减量施氮与秸秆添加对设施菜田N2O的减排效应

采用静态箱–气相色谱法,在宁夏灌区设施菜田研究了不施肥(CK)、单施有机肥(M)、常规施肥(CON)、减量优化化肥(OPT)、优化化肥+调节土壤碳氮比(OPT+C/N) 5种施肥方式对春茬黄瓜和夏休闲期土壤N_2O排放通量、累积排放量和排放系数的影响。结果表明:各施肥处理土壤N_2O排放通量高峰一般出现在黄瓜滴灌施肥或夏休闲期漫灌后第1天或第3天。春茬黄瓜基肥、追肥和夏休闲期,OPT、OPT+C/N处理土壤N_2O排放通量较CON处理分别降低了3.6%～47.2%、5.9%～49.9%和14.7%～46.6%。春茬黄瓜季和夏休闲期各施肥处理的N_2O累积排放量分别为2.05～9.98kg/hm~2和3.55～7.23 kg/hm~2,OPT、OPT+C/N处理较CON处理分别降低了26.2%～34.3%和29.6%～33.7%。春茬黄瓜当季肥料的N_2O排放系数为0.43%～0.71%,而春茬黄瓜–夏休闲期总排放系数为0.54%～1.04%。N_2O总排放量与施氮量呈显著正相关(R~2=0.778);N_2O排放通量与5cm表层地温呈显著或极显著相关(R~2=0.47～0.68),与0～20cm土壤含水量呈极显著相关(R~2=0.63～0.88)。因此,相对于农民常规施氮方式,减施50%化肥氮量或减氮配合添加7.5 t/hm~2的小麦秸秆来调节土壤碳氮比都能达到设施菜田土壤N_2O的减排目标。     

综合产量和土壤N2O排放的马铃薯施氮量分析

施氮可提高作物产量,但同时也增加温室气体N_2O的土壤排放量。研究施氮量与产量和土壤N_2O排放的关系,对保障作物产量并兼顾环境效应的农业生产实践具有重要指导意义。该研究设置N0(0)、N1(67.5 kg/hm~2)、N2(125 kg/hm~2)、N3(187.5 kg/hm~2)4个施氮水平,采用静态箱-气相色谱法对土壤N_2O排放进行田间原位测定,研究施氮量对马铃薯产量、土壤N_2O排放的影响,分析综合产量与土壤N_2O排放的合理施氮量。结果表明:施氮显著增加马铃薯产量和土壤N_2O累积排放量,较不施氮(N0)处理,N1、N2和N3处理马铃薯产量增加78.5%、93.1%和95.6%;生育期N1、N2和N3处理马铃薯土壤N_2O累积排放量分别是N0处理的2.3、4.4和6.7倍。同时,随施氮量增加,N_2O排放系数、硝态氮强度和单产N_2O排放量均显著增加。在低氮处理(N0、N1)时,土壤N_2O排放通量与土壤温度、湿度显著正相关,而在高氮水平时,土壤N_2O排放通量与土壤硝态氮含量显著正相关。施氮67.5 kg/hm~2可确保研究区马铃薯产量并有效降低土壤N_2O排放。     

有机无机氮肥配施对莴苣土壤N2O排放的影响

采用静态箱–气相色谱法研究不同种类有机无机氮肥配合施用对盆栽莴苣土壤N_2O排放规律及排放量的影响。试验设置不施肥(CK)、不施氮肥(PK)、施纯化肥(NPK)、有机无机肥配施1(20%猪粪氮+80%化肥氮,NPKM1)、有机无机肥配施2(20%沼渣沼液氮+80%化肥氮,NPKM2)和有机无机肥配施3(20%猪粪堆肥氮+80%化肥氮,NPKM3)共6个处理。结果表明:莴苣生育期各处理施肥后土壤N_2O排放出现多个峰值,出峰时间和大小不一;累积排放量随着生育期的进程逐渐增加,处理间差异更为明显。莴苣生育期各处理土壤N_2O平均排放通量及累积排放量范围分别为0.10～0.25 mg/(m2·h)和1.37～3.42 kg/hm2,大小均表现为NPKNPKM2PKNPKM1NPKM3CK。土壤N_2O排放系数范围为0.13%～0.68%,大小表现为NPKNPKM2NPKM1NPKM3。与NPK处理相比,NPKM1、NPKM2和NPKM3处理莴苣土壤N_2O累积排放量均分别降低48.08%、25.75%和48.30%,产量分别增加48.66%、22.13%和53.76%。总之,施用纯化肥会促进菜地土壤N_2O的排放,而不同种类有机无机氮肥配施能有效减少N_2O排放且提高作物产量,以猪粪类配施效果最佳。因此,有机无机配施是菜地N_2O减排、降低蔬菜种植中氮素损失的重要途径。     

