关于土壤氮素矿化势作为有效氮指标的研究

以2种作物,12个质地、有机质、全氮及碳氮比不同的土壤进行的盆栽和培养试验表明,利用土壤氮素矿化势计算得出作物生长期间的矿化氮量与作物吸收氮量有密切关系,且两者间有稳定比值。根据土壤氮素矿化势计算作物生长期间可利用的氮素有较为合理的依据,值得重视。用KCl煮沸法所浸取的氮素与短期培养所矿化的氮素是高度正相关,且回归系数接近1,说明二者在表示土壤供氮能力方面有同样价值。     

有机肥与化肥配合施用土壤微生物量氮动态、来源和供氮特征

【目的】揭示有机氮肥的矿化-固持周转过程机理，为合理施用有机肥和化肥提供科学依据。【方法】运用同位素15N交叉标记示踪技术，通过盆栽试验，研究单施化肥、单施猪粪、猪粪与化肥配施、玉米秸与化肥配施、麦秸与化肥配施等5种施肥方式下，土壤中微生物量氮在玉米各生育时期的数量、来源的动态变化以及对玉米的供氮特征。【结果】各处理在同一生育期微生物量氮差异的原因主要是所施肥料种类的不同。不同处理的土壤微生物量氮在玉米各个生育期数量与来源不同，施入的有机肥对土壤微生物量氮贡献大，化肥对土壤微生物量氮的贡献较小，土壤氮仍是构成微生物量氮的主要来源。作物和土壤微生物对土壤氮素存在竞争关系，在氮素胁迫条件下，竞争作用突出，其竞争强度取决于氮源和能源的供应强度以及土壤氮素转化过程。同一处理的土壤微生物量氮在玉米的各个生育期数量差异很大，当土壤中微生物的碳源（能源）物质与氮源物质充足时微生物对氮素的竞争能力较强，作物的竞争能力较弱，随着土壤氮素转化过程的改变，作物的竞争能力逐渐增强，并显著超过微生物，微生物量氮减少。【结论】有机肥与化肥配合施用比单独施用化肥能降低土壤微生物量氮来自土壤氮的百分比；与单施有机肥相比能提高土壤微生物量氮来自土壤氮的百分比。     

土壤氮素矿化与土壤供氮能力——Ⅲ.旱地土壤氮素矿化的数学模型

根据一级化学动力学反应方程,利用数值解的电子计算机优化程序,把矿化氮分为易矿化氮和难矿化氮两部分,分别求出了他们的矿化数量(N_1,N_2)及其矿化速率常数(k_1,k_2),建立了土壤氮素矿化的数学模型。结果表明,易矿化氮约占土壤全氮的10％左右,与作物吸氮量的关系最为密切。其主要来源于酸解性氨基酸氮。     

对一种测定土壤潜在可矿化氮的化学浸取方法的评价

用全氮、有机质、pH、碳氮比及质地不同的12种土壤进行了大麦、燕麦和黑麦等3种作物的盆栽试验,并以KCl煮沸法测定了其可矿化的氮素,以估计土壤潜在的有效氮素。试验表明,KCl浓度及浸取时间长短对NO_3~--N浸出量无明显影响,用1 mol/L KCl煮沸浸取1h之后,NH_4~--N亦增加不多。1 mol/L KCl煮沸1h所释放的氮素与3种作物吸氮量密切相关,证明了这种水解方法能较好地预报盆栽试验条件下不同土壤释放作物可利用氮素的相对能力。一旦包括土壤特性,温、湿度在内的氮素释放模式形成之后,KCl煮沸法有可能用来很好地预报大田条件下作物生长期间转变成有效态氮素的数量。     

土壤氮素矿化与土壤供氮能力——Ⅰ.旱地土壤氮素矿化两种培养方法之比较

以有机质,全氮,C/N差异较大的20种田土和10种盆土,进行了长达262d的通气培养和121d淹水培养矿化试验。测定了土壤矿化氮的动态变化,建立了土壤氮素矿化累积曲线;根据矿化速率和容量,把整个土壤氮素矿化过程分为3个阶段,把盆土氮素矿化分为3个类型,田土分为4个类型。     

