土壤固定态铵的影响因素

本文研究了有机质、全氮、有机氮、粘粒、CEC、溶液中铵浓度、水分、温度等影响土壤固定态铵含量的因素。结果表明,固定态铵与<0.01lmm的粘粒呈显著正相关,但与<0.00lmm的粘粒、有机质、全氮、有机氮、CEC相关性很差。通过拟合Langmuir方程可知河沙泥的最大固铵量为357.2mgN/kg,这与359mgN/kg相近。无论是潮沙泥还是紫泥田,固定态铵含量均有:30oC>20oC,30oC>40oC。除了黄泥田外,紫泥田,河沙泥和潮沙泥三种土壤的固定态铵含量均有:长期淹水>干湿交替8次>长期干燥。     

土壤中固定态铵含量与固铵强度

对全省１３个有代表性的耕层土壤中固定态铵含量和固铵强度进行了研究。并对影响土壤固铵强度的内外因子进行了分析探讨，为氮肥合理施用氮钾肥的配合施用提供了一定的理论依据。     

外源氮添加对不同种植年限设施菜田土壤固定态铵含量的影响

研究外源氮(N)添加对不同种植年限设施菜田土壤固定态铵含量及最大固铵量的影响。选取4个不同种植年限（0年、2年、13年和21年）的设施菜田土壤,分别设置4个外源氮添加处理,进行为期36天的室内培养,测定不同种植年限和外源氮添加处理下的土壤固定态铵含量,并计算其最大固铵量。4个外源氮添加处理分别是:（1）CK,不添加任何氮肥,为对照;（2）CF,常规施氮,添加尿素态N 374 mg kg?1干土;（3）RCF,减量施氮（减N 46%,添加尿素态N 200 mg kg?1干土）;（4）RCF + OM,减量施氮配施有机氮（添加尿素态N 150 mg kg?1干土并以鸡粪形式添加有机态氮50 mg kg?1干土）。结果显示:随设施蔬菜种植年限的增加,土壤本底固定态铵含量呈逐渐增加的趋势,而最大固铵量却呈下降的趋势。同一种植年限下,各施肥处理在培养过程中的土壤固定态铵含量总体表现为CK < RCF + OM < RCF < CF,说明施肥可增加土壤固定态铵含量,但其增幅大小受施肥量的多少和施肥种类影响,其中CF处理土壤固铵量为最大（98.61 mg kg?1）,显著高于RCF和RCF + OM处理,而RCF处理的土壤固铵量（84.76 mg kg?1）又高于RCF + OM处理（77.34 mg kg?1）。设施菜田增施氮肥可提高土壤固定态铵的含量,且化肥较有机肥的效果更优。     

不同粒级土粒固定态铵的初步研究

通过对土 同粒级土粒固定态铵含量及其固铵，释铵数量的测定，得到如下结果：粘土矿物种类对土固定态铵的影响比粘粒含量更为重要；土壤中，粘粒所含固定态铵数量最大，粉粒也含有相当数量的固定态铵；粘粒，粉粒和砂粒都具有释放其固定态铵的能力。     

土壤颗粒组成与固定态铵之间的关系

大量研究表明,固定态铵的含量与土壤质地有关.李生秀等人的研究表明[1],西北地区土壤的固定态铵含量与粘粒含量呈显著正相关,与砂粒含量呈显著负相关;Feigin和Yaalon的测定证明,以色列129种钙质土固定态铵含量与粘粒(＜0.002 mm)含量显著正相关(r=0.63,p＜0.01)[2];施书莲等人[3]报道,棕壤、栗钙土、黑土、棕钙土和红壤带土壤中的固定态铵含量与粘粒、粘粒及细粉砂含量之和的相关均达到0.01显著水准.这些结果说明,固定态铵主要存在于粘粒和粉粒中,而砂粒中几乎没有[4].     

