Novel 1,3,5-triazine derivatives with herbicidal activity

New fluoroalkyl-substituted 1,3,5-triazine derivatives were synthesized and screened for herbicidal activity using a greenhouse pot test. Surprisingly, a series of 2-alkyl-4-fluoroalkyl-6-aralkylamino-1,3,5-triazines e.g. 6-(4-bromobenzylamino)-2-methyl-4-trifluoromethyl-1,3,5-triazine was found to possess strong pre- and post-emergence herbicidal activities, although the conventional herbicidal 1,3,5-triazines generally should have a 2-substituted-4,6-diamino-1,3,5-triazine structure for herbicidal activity. Our compounds show strong Photosynthetic Electron Transport inhibitory activity (PI₅₀ c 7). Although their herbicidal effect is considered to be caused by a process similar to that for the conventional 1,3,5-triazine herbicide atrazine, they can control atrazine-resistant Chenopodium album effectively, and will thus form promising trial compounds for new triazine herbicide design.     

Inhibition of Echinochloa crus-galli var. frumentacea seedling root elongation by chiral 1, 3, 5-triazines in the dark

2-z-Substituted benzylamino-4-substituted-amino-6-chloro-1,3, 5-triazines are herbicidal compounds showing leaf-burning and/or growth inhibition with concomitant greening and stunting. Effects of chiral 1,3,5-triazine compounds in a light-independent seedling root elongation test with Echinochloa crus-galli var. frumentacea Wight demonstrated an interaction between chirality and root growth inhibition. The test compounds inhibited root growth, and this inhibition was due to interference with a system or systems other than photosynthesis. 4-(R)-sec-butylamino-2-(α,α-dimethylbenzyl)amino-6-chloro-1,3, 5-triazine showed the highest inhibitory activity, and 4-methylamino-2-(R)-a-methylbenzylamino-6-chloro-1,3,5-triazine was second. The chiral requirement for a strong inhibition of root growth was the (R)-configuration, contrasting with the requirement for the (S)-configuration for an inhibition of photosystem II.     

吡虫啉和毒死蜱对尿素氮在土壤中转化的影响

为了考察杀虫剂施用对尿素态氮在土壤中转化过程的影响,采用室内培养法,通过测定土壤铵态氮和硝态氮质量分数以及反硝化损失的动态变化,研究了在施用尿素的土壤（有效氮含量为200 mg/kg）中分别添加不同剂量的吡虫啉和毒死蜱2种杀虫剂时,杀虫剂对尿素的水解、土壤氮的硝化及反硝化过程的影响。结果表明:吡虫啉和毒死蜱各剂量处理在第3天时对尿素水解具有显著的促进作用（PPPPP<0.01）,减少反硝化损失量39.69%。     

青海高原长期复种绿肥毛叶苕子对土壤供氮能力的影响

利用绿肥的培肥效应,小麦收获后复种绿肥毛叶苕子。在复种绿肥毛叶苕子的情况下,研究后茬作物油菜生育期土壤全氮、碱解氮、硝态氮、铵态氮的时空变化。结果表明,油菜生育期0～100 cm土层全氮、碱解氮、铵态氮积累量均表现为有毛叶苕子处理高于无毛叶苕子处理,硝态氮积累量均表现为有毛叶苕子处理低于无毛叶苕子处理。毛叶苕子与化肥配施效果好,毛叶苕子施用对提高和保持土壤全氮、碱解氮、铵态氮含量,相比CK提高9.54%～18.33%,相比纯施化肥提高0. 94%～19. 28%。化肥配施毛叶苕子处理较单施化肥土壤硝态氮含量降低7.01%～38.51%。绿肥引入小麦(油菜)种植体系后,对小麦(油菜)生长季内土壤氮库、氮素循环及培肥土壤产生一定影响。     

