Research on the Adsorption States of Ammonium Nitrogen in a Sandy Soil

[Objective] This research aimed to explore the existing forms of ammonium nitrogen adsorbed in a sandy soil with different particle sizes by extraction experiments and provide references for investigating the transport and transformation of the ammonium in the vadose zone.[Method] Sandy soil sample was collected from a landfill and sieved into coarse sand and fine sand.The three kinds of samples were soaked in NH4Cl solution with different initial concentrations,respectively.Then,ammonium adsorbed in soil samples were extracted by three kinds of extraction agents with different extraction capacity,including water,KCl and CaCl2.[Result] The order of extraction capacity of different extraction agents was：water KCl CaCl2;when the concentration of ammonium was low in solution,the ammonium preferentially adsorbed in the exchangeable positions of minerals and mainly existed in the form of exchangeable ammonium;with the increase of concentration,ammonium entered inside the 2：1 clay minerals with enough driving force of the concentration differences and existed in the form of fixed ammonium;little fixed ammonium was observed in coarse sand samples,which was mainly existed in 2：1 clay minerals with strong extraction capacity.[Conclusion] The existing forms of ammonium were closely related to the mineral compositions in soil and the initial concentrations of ammonium.

Identification of Differentially Expressed Genes Induced by Ammonium Nitrogen in Rice Using mRNA Differential Display

RNAs isolated from ammonium- and nitrate-treated rice leaves were used to screen differentially expressed genes through mRNA differential display. A total of 72 bands appeared significant differences and some of them were further confirmed by reverse Northern and Northern blot. The results showed that two genes, A-02 （Oryza sativa drought stress related mRNA） and A-03 （Zea mays partial mRNA for TFIIB-related protein） were highly up-regulated in the ammonium-fed rice leaves. The enzyme assays showed that the activities of the two anti-oxidative enzymes, catalase and peroxidase, and the content of a non-enzymic antioxidant, glutathione, were significantly higher in the ammonium-fed rice leaves than those in the nitrate-fed ones, indicating that the ammonium nutrition might be beneficial for rice plants to improve the stress resistance during growth and development.

Nitrogen Fertilization as Ammonium or Nitrate-N on <i>Hippeastrum hybridum</i>Bulb Growth

Hippeastrum (Hippeastrum hybridum), a native of Central and South America, is a bulbous ornamental flowering plant in the Amaryllidaceae family. However, the correct balance of NH4 to NO3-nitrogen in a fertilizer mix for Hippeastrum plants is largely unknown. Nitrogen was applied 2x weekly following irrigation at either 0.6 g (high), 0.3 g (medium) or 0.15 g (low) total N every four months. Nitrogen was supplied in different combinations of NO3 and/or NH4. Nitrate:NH4-N ratios were either 100% NO3:0% NH4 (100NO3), 70% NO3:30% NH4 (70NO3), 50% NO3:50% NH4 (50NO3) (second group only), 30%NO3:70%NH4 (30NO3), or 0% NO3/100% NH4 (100NH4). Growth in bulb diameter after one year of fertilizer treatments not only increased from 0.15 to 0.6 g N (low to high level), but also differed with the form of N supplied to the plant. The largest diameter bulbs were produced in the 70NO3 and 50NO3 high N treatments. Within any NO3/NH4-N ratio grouping, fertilization at the high N rate resulted in larger diameter bulbs. No significant differences existed between treatments in the number of bulbs produced. Bulb growth was greater with a portion of N supplied as NO3 than with NH4-N alone. These results indicate that application of N as a mixture of NH4 and NO3 at 0.6 g per 4 months produces the largest increase in bulb diameter.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Natural Nitrogen-15 Abundance of Ammonium Nitrogen and Fixed Ammonium in Soils

The present article deals with the natural nitrogen-15 abundance of ammonium nitrogen and fixed ammonium in different soils. Variations in the natural 15N abundance of ammonium nitrogen mineralized in soils under anaerobic incubation condition were related to soil pH. The δ 15N of mineralizable N in acid soils was lower but that in neutral and calcareous soils was higher compared with the δ 15N of total N in the soils. A variation tendency was also found in the δ 15N of amino-acid N in the hydrolysates of soils. The natural 15N abundance of fixed ammonium was higher than that of total N in most surface soils and other soil horizons, indicating that the increase of δ 15N in the soil horizons beneath subsurface horizon of some forest soils and acid paddy soils was related to the higher δ 15N value of fixed ammonium in the soil.

