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1.
Summary The contribution of associative N2 fixation to the N nutrition of lowland rice was estimated in a long-term pot experiment with ten consecutive crops of rice. The experiment comprised two N and two K levels with wet (WF) and dry fallow (DF) between the cropping seasons. Growth of N2-fixing cyanobacteria was prevented. Greatest yields were obtained in the high NK fertilizer treatment, but with continuation of the experiment yields responsed more to DF than to WF. Nitrogenase activity, however, was favoured by WF. Higher K application increased and higher N application decreased nitrogenase activity. Under WF treatments the organic C and total N contents of the soil remained unchanged during the experimental period, but alternate drying and flooding in DF treatments caused a decline. Lower N fertilizer rates in the second five-crop period did not affect yields, but increased the ratio of N removed to N applied. For the ten-crop period the estimated N balance was positive in the low-N and negative in the high-N treatments. N balances were also established separately for both the first and the second halves of the ten-crop period. In the first period N losses were higher, and the N balance was mostly negative. In the second period only high-N combined with low-K fertilization resulted in a negative N balance. DF favoured N losses in the first but not in the second period. The highest N gain in the second period was found in the DF treatment with low-N and high-K application. In this treatment, nearly one-quarter of the N taken up by the above-ground parts of the plants could be ascribed to associative N2 fixation. In the corresponding treatment with the higher N level and a 49% higher yield, the contribution of fixed N declined to less than 5%. When harvested straw contained more than 10 mg N g–1, the N balance was mostly negative, while at N contents less than 10 mg N g–1, the N balance was generally positive.  相似文献   

2.
Summary The influence of soil moisture on denitrification and aerobic respiration was studied in a mull rendzina soil. N2O formation did not occur below –30 kPa matric water potential (m), above 0.28 air-filled porosity (a) and below 0.55 fractional water saturation (v/PV volumetric water content/total pore volume). Half maximum rates of N2O production and O2 consumption were obtained between m = –1.2 and –12 kPa,a = 0.05 and 0.23, and v/PV = 0.63 and 0.92. No oxygen consumption was measured at v/PC 1.17. O2 uptake and denitrification occurred simultaneously arounda = 0.10 (at m = –10 kPa and v/PV = 0.81) at mean rates of 3.5 µl O2 and 0.3 µl N2 h–1g–1 soil. Undisturbed, field-moist soil saturated with nitrate solution showed constant consumption and production rates, respectively, of 0.6 µl O and 0.22 µl N2O h–1g–1 soil, whereas the rates of air-dried remoistened soil were at least 10 times these values. The highest rates obtained in remoistened soil amended with glucose and nitrate were 130 µl O2 and 27 µl N2O h–1g–1 soil.  相似文献   

3.
In a greenhouse study, the effect of moisture regimes (continuously flooded, continuously nonflooded, alternately flooded) on methane efflux from an alluvial soil planted to rice was studied using the closed chamber method. Methane efflux was almost 10 times more pronounced under continuously flooded conditions than under continuously nonflooded conditions. Intermittently flooded regimes (alternately flooded and nonflooded cycles of 40 or 20 days each) emitted distinctly less methane than the continuously flooded system. A significant negative correlation was found between methane emission under different water regimes and rhizosphere redox potential. Extractable Fe2+, readily mineralizable carbon (RMC) and root biomass presented a significant positive correlation with cumulative methane emission. The correlation of methane emission with other plant parameters and microbial biomass was not significant. Our results further suggest the possibility of reduced methane emissions through appropriate water management in a rainfed rice ecosystem. Received: 4 June 1996  相似文献   

4.
Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH4 emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH4 emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH4 emission. A lower CH4 emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH4 emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH4 emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH4 emission significantly. Urea fertilization promoted CH4 emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH4 entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH4 emissions to the atmosphere.  相似文献   