局部根区滴灌与穴施尿素对土壤氮素空间分布的影响

为研究节水灌溉条件下穴施尿素、滴灌施肥对土壤铵态氮、硝态氮和碱解氮运移的影响,2019年在甘肃农业大学遮雨棚内开展施肥与灌溉试验,采用穴施尿素和滴灌施肥两种施肥方式,施纯氮量240 kg·hm^-2和180 kg·hm^-2,充分灌溉量和局部根区滴灌量分别是14 L和7 L。测定在距离滴头水平30 cm、垂直40 cm范围内土壤铵态氮、硝态氮和碱解氮含量,分析施肥与灌溉后土壤氮素转化及迁移特征。结果表明,土壤硝态氮更容易随灌水发生水平迁移,而土壤铵态氮更容易向土壤纵深迁移。土壤氮素含量的空间变异大小依次为：硝态氮>铵态氮>碱解氮;土壤硝态氮、铵态氮和碱解氮含量的平均变幅分别为32%~40%、26%~37%和6%~12%。局部根区滴灌土壤硝态氮含量的空间变幅比充分灌溉减小16%~20%。穴施尿素土壤铵态氮含量的空间变幅比滴灌施肥减小12%~28%。穴施尿素和局部根区滴灌调控土壤氮素转化速率,赋予肥料养分缓释性能,从而提高土壤氮素供应能力。因此,穴施尿素结合局部根区滴灌是较优的施肥与灌溉方式。     

滴灌施肥条件下土壤水氮运移数值模拟

为了研究滴灌施肥条件下土壤水、氮的运移分布规律,本文通过室内土柱滴灌水氮入渗试验,研究了滴灌结束时及再分布过程中土壤水、氮的运移变化规律;同时用HYDRUS软件建立了土柱滴灌水氮入渗的几何模型,用来模拟滴灌土壤水氮运移过程。对试验及模拟中12个观测点测得的土壤含水率、土壤铵态氮、硝态氮质量浓度进行对比分析,结果表明：土壤含水率模拟值与实测值的相对误差变化在10%以内;土壤铵态氮、硝态氮质量浓度的模拟值与实测值变化范围在20%以内。滴灌结束时土体剖面内土壤含水率随距滴头距离的增大而减小,再分布72 h土层25~30 cm土壤含水率增大到0.2 cm³·cm^-3,120 h后土体剖面内土壤含水率较滴灌结束时下降了18%。土壤铵态氮质量浓度主要分布于距滴头20 cm的范围;24 h土壤铵态氮质量浓度最大,且随着时间的推移逐渐减小,到120 h时减少了40%;各观测点24 h至120 h土壤硝态氮质量浓度随着时间的推移逐渐增大,且硝态氮质量浓度在滴头20 cm的范围内由0.442 mg·cm^-3增加到1.2 mg·cm^-3。各观测点24 h土壤硝态氮质量浓度在空间分布上差异不大,其中观测点1,3,6,8,5的土壤硝态氮质量浓度分别为0.437,0.467,0.451,0.482 mg·cm^-3和0.447 mg·cm^-3,差值均小于0.05 mg·cm^-3;48 h后土体剖面内土壤硝态氮质量浓度空间分布随离滴头距离的增加而减小,垂直方向上从距滴头5 cm的观测点1到距滴头25 cm的观测点8减少了53%。依据研究结果,可用数值模型模拟滴灌施肥条件下土壤水氮运移的变化规律。     

The analysis of crops and soils for the triazine herbicide cyanazine and some of its degradation products. II. Results

Crops and soils from field trials in 1967–1970 in several countries have been analysed for residues of the triazine herbicide cyanazine (‘BLADEX’

1 Shell Registered Trade Mark.

^a or ‘FORTROL’^a' 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine) and for its degradation products 2-chloro-4-(1-carbarmoyl-1-methylethylamino)-6-ethylamino-1,3,5-triazine ( II ), 2-chloro-4-(1-cyano-1-methylethylamino)-6-amino-1,3,5-triazine ( V ) and 2-chloro-4-(1-carbonyl-1-methylethylamino)-6-amino-1,3,5-triazine ( VI ). The time for the concentration of cyanazine in soils to fall to half the initial value was in the range 1.3 to 5 weeks with a mean value of 2.4 weeks. The rate of loss was not affected by sparse crop cover and there was some indication that the rate was greater under moist soil conditions. Residues of up to 0.5 part/million of ( II ) and up to 0.08 part/million of ( VI ) were detected in soils at 4 weeks from cyanazine application at 2 kg/ha. The residues of cyanazine and the degradation products declined rapidly and were 0.07 part/million or less at 16 weeks from treatment. Repeated annual applications did not lead to a detectable build up of residues in soil. Neither residues of cyanazine nor those of ( II ), ( V ) or ( VI ) could be detected in a wide range of crops harvested from soil treated in accordance with the likely recommendations and the limits of detectability were 0.01 to 0.04 part/million.     