Influencing Factors of Ammonium Nitrogen Removal by Composite Phosphate and Magnesium

It is necessary to adjust reaction pH when a single kind of PO4^3- is used as phosphorus source to remove NH4^＋- N in a chemical precipitation process. However, this tedious step could be avoided in experiments that use the buffering effect of the composite phosphate and employ PO4^3- and HPO4^2- as phosphorus sources, pH was controlled by properly changing the proportion of PO4^3- to HPO4^2-. The influences of pH, material proportion and different addition modes of magnesium on NH4^＋-N removal efficiency were investigated, with NH4^3--N concentration in influent being 200 mg/L. It showed that the ratio of HPO4^2- ： PO4^3- was concerned with phosphorus and NH4^＋-N removal. Under the condition that the total amount of phosphate is definite, the removal efficiency of NH4^＋-N decreased with the enhancement of HPO4^2- concentration, while the efficiency of phosphorus increased. When increasing PO4^3- concentration, it benefited the removal of NH4^＋-N, but the remaining phosphorus was high. The results showed that NH4^＋-N concentration decreased from the initial 200 mg/L to 39.14 mg/L with the remaining PO4^3- at 5.14 mg/L if the ratio of HPO4^2- ： PO4^3- remained at 1：3.

Transformation of ammonium nitrogen and response characteristics of nitrifying functional genes in tannery sludge contaminated soil

High concentrations of ammonium nitrogen released from tannery sludge during storage in open air may cause nitrogen pollution to soil and groundwater.To study the transformation mechanism of NH_(4)^(+)-N by nitrifying functional bacteria in tannery sludge contaminated soils,a series of contaminated soil culture experiments were conducted in this study.The contents of ammonium nitrogen(as NH_(4)^(+)-N),nitrite nitrogen(as NO_(2)^(−)-N)and nitrate nitrogen(as NO_(3)^(−)-N)were analyzed during the culture period under different conditions of pollution load,soil particle and redox environment.Sigmodial equation was used to interpret the change of NO_(3)^(−)-N with time in contaminated soils.The abundance variations of nitrifying functional genes(amoA and nxrA)were also detected using the real-time quantitative fluorescence PCR method.The results show that the nitrification of NH_(4)^(+)-N was aggravated in the contaminated silt soil and fine sand under the condition of lower pollution load,finer particle size and more oxidizing environment.The sigmodial equation well fitted the dynamic accumulation curve of the NO_(3)^(−)-N content in the tannery sludge contaminated soils.The Cr(III)content increased with increasing pollution load,which inhibited the reproduction and activity of nitrifying bacteria in the soils,especially in coarse-grained soil.The accumulation of NO_(2)^(−)-N contents became more obvious with the increase of pollution load in the fine sand,and only 41.5%of the NH_(4)^(+)-N was transformed to NO_(3)^(−)-N.The redox environment was the main factor affecting nitrification process in the soil.Compared to the aerobic soil environment,the transformation of NH_(4)^(+)-N was significantly inhibited under anaerobic incubation condition,and the NO_(3)^(−)-N contents decreased by 37.2%,61.9%and 91.9%under low,medium and high pollution loads,respectively.Nitrification was stronger in the silt soil since its copy number of amoA and nxrA genes was two times larger than that of fine sand.Moreover,the copy numbers of amoA and nxrA genes in the silt soil under the aerobic environment were 2.7 times and 2.2 times larger than those in the anaerobic environment.The abundance changes of the amoA and nxrA functional genes have a positive correlation with the nitrification intensity in the tannery sludge-contaminated soil.

