氮肥形态耦合促进马铃薯生长

为明确氮素形态耦合及土壤氮转化过程调控措施对作物氮肥利用率的影响,在田间试验条件下研究了不同铵态氮肥用量(纯氮225.0、168.8和112.5 kg/hm²)±硝化抑制剂、不同硝态氮肥用量(纯氮225.0、168.8和112.5 kg/hm²)对马铃薯生长的影响。研究结果显示,与施用硝态氮肥相比,铵态氮肥的施用显著提高了马铃薯的产量和氮素吸收量;随铵态氮肥用量的提高,马铃薯产量具有增加的趋势,而不同硝态氮肥用量处理对马铃薯薯块产量无显著影响;铵态氮肥配施双氰胺(DCD)可以有效提高土壤铵态氮含量,增加马铃薯薯块产量(特别是大中薯产量)。马铃薯产量与土壤铵态氮含量呈显著正相关关系,与硝态氮含量没有明显关系。研究结果说明氮素形态耦合能够促进作物生长、提高作物氮肥利用率,对氮肥减量增效具有重要的指导意义。     

小麦——土壤系统氮肥转化利用的研究进展

施用氮肥是提高小麦籽粒产量、改善品质的重要措施,但是不合理施氮会导致氮肥利用率的降低,氮肥损失的增加。本文综述了小麦-土壤系统中氮肥对土壤氮素转化和小麦氮素吸收利用的影响及氮素损失等方面的研究进展。     

长期施肥对农田土壤氮素关键转化过程的影响

当前,如何合理施肥、提高作物产量、维持土壤肥力、并兼顾生态环境效应是农业研究的主要挑战之一。本文综述了长期施肥对农田土壤氮素关键转化过程的影响,主要从土壤氮转化过程的初级转化速率角度综述肥料(有机肥和化学氮肥)对土壤氮素关键转化过程的影响。土壤氮素矿化-同化循环是自然界氮循环过程中两个至关重要的环节,是决定土壤供氮能力的重要因素。总体而言,长期施用氮肥,尤其是有机肥能显著提高初级矿化-同化周转速率;长期施肥可以刺激自养硝化作用,且有机肥的刺激作用更明显;施用化学氮肥和有机肥均能提高反硝化速率,且有机肥的刺激作用高于化学氮肥。有机肥一直被提倡和实践用来改善土壤肥力和提高土壤固碳能力,无论是单施有机肥还是有机-无机配施,均能有效地减轻硝酸盐污染,改善土壤肥力并提高作物产量。但是有机肥的施用并不是多多益善,有机肥过多施用也会增加氮损失的风险。因此,本文综述了长期施肥对农田土壤氮素关键转化过程初级转化速率的影响,讨论了各个氮转化过程之间的联系,以期增强人们对长期施肥措施影响农田土壤氮素循环的理解,并为合理施用氮肥、提高氮肥利用率、减少与氮相关的环境污染提供理论依据。     

氮肥有效率的概念及意义——兼论对传统氮肥利用率的理解误区

自氮肥发明和施用以来,人们一直想通过氮肥利用率来度量氮肥施用效果。传统氮肥利用率是指当季作物吸收肥料氮占施用肥料氮的百分率,而没有反映氮肥对土壤氮消耗的补偿效应。由于概念和算法本身缺陷,加之对结果解析和理解不够,在文献和日常交流中产生了许多误区。为此,国内外研究者尝试了许多改进算法,虽涉及到氮肥在后茬作物上的残效,但并未触及到残留肥料氮对土壤氮消耗补偿效应这一核心问题。本文根据土壤-作物体系氮素主要流动通量,及肥料氮-土壤氮-作物吸氮"三氮"之间关系,提出了氮肥有效率的概念和算法,其核心是将残留肥料氮作为补偿土壤氮消耗的有效部分。文章分析了国内15N示踪试验资料,认为我国现有农田管理水平的氮肥有效率在50%~60%,损失率在40%~50%之间,损失率很高。采取改进氮肥和农艺管理措施,我国未来将氮肥有效率提高至70%~90%,是完全有可能的。氮肥有效率拓展了氮肥效应理念,在解析氮肥对作物增产、维持土壤氮肥力的真实效果,对环境的实质影响方面具有重要意义。     