氮肥与有机肥配施协调土壤固定态铵与可溶性氮的研究

【目的】 土壤固定态铵是肥料氮的一个“临时贮藏库”,可逐渐释放以供作物利用,土壤可溶氮则是土壤固定态铵的重要来源,因此研究设施条件下氮肥与有机肥配施对土壤固定态铵和可溶性氮含量的动态变化以及相互关系的影响,对于设施生产中安全高效的施肥管理有着重要意义。 【方法】 以番茄为试材,温室内连续两年进行田间小区试验,设不施肥(CK)、施N量0、187.5、375. 562.5 kg/hm2 (N0、N1、N2、N3)、单施有机肥(M,75000 kg/hm2)以及有机肥与氮肥配施处理(MN0、MN1、MN2、MN3)。分析了土壤固定态铵和可溶性氮(土壤矿质氮和可溶性有机氮)含量动态变化。 【结果】 施肥显著提高了0-30 cm土层土壤固定态铵和可溶性氮的含量(P < 0.01);各施肥处理均以第1穗果膨大期时含量最高。总体来看,不施有机肥条件下,土壤固定态铵和矿质氮、可溶性有机氮的含量均以施N 375.0 kg/hm2处理为最高,而在氮肥与有机肥配施条件下,以施N 375.0 kg/hm2与有机肥75000 kg/hm2配施处理和施N 562.5 kg/hm2与有机肥75000 kg/hm2配施处理的土壤固定态铵和矿质氮、可溶性有机氮含量为最高,但未发现氮肥施用量对土壤固定态铵含量产生显著影响;除收获期20-30 cm土层外,整个生长季内土壤固定态铵和矿质氮含量之间均有显著的正相关关系(P < 0.05),部分土层土壤固定态铵与可溶性有机氮之间也有显著的正相关关系(P < 0.05)。 【结论】 设施番茄栽培条件下,土壤固定态铵和可溶性氮在土壤氮素的固持与释放方面极显著相关,施无机N 375.0 kg/hm2配合有机肥75000 kg/hm2,可较好地提高土壤中的氮的有效性,更好地协调土壤供氮能力。     

黄土高原典型土壤矿物固定态铵变化的南北差异

采集从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨陵)等典型土壤剖面0200.cm土层土样,通过测定土样全氮和矿物固定态铵,以阐明黄土高原典型区域土壤全氮和矿物固定态铵及二者比率随地理位置和土层的变异规律,为全面了解黄土高原土壤相对稳定氮库累积提供科学数据。结果表明,不同地理位置、不同土层全氮和矿物固定态铵含量存在显著差异。从南到北全氮和矿物固定态铵呈下降趋势,但各土壤全氮和矿物固定态铵的分布显著不同,全氮含量在060.cm随土层深度增加下降很明显,60120.cm有一定下降,120.cm以下低而稳定。矿物固定态铵在全剖面上的分布比较均匀,随土层深度的变化差异不显著,不同土层间的差异基本在误差范围内,土垫旱耕人为土、黄土正常新成土和干润砂质新成土表层(010.cm)矿物固定态铵平均含量分别为215.807.45、165.808.73和146.501.83.mg/kg,表层以下(10200.cm)平均含量分别为193.409.67、157.145.75和142.025.47.mg/kg。从地理位置分析,干润砂质新成土、黄土正常新成土和土垫旱耕人为土表层(010.cm)矿物固定态铵占全氮的百分比分别为(39.570.78)%、(32.916.82)%和(29.747.01)%;在表层以下所占比例更高,干润砂质新成土10200.cm土壤矿物固定态铵含量占全氮比例为(89.5213.42)%,黄土正常新成土为(59.5213.86)%,土垫旱耕人为土为(47.269.01)%。供试土壤中矿物固定态铵与0.01.mm物理性粘粒含量存在极显著正相关关系,说明物理性粘粒是矿物固定态铵的主要载体;矿物固定态铵与全氮含量也有极显著正向相关性。以上结果揭示,在黄土高原黄土母质上形成的土壤,全剖面矿物固定态铵相对均匀,而有机氮相差较大,两种氮库的这种地理位置和剖面分布特征,是黄土母质形成的必然结果,也进一步支持了黄土高原黄土母质的风成学说;同时也反映了需要对有机氮占全氮比例及矿物固定态铵在全氮中地位的传统观念予以重新评价。     