Difference in Nitrogen Starvation-Inducible Expression Patterns among Phylogenetically Diverse Ammonium Transporter Genes in the Red Seaweed <i>Pyropia yezoensis</i>

Nitrogen deficiency induces senescence and the expression of genes encoding ammonium transporters (AMTs) in terrestrial plants where the AMT family is subdivided into AMT1 and AMT2 subfamilies. Nitrogen starvation in the red seaweed Pyropia yezoensis causes senescence-like discoloration. In this study, we identified five genes in P. yezoensis encoding AMT domain-containing proteins, which were phylogenetically categorized into the AMT1 subfamily. We also found a gene encoding a Rhesus protein (Rh) that was related to, but diverged from, AMTs. Moreover, our phylogenetic analysis showed that AMT domain-containing proteins from micro- and macro-algae belonged to either the AMT1 or Rh subfamily, indicating the absence of AMT2 in algae. Gene expression analyses revealed the presence of gametophyte- and sporophyte-specific AMT1 genes that were up-regulated transiently and continually, respectively, under nitrogen-deficient conditions. In addition, up-regulated sporophyte-specific gene expression was suppressed when nitrogen was resupplied. Accordingly, an expansion of the ancient AMT gene has produced AMT1 functional variants differing in temporal and nitrogen starvation-inducible expression patterns during the life cycle of P. yezoensis. These findings help elucidate the unique nutrition starvation responses involving functionally diverse AMT1 and Rh subfamilies in red seaweed.

长期紫云英配施减量化肥对土壤铵态氮吸附解吸特征的影响

为明确长期紫云英配施减量化肥对土壤铵态氮吸附解吸特征的影响,以13年长期定位试验为平台,设不施肥(CK)、单施化肥(CF)、22500 kg/hm^(2)紫云英+80%化肥(G+0.8CF)、22500 kg/hm^(2)紫云英+60%化肥(G+0.6CF)、22500 kg/hm^(2)紫云英+40%化肥(G+0.4CF)共5个处理,研究了不同施肥处理对土壤铵态氮吸附解吸特征的影响,并分析了土壤吸附解吸特征参数与土壤理化性质的关系。结果显示,Langmuir等温吸附方程能较好地拟合土壤铵态氮的吸附特征(R^(2)为0.9969~0.9979,P<0.01)。与CK相比,紫云英配施减量化肥处理土壤铵态氮的最大吸附量、最大缓冲容量分别降低了4.85%~13.46%、4.55%~7.36%;土壤铵态氮的平均解吸量和解吸率为G+0.8CF>G+0.6CF>G+0.4CF>CF>CK。与CK相比,紫云英配施减量化肥处理土壤全氮和速效氮含量分别增加了19.42%~46.60%、15.24%~25.88%。相关性分析结果显示,解吸率与土壤全氮、土壤速效氮呈显著正相关,与土壤pH呈显著负相关;冗余分析结果显示,pH和速效氮是造成土壤铵态氮吸附解吸特征参数差异的主要因素,分别解释了全部变异的56.7%和39.1%(P<0.05)。综上所述,长期紫云英配施减量化肥降低土壤对铵态氮的吸附,增加土壤对铵态氮的解吸,减少了土壤对氮的固持,提高氮的有效性。综合考虑土壤铵态氮的吸附解吸特性及土壤养分含量,以减量20%~40%化肥配施22500kg/hm^(2)紫云英处理效果较好。

浮萍人工培养和调控及其在稻田生态系统中的作用

文章介绍了浮萍的生理生态特点、发生分布规律以及自然状态下的繁殖方式;基于这些特征特性,进一步归纳了关于浮萍实验室内的制备和培养塘等规模化养殖方法的最新研究和探索,系统梳理了影响浮萍生长的环境因素,重点阐述了浮萍在稻田水体中对氨氮转化和利用的作用。在农业生态领域,还需进一步开展关于稻田浮萍时空变化规律及其与水稻间互作关系等方面的研究,在降低因伴生浮萍过快生长造成的水稻产量下降风险的同时,充分发挥浮萍在稻田生态系统中的平衡效应,提升稻田生态系统的多样性和稳定性。