不同形态氮肥在坡耕地雨季土壤氮素流失动态特征

为有效控制紫色丘陵区坡耕地氮素流失,采用二因素四水平随机区组试验,利用模拟径流小区观测方法,研究氮肥形态对坡耕地雨季土壤氮素流失动态的影响,结果表明,整个雨季氮素流失量占玉米季氮肥施用量的3.29%,其中玉米生长季的氮素流失量占氮肥施用量的1.63%,玉米收获后径流氮素流失量占氮肥施用量的1.65%。氮素流失动态差异受氮肥形态和施肥距径流产生时间间隔的共同作用。在攻苞肥施用之前的5月22日,各氮肥形态处理相比差异不显著;在接近作物收获的7月30日和8月4日,铵态氮处理和酰胺态氮处理两次总的氮素损失量(3.65和4.35 kg/hm2)较其它处理高。玉米收获后的9月16日,硝态氮肥处理和缓控释肥处理的氮损失分别是2.95和3.17 kg/hm2,较铵态氮肥处理的氮损失低119.95%和103.96%,较酰胺态氮肥处理的氮素损失低85.04%和71.60%。可见,施用硝态氮肥和缓控释肥能够有效降低攻苞肥施用后的径流氮流失量,而铵态氮加地膜以及酰胺态氮肥处理增加攻苞肥施用后壤中流和总径流氮流失浓度和流失量。从有效控制农业面源污染的角度考虑,建议玉米生产上,在肥料种类选择时以缓控释肥和硝态氮肥为主。     

不同控释氮肥减量施用对双季水稻产量和氮素利用的影响

研究不同控释氮肥在减氮量施用条件下早、晚稻产量效应、氮素吸收利用、土壤氮素养分特性和养分释放规律的差异,为南方双季稻区控释氮肥在水稻高产节肥栽培上的应用提供参考。采用静水溶解试验和田间小区试验研究了2种控释氮肥(树脂包膜尿素和硫包膜尿素)的养分释放特性和在常规尿素施氮量基础上节氮15%和30%对早、晚稻产量、产量构成因素、氮素养分吸收利用及土壤氮养分含量的影响。结果表明,2种控释氮肥的氮素累积释放曲线均为"S"形,但在培养期间硫包膜尿素氮素累积释放率均高于树脂包膜尿素。在田间条件下,与常规尿素处理相比,早稻减氮15%和30%施用硫包膜尿素和树脂包膜尿素均表现为增产,而晚稻施硫包膜尿素增产,施树脂包膜尿素减产。株高、每穗实粒数、结实率和千粒重的增加是早、晚稻增产的主要原因。施用2种控释氮肥均能促进早、晚稻水稻植株氮素养分的吸收积累,施用相同种类控释氮肥早晚稻稻谷、稻草和植株氮养分积累量随施氮量提高而提高。减氮15%和30%施用2种控释氮肥有利于氮肥回收利用率、氮肥偏生产力和氮肥农学效率的提高,在同一施氮水平下,硫包膜尿素的提高效果优于树脂包膜尿素。常规尿素处理、减15%氮的2种控释氮肥处理均能保持较高的土壤氮素水平,减30%氮的控释氮肥处理土壤氮素肥力较试验前有所降低。适当降低氮用量施用控释氮肥,能促进双季水稻增产、增加氮素利用效率、维持或提高土壤氮素肥力和可持续生产力,控释氮肥养分释放规律的差异是导致其作用效应不同的主要原因。     

有机、无机肥料氮在水稻-土壤系统中的转化与分配

在农业生产中,氮肥是决定作物产量的一个重要因素.有关氮肥的施肥方法和增产效果,长期以来已有很多报道,但是,对于有机态氮肥,如绿肥以及有机、无机肥结合施用以后,肥料氮素和土壤氮素在作物—土壤系统中的转化和分配动态研究较少.有机肥和绿肥是我国农业生产中的主要肥源.解放以后,全国开始普遍施用化肥,当前有机、无机肥结合施用已是我国施肥方法中的主要特点.     