施氮量对砂姜黑土小麦-玉米轮作体系N_2O排放的影响

砂姜黑土是黄淮海平原重要的中低产土壤,由于其剖面含有砂姜层,易产生裂隙,影响了氮素在土壤剖面的迁移分布,可能导致砂姜黑土的N_2O排放存在一定的独特性。基于此,本研究以砂姜黑土小麦-玉米轮作体系为研究对象,设置4个处理,分别为不施肥(CK)、传统施肥(TR)、优化施肥(OPT)和再优化施肥(ZOPT),通过静态箱-气相色谱法结合常规土壤参数的监测与分析,探究砂姜黑土不同施氮条件下N_2O排放特征、累积排放量及关键驱动因素。结果显示,砂姜黑土小麦季的N_2O平均排放通量为14.2～21.6μg·m~(-2)·h~(-1),累积排放量为0.82～1.24kg(N)·hm~(-2);玉米季的N_2O平均排放通量为14.4～24.5μg·m~(-2)·h~(-1),累积排放量为0.42～0.71 kg(N)·hm~(-2);不同处理小麦季的N_2O累积排放量均高于玉米季。小麦季追肥期与基肥期的N_2O累积排放量分别为0.27～0.41 kg(N)·hm~(-2)和0.55～0.83 kg(N)·hm~(-2),玉米季分别为0.18～0.30 kg(N)·hm~(-2)和0.24～0.41 kg(N)·hm~(-2),追肥期N_2O累积排放量均高于基肥期。相关性分析结果显示, CK处理的N_2O排放量与土壤温度、含水量和硝酸盐含量均表现出明显的多元线性相关(P0.05), TR、OPT和ZOPT仅与土壤硝酸盐含量呈极显著多元线性相关(P0.01),而与土壤温度和土壤含水量未表现明显的相关性,说明施肥条件下,土壤硝酸盐含量的高低成为影响砂姜黑土农田土壤N_2O排放最关键的影响因素。除此之外,不同施氮量的N_2O累积排放量差别明显(P0.05), TR处理的N_2O排放量最高,小麦玉米季分别为1.24 kg(N)·hm~(-2)和0.71 kg(N)·hm~(-2),显著高于OPT处理[0.99 kg(N)·hm~(-2)和0.51 kg(N)·hm~(-2)]和ZOPT处理[0.82kg(N)·hm~(-2)和0.42 kg(N)·hm~(-2)]。无论小麦季还是玉米季N_2O的累积排放量均随施氮量的增加而呈指数增加趋势,相关性系数分别达0.997和0.977 (P0.05),说明砂姜黑土传统施氮N_2O存在过量排放问题。总而言之,尽管与其他土壤相比,砂姜黑土不属于N_2O高排土壤,但传统施氮量导致的N_2O排放量仍不可忽视。     