有机-无机肥配施对黄土高原半干旱区农田土壤N2O排放的影响

为探明不同施肥方式对旱作麦田土壤N₂O排放的影响,以不施肥(CK)为对照,设置单施有机肥(M)、单施无机肥(N)、有机-无机肥配施(MN)3种施肥方式,采用静态箱-气相色谱法对春小麦地土壤N₂O排放通量进行测定,并对其影响因子(NO^-₃-N、NH⁺₄-N、土壤温度、土壤含水量)和春小麦产量进行同期测定。结果表明：春小麦地在整个生育期内表现为N₂O排放源,各处理均在施肥后出现N₂O排放峰。不同处理土壤N₂O累积排放量表现为N>MN>M>CK,N₂O净损失量(以氮计算)为1.175 8～1.428 kg·hm^-2,占当季施氮量的1.12%～1.36%,有机-无机肥配施降低了氮肥中氮素以气态形式的损失量。MN、N、M处理春小麦产量分别较CK处理增加了45.1%、31.0%、18.8%,各处理土壤NO^-_3<...     

耕作方式对旱地麦田土壤团聚体及其碳氮组分分布的影响

为明确蓄水保墒耕作方式下旱地麦田土壤团聚体稳定性、有机碳及碳组分和全氮及氮组分在不同粒径团聚体组分中的分布特征,深入了解不同耕作方式下土壤碳氮固持机制,以连续3 a(2017—2020年)实施不同耕作方式(免耕、深松、深翻)后冬小麦收获期0～20 cm土壤为研究对象,采用湿筛法测算土壤团聚体的构成与稳定性(R_0.25,>0.25 mm团聚体含量;MWD,平均重量直径;GMD,几何平均直径),并测定各粒径团聚体有机碳(SOC)和碳组分(重组有机碳,HFOC;轻组有机碳,LFOC;易氧化有机碳,EOC;可溶性有机碳,DOC;颗粒有机碳,POC)含量、全氮(TN)和氮组分(硝态氮,NO^-₃-N;铵态氮,NH⁺₄-N;可溶性有机氮,SON)含量,分析了碳氮组分的相关关系。结果显示：(1)免耕和深松处理>2 mm团聚体土壤比例较深翻处理分别提高8.8%和22.1%,免耕有利于增加<0.053 mm粉黏粒比例,较深松和深翻处理分别提高46.4%和27.7%。深松处理较深翻...     

The analysis of crops and soils for the triazine herbicide cyanazine and some of its degradation products. I. Development of method

Radiochemical techniques have been used to develop efficient procedures for the extraction of residues of cyanazine herbicide [‘BLADEX’,

1 BLADEX and FORTROL are Shell registered Trade Marks.

^a ‘FORTROL’,^a 2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-1,3,5-triazine] and its metabolites 2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-ethylamino-1,3,5-triazine ( II ), 2-chloro-4-(1-cyano-1-methylethylamino)-6-amino-1,3,5-triazine ( V ) and 2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-amino-1,3,5-triazine ( VI ) from crops and soils. Partition and column chromatographic techniques have been established for the purification of the extracts. The full analytical procedure is described and the final determination of all four compounds is by g.l.c. with electron capture detection with blank values for field samples generally 0.02 part/million and with good recoveries.     

Effects of isoproturon in the rhizosphere of wheat

In a field experiment, isoproturon (as Arelon) applied to soil at 2·5 kg ai ha^?1 caused variable effects in the rhizosphere of winter wheat. These included transient increases and decreases in the number of bacterial and fungal propagules. No changes in soil levels of NH₄⁺-N, NO₂^?-N, NO₃^?-N or PO₄^3? were detected. Similar results were recorded with wheat grown in pots and in laboratory-incubated soil. Arelon (1–60 μg ai ml^?1) did not affect pure cultures of bacteria but at the highest concentration (approximating to fifty times field rate) inhibited growth of some fungi. The value of laboratory and field experiments for studying effects of pesticides on micro-organisms is discussed. The results suggest that Arelon, in practical use, is unlikely to have harmful effects on the micro-organisms or fertility of soil.     