包膜控释和常用氮肥氮素淋溶特征及其对土水质量的影响

大量施用氮素化肥所引起的氮素损失和环境污染正日益受到重视。通过土柱模拟氮养分的淋洗试验。探讨包膜控释氮肥和常用氮肥的氮素淋失特点及其对土壤和地下水质量的影响。研究结果表明，不同氮肥施入土壤后氮素的淋失率有着显著的差异，其中硝酸钾中氮素淋失率最高，其次为尿素，硫酸铵和碳铵的氮素淋失量明显较小。然而控释氮肥因其控制释放的特点。在氮素释放的高峰期，其模拟淋失量较高，但如果在田间条件下此释放高峰期与作物吸肥高峰期相吻合，则会显著地降低其淋失率。除尿素外，被淋失的氮素均以硝态氮为主，尿素则以酰胺分子态被林溶。大量速效化肥的施入会形成土壤中的肥料“微域点”，引起交换性Ca^2 、Mg^2＋离子的淋失，从长远来看可引起土壤结构的破坏，而施用控释肥则很少形成这种“微域点”，有利于土壤结构和肥力的维持。不同氮肥处理淋洗后对土壤pH值和有效氮含量变化的影响差异较大，其中以控释肥对土壤pH值变化的影响较小。大多数氮肥处理在淋洗后，土壤中各层速效氮含量较淋洗前有所降低，然而两种控释氮肥处理的土壤表层却能持续保持较高的有效氮含量。     

氮肥利用率的问题与改进

传统差减法计算氮肥利用率变异较大,影响了氮肥利用率的应用,科学的氮肥利用率计算方法对氮肥的合理施用十分重要。本文概述了氮肥利用率50多年的研究过程,并划分为3个创新研究阶段,提出差减法计算氮肥利用率各个创新研究阶段的主要创新点。采用常规计算方法和定位试验研究资料计算了氮肥利用率,阐明常规计算方法计算的氮肥利用率结果存在的问题;归纳了氮肥利用率变异较大的主要原因:1)采用土壤氮素养分系统没有达到平衡或接近平衡的试验结果;2)常规计算方法仅考虑氮肥用量和作物吸收氮量,没有考虑土壤残留氮(或消耗土壤氮)。建立了2个氮肥利用率计算的新方法:1)土壤氮素养分系统平衡状态计算公式:氮肥利用率=(施肥作物吸收氮-报酬递减系数×对照作物吸收氮)/施肥氮;2)土壤氮素养分未达到平衡状态计算公式:氮肥利用率=(施肥作物吸收氮-报酬递减系数×对照作物吸收氮)/(施肥氮+施肥处理土壤氮素消耗量-对照处理土壤氮素消耗量)。     

小麦-玉米轮作体系下氮肥对长期不同施肥处理土壤氮含量及作物吸收的影响

以长期不同施肥处理土壤为对象,研究了不同施肥土壤中施用氮肥后土壤氮素含量、微生物固持及释放和作物吸收及利用特性。结果表明,施用氮肥显著增加长期不施肥土壤(NF)矿质氮含量,对长期施用化肥土壤(NPK)和有机无机配施土壤(MNPK)矿质态氮含量无显著影响;施用氮肥对NF中土壤微生物生物量氮(SMBN)含量无显著影响,使拔节期NPK和MNPK中SMBN含量分别增加了4.3倍和0.8倍。从小麦拔节期到开花期,NPK和MNPK中土壤微生物生物量氮含量分别显著降低51%和56%。小麦收获时NPK和MNPK土壤氮肥的利用率分别为36%和45%;而NF土壤所施入的氮素几乎未被小麦吸收利用,但在玉米季有34%被吸收。小麦收获时,NF土壤施入的氮肥有50%以上淋溶至土壤30 cm以下土层,施氮也显著提高了NPK土壤30～50 cm土层硝态氮含量,但施用氮肥对MNPK土壤0～100 cm剖面硝态氮含量无显著影响。说明长期有机无机配施增强了土壤氮素的缓冲能力,协调了土壤氮素固持与作物吸氮间的关系,为提高氮素利用率,减少氮素对环境影响的有效手段。     