适宜施氮量降低京郊小麦-玉米农田N2O排放系数增加产量

为明确京郊地区小麦-玉米轮作农田的N_2O排放特征,寻求既能减少N_2O排放又保证粮食产量的切实有效措施,以京郊地区冬小麦-夏玉米轮作农田为研究对象,运用静态箱法对8个施氮水平的农田N_2O交换通量进行了连续一年对比研究,每季作物施肥量分别为N0(0 kg/hm~2),N1(50 kg/hm~2),N2(100 kg/hm~2),N3(150 kg/hm~2),N4(200 kg/hm~2),N5(250 kg/hm~2),N6(300 kg/hm~2),和N7(400 kg/hm~2)。在N0-N7施氮量条件下冬小麦季N_2O排放量为0.08~0.52 kg/hm~2;夏玉米季0.26~3.70 kg/hm~2。整个轮作周期,小麦季各处理N_2O排放损失率为0.05%~0.13%;玉米季0.78%~1.02%。在京郊地区冬小麦-夏玉米轮作体系中夏玉米季氮肥施入农田土壤后,土壤N_2O排放通量高于小麦季。京郊农田土壤N_2O排放通量表现出明显的季节性和日变化规律。综合考虑本试验条件下施肥量、N_2O排放量和京郊地区潮土农田小麦-玉米产量,研究认为该轮作体系中每季作物的施肥量为N4(200 kg/hm~2)比较合理,可为合理施肥及估算中国农田温室气体排放量提供参考。     

不同氮肥管理方式对华北粮田N_2O排放和作物产量的影响分析

通过华北小麦和玉米田已发表文献分析,明确不同施氮量、氮肥基追比及氮素调控措施对土壤N_2O排放和作物产量的影响。结果表明:高氮水平下减少氮肥用量并调整基追比有助于减少土壤N_2O排放;添加硝化抑制剂双氰胺(DCD)对小麦和玉米产量的提高和土壤N_2O的减排效果均较好。兼顾华北粮田N2O减排和作物产量,小麦季推荐合理施氮量167~174 kg·hm~(-2),基追比1∶1,添加DCD,土壤N_2O总排放量为0.31 kg·hm~(-2),籽粒产量6 200 kg·hm~(-2)以上;玉米季推荐合理施氮量177~181 kg·hm~(-2),基追比2∶3~1∶2,添加DCD,土壤N_2O总排放量1.70 kg·hm~(-2),籽粒产量9 000 kg·hm-2以上。     

施肥方式对紫色土农田生态系统N2O和NO排放的影响

依托紫色土施肥方式与养分循环长期试验平台(2002年—),采用静态箱-气相色谱法开展紫色土冬小麦-夏玉米轮作周期(2013年10月至2014年10月)农田生态系统N_2O和NO排放的野外原位观测试验。长期施肥方式包括单施氮肥(N)、传统猪厩肥(OM)、常规氮磷钾肥(NPK)、猪厩肥配施氮磷钾肥(OMNPK)和秸秆还田配施氮磷钾肥(RSDNPK)等5种,氮肥用量相同[小麦季130 kg(N)×hm~(-2),玉米季150 kg(N)×hm~(-2)],不施肥对照(CK)用于计算排放系数,对比不同施肥方式对紫色土典型农田生态系统土壤N_2O和NO排放的影响,以期探寻紫色土农田生态系统N_2O和NO协同减排的施肥方式。结果表明,所有施肥方式下紫色土N_2O和NO排放速率波动幅度大,且均在施肥初期出现峰值;强降雨激发N_2O排放,但对NO排放无明显影响。在整个小麦-玉米轮作周期,N、OM、NPK、OMNPK和RSDNPK处理的N_2O年累积排放量分别为1.40 kg(N)×hm~(-2)、4.60 kg(N)×hm~(-2)、0.95 kg(N)×hm~(-2)、2.16kg(N)×hm~(-2)和1.41 kg(N)×hm~(-2),排放系数分别为0.41%、1.56%、0.25%、0.69%、0.42%;NO累积排放量分别为0.57 kg(N)×hm~(-2)、0.40 kg(N)×hm~(-2)、0.39 kg(N)×hm~(-2)、0.46 kg(N)×hm~(-2)和0.17 kg(N)×hm~(-2),排放系数分别为0.21%、0.15%、0.15%、0.17%、0.07%。施肥方式对紫色土N_2O和NO累积排放量具有显著影响(P0.05),与NPK处理比较,OM和OMNPK处理的N_2O排放分别增加384%和127%,同时NO排放分别增加3%和18%;RSDNPK处理的NO排放减少56%。表明长期施用猪厩肥显著增加N_2O和NO排放,而秸秆还田有效减少NO排放。研究表明,土壤温度和水分条件均显著影响小麦季N_2O和NO排放(P0.01),对玉米季N_2O和NO排放没有显著影响(P0.05),土壤无机氮含量则是在小麦-玉米轮作期N_2O和NO排放的主要限制因子(P0.01)。全量秸秆还田与化肥配合施用是紫色土农田生态系统N_2O和NO协同减排的优化施肥方式。     