5.
结实期土壤水势对水稻籽粒品质及其粒间差异的影响   总被引:1,自引:1,他引:0  
为探讨结实期土壤水分对水稻籽粒品质的影响, 以中熟籼稻“扬稻6 号”和中熟粳稻“扬粳9538”为材料, 在盆栽条件下, 研究了不同土壤水势(0 kPa、-15 kPa、-30 kPa、-45 kPa)对水稻籽粒品质的影响, 并进一步探讨了不同粒位间的差异。结果表明, 结实期土壤水分对稻米籽粒品质有较大影响, 且影响程度因品种、粒位不同而异。与对照(0 kPa)相比, 土壤轻度胁迫(土壤水势在-15~-30 kPa 之间)籽粒的精米率、整精米率和崩解值增加, 垩白度和消碱值降低; 不同粒位间比较, 土壤轻度胁迫对水稻穗上二次枝梗或同一枝梗上较迟开花籽粒的影响较大。随土壤水势进一步降低稻米品质变劣。在0 ~ -45 kPa 范围内, 随土壤水势的降低,粗蛋白含量和胶稠度增加。灌浆期土壤轻度落干(土壤水势在-15 ~-30 kPa)有利于稻米品质的改善。  相似文献   

6.
ABSTRACT

Irrigated rice cultivation is a major source of greenhouse gas (GHG) emissions from agriculture. Methane (CH4) and nitrous oxide (N2O) are emitted not only throughout the growing season but also in the fallow period between crops. A study was conducted for two transition periods between rice crops (dry to wet season transition and wet to dry season transition) in the Philippines to investigate the effect of water and tillage management on CH4 and N2O emissions as well as on soil nitrate and ammonium. Management treatments between rice crops included (1) continuous flooding (F), (2) soil drying (D), (3) soil drying with aerobic tillage (D + T), and (4) soil drying and wetting (D + W). The static closed chamber method was used to measure CH4 and N2O fluxes.

Soil nitrate accumulated and N2O was emitted in treatments with soil drying. Nitrate disappeared while ammonium gradually increased after the soil was flooded during land preparation, indicating net nitrogen mineralization. N2O emissions were highest in both transition periods in D + W (437 and 645 µg N2O m?2 h?1). Methane emissions were significant in only the F treatment. The highest global warming potential (GWP) in the transition between rice crops occurred in F, with CH4 contributing almost 100% to the GWP. The GWP from other treatments was lower than F, with about 60–99% of the GWP attributed to N2O emissions in treatments with soil drying. The GWP in the transition between rice crops represented up to 26% of the total GWP from harvest to harvest. This study demonstrates that the transition period can be an important source of GHG emissions with relative importance of CH4 and N2O depending on the soil water regime. Therefore, the transition period should not be disregarded when estimating GHG emissions for rice cropping systems.  相似文献   

7.
张广斌  张晓艳  纪洋  马静  李小平  徐华  蔡祖聪 《土壤》2010,42(6):895-900
有机肥施用和土壤水分管理是影响稻田CH4排放最重要的2个因素。本文通过室内培养和田间试验研究了冬季秸秆还田对冬灌田水稻生长期CH4的产生、氧化和排放的影响。结果表明:淹水混施处理CH4产生潜力在水稻移栽后35和51天显著大于淹水不施肥处理(p0.05),其余时间则无显著差异(p0.05);冬季秸秆还田对CH4氧化潜力无显著影响(p0.05),水稻生长期土温和稻田施用氮肥可能是较其更重要的影响因素;淹水混施处理CH4平均排放通量(CH426.7mg/(m2·h))显著大于淹水不施处理(CH420.3mg/(m2·h))(p0.05)。  相似文献   