Development of Soil N Testing for Wheat Production using Soil Residual Mineral N

The effects of soil residual nitrate (NO₃-N) and ammonium (NH₄-4) on wheat (Triticum aestivum L.) grain yield and N uptake were evaluated in a three-year experiment from 1991 to 1993, in the province of Quebec, Canada. Soil samples were collected at harvest from the depth of 0-30 and 30–60 cm from 20 wheat sites and analyzed in the laboratory for NO₃-N and NH₄-N. Wheat yield and N-uptake was also determined. Using statistical analysis system (SAS) and Matlab, data were analyzed and the best-fitted regression equations were plotted. Significant amounts of soil NO₃-N was found in the soil ranging from 31.6 to 61.6 kg/ha. The amount of soil NH₄-N varied from 9.2 to 23.3 kg/ha. The statistical effects of model parameters indicated that soil NO₃-N and soil NH₄-N significantly influenced wheat yield and N uptake. It may be possible to investigate wheat behavior at harvest using soil residual NO₃-N and NH₄-N.     

旱地土壤矿质氮和可矿化氮与土壤供氮能力的关系

在具有典型半干旱气候特征的陕西永寿选取22个不同肥力水平的田块,分层采集0－100cm土样,研究矿质氮、可矿化氮和土壤供氮能力之间的关系。结果表明,NH4－M与可矿化氮之间没有明显关系;15－80cmNO3－N与各层可矿化氮显著相关,0－15cm和80－100cmNO3－N与之大多相关不显著。通径分析表明,30－45cm的可矿化氮和NO3－N对作物吸氮量的直接贡献最大（后者稍低于前者）;其次是60－80cm的NO3－No0-100cmNO3-N总的直接和间接贡献均大于可矿化氮。作为土壤供氮指标,0－45cm可矿化氮和0-100cmNO3-N都可靠,尤以后者效果更好。     

长期施肥对土壤有机氮影响研究Ⅰ氮肥及其配施下土壤有机氮组分变化

试验布置在典型的黄土高原的沟壑区，长武试验示范区，在长期的小麦连作的基础上，通过单施氮肥以及氮肥与其它肥料的配合使用，研究不同施肥对土壤有机氮组分的影响，试验结果表明，长期施肥对土壤铵氮和氨基糖氮影响较小，而对土壤氨基酸态氮和酸解和未知态氮影响较大，特别是化学氮肥和有机肥的配施效果较好。     

Soil N Losses by Denitrification Evaluated Using the 15N Tracer Method

Molecular nitrogen (N₂) and nitrous oxide (N₂O) generated by denitrification increase N losses in the soil–plant system. This study aimed to quantify N₂ and N₂O from potassium nitrate (K¹⁵NO₃) applied to soils with different textures and moisture contents in the absence and presence of a source of carbon (C) using the ¹⁵N tracer method. In the three soils used (sandy texture (ST), sandy clay loam texture (SCLT), and clayey texture (CT)), three moisture contents were evaluated (40%, 60%, and 80% of the water holding capacity (WHC)) with (D⁺) and without (D^?) dextrose added. The treatments received 100 mg N kg^?1 (KNO₃ with 23.24 atom% ¹⁵N). N₂ emissions occurred in all of the treatments, but N₂O emissions only occurred in the D⁺ treatment, showing increases with increasing moisture content. SCLT with 80% WHC in the D⁺ treatment exhibited the highest accumulated N emission (48.26 mg kg^?1). The ¹⁵N balance suggested trapping of the gases in the soil.     

供氮方式对黑土土壤无机氮浓度的影响

采用好气恒温培养法,通过一次和分次供氮的方式,研究不同尿素施用量对黑土土壤无机态氮浓度的短期效应。结果表明:CK处理(不供氮方式)在培养期间,NH4+-N的浓度始终保持较低水平,而NO3--N浓度则呈稳步上涨的变化态势;pH值稳定在6.0～6.3之间;硝化率则稳定在90%左右。一次供氮方式各处理NH4+-N的浓度,在施氮后第3d时达到最大,第20d后趋于稳定;NO3--N的浓度则呈稳步增长的态势;土壤的pH值与NH4+-N的浓度的变化规律相似,在培养后的第3d达到峰值,而后开始下降,在培养第10d时,各处理的pH值趋于稳定,且明显低于CK;而硝化率则随着培养时间的延长,呈逐渐增加的变化趋势,在第20d时已与CK无显著差异,趋于平缓。分次供氮各处理在第1次施氮1d后,NH4+-N浓度达到峰值,之后开始呈下降的变化趋势,另外3次施氮后NH4+-N浓度变化与此类似,且每次施肥后第3d和第10d土壤NH4+-N浓度之间差异不显著;NO3--N浓度在第1次施氮1d后,各处理差异不明显,第3d达到最大,但整体上是呈稳步增长的变化趋势;各处理的pH值的变化情况与一次供氮的情况相似;土壤硝化率硝化率呈先下降后上升的趋势,整体呈逐步上升的变化趋势。     