不同施氮量对设施甜椒温室气体排放及净温室效应的影响

本研究在华北地区进行温室甜椒(Capsicum)栽培肥料试验,通过测定不同施氮处理土壤N_2O和CH_4排放量、排放特征和土壤呼吸强度,估算化肥投入、灌溉能源消耗、机械燃油、农药施用等生产投入产生的CO_2当量进而计算净温室效应,探讨了氮肥用量对当地温室蔬菜栽培温室气体排放、净温室效应的影响。田间试验设当地农民传统施肥量(C)、不施氮肥(CK)、推荐施氮量(T1)、推荐施氮量+硝化抑制剂(NP)(T1+NP)4个处理,土壤排放的温室气体用静态箱法采集、Agilent 6820型气相色谱仪测定,土壤呼吸用LI-8100土壤碳通量自动监测系统监测。结果表明,与传统施肥量处理相比,推荐施肥量处理,N_2O排放量明显下降;而4个处理的土壤CO_2累积排放量分别为3.36、3.19、3.25、3.07 thm~(-2),处理间无明显差异,CH_4累积排放量表现出随施氮量升高而下降的趋势;4个处理的净温室效应分别为5460.91、3439.28、4873.21、4622.85 kghm~(-2),因此,可以认为N_2O排放和土壤CO_2当量随施氮量的增加而升高,减少氮肥投入使之保持在适当水平,可降低N_2O、CH_4等温室气体的排放;而在等氮肥投入量的条件添加硝化抑制剂也能,减少温室气体排放和减轻净温室效应。     

施肥方式对冬小麦—夏玉米轮作土壤N_2O排放的影响

氧化亚氮(N_2O)是一种重要的农田温室气体,本研究利用紫色土长期施肥试验平台,采用静态箱/气相色谱法对紫色土旱作农田冬小麦—夏玉米轮作系统的N_2O排放进行了定位观测(2012年11月至2013年9月),研究单施氮肥(N)、常规氮磷钾肥(NPK)、猪厩肥(OM)、猪厩肥配施氮磷钾肥(OMNPK)和秸秆还田配施氮磷钾肥(ICRNPK)等施肥方式对紫色土N_2O排放特征的影响;不施肥(NF)作为对照计算排放系数,以探寻紫色土地区可操作性强、环境友好的施肥方式。结果表明,所有施肥方式的N_2O排放均呈现双峰排放,峰值出现在施肥初期;玉米季N_2O排放峰值显著高于小麦季(p0.05)。在相同的施氮水平(小麦季130 kg hm~(~(-2)),玉米季150 kg hm~(~(-2)))下,施肥方式对N_2O排放和作物产量均有显著影响(p0.05)。N、OM、NPK、OMNPK和ICRNPK处理的土壤N_2O周年累积排放量分别为1.93、1.96、1.12、1.50和0.79 kg hm~(~(-2)),排放系数分别为0.62%、0.63%、0.33%、0.47%和0.21%,全年作物产量分别为4.35、11.95、8.39、9.77、10.93 t hm~(~(-2))。施用猪厩肥显著增加N_2O排放量,而秸秆还田在保证作物产量的同时显著降低N_2O排放量,可作为紫色土地区环境友好的施肥方式。土壤无机氮(NO_3~--N和NH_4~+-N)是N_2O排放的主要限制因子。因此,在施氮水平相同时,施肥方式对紫色土活性氮含量的影响导致N_2O排放差异显著,是土壤N_2O排放差异的根本原因。土壤孔隙充水率也是影响N_2O排放的重要环境因子,并且其对N_2O排放的影响存在阈值效应。     