8.
太湖地区不同水旱轮作方式下稻季甲烷和氧化亚氮排放研究   总被引:15,自引:0,他引:15  
为准确编制我国稻田温室气体排放清单及制定合理减排措施提供基础数据,选择太湖地区典型水稻种植区江苏省苏州市,研究设计了休闲水稻(对照,CK)、紫云英水稻(T1)、黑麦草水稻(T2)、小麦水稻(T3)和油菜水稻(T4)5种水旱轮作方式,采用静态箱气相色谱法,开展了不同水旱轮作方式下水稻生长季田间甲烷(CH4)和氧化亚氮(N2O)排放监测试验。试验结果表明:不同水旱轮作方式下水稻生长季CH4排放通量呈先升高后降低的变化趋势,CH4排放峰值出现在水稻生育前期,移栽至有效分蘖临界叶龄期CH4累积排放量占全生育期排放总量的比例为65%~81%,而N2O仅在水稻烤田期间有明显排放。水旱轮作方式对稻季CH4和N2O排放有极显著(P 0.01)影响,CH4季节总排放量表现为T1(283.2 kg.hm 2)CK(139.5 kg.hm 2)T3(123.4kg.hm 2)T4(114.7 kg.hm 2)T2(100.8 kg.hm 2),N2O季节总排放量顺序为T1 T4 T3 T2 CK,依次为1.06kg.hm 2、0.87 kg.hm 2、0.81 kg.hm 2、0.72 kg.hm 2和0.53 kg.hm 2。T1处理稻季排放CH4和N2O产生的增温潜势最高[7 396 kg(CO2).hm 2],显著(P 0.05)高于其他处理,比CK[3 646 kg(CO2).hm 2]增加103%,T2[2 735kg(CO2).hm 2]较CK减少25%(P 0.05)。紫云英水稻轮作方式增加了太湖地区水稻生长季的温室效应。  相似文献   

9.
In order to ensure sustainable agriculture, and for evaluating the effects of management practices on soil processes, tools for assessing soil quality are required. The development and use of a multiparameter index, which includes a wide range of soil properties, have been tested and found useful by several studies. However, soil quality measurements are ‘stand-alone’ tools unless they are either linked to important soil functions, used to characterize (agro)ecosystems or used to predict sustainability or productivity. In our study, the relationship between crop production and soil quality was assessed in a six year old field experiment studying the effect of farm compost (FC) amendment in a crop rotation of potato, fodder beet, forage maize and Brussels sprouts. To justify the hypothesis that repeated FC amendment results in both improved soil quality and consequently higher crop yields, a wide range of chemical, biological and physical soil properties were measured and integrated into a soil quality index (SQI). Next, crop yields were used as a functional goal to verify the causal relationship between SQI and crop production. Our results showed that there were significant changes in chemical, physical and biological soil quality as a result of repeated FC amendment. This was evidenced for example by a remarkable increase in both soil organic carbon (SOC) and total N content. Microbial biomass, the relative amount of bacterivorous nematodes and earthworm number were significantly increased as well and, together with SOC and total N, indicated as the dominant factors in assessing soil quality. The integration of these key indicators into the SQI revealed higher SQI values when FC was applied. In addition, crop yields were increased in all FC treated plots by which SOC was pointed out as the most important indicator influencing crop production. Finally, a causal relationship was observed between soil quality and the yield of potato and fodder beet. We conclude that our SQI may be a promising and useful tool to compare different (soil) management practices in relation to a strategic, regional goal, e.g., sustainable high yields. Before generalizing, we recommend a thorough validation of our SQI in other long-term field experiments.  相似文献   

10.
利用控制条件下的水培试验方法,研究了两种铵硝配比(NH4+/NO3-为100/0和75/25)营养条件对4种不同硝响应型水稻品种苗期根系生长的影响。结果表明,在增硝营养(NH4+/NO3-为75/25)条件下,不同水稻品种NO3-的反应差异明显。与全NH4+营养条件相比,增硝营养条件下对NO3-强响应的水稻品种南光的根系干重和氮积累量显著增加,增幅达50%和79%;同时南光的根系总根长、总不定根长和总侧根长增幅均达到显著水平;不定根数、新根数和侧根数亦显著增加;平均不定根长和平均侧根长差异不显著;对硝弱响应型的水稻品种上海97、辽粳和Elio在增硝营养培养下的根系不定根、新根和侧根的长度和数量差异均不显著。这表明增NO3-营养仅仅促进了对NO3-强响应型水稻南光根系的不定根和侧根的发生,进而促进根系对氮素的吸收,并没有促进不定根和侧根的伸长。从本试验的结果可推论,水稻根系对硝态氮的响应度强弱可能是水稻品种氮素效率差异性的因子之一。  相似文献   

