grasslands were much higher than in plantations and croplands. Land use alone explained 37.2% and 38.4% of variations in SOC and TN contents, respectively. The optimal models for SOC and TN, achieved by multiple regression analysis combined with principal component analysis (PCA) to remove the multicollinearity among site variables, showed that elevation, slope, soil clay and water contents were the most significant factors controlling SOC and TN contents, jointly explaining 70.3% of SOC and 67.1% of TN contents variability. Only does additional 1.9% and 3% increase in the interpretations of SOC and TN contents variability respectively when land use was added to regressions, probably due to environment factors determine land use. Therefore, environmental variables were more important for SOC and TN variability than land use in the study area, and should be taken into consideration in properly evaluating effects of future land use changes on SOC and TN on a regional scale.  相似文献   

18.
江西省不同农田利用方式对土壤碳、氮和碳氮比的影响   总被引:6,自引:0,他引:6  
基于江西省16582个农田耕层(0~20 cm)土壤样点数据,运用实地调查、数理统计与地统计学等分析方法,探讨了不同农田利用方式(水旱轮作、一季旱地、两季旱地、一季水田和两季水田)对土壤有机碳(SOC)、氮含量(TN)和碳氮比(C∶N)的影响.结果表明,江西省耕层土壤SOC、TN含量和C∶N比分别为5.22~34.56 g·kg~(-1)、0.26~3.06 g·kg~(-1)和2.98~52.67,均处于中等偏上水平.经半方差函数分析,江西省土壤SOC、TN和C∶N比的空间变异主要是由随机性因素引起的;方差分析显示,不同土地利用方式下耕地土壤中SOC、TN和C∶N比存在显著差异,土壤SOC和TN含量表现为两季水田水旱轮作一季水田一季旱地两季旱地,而土壤C∶N比则表现为两季水田两季旱地一季水田水旱轮作一季旱地,土壤C∶N比对估测区域土壤有机碳储量具有良好的指示作用,因此,从土壤C∶N比角度考虑,水田更有利于SOC的贮存,有利于增加土壤汇集碳氮的能力.Pearson相关性分析表明,5种利用方式下经度、纬度和海拔与土壤SOC、TN含量和C∶N比具有显著的相关关系.  相似文献   

19.
Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.  相似文献   

20.
福建是全国第一个开展林权制度改革的省份。本文通过在福建省三明市和永安市实地调研的基础上,探讨福建省森林资源经营的改变对环境的影响。研究发现,林区的绝大部分林农对林权改革持满意的态度,认为林权改革前后对环境的影响有变化。数据分析显示,林改后,对林业的投入对于森林旅游的影响成正比;家庭年均收入对空气质量的影响成负相关。研究建议,继续加大对林业的投入,科学编制森林经营规划和经营方案,促进生态环境改善和林农的增收。  相似文献   

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