Potassium uptake in atrazine-treated roots of sensitive and resistan plants

The action of atrazine and its biodegradation products on the membrane transport of potassium in roots was evaluated in both sensitive and resistant plants. Excised roots of maize and oat showed inhibition of potassium uptake efficiency in the presence of 1.4 × 10^?4M atrazine and 1.4 × 10^?4M deethylated atrazine. Other biodegradation products such as 2-chloro-4-amino-6-ethylamino-1,3,5-triazine,2-chloro-4,6-,bisamino-1,3,5-triazine, and 2-chloro-4-amino-1,3,5-triazine showed no inhibitory effect on the K⁺ uptake capacity. Two maize hybrids showing different uptake efficiency were inhibited differently by atrazine. We suggest that atrazine and deethylated atrazine inhibited the K⁺ transport interacting directly with the plant cell membranes without discerning between resistant and sensitive plants.     

陕西省新老苹果产区果园土壤硝态氮累积特性研究

以陕西省新、老果区（分别为洛川及礼泉）为研究对象,调查了两县各15个成龄果园的施肥现状,计算了果园氮素表观平衡,并测定了这15个果园的0~200 cm土壤剖面硝态氮含量,分析了树龄、施氮量与土壤剖面硝态氮累积量的关系。结果表明：新、老果区苹果园均过量施用氮肥,平均施氮量分别高达1 287±244 kg·hm^-2（洛川）和1 193±300 kg·hm^-2（礼泉）,导致土壤中盈余了大量的氮素。新、老果区土壤0~200 cm硝态氮累积量分别达2 724 kg·hm^-2和5 226 kg·hm^-2, 老果区土壤剖面硝态氮累积量显著高于新果区。相关分析表明,果园土壤剖面累积的硝态氮与树龄和施氮量呈正相关,与树龄的相关系数为0.641,与洛川、礼泉果园施氮量的相关系数分别为0.402和0.306。因此,建议研究区域采取措施控制果园施氮量,减少果园土壤硝态氮累积带来的资源浪费及环境污染。     

包气带土壤pH对灌溉施肥响应的变异过程

为了分析灌溉施肥活动引起的包气带土壤pH值变异特征及其对地球化学条件的响应,通过历时3 a的野外原位灌溉施肥试验,应用不同季节灌前、灌后6 m土层中不同深度的测定资料,系统分析了土壤pH对灌溉、施肥的响应过程,结果表明：各深度pH值呈弱变异性（CV=1.01%~2.28%）,与灌溉前相比,灌后土壤pH值的均值和变异系数均呈现明显的变化;灌前包气带各层pH具有强烈的空间自相关性,灌后受水分、基质等相互作用影响,pH的空间自相关性有所减弱,C₀/(C₀+C)和变程a分别由7.23 m和3.54 m(灌前0 d)减少到3.26 m和2.76 m(灌后第10天)。土壤基质是决定土壤酸碱性的主要因素,在灌溉施肥活动对pH的响应过程中,地球化学条件（土壤含水量、土壤温度、土壤有机质(SOM)、氧化还原电位（RP）等)、土壤基质组成和氮底物浓度（NH⁺₄-N）等的交互作用影响pH的动态。土壤含水量和温度单独对pH影响不显著,两者交互作用对pH有显著影响。引起土壤pH变化的主要变异源为Cl^-、土壤有机质(SOM)、NO^-₃-N、NH⁺₄-N等营养物质和不同空间深度土壤基质的差异,表明灌溉施肥改变了包气带pH地球化学动力场、营养物质和土壤基质的交互作用,引起各深度的生物地球化学反应,控制pH值的空间变异特性。当包气带介质土壤水分变化时,首先营养物氨态氮以分子态或水合态形式被介质吸附,H⁺得到释放,使得灌后第4天pH值下降。随着氨氧化过程中H⁺的释放,pH在灌前和灌后第10天和第30天有显著差异。氨的氧化引起硝酸盐含量不断增加,使得硝酸盐对pH值的影响在灌后不断增强,相关系数由0.24(0 d,P<0.05)增加到0.41(30 d,P<0.01),而氨态氮对pH值的影响逐步降低,相关系数由0.43(0 d,P<0.01)降低为0.19(30 d,P>0.05)。     

Effect of dalapon-sodium on nitrification and denitrification in a tropical loam soil