土壤全氮含量和施氮水平对棉花产量及氮肥利用效率的影响

为探讨不同土壤全氮含量水平下棉花的氮肥施用效应,采用盆栽试验,研究不同土壤全氮含量(0.58、0.64、0.74、0.83、1.29 g·kg~(-1))和施氮水平(每盆施加量分别为0、1.75、3.50 g)对棉花籽棉产量、氮素吸收、氮肥利用率的影响。结果表明,棉花单株籽棉产量和干物重随施氮量增加而显著增加,土壤全氮含量与施氮水平对棉株根、茎、铃壳部位的干物质积累具有显著的互作效应。同一土壤条件下,棉花单株氮素积累量随施氮水平增加而显著增加。氮肥表观回收率随土壤全氮含量上升呈先降后升的变化趋势,且在土壤全氮含量0.74 g·kg~(-1)时较低,但土壤全氮含量在0.58~0.83 g·kg~(-1)内,不同施氮处理间氮肥表观回收率差异不显著。氮肥农学利用率随土壤全氮含量增加呈下降趋势。土壤全氮含量0.74 g·kg~(-1)时的氮肥生理利用率高于土壤全氮含量0.58、0.64和0.83 g·kg~(-1)。土壤全氮含量1.29g·kg~(-1)条件下,低氮水平氮肥利用效率(表观回收率、农学利用率、生理利用率)显著优于高氮水平;土壤全氮含量0.58~0.74 g·kg~(-1)时,高氮可实现增产增效;土壤全氮含量0.83~1.29 g·kg~(-1)时,低氮能维持较高的产量和氮肥利用率。本研究结果为不同土壤全氮条件下棉花氮肥投入提供了参考。     

Soil N dynamics and N yield of barley grown on Breton loam using N from biological fixation or fertilizer

Summary Soil N dynamics and barley yields (Hordeum vulgare L.) were compared in pot experiments using surface samples from a Gray Luvisol under three cropping systems at Breton, Alberta: (1) an agroecological 8-year rotation including cereals, forage, and fababeans (Vicia faba L.) as green manure, from wich two plots were selected, one following fababeans, and the second following 3 years of forage; (2) a continuous grain system, with fertilizer N at 90 kg ha^-1 year^-1; and (3) a classical Breton 5-year rotation [following oats (Avena sativa L.)] involving forage and cereals, without returning crop residues to the land, selecting one plot with PKS treatment and a second as control. The fertilizer N equivalent for the cropping system; A_N value and A value (analogous to A_N), but in fertilizer ¹⁵N units, soil biomass, and C and N mineralization were monitored. In the first agroecological plot (after fababeans), grain and total plant biomass production were 116% greater than from the continuous grain treatment. Barley plants in the two agroecological plots derived 48.5% and 37.8%, respectively, of their N requirement from non-labelled soil N sources not present in the continuous grain plot. At crop maturity, the recovery of ¹⁵N microbial biomass was 1.5 times higher in soil from the first agroecological plot than from the continuous grain plot. The fertilizer N equivalent was 2670 mg pot^-1 (485 kg ha^-1) for the first and 1850 mg pot^-1 for the second agroecological treatment. Fertilizer N equivalent values exceed net amounts of N mineralized by a factor of 4. Recovery by the barley crop of ¹⁵N added at 55 mg pot^-1 was more efficient in the agroecological treatments (45%–51%) than in the continuous grain or classical Breton treatments (35%–37%). It was concluded (1) that past soil history may be associated more with the ability of barley plants to compete for available N, and hence the use of N, than with net soil N mineralization; and (2) an increased supply of N to crops following the incorporation of fababean residues, manure application, and the soil N-conserving effect of growing legumes were all partly responsible for the observed differences in soil fertility.     