生物炭包膜尿素的制备及其固氮潜力的研究

为了探究生物炭包膜尿素的缓释性能及对土壤固氮的影响,以300、500和700℃下制备的杨木生物炭为包膜材料制备了3种生物炭包膜尿素,采用间歇土柱淋溶试验对氮素的释放特征进行分析。结果表明,杨木生物炭对铵态氮和硝态氮具有较好的吸附性能,低温下制备的生物炭对铵态氮吸附效果更好;与尿素相比,施用生物炭包膜尿素土壤的总氮淋溶量减少了9.73%~14.67%,铵态氮淋溶量减少了25.28%~30.36%,硝态氮淋溶量减少了10.34%~18.38%;在同等施氮水平下,生物炭包膜尿素相较于尿素可以显著增加土壤铵态氮和硝态氮的含量。其中,土壤中铵态氮含量增加了66.4%~200.1%,土壤硝态氮的含量增加了477.9%~537.6%。因此,生物炭用作肥料的包膜材料具有广阔的应用前景。

不同铵态氮肥配施对麦茬水稻生长、氮素利用及产量的影响

碳铵施用可促进稻田秸秆腐解和秧苗生长,但碳铵易分解和不能造粒使其应用受限,研究碳铵替代铵态氮肥将促进该技术的生产应用。基于2年小区定位试验和统计分析,以不施肥(CK)为对照,设置总施氮量20%碳铵+30%复合肥(V1)、20%氯化铵+30%复合肥(V2)、20%磷酸二铵+30%复合肥(V3)、20%硫酸铵+30%复合肥(V4)等5个不同的速效氮肥+复合肥的铵态氮肥筛选试验,研究不同铵态氮肥对麦茬水稻生长、氮素利用及产量的影响。结果表明:处理V2产量达10.34×10^(3)kg/hm^(2),较其他处理均达到显著增产的效果,处理V1、V3、V4间产量差异不显著;处理V2的平均穗粒数、叶面积指数和干物质积累量显著高于其他处理;施肥后12 d,处理V2的铵态氮含量显著性大于其他处理,硝态氮含量显著大于除处理V4外的其他处理,处理V2的pH低于其他处理,达显著水平;处理V2较其他处理显著提升茎蘖数7.48%~20.9%,处理V2与其他速效铵态氮肥处理相比显著地提升了氮素积累量、氮素表观利用率、氮素农学利用率和偏生产力。可见氯化铵配施可降低土壤pH,增加土壤铵态氮和硝态氮的含量,增加水稻平均穗粒数,提高氮素利用效率,具有平衡秸秆腐解和作物产量关系的作用。

生物炭辅配硫酸铵对土壤氮素淋溶的影响

为探究添加生物炭对硫酸铵肥料中氮素释放性能的影响。通过土柱淋溶模拟试验研究不同炭肥比(1∶3、1∶4、1∶5)下制备的生物炭-硫酸铵肥料(BC-AS_(1/3)、BC-AS_(1/4)、BC-AS_(1/5))的氮素淋失特征。结果表明:1)添加生物炭能够有效吸附硫酸铵肥料,减缓硫酸铵的氮素释放速率。3种不同炭肥比下,BC-AS1/4处理的生物炭-硫酸铵颗粒表面最为光滑紧密,成型性最好;2)与常规硫酸铵处理AS相比,不同炭肥处理均显著改善了土壤保水保肥性能,减少了土壤无机氮淋失。其中BC-AS(1/4)处理的铵、硝态氮累积淋出量相较于AS处理分别降低80.83%、11.56%,表现出最小的淋出速率和累积淋失量,缓释效果最好;3)相较于常规硫酸铵处理AS,不同炭肥处理均提高了土柱土壤氮素累积。其中BC-AS1/4处理表现出最好的养分固持效果;4)各土层土壤有机碳含量与土壤全氮呈正相关关系,生物炭-硫酸铵肥料中碳的投入能够有效提高土壤养分的持有能力。综上,生物炭-硫酸铵肥料能够有效减缓氮素释放速率,减少氮素养分淋失,提高土壤养分持有能力,有利于提高肥料利用效率。其中炭肥比为1∶4时生物炭与硫酸铵结合效果最好,表现出最佳的缓释效果及培肥特征。