A loamy soil treated with dalapon-sodium was incubated under aerobic or anaerobic conditions with added ammonium or nitrate nitrogen respectively. The incubated dalapon-sodium treated soil and controls were analysed periodically for NH₄+N and NO₃^-N. Results indicated that the herbicide retarded nitrification and denitrification by up to 8 and 12 weeks respectively. Effet du dalapon-sodium sur la nitrification et la dénitrification dans un sol de limon tropical Un sol de limon traité avec du dalapon-sodium a été mis en incubation dans des conditions aérobies ou anaérobies avec addition d'azote ammoniacal ou nitrique respectivement. Le sol traité avec du dalapon-sodium et mis en incubation a été analysé périodiquement, ainsi que les témoins, pour NH₄^+N et NO₃^-N. Les résultats ont montré que l'herbicide retardait la nitrification et la dénitrification respectivement jusqu’à 8 et 12 semaines. Wirkung von Dalapon-Na auf Nitrifikation und Denitrifikation in einem tropischen Lehmboden Einem mit Dalapon-Na behandelten Lehmboden wurde Ammon- bzw. Nitratstickstoff zugesetzt und unter aeroben bzw. anaeroben Bedingungen gelagert. Der mit Dalapon-Na behandelte Boden und die entsprechenden Kontrollen wurden periodisch auf NH₄⁺- und NO₃^--Stickstoff untersucht. Die Ergebnisse zeigten, dass das Herbizid die Nitrifikation um bis zu 8 und die Denitrifikation bis zu 12 Wochcn verzögerte.     

不同覆盖方式对旱作农田土壤碳氮含量及玉米产量的影响

设置垄膜沟播(R)、平作全覆膜(P)和平作秸秆覆盖(S)3种不同覆盖栽培模式,以传统平作(CK)为对照,通过3 a大田定位试验,研究不同覆盖方式对农田土壤碳氮及其组分变化、玉米干物质积累和籽粒产量的影响。结果表明:连续覆盖3 a后,R和P处理土壤有机碳和全氮含量及储量均呈逐渐下降趋势,而S处理则呈上升趋势且每年的增幅逐渐增大;各处理0～40 cm土层土壤有机碳储量均表现为S>R>P>CK,全氮储量表现为S>CK>R>P,S处理有机碳和全氮储量分别较CK提高3.4%和7.5%;与CK相比,R和P处理可提高土壤碳氮比,在0～20 cm土层平均分别提高7.9%和9.6%(P<0.05),而S处理0～20 cm土层土壤碳氮比平均降低了9.9%(P<0.05);各覆膜处理(R和P)均较CK显著降低了0～40 cm土层土壤可溶性有机碳(DOC)和土壤可溶性有机氮(DON)含量,而S处理较CK处理0～60 cm土层DOC和DON含量2 a平均均提高6.2%;各处理收获期硝态氮含量在0～100 cm剖面中的垂直分布与CK无明显差异;各处理土壤铵态氮含量均...     

Rhizome-induction activity of chiral 2-α-methylbenzylamino-4-alkylamino-6-chloro-1, 3, 5-triazines in Cyperus serotinus Rottb.

A cytokinin-like effect of chiral 2-α-methylbenzylamino-4-alkylamino-6-chloro-1,3,5-triazines was found using a rhizome-inducing assay with Cyperus serotinus Rottb. tubers. C. serotinus tubers germinated in distilled water yielded plantlets with roots and leaves. Secondary rhizomes were normally not observed within the regular 14-day incubation time in water culture, whereas after increasing incubation periods a very short rhizome appeared (controls). 6-Benzylaminopurine (BA) significantly stimulated rhizome induction, while other plant hormones were inactive. The (R)-isomers of the 1, 3, 5-triazine compounds also stimulated induction of the rhizomes, whereas the (S)-isomers did not. The described rhizome induction system seems to be suitable as a cytokinin bioassay. The (R)-1, 3, 5-triazine compounds showing rhizome-inducing activity (RI activity) inhibited root formation and plant growth at high concentrations with symptoms which were very similar to those of BA. Therefore, the (R)-isomers appear to act as cytokinins in the rhizome induction assay.     