红黄泥土壤供氮特性的研究 Ⅲ.土壤供氮量的预测

以淹水密闭培养法和田间定点取样测定研究了2种条件下的土壤氮素矿化过程,用红黄泥5个土样进行淹水密闭培养,矿化氮素完全符合有效积温幂函数式,但n值不能反映该类土壤氮矿化特征。且矿化氮量与土壤供氮量相关性差,红黄泥种植水稻早晚2季土壤供氮量都较接近4.7kg/亩,供氮率2.5％左右,同时,土壤供氮量与高于15℃气积温及移栽后的天数有极显著的直线关系。为预测土壤供氮量提供了可能性。     

不同覆盖方式土壤矿化氮素量及其对烤烟生长的影响

为减少土壤后期对烤烟供氮,降低上部烟叶烟碱含量,本试验通过不同起垄方式及覆盖方法对土壤氮素矿化量、烤烟生长、上部烟叶烟碱含量等因素进行研究.结果表明,提前1个月起垄并覆盖地膜的栽培方法能提前矿化土壤中的氮素,提高根系活力;该栽培方法能提高烟叶产量产值,在海拔较高的区域对降低上部烟叶烟碱含量有一定作用.稻草覆盖与对照相比较结果不理想.     

稻田轮耕土壤氮素矿化及土壤供氮量的研究

在稻田连续少耕3季的基础上，分区设定“2年4熟”一个轮耕周期的试验组合，对试验第3季的水稻进行较系统的测定。结果表明：①淹水密闭培养测定的矿化氮，连少耕土壤较高，连耕、轮耕土壤较低。②施氮处理植株含氮率轮耕前期较低，后期较高；土壤供氮量连耕较高，连少耕最低，与培养法测定的矿化氮结果相反。③轮耕有较高的氮肥利用效率，在生产上，与常规耕和连续少耕相比，轮耕可适当减少氮肥施用量。④轮耕后土壤容重和穿透阻力居于连少耕和连耕之间，但仍保持在水稻生长的适宜范围内；连少耕7～14cm土层紧实，影响水稻根系生长和对氮素的吸收。     

不同肥力土壤氮素矿化与模拟

利用田间原位测定,分析了不同肥力土壤氮素矿化规律,可用Logistic累积函数加以模拟,决定系数均达到显著水平,不同肥力土壤氮素矿化量之间存在显著差异,土壤氮素总矿化量占棉花吸氮量的65;～79;,因此,在施肥前,针对不同肥力的田块,利用模型估计土壤某一阶段氮素矿化量,进行氮肥分期动态调控,模型的作用是不可低估的.     

培养条件对土壤氮素矿化的影响

采用间歇淋洗培养法和一级动力学模型研究了培养条件对土壤Ｎ素矿化的影响。结果表明：风干土样改变了土壤的氮素矿化速率、培养前１０ｄ有较高的矿化量。培养时加砂比例对新鲜土壤氮素矿化影响不大，而对风干土壤有较大影响，加入作物秸秆培养，前期表现为矿化氮的固定，２０ｄ左右后由固定转化为矿化。氮素矿化量随土层加深而降低，２０￣６０ｃｍ土层的氮素矿化势仍占有一定比例。     

Estimation of the Biological Methods of Assessing Soil N-Supplying Capacity in Calcareous Soil