施氮及添加硝化抑制剂对苜蓿草地N2O排放的影响

为探究旱作紫花苜蓿(MedicagosativaL.)栽培草地氧化亚氮(N_2O)排放对施氮水平及添加硝化抑制剂的响应特征,采用传统静态箱法研究了不同施氮水平[0kg(N)·hm~(-2)(N0)、 50kg(N)·hm~(-2)(N50)、 100kg(N)·hm~(-2)(N100)和150kg(N)·hm~(-2)(N150)]以及添加硝化抑制剂双氰胺(DCD)150kg(N)·hm~(-2)(N150+DCD)对陇东苜蓿草地N_2O排放特征的影响。结果显示,监测期内N0、N50、N100和N150处理N_2O平均排放速率分别为3.5μg·m~(-2)·h~(-1)、4.1μg·m~(-2)·h~(-1)、5.0μg·m~(-2)·h~(-1)和6.1μg·m~(-2)·h~(-1),随着施氮梯度的增加, N_2O排放速率呈增加趋势。添加硝化抑制剂DCD对N_2O排放产生明显的抑制作用。与N150处理相比, N150+DCD处理下苜蓿草地N_2O平均排放速率下降50.7%, N_2O累计排放量显著降低61.6%(P0.05)。施氮对苜蓿产量没有显著影响,而N0、N50、N100和N150处理下单位苜蓿产量N_2O排放量随氮肥梯度的增加而增加,各处理分别为6.5 mg·kg~(-1)、7.8 mg·kg~(-1)、11.3 mg·kg~(-1)和12.5 mg·kg~(-1)。N_2O排放受土壤含水量影响深刻,生长季N_2O排放通量与土壤水分呈显著正相关关系(P0.05),而与土壤温度无显著相关性(P0.05)。综上,旱作紫花苜蓿栽培草地N_2O排放通量随施氮水平的增加明显增加,在相同施氮水平下添加硝化抑制剂DCD能显著抑制N_2O排放。相关研究结果对于该区域苜蓿草地合理施肥以及N_2O减排具有一定的实践指导意义。     

Absorption and transport of Na and Cl in rice cultivars differing in their tolerance to salinity: An examination of the effects of ammonium and potassium salts

The absorption and transport of Na and Cl from 0.1 mM and 10 mM ²²Na labelled NaCl or ³⁶Cl labelled KCl were examined in 15 days old seedlings of 3 cultivars of rice differing in their tolerance to salinity. Furthermore, the effects of 10, 100 and 1000 ppm (N)₂S on their uptake were studied. It was found that in general, the salt‐tolerant cultivars BR and PNL‐1 absorbed more Na and translocated a lesser proportion of it to the shoot, compared to the salt‐sensitive IR‐8, from 0.1 mM NaCl. The presence of (N)₂S reduced the uptake of Na in all the cultivars. It was also found that the presence of 100 ppm K, KN or NNreduced Na absorption from 0.1 mM NaCl significantly in all the cultivars, and the translocation to shoot in BR‐ Chloride transport from 0.1 mM NaCl was reduced by (N)₂S in all the cultivars. The 3 cultivars differed significantly in the rates of absorption and transport of Na and Cl. The results indicate that PNL‐1 which is a cross of IR‐8 X BR, has inherited the salt tolerance trait from BR. Lower rates of Na translocation to the shoot can be used as an index of salt tolerance in rice.     

An examination of the total analysis of major elements in soil samples

Recently conventional chemical analyses were mostly replaced by instrumental analysis. Although results from both methods were examined in details after the samples had been solubilized or extracted by appropriate techniques, the solubilization method was considerably altered so as to be convenient for the following analysis. In atomic absorption spectrophotometry (AAS), for example, fusion technique was mostly inadequate because of the higher salts concentration in the obtained solution. The use of H₂SO₄ must also be avoided in acid digestion for SO₄ ^2- precipitates with Sr²⁺ or La³⁺ which must be added to eliminate interferences in the succeeding procedure. Therefore, it is essential to consider the whole scheme including sample treatments to evaluate the suitability of instrumental analysis. In this experiment, the suitability of the methods which have been employed in our laboratory was examined by analyzing 9 rock standards.     