烤田对土壤中氮素和与氮有关的酶活性影响

在水稻分蘖期对5种不同尿素氮肥水平的小区进行烤田5天的试验。试验结果表明,在烤田过程中,脲酶活性变化不明显,呈微弱增加趋势。硝酸还原酶活性急剧降低,羟胺还原酶活性呈波动变化,几乎检测不到亚硝酸还原酶活性。土表的铵态氮也呈波动变化,随着烤田时间的增加铵态氮含量降低。土表的硝态氮浓度不断增加,烤田增大了复水后硝态氮向地下水淋溶的趋势。施氮量越多,土表的矿质氮含量也越多。土壤烤田的主要目的是通过降低土壤的含水量,提高土壤的氧化还原电位,改善土壤的通气状况。     

氮肥对水稻不同生长期土壤不同深度氮素渗漏的影响

为了探明太湖地区氮肥施用对水稻不同生长期稻田土壤氮素渗漏的影响,利用渗漏管进行了原位监测。结果表明：①土壤各层(20 ~ 40、40 ~ 60、60 ~ 80和80 ~ 120 cm)渗漏液中铵态氮(NH4+-N)的平均浓度在水稻分蘖期较高,而硝态氮(-N)和全氮(TN-N)的平均浓度则在苗期相对较高。渗漏液中NH4+-N和TN-N浓度随土壤深度增加基本呈降低趋势。②以土壤80 ~ 120 cm深处渗漏量为进入地下水的氮素渗漏量,发现TN-N渗漏量占施肥量的比例为1.69% ~ 2.04%。分蘖期的NH4+-N渗漏量相对较多,而苗期-N和TN-N相对较多,总TN-N渗漏量中NH4+-N和-N基本无差异。③氮肥用量增加降了氮肥利用效率,加剧了土壤各层氮素渗漏风险。当施氮量由N 200增至270 kg/hm2时,氮肥表观利用率下降7.14%,下渗至地下水中的TN-N增加12.3%。     

Soil microbial and extractable C and N after wildfire

 The effect of wildfire on soil microbes and extractable C (C_ext) and N (N_ext) changed with respect to the time from burning and soil depth. Initially, microbial biomass C (C_mic) and N (N_mic) were drastically reduced in the soil surface layer (0–5 cm) and reduced by 50% in the subsurface (5–10 cm), whereas C_ext increased by 62% in the surface layer and did not significantly change in the subsurface. These parameters were affected for the following 4 years, during which the average reductions in the soil surface and subsurface layers were, respectively, 60% and 50% for C_mic, 70% and 45% for N_mic, 60% and 40% for the ratio C_mic: organic C (C_org) and 70% and 30% for the ratio N_mic: total N (N_tot), while for C_ext the surface layer was the only zone consistently affected and C_ext decreased by up to 59%. Immediately after a fire, the C_ext : C_org ratio increased by 3.5-fold and 2-fold in the surface and subsurface layers, respectively; thereafter for 2 years, it decreased in the surface layer (by up to 45%) while the effect on the subsurface layer was not consistent. The effect of burning on N_ext lasted 1 year, in which N_ext increased by up to 7- and 3-fold in the surface and subsurface layers, respectively, while the average N_ext : N_tot ratio doubled in the surface layer and increased by 34% in the subsurface. During the time in which each parameter was affected by burning, the soil factor explained a high percentage of variance in the fluctuations of C_mic, N_mic, C_mic : C_org and N_mic : N_tot, while those of N_ext and N_ext : N_tot, but not those of C_ext and C_ext : C_org depended on both the soil and its depth. In the burned soils similar patterns of response were found between the following parameters listed in pairs: C_mic and N_mic; C_mic : C_org and N_mic : N_tot; C_ext and N_ext; and C_ext : C_org and N_ext : N_tot. However, after the fire relationships found previously between the parameters studied and many other soils properties were either no longer evident, or were inverted. Although the addition of cellulose to the burned soil favoured fungal mycelium development and increased C_mic and C_ext contents, the negative effect of burning on the microbial biomass and the C_ext was not counteracted even under incubation conditions suitable for both microbial growth and C mineralization. Received: 28 May 1997