Although many biological methods are used to determine soil nitrogen supplying capacity, there are certain differences in the results for different types of soils and various ways of measurement due to the complexity of soil N conformation, the high variance of soil and microorganism, and the difference of environment. Therefore, it is not clear about which biologic incubation method is better for calcareous soil. In this study, pot experiments were performed by using 25 different calcareous surface soil samples on the Loess Plateau and taking the N uptake of wheat and corn with leaching soil initial nitrate and without leaching in pot experiments as the control to investigate the difference of eight biological incubation methods for reflecting soil nitrogen supply capacity. The eight biological methods are waterlogged incubation, aerobic incubation for 2 weeks and for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks, long-term alternate leaching aerobic incubation (and N mineralization potential, N^o), short-term leaching aerobic incubation, microbial biomass carbon (B_c), and microbial biomass nitrogen (B_N) method, respectively. Among these methods, the dry-wet alternation aerobic incubation and aerobic incubation for 4 weeks were the modification of the method of aerobic incubation for 2 weeks according to the actual farmland moisture. The results showed that the correlation coefficients between these methods and crop uptake N w with leaching soil initial nitrate were 0.530, 0.700, 0.777, 0.768, 0.764 (and 0.790, N₀), 0.650, 0.555, and 0.465, respectively (r_0.05 = 0.369, r_0.01 = 0.505). While without leaching soil initial nitrate, their coefficients were 0.351, 0.963, 0.962, 0.959, 0.825 (and 0.812, N₀), 0.963, 0.289, and 0.095, respectively (r_0.05 = 0.369, r_0.01=0.505). In conclusion, excluding the soil initial nitrate, the correlation coefficients between the eight methods and crop uptake N were, from high to low, N₀, aerobic incubation for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks, and long-term alternate leaching aerobic incubation, while including the soil initial nitrate the correlation coefficients between them increased significantly and the values were all beyond 0.950 for these four methods, including aerobic incubation for 2 weeks and for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks and short-term leaching aerobic incubation. The waterlogged incubation method, B_C and B_N in the calcareous soil, had lower correlation coefficient with crop uptake nitrogen compared with other methods. Thus, dry-wet alternation aerobic incubation for 2 weeks was a better index for evaluating calcareous soil N supply capacity due to some other methods having disadvantages and not suitable for the actual farmland characteristics.     

KCl煮沸法浸取石灰性土壤可矿化氮存在的问题及改进

用KCl煮沸法浸取石灰性土壤中的可矿化氮时,会造成氨态氮的挥发,浸取出的NH_4~+-N反而比不煮沸时为低。为了解决这一问题,进行了不同温度下的保温静置、水浴加热等处理,浸取出来的铵态氮均未显著增加。采取酸化KCl溶液后再进行煮沸,显著地提高了NH_4~+-N的浸出量,且浸出结果与作物吸氮量有密切的相关性。     

施氮量对不同肥力土壤氮素转化及其利用率的影响

【目的】评价不同施氮量下不同肥力土壤在小麦孕穗期的土壤活性氮组分（土壤矿质氮、可溶性有机氮和微生物量氮）的转化与氮肥利用率的变化。【方法】以长期（37年）定位试验下不同施肥处理土壤（贫瘠土壤-NF：长期不施肥;低肥力土壤-LF：长期施用化肥;中肥力土壤-MF:长期施用低量有机肥配施无机肥;高肥力土壤-HF：长期施用高量有机肥配施无机肥）为研究对象,通过盆栽试验,利用¹⁵N示踪法,研究添加外源硫酸铵氮肥（N0：0、N1：135 kg·hm^-2、N2：180 kg·hm^-2）之后,小麦生长旺盛时期（孕穗期）土壤活性氮组分在不同肥力土壤中的变化以及与土壤供氮效应之间的联系。【结果】随施氮量增加,不同肥力土壤的可溶性氮均呈先增加后降低的趋势,在N1处理最高,而各处理的土壤微生物量氮在N2达到最大,N1最低;不同肥力土壤可溶性氮变化均为高肥力土壤＞中肥力土壤＞低肥力土壤＞贫瘠土壤,而微生物量氮变化均为高肥力土壤＞中肥力土壤＞贫瘠土壤＞低肥力土壤（P＜0.05）;施氮对不同肥力土壤可溶性氮和微生物量氮的影响在低肥力土壤最大,而在高肥力土壤增幅最小。不同肥力土壤供氮量、氮肥利用率以及吸氮总量和吸15N量的变化均为高肥力土壤＞中肥力土壤＞低肥力土壤＞贫瘠土壤（P＜0.05）,其中,吸收15N量所占小麦吸收总氮的百分比大小变化为低肥力土壤＞中肥力土壤＞高肥力土壤＞贫瘠土壤（P＜0.05）。相同肥力不同处理下,土壤供氮量、氮肥利用率以及小麦吸氮量和吸15N肥料的量随施氮量的增加呈先增加后降低的趋势,均以N1处理显著高于其他处理（P＜0.05）,总体上施氮处理下小麦吸肥料氮所占吸收总氮的百分比的平均值为44%;各肥力土壤中肥料损失量均为贫瘠土壤＞低肥力土壤＞中肥力土壤＞高肥力土壤（P＜0.05）,而且氮肥损失量均随施氮量的增加而增加,在N2处理最大;土壤活性氮组分与土壤供氮、氮肥利用率、小麦吸氮之间均具有显著的正相关关系（P＜0.05）。【结论】在高肥力土壤上添加适宜氮量（135 kg·hm^-2）利于土壤中活性氮组分的转化,能更好地协调土壤供氮与作物需氮间的关系,提高氮肥利用率,减少氮素在土壤中的损失。     