我国酸性硫酸盐土壤中铁锰形态转化及迁移

酸性硫酸盐土壤酸性很强，有机质含量高，造成了这种土壤所特有的铁锰淋洗、转化和迁移规律。研究结果表明：在酸性硫酸盐土壤中全铁含量较低，一般在３５－５０ｇ／ｋｇ（以Ｆｅ２Ｏ３计），全锰含量也低，一般在０．２５－０．５５ｇ／ｋｇ（以ＭｎＯ计），一般滩涂中全铁大于６０ｇ／ｋｇ，全锰大于１ｇ／ｋｇ。酸性硫酸盐土壤中，铁的游离度较小，一般在３７－７０％，铁的活化度较大，一般在８－２０％，而滩涂中铁的游离度一般     

Availability and extractability of soil manganese in a liming experiment

Abstract

The availability of soil Mn to corn in relation to extractability of soil Mn by EDTA, Mg(NO₃)₂, CH₃COONH₄, hydroquinone, H₃PO₄, and NH₄H₂PO₄ as affected by liming was evaluated under field conditions on a single soil type. EDTA, Mg(NO₃)₂ and CH₃COONH₄‐extractable Mn were related inversely to available Mn. No useful relationships were found between hydroquinone, H₃PO₄, and NH₄H₂PO₄‐extractable soil Mn and Mn uptake by sweet corn.     

CO2, CH4 and N2O fluxes of upland black spruce (Picea mariana) forest soils after forest fires of different intensity in interior Alaska

Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO₂ flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO₂ flux was highest at PB (128 ± 85 mg CO₂-C m^?2 h^?1) and lowest at SB1 (47 ± 19 mg CO₂-C m^?2 h^?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO₂ flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO₂ flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH₄ uptake rate was highest at SB1 [–91 ± 21 μg CH₄-C m^?2 h^?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH₄ uptake rate increased with increasing soil temperature because methanotroph activity increased. The N₂O flux was highest [3.6 ± 4.7 μg N₂O-N m^?2 h^?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.     

Denitrification potential in a grassland subsoil: effect of carbon substrates

We examined the potential of a subsoil to denitrify nitrate under optimal anaerobic conditions in a laboratory-based incubation when supplied with a range of C substrates of increasing recalcitrance. Both topsoil and its associated subsoil were supplied with nitrate and either glucose, starch or cellulose. Microbial respiration and the evolution of N₂O and N₂ were measured. The subsoil supported low amounts of microbial activity and responded only to the glucose treatment; with less than one-fifth of the N₂O production measured in the top soil. Overall, our findings demonstrated that the denitrification potential of this particular subsoil is relatively low and that only simple carbohydrates could be utilised readily by the resident microorganisms.     

Acidifying emissions in The Netherlands

The emission of acidifying compounds to air in the Netherlands, expressed as acidifying equivalents, consisted in 1992 mainly of NO_X (45%), NH₃ (35%) and SO₂ (20%). Transportation, agriculture and large combustion plants each contributed about 30% to the national total emission of acidifying compounds. The emissions from transportation activities mainly consisted of NO_X, while in agriculture NH₃ emission strongly dominated. Combustion processes in large combustion plants resulted both in SO₂ emissions (especially from refineries) and NO_X emissions (especially from public power plants). The total emission of acidifying substances decreases steadily in the Netherlands. The emission in 1992 was 24% lower than in 1985. It is expected to decrease further in future. The emission levels in 1992 and 1993 still are more than twice as high as the emission objective for the year 2000, set by Dutch environmental policy.     