土壤残渣有机质与固定态铵之间的关系

采集了全国不同类型的土壤40个,分析了土壤全氮、有机质、固定态铵、剩余有机质（KOBr处理后的土壤有机质）、残渣有机质（KOBr-HF处理后的土壤有机质）含量.结果表明,以2∶1型粘粒矿物为主土壤的残渣有机质含量与固定态铵含量之间呈极显著正相关（r=0.831^＊＊）,晶格之间存在的有机质（即残渣有机质与剩余有机质之差值）含量则与固定态铵含量之间也呈极显著正相关（r=0.832^＊＊）,而以1∶1型粘粒矿物为主土壤的残渣有机质含量和晶格有机质含量与固定态铵含量不相关;土壤剩余有机质、残渣有机质的含量分别为2.59 g kg^-1、3.70 g kg^-1,分别占土壤有机质的10%和16%.土壤残渣C/N比（平均值为16.69）明显高于原土壤（平均值为5.37）.     

长期施肥对土壤固定态铵含量及其有效性影响

棕壤连续13年定位试验表明,长期施用化肥或低量有机肥对土壤固定态接含量均无显著影响;而施用高量有机肥区固定态接含量比试验前平均增加30.2％。这部分增加的固定态按主要来自土壤有机氮矿化补充。施肥后固定态铵的净增加量超过作物施氮量是土壤激发效应的结果。土壤原有固定态铵含量在113～116mg／kg,对作物无效,而新固定态按时作物有效。生长季耕层土壤固定态铵总释放量（N）对照区为43kg／hm2,化肥区平均为110kg／hm2;有机肥与化肥配合区平均为165kg／hm2。施钾对固定态铵的释放有一定抑制作用。     

氮肥施用对土壤固定态铵有效性和剖面变化特征的影响

农田生态系统中肥料氮素施用通过改变土壤中"原有的"固定态铵和肥料来源"新"固定态铵的动态,从而影响固定态铵的有效性以及其剖面变化特征。固定态铵相对含量在垂直剖面的大小顺序为10~20 cm0~10 cm40~60 cm20~40 cm,在多年淋溶渗透作用下,土壤中黏粒和氮素养分不断向下迁移,从而随着深度增加固定态铵含量升高。在连年施肥的条件下,土壤中固定态铵的含量和碱解氮之间呈极显著正相关关系(r=0.756,p0.01),而且肥料来源部分的相关性显著高于土壤中"原有的"固定态铵。固定态铵含量与植株中氮含量呈显著负相关(r=-0.525,p0.05),同时肥料氮素在固定态铵中的残留与植株中15N含量呈显著负相关(r=-0.526,p0.05),表明固定态铵可以通过长期的固定-释放过程持续为植物供给有效氮源。肥料来源固定态铵的有效性高于土壤中原有部分。连年施肥条件下,固定态铵对作物氮素利用的调节作用十分显著。     

保氮复合碳铵的肥效及增产机理研究

本研究研制出一种保氮复合碳铵 ,它与碳铵相比能提高氮肥利用率 5 2 %～ 1 5 % ;减少氨挥发损失 5 %～ 1 2 % ,使水稻增产 5 %～ 1 0 % ,棉花增产 6%～ 2 0 %。而且具有不结块、氨臭味减少、生产成本降低、施用方便、实用性广等特点。经 1 3.3hm2 大田示范 ,均获良好增产效果。     