缓控释肥配施脲铵运筹对水稻产量、氮素利用效率和土壤养分的影响

通过田间试验,以传统配方肥+尿素一基两追施肥模式(CG)为对照,研究了以脲甲醛类缓控释肥(NC)和木质素类缓控释肥(MC)为基肥、脲铵为分蘖或穗分化追肥的缓控释肥+脲铵一基一追施肥模式对水稻产量、氮吸收累积、氮素利用效率以及土壤养分的影响。结果表明:缓控释肥+脲铵一基一蘖施肥模式水稻产量与CG处理相比无明显差异,但脲甲醛类缓控释肥+脲铵(NC-S)和木质素类缓控释肥+脲铵一基一穗(MC-S)处理分别比CG处理明显增产3.96%和6.01%,主要原因为NC-S和MC-S处理每穗粒数分别比CG处理明显增加16.7%和17.6%;与CG处理相比,脲甲醛类缓控释肥+脲铵(NC-F)和木质素类缓控释肥+脲铵一基一蘖(MC-F)处理成熟期地上部氮累积分别比CG处理增加2.50%和5.89%,NC-S和MC-S处理分别比CG处理明显增加10.0%和11.6%;NC-S和MC-S处理氮素利用效率(NUE)分别比CG处理高3.96%和6.01%。缓控释肥+脲铵一基一追施肥模式增加了水稻氮吸收效率(NupE)和表观氮肥回收效率(ANR),其中MC-S处理的NupE明显比CG处理高11.6%,NC-S和MC-S处理的ANR分别比CG处理明显高25.4%和29.3%。缓控释肥+脲铵一基一追施肥模式土壤碱解氮含量明显比CG处理增加6.58%~10.7%,其中,一基一穗施肥模式增加比例更大;另外,土壤有机质含量比CG处理增加1.11%~7.56%。由此可见,缓控释肥+脲铵一基一穗施肥模式更有利于提高水稻产量和氮素利用效率,增加土壤肥力。

华北平原制革废水Cr(Ⅲ)和氨氮在典型包气带中迁移模拟与污染评价

【研究目的】为探明制革废水中的特征污染物铬(Cr(Ⅲ))和氨氮(NH_(4)^(+)–N)在华北平原典型包气带中的迁移规律,评价其可能产生的土壤与地下水污染风险。【研究方法】采用土柱淋滤实验研究Cr(Ⅲ)和NH_(4)^(+)–N在典型粉土中的吸附和迁移转化特征,结合Hydrus–1D建立的包气带水流和溶质运移模型,模拟预测深0.5 m渗坑中NH_(4)^(+)–N连续入渗状态下通过包气带到达地下水面所需时间及不同深度浓度值的变化规律。【研究结果】在3 cm定水头,污染液(Cr(Ⅲ)20 mg/L,NH_(4)^(+)–N 250 mg/L)定浓度持续淋滤120 d的情况下,Cr(Ⅲ)在土柱中垂向迁移距离小于10 cm,且以残渣态(73%)为主,未检出Cr(VI)。NH_(4)^(+)–N则迁移能力较强,淋滤40 d后即穿透50 cm厚粉土柱。在高含盐量(电导率为10.08 ms/cm)条件下,NH_(4)^(+)–N在粉土中的迁移主要受吸附作用控制,土-水分配系数为25.87 L/kg,未发生硝化作用。持续淋滤150 d时NH_(4)^(+)–N迁移至地下水面(18 m埋深)且浓度超过Ⅲ类地下水质量标准(0.5 mg/L,GB/T 14848–2017),在223 d完全穿透包气带,严重污染地下水。【结论】高含盐量制革废水中Cr(Ⅲ)在粉土中迁移能力较弱,且难以被氧化为Cr(Ⅵ),对地下水威胁较小。NH_(4)^(+)–N则随水流快速迁移至地下水面,严重威胁地下水安全。