11.
水稻产量对长期不同施肥和环境的响应   总被引:1,自引:1,他引:1  
以开始于1982年的不同施肥长期定位试验为平台,选择氮磷钾肥(NPK)、有机肥(牛粪,M)、氮磷钾肥+有机肥(NPKM)、氮磷肥+有机肥(NPM)、氮钾肥+有机肥(NKM)和磷钾肥+有机肥(PKM)共6个处理,采用产量年际变化、变异系数(CV)、产量可持续指数(SYI)、肥料增产贡献率及AMMI模型对影响双季稻稻谷总产量稳定性的施肥处理、环境和二者互作进行综合分析,研究历年稻谷产量(1982—2012年)对长期不同施肥和环境的响应特征。结果表明:NPKM处理稻谷产量最高;在养分投入量相同的情况下,单施有机肥和单施化肥对于早稻产量的影响效果一致,但单施有机肥较单施化肥有利于提高晚稻稻谷产量。不同施肥处理稻谷产量CV随试验时间延长逐渐降低,有机无机配施相比较单施化肥能够减小产量CV,各处理晚稻产量的CV大于早稻,但其SYI值小于早稻。NPKM处理的SYI值最高,为0.51;M和NPK处理的SYI值分别为0.44和0.42。肥料对于产量的贡献率表现为:有机肥化肥氮化肥磷化肥钾。AMMI模型交互效应主成分(IPCA)表明,不同施肥处理在不同试验年份对环境的响应不一样。综合以上分析结果,氮磷钾完全肥基础上配施有机肥(NPKM)是该区域双季稻高产和稳产的最佳施肥措施。  相似文献   

12.
Bulk density and soil strength are two major soil physical factors affecting root growth of pea seedlings. This study was conducted to determine the influence of soil texture, organic carbon content and water content on critical bulk density and strength. Soil from the plough layer (PL) and beneath the sub-soil (SUB) was used. By soil packing and adjusting the water content between 30% and 100% of field water capacity (FWC) a wide range of bulk density (1.3–1.7 Mg m−3) and strength (0.24–6.66 MPa) were obtained. Pea (Pisum sativum L.) was grown in the packed cores of 100 cm3 for 72 h at 20°C. Regression models were developed to explain root growth in terms of bulk density, soil strength, silt and clay (<60 μm) content, organic carbon, and water content. The regression curve of root growth as a function of soil strength showed that 40% of maximum root length can be regarded as an indicator of very poor root growth. By substituting this value into the root growth equations we calculated a critical bulk density and strength in terms of fraction<60 μm, organic carbon percentage and water content. The values of critical bulk density in both layers and of critical soil strength in the sub-soil increased with a decreasing content of fraction<60 μm. Irrespective of fraction<60 μm content, the critical bulk density and strength decreased as soil water content decreased. Critical soil strength was more sensitive than critical bulk density to changes in fraction<60 μm content and water content. This study provides data and a method for predicting critical bulk density and soil strength in relation to other soil properties for pea seedling root growth.  相似文献   

13.
选用两个耐铝性差异较大的水稻品种武运粳7号(耐铝品种)和扬稻6号(铝敏感品种)作为实验材料,利用水培铝-磷交替处理试验研究了磷对水稻铝胁迫下苗期生长的影响及水稻耐铝性与磷效率之间的关系。结果表明,从水稻铝-磷交替处理下的生物量和根系形态等指标来看,P缓解了Al对两个水稻品种的毒害作用,且对敏感品种扬稻6号的缓解作用更加明显。铝-磷交替处理下,武运粳7号的体内磷含量显著高于扬稻6号的,而根部铝含量显著低于扬稻6号,因此武运粳7号体内的P/Al显著高于扬稻6号;同时,虽然两个品种间根表及根自由空间中Al浓度没有差别,而武运粳7号根表及根自由空间中P浓度显著高于扬稻6号,表现出耐铝品种更强的质外体解铝毒能力,这可能与武运粳7号较强的磷吸收效率有关。此外,与耐铝品种武运粳7号相比,铝敏感品种扬稻6号虽然磷吸收效率低,但利用效率高,即两个水稻品种的耐铝性与水稻的磷吸收效率和利用效率不一致,这为酸性土壤水稻育种提供了理论基础,即选育适应酸性土壤的水稻基因型不仅要关注其耐铝性还要关注其磷利用效率。  相似文献   

14.
Abstract

Response of jojoba [simmondsia chinensis (Link) Schneider] cuttings to fertilization during mist propagation was studied during two spring seasons and a summer season, using a soluble fertilizer (Peter's 20–8.6–16.5) and 3 controllled release fertilizers: Osmocote 19–2.6–10, Isobutylidene dlurea 20–2.1–4 and sulfur coated urea, 36–0–0.