CHANGES IN FOLIAR AMMONIUM CONCENTRATIONS IN SUBSTRATE-GROWN STRAWBERRY

Strawberries (Fragaria × ananassa Duch. cv. Nyoho) grown in peat-based substrate often suffer interveinal chlorosis in their immature leaves 10–20 d after planting. Based on our previous results and observations from growing practice, we hypothesized that the cause of this phenomenon could be due to drastic changes in plant nitrogen (N) nutrition in strawberries just after planting into peat bags. To determine optimal sampling time, diurnal variations in foliar ammonium (NH₄)-N concentration were evaluated under greenhouse conditions. Results showed a broadly similar pattern of diurnal variation, with the rates increasing to a maximum at midday and decreasing steadily during the second-half of the light period. However, foliar NH₄-N concentration was higher under sunny than under cloudy or shaded light conditions. In the second part of this study, changes in foliar NH₄-N and in nitrate (NO₃)-N in petioles in relation to the occurrence of interveinal chlorosis were investigated. When the plants were supplied with 30 (control) or 50% ‘Ohtsuka A’ nutrient solution for two weeks after planting, foliar NH₄-N concentrations increased earlier than petiole NO₃-N concentrations, and reached their peak 8 and 10 days after planting in 50% (1.90 μmol g^?1 FW) and 30% (1.78 μmol g^?1 FW) treatment respectively. Interveinal chlorosis was observed in immature leaves in 50% treatment about 10 days after planting while there was no chlorotic symptom in control treatment. The absence of interveinal chlorosis in immature leaves in control plants, led to the conclusion that a high leaf NH₄-N concentration and related accumulation of NH₄-N play an important role in triggering interveinal chlorosis.     

DOUGLAS-FIR SEEDLING RESPONSE TO A RANGE OF AMMONIUM: NITRATE RATIOS IN AEROPONIC CULTURE

The objective of the experiment was to identify the most favorable nitrogen (N) source ratio of ammonium (NH₄ ⁺) and nitrate (NO₃ ^?) for aeroponically-grown Douglas-fir when pH was maintained at pH 4.0. Seedlings were grown in controlled environments with solutions containing 0:100, 20:80, 40:60, 60:40, 80:20 or 100:0 NH₄ ⁺:NO₃ ^? ratios. Nutrient additions in the aeroponic culture units were controlled by solution conductivity set points. Seedling growth and nutrient allocation was observed for 45 days. Different NH₄ ⁺:NO₃ ^? ratios resulted in significant differences in the rate of N addition, growth, morphology, and nutrient allocation. Seedlings grown in solutions containing 60 or 80% NO₃ ^? were characterized by a combination of high growth and photosynthetic rates, high and stable internal plant N concentrations, and sufficient levels of other essential nutrients. High proportions of NH₄ ⁺ in solution resulted in low rates of N addition, stunted lateral root growth, and may have been toxic.     

INFLUENCE OF ARBUSCULAR MYCORRHIZAL FUNGI AND AMMONIUM:NITRATE RATIOS ON GROWTH AND PUNGENCY OF SPRING ONION PLANTS

A pot experiment was carried out to study the growth and pungency of Allium fisutulosum grown in Perlite as affected by colonization by the arbuscular mycorrhizal (AM) fungi Glomus etunicatum, Glomus vesiforme, and by ammonium (NH⁺ ₄ ):nitrate (NO^? ₃ ) ratios of 5:95, 50:50, and 95:5 in 4 mM solutions. Plants were grown in a greenhouse for 20 weeks and then harvested. In general, NH⁺ ₄ :NO^? ₃ ratio of 50:50 supplied resulted in the highest shoot dry weight regardless of non-mycorrhizal and mycorrhizal plants while the effect of inoculation treatment on plant biomass was not significant. The plant sulfur (S) concentrations were usually higher in mycorrhizal plants than controls irrespective of nitrogen ratio and therefore inoculation with G. etunicatum increased the enzyme produced pyruvic acid (EPY) while inoculation with G. versiforme decreased the EPY compared with the non-mycorrhizal plants. In general, shoot pungency was lowest when NH⁺ ₄ :NO^? ₃ ratio of 95:5 supplied irrespective of mycorrhizal treatment. Colonization by both AM fungi made a substantial contribution to spring onion sulfur nutrient status but show different way on flavor characteristics of host plants.     