不同持水量和氮肥形态对丛枝菌根真菌调节柑橘幼苗生长和氮积累的影响

以柑橘幼苗为研究对象,采用分室(分生长室与菌丝室)根箱装置,比较了不同水分处理[60%WFPS(Water-filled pore space);80%WFPS]与两种氮肥形态(NH_(4)^(+);NO_(3)^(-))下,丛枝菌根真菌(CK:无菌丝无根系;AMF:有菌丝无根系;RAMF:有菌丝有根系)对土壤氮含量、植株生物量和氮积累的影响.结果表明:水分水平、氮肥形态和丛枝菌根真菌均显著影响土壤氮含量、柑橘幼苗生物量及植株氮积累量;与60%田间持水量相比,80%田间持水量的土壤硝态氮和总有效氮含量分别降低了26.42%和8.28%,柑橘地上部和总生物量分别显著提高了20.66%和8.93%,柑橘地上部和总氮积累量分别提高了13.57%和6.21%;与添加铵态氮相比,添加硝态氮的柑橘地上部和总氮积累量分别提高了12.59%和5.64%,柑橘地上部和总生物量分别提高了15.68%和9.56%;不同水分和氮形态处理下,AMF均能促进柑橘幼苗生长和植株氮积累;与CK处理相比,AMF处理的地上部和总生物量分别提高了18.57%和15.06%,而RAMF处理分别提高了26.60%和25.48%;AMF处理柑橘地上部和总氮积累量分别较CK处理提高了19.49%和12.88%,RAMF处理分别提高了23.10%和20.10%.因此,不同水分和氮形态下,丛枝菌根真菌与柑橘根系共生均能促进柑橘幼苗生长,提高氮素积累能力.

不同硝态氮、铵态氮素配比对植烟土壤和烤烟生长及产质量的影响

为探究不同硝态氮、铵态氮素配比对贵州安顺地区植烟土壤和烤烟生长及产质量的影响,寻找适宜于当地烟叶优质生产的最佳配比,设置了5个处理(CK;T_(1):100%硝态氮肥;T_(2):70%硝态氮+30%铵态氮;T_(3):50%硝态氮+50%铵态氮;T_(4):30%硝态氮+70%铵态氮;T_(5):100%铵态氮),分析了不同处理下的烤烟生育期、农艺性状、经济性状、病害发生情况以及烤后烟叶化学成分及根际土壤理化性状和酶活性,以期为该地区优化烟草施肥、改善植烟土壤、提高烟叶产质量提供一定的理论依据。结果表明:T_(2)处理大田生育期为112 d,现蕾期较T_(3)处理提前了6 d,T_(2)、T_(4)、T_(5)处理有效叶数显著高于T_(3)处理;T_(2)处理发病率最低,SPAD值显著高于T_(1)、T_(3)、T_(4)和T_(5)处理,发病率与土壤速效钾含量呈极显著负相关;T_(2)和T_(3)处理烤后烟叶的经济性状表现较好,T_(2)处理增加了中上等烟比例;T_(3)、T_(4)处理烤烟的钾含量显著高于T_(1)、T_(2)、T_(5)处理,且符合优质烟标准,T_(2)处理的烟碱含量显著高于T_(1)、T_(4)和T_(5)处理,氯含量显著低于其他处理,化学成分协调性综合评分最高;T_(2)处理显著增加了成熟期根际土壤pH值及酸性磷酸酶、脲酶、蔗糖酶活力。因此,综合考虑烟株的生长情况、发病率、烤后烟叶的化学成分以及植烟土壤肥力状况,在安顺地区硝铵氮素配比为7∶3施用效果更优,更有利于云烟87的生长。