Initial leaf concentrations of N, P and K were lower in spring than in summer and greater at lining‐out for fertilized cuttings. Leaf N and K content were positively correlated to root and shoot growth in spring and to shoot growth in summer. Leaf Zn and Mn were positively related to shoot and root growth in spring.  相似文献   

15.
萌芽开花期梨枣对土壤水势的响应   总被引:2,自引:0,他引:2  
本试验选取4年生梨枣(Ziziphus jujuba Mill.)为试验材料,设置-31~-51 kPa、-41~-84 kPa、-59~-132kPa和-161 kPa(不灌溉)4个土壤水势水平,结合茎直径微变化、营养生长与生殖生长量,分析了梨枣在萌芽开花期对土壤水势的响应。结果表明:1)在梨枣萌芽期,土壤水势在-41~-84 kPa范围波动时,茎直径日最大收缩量最小,营养生长与生殖生长最旺盛,是该时期适宜的土壤水势范围;花芽分化适宜的土壤水势范围为-41~-132 kPa。梨枣萌芽期适当的水分亏缺不影响花芽分化,但减弱了营养生长量,优化了营养生长与生殖生长的比例。2)在梨枣开花期,土壤水势范围为-54~-78 kPa时,茎直径日最大收缩量最小,坐果率较高,为开花期适宜的土壤水势范围;土壤水势为-79~-114 kPa时坐果率最高。开花期轻度的水分亏缺可显著提高坐果率。3)土壤水势过高或过低都抑制梨枣的营养生长、生殖生长和坐果,但水涝能促进茎直径生长,水分缺亏则抑制茎直径生长。4)在平水年,梨枣的萌芽期无需灌水,自然降雨即能满足其萌芽展叶、花芽分化的需要,但开花期,降雨不能满足梨枣高坐果率的需要。  相似文献   

16.
不同时期施用生物炭对稻田N_2O和CH_4排放的影响   总被引:7,自引:0,他引:7  
通过分别在水稻季(R)和小麦季(W)设置对照(RB0-N0、WB0-N0)、单施氮肥(RB0-N1、WB0-N1)、20 t hm-2生物炭与氮配施(RB1-N1、WB1-N1)、40 t hm-2生物炭与氮配施(RB2-N1、WB2-N1)等8个处理,研究稻麦轮作周年系统N2O和CH4排放规律及其引起的综合温室效应(Global warming potential,GWP)和温室气体强度(Greenhouse gas intensity,GHGI)特征。结果表明:稻季配施20 t hm-2生物炭对N2O和CH4的排放、作物产量及GWP和GHGI均都无明显影响;稻季配施40 t hm-2生物炭能显著降低8.6%的CH4的排放和9.3%的GWP,显著增加作物产量17.2%。麦季配施20 t hm-2生物炭虽然对温室气体及GWP影响不明显,但显著增加21.6%的作物产量,从而显著降低21.7%的GHGI;麦季配施40 t hm-2生物炭能显著降低20.9%和11.3%的N2O和CH4排放,显著降低15.7%和23.5%的GWP和GHGI。因此麦季配施生物炭对减少N2O和CH4的排放、增加稻麦轮作产量及降低GWP和GHGI的效果较稻季配施生物炭效果更好。  相似文献   