湖南几种耕地土壤固定添加铵的动力学研究

通过野外调查取样、室内培养试验和分析测定，研究了湖南省几种成土母质发育的旱地土壤和稻田土壤固定添加铵的动力学特性。结果表明，供试土壤对添加铵的固定速度很快，尤其在反应的前8～12h内速度更快，12h后速度逐渐变慢，24h以后，土壤对外源铵的固定已基本达到平衡。数学拟合表明，一级动力学方程和Elovich方程两种动力学模型能较好地拟合供试土壤固定添加铵的动力学特性，经统计均达极显著水平，抛物扩散方程也有较好的拟合效果，零级方程较差。由一级动力学方程求得的不同土壤固铵动力学参数：理论最大固铵量（A）、反应速率常数（b）以及反应半时值明显不同。耕型石灰性紫色土、耕型酸性紫色土、耕型棕色石灰土和耕型石灰岩红壤的理论最大固铵量和反应半时值分别为212．3mg kg^-1、179．0mg kg^-1、142．9mg kg^-1.13．7mg kg^-1和29．75h、25．96h、27．18h、23．49h；紫泥田、河沙泥、灰泥田和红黄泥的理论最大固铵量和反应半时值分别为86．2mg kg^-1、68．7mg kg^-1,31．8mg kg^-1、19．1mg kg^-1和14．50h、15．10h、15．51h、18．43h。耕型石灰性紫色土、耕型酸性紫色土、耕型棕色石灰土和耕型石灰岩红壤的反应速率常数分别为0．0233 h^-1、0．0267h^-1、0．0255h^-1、0．0295h^-1；紫泥田、河沙泥、灰泥田和红黄泥的反应速率常数分别为0．0478h^-1、0．0459h^-1、0．0447h^-1、0．0376h^-1.除耕型石灰岩红壤以外，旱地土壤的理论最大固铵量和反应半时值均明显大于水田土壤，而反应速率常数明显小于水田土壤。     

固氮斯氏假单胞菌铵载体amtB基因的功能和结构分析

固氮斯氏假单胞菌(Pseudomonas stutzeri)A1501是分离自水稻根际的联合固氮细菌,属变形细菌γ亚族。全基因组序列分析表明该菌含有2个紧密连锁的的铵载体蛋白编码基因amtB1和amtB2,位于同一个操纵子中glnK基因下游。铵载体蛋白AmtB1和AmtB2分别包含12和11个跨膜结构域。为研究amtB的功能,构建了amtB极性双突变株(PKOB1)。amtB极性双突变导致菌株生长缓慢;在铵浓度分别为3.3和10mmol/L条件下,其固氮酶活仍保持在0.01mmol/L的最佳固氮条件的87%和74%,而野生型已经基本尚失固氮能力。以硝酸盐为唯一氮源时,突变株细胞培养液的铵浓度可达到3.4mmol/L,而野生型并未检测到铵,表明AmtB可能参与了P.stutzeriA1501的铵离子转运,并与固氮酶活和氮代谢相关。     

EFFECTIVENESS,AMMONIUM IMPACT AND POTASSIUM ADEQUACY OF SOYBEAN-BASE LIQUID FERTILIZER ON BEDDING PLANTS

A greenhouse study was conducted to compare the effectiveness of a soybean-base liquid fertilizer [Daniels Plant Food; 10 nitrogen (N):1.8 phosphorus (P): 2.5 potassium (K)] to two inorganic, greenhouse-type formulations containing 25 and 75% of nitrogen in the ammoniacal form on four bedding plant species (pansy, petunia, salvia, and vinca). Flowering was unaffected, foliage was deeper green, and substrate electrical conductivity was lower when fertilized with the soybean-base fertilizer. Plants were desirably more compact (lighter with less leaf area) when fertilized with the soybean-base and 75% ammoniacal fertilizer. While ammonium toxicity did not develop in any treatments at the standard lime rate, it occurred at low lime in all species with 75% ammoniacal and only lightly in pansy with soybean-base fertilizer, in spite of its 81% reduced nitrogen. Soybean fertilizer caused less acidification than 75% ammoniacal fertilizer. The potassium content of the soybean-base fertilizer was adequate to meet the requirements of the four species tested.