碳酸氧镧改性生物炭材料的合成及对磷酸盐去除性能

为高效去除废水中过量的磷酸盐为目的，该研究将研究利用艾草生物质与镧溶液共生共热的方法制成具有大量纳米级碳酸氧镧突起的镧基复合生物炭材料，研究了材料投加量、初始磷酸盐浓度、吸附时间、初始溶液pH值和共存离子对其吸附磷酸盐性能的影响及饱和磷吸附镧基复合生物炭材料（La-CB2-P）对生菜种子发芽率的试验。试验结果表明：La-CB2最佳投加量为1 g/L，最佳吸附温度为25 ℃，对磷酸盐的吸附主要为多分子层吸附，Langmuir模型模拟最大吸附容量为126.82 mg/g，并在12h内达到吸附平衡，酸性至中性水环境中La-CB2吸附性能更优，并对碱性水环境的pH值具有缓冲作用，在pH值为3时La³⁺浸出率为7.66%，其他pH值条件下仅为0.029%左右，在磷吸附过程中La-CB2的DOC溶出量随着初始溶液pH值的升高呈先增后减的趋势，在多种共存阴离子中对磷酸盐具有很强的选择性吸附，水体中的腐殖酸会大幅度降低La-CB2对磷酸盐的吸附性能。饱和磷吸附镧基复合生物炭材料（La-CB2-P）能够作为磷缓释肥显著促进生菜发芽，对La-CB2在富营养水体的磷吸附及资源回收提供了大量的理论基础。     

Effects of NaHCO3 on photosynthetic characteristics,and iron and sodium transfer in pomegranate

In order to study effects of sodium bicarbonate (NaHCO₃) stress in irrigation water on photosynthetic characteristics and iron (Fe) and sodium (Na⁺) translocation content of pomegranate plants, a factorial experiment was conducted based on completely randomized design with three cultivars of pomegranate (“Gorch-e-Dadashi,” “Zagh-e-Yazdi,” and “Ghermez-e-Aliaghai”) and four concentrations of NaHCO₃ (0, 5, 10, and 15 mM), with three replications. The results of plant analysis indicated that NaHCO₃ affected chlorophyll index, F_v/F_m, and performance index (PI) in upper and lower leaves of shoots and also the translocation of Na⁺ and Fe. The results also showed that Fe translocation from root to shoot reduced at 15 mM level of NaHCO₃. The highest Na translocation and the lowest Fe translocation were observed in Zagh-e-Yazdi and Ghermez-e-Aliaghai cultivars, respectively. The ratio of sodium/potassium (Na⁺/K⁺) in stems was higher than that in roots and leaves, and the observed chlorophyll content of upper leaves was also lower than that of lower leaves. Based on the measured parameters Gorch-e-Dadashi cultivar showed less relative sensitivity than other cultivars to NaHCO₃ of irrigation water through maintaining the lower Na⁺ transport to the shoots, and improvement of Fe transport to shoots.     

Factors regulating acetylene reduction assay for measuring heterotrophic nitrogen fixation in water-logged soils

In the C₂H₂-C₂H₄ assay for measurement of heterotrophic N₂ fixation in water-logged soils, the diffusion of C₂H₂ into the soil and the recovery of C₂H₄ from it are critical factors regulating the assay result. To establish an C₂H₂-C₂H₄ assay technique suitable for waterlogged soils, the C₂H₂-reducing activities (ARA), assayed by varying the method of assay gas filling, the pC₂H₂ of the assay gas, the duration of assay incubation and of soil vibration before the gas sampling, were compared.

A maximum ARA was measured when the following set of procedures were applied to the soil sample in assay flasks: 1) a 4-fold repetition of I-min evacuation under 0.01 atmospheric pressure and the subsequent I-min filling under 1 atmospheric pressure with assay gas at pC₂H₂ of 0.1 atm, 2) an assay incubation for 3 hr, and 3) a sampling of an aliquot of the headspace gas after strongly vibrating the flask for 1 min.

The ARA measured by this technique was several times larger than those measured by the techniques hitherto applied, and corresponded to an almost 80% of the V _max of the sample. This technique was, therefore, proposed for the assay of heterotrophic N₂ fixation in waterlogged soils.

A striking depression of ARA in the soil sample prepared with agitation indicated that a microbial ecosystem established in the soil should be kept as undisturbed as possible throughout the C₂H₂-C₂H₄ assay.