17.
Coffee (Coffea arabica L.) is the major crop grown in highland and mountainous areas of Colombia, where the most common yield‐limiting factors are nitrogen (N) and soil water content. Since the eventual success of a plantation is determined by the performance of coffee plants during critical early stages, our goal was to better understand plant response to these limiting factors. Four different levels of N and soil water content were evaluated under greenhouse conditions for their effect on growth, water use efficiency, fertilizer‐N recovery efficiency (FNRE), and stem lignin and cellulose of coffee seedlings. The interaction between N and moisture did not produce a significant response in coffee growth. However, by increasing N, both water use efficiency and 13C content were enhanced, while growth, recovery of urea by plants, and stem strength were decreased. Water stress due to low soil water content increased water use efficiency, 13C content, and root to shoot ratio, but decreased shoot growth. These results demonstrate the effects of N supply and water balance and highlight the excessive amount of N typically applied to coffee seedlings as well as the importance of the acclimation process of young plants to changes in soil N and water. All of these are important considerations in improving management strategies to reduce environmental impact while sustaining optimal productivity.  相似文献   

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The surface chemical properties of soil samples i.e., surface charge and zeta potential, and the mineralogy of soil clay fraction were investigated with reference to soil weathering extent for four different soils derived from Quaternary red earth using the ion adsorption method, a micro-electrophoresis method and the X-ray diffraction analysis. Results indicated that all these soil samples contained kaolinite and gibbsite. The Ultisols from Guizhou, Hunan and Jiangxi possessed the 2:1 type clay minerals of mica and vermiculite. Hematite and magnetite were found in the Ultisols from Guangxi, Hunan and Jiangxi. Goethite was found in the Ultisols from Jiangxi, Hunan and Guizhou. The positive surface charge for these soils decreased with the order: the Ultisol from Guangxi ≅ the Ultisol from Guizhou > the Ultisols from Hunan and Jiangxi from south to north when pH < 5.0. This is consistent with the content of free Fe/Al oxides present in these soils. On the other hand, the value of negative surface charge on the Ultisol from Guangxi was found much lower than the other soils perhaps because of the intensive weathering of the soil. Both permanent and variable negative charges for the former were also lower than the latter, whereas the point of zero salt effect (PZSE) for the former was greater than that of the latter. The variability of soil negative surface charge followed the order: the Ultisol from Guangxi > the Ultisol from Guizhou > the Ultisol from Jiangxi ≅ the Ultisol from Hunan. The zeta potential and isoelectric point (IEP) of soil colloids and soil net surface charge followed the same order: the Ultisol from Guangxi > the Ultisol from Guizhou > the Ultisols from Hunan and Jiangxi. A good correlation between zeta potential and net surface charge of these soils was observed. Therefore, the magnitudes of the PZSE, IEP and zeta potential of these soils were in agreement with the weathering extent of the soils and can be employed as reference criteria for classification and evolution of soils.  相似文献   

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在泥鳅养殖水体中添加稻秆粉模拟水稻残遗物生境,研究了泥鳅生长和肝胰脏抗氧化酶(SOD、CAT)与解毒酶(GST)活性对转Cry1Ab/Ac基因水稻‘华恢1号’(HH1)的响应。设计以HH1稻秆粉10 mg·L?1、50 mg·L?1、100 mg·L?1和200 mg·L?1 4个梯度浓度处理泥鳅为试验组,以非转Bt基因水稻‘明恢63’(MH63)稻秆粉处理组为阴性对照,不加稻秆粉的基础饲养组为空白对照。结果显示:在4种稻秆粉浓度下,HH1组与MH63对照组泥鳅的特定生长率、肥满度、内脏系数及SOD、CAT和GST酶活性均无显著差异(P0.05);与空白对照比较,稻秆粉浓度升高对泥鳅生长的抑制逐渐增强,当浓度达到200 mg·L?1时,HH1组和MH63对照组泥鳅的特定生长率、内脏系数与CAT活性降低。研究结果表明,水体中低含量的转融合基因Cry1Ab/Ac水稻HH1稻秆粉对泥鳅的生长与生理酶活性没有明显影响,高浓度HH1和MH63稻秆粉均使泥鳅的生长和生理酶活性显著降低,这可能与养殖水体中浓度较高的悬浮稻秆粉妨碍了泥鳅的呼吸和滤食,及稻秆粉的分解降低了水体p H和溶氧量有关。  相似文献   

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