Nitrogen Uptake by Corn and N Recovery in Grain in Dry Farmland

There have been considerable concerns with the reduced beneficial yield response to fertilizer and the less efficient use of fertilizers with the fast growth in fertilizer consumption in China, as well as problems with low and unstable fertilizer use effectiveness in dry farmland. The paper discusses the effect of precipitation, corn stover incorporation and fertilizer management on N uptake by corn and fertilizer N use efficiency in dry farmland. The results showed that in the areas with 520 mm rainfall under the cropping system of one crop of spring corn per year, N uptake and N recovery by corn, and yields were higher at rates of 105 kg fertilizer N, 1 500 kg cattle manure and 6 000 kg corn stover incorporated per hectare. N uptake was significantly affected by precipitation during growing periods and soil moisture at sowing, fertilizer N apparent recovery varied from 58% in a rainy year to 7% in the year with a very dry soil, and the average of 7 years (1993-1999) was about 30%. The 15N tracer experiment showed that around 40% of N uptake was derived form fertilizer N and 60% from soil N. The results from 3-year 15N tracer study (1997-1999) indicated that the 1st years N recovery in grain with and without stover incorporated was about 24% and 17%, respectively, the accumulative 3-year total about 36% and 25%,the percentage of N recovery with stover incorporated increased about 11. The accumulative 3-year N loss with and without stover incorporated was about 26% and 45%, respectively, the percentage of N loss with stover decreased about 19. The studies supply information on land applications of fertilizer N and corn stover in dry farmland.     

土壤交换性钙对烤烟氮、磷、钾含量和吸收量的影响

土壤培育试验研究黄泥田施用不同钙肥后土壤交换性钙含量的变化情况,以钙肥为变量,通过室温培育土壤方法。结果表明:在黄泥田中各钙肥释放交换性钙的速度:硝酸钙>氢氧化钙=磷酸二氢钙>钙镁磷肥>白云石粉。盆栽试验研究土壤交换性钙对烤烟氮、磷、钾含量和吸收量的影响,试验采用单因素随机设计,试验设8个处理,4个重复。结果表明:随着钙肥施用量的增加,烟叶的含氮量、含磷量以及吸收量均呈现下降的趋势,Ca8处理烟叶含氮量及吸收量均比Ca1处理下降了24.17%和17.47%;Ca7处理烟叶含磷量及吸收量均比Ca1处理下降了38.46%和29.62%。烟叶的含钾量及吸收量均呈先增加后减少的趋势,Ca3处理的含钾量最大,Ca6处理的钾吸收量最大,分别比Ca1处理提高了13.99%和23.69%。烟根和烟茎的含氮量、含磷量和含钾量以及吸收量与烟叶的含钾量有类似的规律。整株的氮吸收量呈下降的趋势,最低的Ca8处理比Ca1处理减少了22.64%。整株的磷和钾吸收量均呈先增加后减少的趋势,均以Ca3处理的最大,分别比Ca1处理增加了6.17%和17.84%。     

EUF析滤出的矿质氮源及其反映土壤供氮能力方面的效果

分别用EUF,KCl和水析滤浸取了肥力不同的12种土壤中的氮素,并研究了不同方法浸出的氮素与黑麦草吸氮量的关系。研究表明,EUF法析滤出来的NO_3~--N与KCl和水浸出的大致接近,并没有使土壤中易矿化的有机氮氧化成NO_3~--N而浸出;析滤出来的NH_4~+-N仍是土壤中的可代换铵,既没有担负固定铵释放的信息,也没有提供易矿化有机N分解的信息。不同方法浸取的NO_3~--N都与黑麦草吸氮量有密切关系,而获得的NH_4~+-N情况相反。用KCl浸取的NO_3~--N与黑麦草吸氮量的关系比EUF析滤出来的NO_3~--N更为密切,而浸取方法的简单方便又为EUF所不及。     