Effect of s-triazine and phenoxyalkanoic acid herbicides on UDP-glucuronosyltransferase in rat liver microsomes

Twelve herbicides, representatives of two chemical groups, substituted phenoxyalkanoic acids and s-triazines, were tested for their inhibitory effect on the glucuronidation of 4-nitrophenol (4-NP), phenolphthalein (PPh) and 4-methylumbelliferone (4-MU) by rat liver microsomes. One millimole MCPA, ametryn and cyanazine significantly decreased PPh UDP-glucuronosyltransferase (UGT) activity, while propazine was found to be a most potent inhibitor of 4-NP glucuronidation. Concentrations of 0.1 mM dichlorprop and cyanazine were still inhibitory against PPh-UGT. The inhibition of 4-MU glucuronidation by the herbicides was low and not specific. As a whole, s-triazine derivatives were more inhibitory than the substituted phenoxyalkanoic acids. Kinetic studies with propazine revealed a non-competitive type of inhibition towards the acceptor substrate 4-NP, with an apparent K_i value of 0.540 mM . With ametryn, an uncompetitive type of inhibition against PPh and a mixed type of inhibition towards UDPGA were found, with apparent K_i values of 0.330 mM and 0.380 mM , respectively. © 1999 Society of Chemical Industry     

连续施用不同氮量对半干旱地区马铃薯根际真菌群落结构的影响

针对马铃薯生产中因氮肥过量施用导致的土壤微生物群落结构失衡和多样性下降等问题,在始于2013年的不同氮肥用量(N0:不施氮,对照;N75:施氮量75 kg·hm~(-2);N150:施氮量150 kg·hm~(-2);N225:施氮量225 kg·hm~(-2);N300:施氮量300 kg·hm~(-2);N375:施氮量375 kg·hm~(-2))田间定位试验中,于2017年马铃薯成熟期采集根际土壤,应用Illumina PE250测序等分子生物学手段,研究连续5 a施用不同氮量对半干旱地区马铃薯根际真菌群落结构的影响。结果表明:不同施氮量对马铃薯根际真菌群落物种组成造成了显著影响,子囊菌门、Mucoromycota和担子菌门是3个优势门类真菌(相对丰度1.0%),以子囊菌门的相对丰度最大,占总序列的75.48%～83.95%,其优势属是Plectosphaerella(29.92%)和镰刀菌属(13.54%);马铃薯干腐病和枯萎病的病原菌——镰刀菌属的相对丰度随施氮量增加呈增大的趋势。马铃薯根际真菌Alpha多样性随施氮量的增加而降低。连续5 a超量施氮导致了0～20 cm表层土壤中NO~-_3-N含量显著增加,N375处理的NO~-_3-N含量是N0处理的3.76倍。连续5 a超量施氮也显著降低了根际pH值和速效磷含量,N375处理比N0处理pH值和速效磷含量分别降低了0.17个单位和32.10%。RDA及相关性分析结果表明,土壤硝态氮含量是影响马铃薯根际真菌群落结构变化的主要因素(F=1.571,P=0.043~*)。连续大量施用氮肥显著降低了马铃薯块茎产量,连续施氮5 a后,由于土壤剖面中NO~-_3-N的积累,最高产量施肥量由2013—2014年的N225减低为N75,其它施氮处理较N75分别减产了3.46%、22.81%、26.05%和25.32%。长期过量施用氮肥使马铃薯根际硝态氮大量累积,导致pH值降低,进而使根际真菌多样性降低;同时过量氮肥施用会使根际中土壤真菌病原菌相对丰度增加,不利于土壤的健康和马铃薯的高产。     

干旱胁迫对玉米根际氮的有效性及其相关酶活性和细菌的影响

通过盆栽试验,研究了干旱胁迫下两基因型玉米根际有效态N及其两种相关酶活性和细菌的变化.结果表明:除白单9苗期外,干旱胁迫增加了玉米根际NH4 -N的含量,增加幅度为白单31＞白单9;NO3--N受干旱胁迫的影响比较小.干旱胁迫增加了玉米苗期根际蛋白酶的活性,减少了拔节期和抽雄～开花期的活性;脲酶活性受干旱胁迫的影响随基因型和生育时期而发生变化.干旱胁迫减弱了玉米氨化细菌的根际效应,与对照根际氨化细菌数量相比,白单31在苗期和拔节期根际氨化细菌数量受干旱胁迫的影响达极显著水平,在抽雄～开花期达显著水平;根际硝化细菌数量在干旱胁迫下有所增加.干旱胁迫改变了玉米根际NH4 -N和NO3--N与蛋白酶、脲酶、氨化细菌和硝化细菌的相关性.