强降水对不同肥期麦田氨挥发损失的影响

在极端降水事件频发的背景下,为明确强降水对麦田不同肥期氨挥发损失的影响,本研究利用田间模拟降水试验,研究了强降水对麦田氨挥发损失和耕层土壤铵态氮含量及硝化潜势的影响,并结合微域试验分析了氨挥发损失与土壤含水量的关系。田间试验设置施氮处理(CF)与不施氮(CK)对照,以CF处理施肥时间为基准,分别在基肥、越冬肥和穗肥施肥后第7天模拟强降水(90 mm),监测农田氮素径流和渗漏损失,并进行连续10 d的氨挥发排放监测。结果表明,施肥显著提高中上层(0~10 cm)土壤的铵态氮含量,增加了降水驱动的生育前期(基肥期,越冬肥期)氮径流和渗漏损失,而穗肥期损失量相当。施肥和降水对基肥期氨挥发排放强度(AVI)无显著影响,但对追肥期(越冬肥期,穗肥期)的AVI影响显著。降水-施肥处理(CF-R)的追肥期AVI(越冬肥期35.02 mg·m^(-2)·d^(-1);穗肥期12.84 mg·m^(-2)·d^(-1))显著高于其他处理(越冬肥期15.46~17.29 mg·m^(-2)·d^(-1);穗肥期7.95~11.23 mg·m^(-2)·d^(-1))。此外,越冬肥期氨挥发损失对平均AVI的差异贡献高于穗肥期和基肥期。相关分析表明,表层(0~5 cm)土壤铵态氮含量与氨挥发损失强度呈显著线性关系(P<0.05)。但值得注意的是,非降水条件下CF和CK处理的追肥期AVI均无显著差异,且培养系统的NH_(3)挥发损失量随土壤持水量的增加而降低。而土壤硝化潜势分析表明,施肥对不同土层土壤的硝化潜势均无显著影响,但降水显著降低了中上层土壤的硝化潜势。研究表明,降水对施肥处理的氨挥发驱动效应是施肥后表层土壤氮素含量升高和降水后硝化潜势降低的叠加作用结果。除驱动麦田氮素径流和渗漏损失,强降水对追肥期氨挥发损失的激发效应应予重视,特别是在越冬肥期。

核桃铵态氮转运蛋白基因JrAMT2的功能分析

【目的】研究高效利用氮素基因铵态氮转运蛋白基因JrAMT2,对核桃Juglansregia的品种改良、快速生长及产量形成有重要意义。【方法】以核桃JrAMT2过表达幼苗为实验材料,对JrAMT2基因进行生物信息学分析。通过基因表达量和表型测定对核桃JrAMT2过表达植株生长发育、氮素吸收、叶绿素质量分数、叶绿素荧光进行理化分析。【结果】JrAMT2基因在核桃JrAMT2过表达植株中稳定表达。与野生型相比,核桃JrAMT2过表达株系的株高、节间长、生物量等生长参数显著提高(P<0.05),核桃幼苗的株高、节间长增加,最高可增加68.2%和50.3%,植株地上部分、地下部分生物量显著增加,地上部分最高可增加56.26%(鲜质量)和56.26%(干质量),地下部分最高可增加344.38%(鲜质量)和354.33%(干质量);核桃JrAMT2过表达株系地下部分对铵态氮及硝态氮的吸收显著提高(P<0.05),最高可提高114.1%和70.3%,其中JrAMT2基因介导了铵态氮从地下部分到地上部分的运输,地上部分铵态氮质量分数显著增加(P<0.05),最高可增加59.1%;核桃JrAMT2过表达植株叶绿体表面积与单层细胞表面积比率、叶绿素质量分数显著增加(P<0.05),最高可增加22.94%和74.3%;对叶绿素荧光参数分析,核桃JrAMT2过表达植株叶片放氧复活体活性、量子产额、电子传递效率均显著提高(P<0.05)。【结论】核桃JrAMT2基因在核桃幼苗生长发育、氮素吸收和光合作用中均有积极显著调控的作用,为进一步研究核桃快速繁育提供一定的理论依据,且为筛选优良品种奠定一定基础。