电超滤法(EUF)浸提测定15N标记植物残体有机氮和无机氮的转化

采用电超滤法浸提土壤,分析浸提液中的N-NH₄⁺、N-NO₃^-和有机氮.测试土壤采自德国汉森的斑状砂土,用¹⁵N标记的植物残体(油菜)施入土壤,20℃恒温培养80天,以不施(油菜)为对照,培养期间共取样12次.结果表明,EUF法对¹⁵N标记的有机N的浸提能力比土壤全N中的有机N的浸提能力高出7.7倍.EUF浸提的有机氮比率较常规浸提过程的更高.前40天,培养试验中38%的有机氮被矿比,其后没有发生大的矿化.标记的有机氮的矿化在第2天达到高峰之后一直减少,直到第40天,随后处于稳定状态.标记的EUF有机氮对标记的无机N只有很微小的积累.标记的有机氮主要在第2～9天减少,但大约80%的标记无机氮在9天后明显增加.原土氮的矿化过程是明显的零级动力学,基础浓度任何时候不限制矿化.说明易矿化氮化合物总是不断得到土壤相对稳定的有机氮的补充.如果稳定状态在N矿化过程中起主要作用的话,就不可希望EUF浸提的易矿化有机氮的减少.通过氮矿化库的变化量对预测氮矿化更重要,因此,寻找适当的矿化指标来制约土壤有机氮形式和变化量显得更为紧迫.     

Effects of Soluble Organic N on Evaluating Soil N-Supplying Capacity

It is important to study the soluble organic N （SON） extracted during water-logged incubation for evaluating soil Nsupplying capacity. Soil initial SON and mineral N （Nmin）, cumulative soluble organic N and NH4＋-N in leachates during water-logged incubation, mineralization potentials of both easily decomposable N （ND） and resistant N （NR）, and their relationships with N uptake by crop in pot experiment were investigated by using 10 kinds of farmland soils with widely different physical and chemical properties on the Loess Plateau, China, and the effects of SON on evaluating soil Nsupplying capacity were studied. The results showed that the average content of initial SON （23.9 mg kg^-1） of 10 soils was 28.8% of initial total soluble N and 2.4% of soil total N. The percentage of cumulative SON in leaching total soluble N （118.1 mg kg^-1 was 46.4%, higher than the percentage of initial SON （28.8%）, and almost close to the percentage of cumulative NH4^＋-N in the leachates. ND had close correlation with total N, and the correlation coefficients were 0.92 （P 〈 0.01, excluding SON in estimating ND） and 0.88 （P 〈 0.01, including SON in estimating ND）, respectively. N mineralization potential and mineralization rate constant were different with the soil types. ND of Los-Orthic Entisols and Ust-Sandiic Entisols were lower than that of Eum-Orthrosols. Mineralization rate constant for the fast decomposable N-fraction （kD） decreased and the mineralization rate constant of resistant materials （kR） increased when SON was taken into account. Cumulative NH4^＋-N was a better evaluation index of soil N-supplying capacity, and it is not only suitable for the first season crops but also for two successive season crops. Cumulative SON alone was not a satisfactory index for the potential of mineralizable N. But it would be more accurate for ND in revealing the potential mineralizable N when SON was taken into account. Cumulative TSN, to some extent, could also be taken as an index for     

施氮量对膜下滴灌棉花氮素吸收、积累及其产量的影响

2004年在膜下滴灌条件下,研究了施氮量0、180、270、360 kg/hm2对膜下滴灌棉花氮素的吸收、累积和产量及氮肥利用率的影响.结果表明:施用氮肥可以显著提高棉花的生物和经济产量及地上部分总吸氮量,但过量施用氮肥对经济产量和生物产量增产不显著,各施氮处理氮肥利用率在27.6;～33.8;,随施氮量的增加而降低.植株中氮素含量随生育延长而降低,氮素累积总体呈增加趋势,施氮量对棉花氮素吸收有显著影响,同一生育时期,氮素含量和累积量都随着施氮量增加而提高.试验条件下,棉花的合理施氮量应控制在270 kg/hm2左右.