用^(15)N同位素稀释法研究沸石对氮肥利用率的影响

通过15N示踪研究不同沸石水平处理对玉米氮肥利用率的影响。结果表明 :( 1 )沸石和肥料混合使用促进了玉米的生长 ,第一茬玉米氮肥利用率以 0 7g kg土沸石用量为最高 ,其次是 1g kg土 ;( 2 )第二茬玉米的氮肥利用率则是以 0 1 %的沸石用量最高 ,其次是 0 1 3 %的沸石用量水平 ,与对照相比 ,沸石处理使两茬玉米的氮肥利用率分别提高了 2 3 2 %～ 3 3 1 % ;( 3 )沸石处理可以显著降低土壤中氮肥的损失 ,与对照相比 ,降低率达 2 5 9%～3 0 6% 。

Estimation of N_2 Fixation by Some Legumes Using ^（15）N－Labelled Soil in Greenhouse Experiment

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Symbiotic nitrogen fixation in black locust (Robinia pseudoacacia L.) seedlings from four seed sources

We conducted a greenhouse experiment to investigate the role of seed source in growth and symbiotic nitrogen fixation of black locust （Robinia pseudoacacia L）. Seeds from different sources were planted in the same environmental conditions and inoculated with a suspension of mixed Rhizobium. We used the modified ^15N isotope dilution method to estimate biological nitrogen fixation of Robinia trees. Different Robinia seed sources differed significantly in terms of tissue dry weight （50.6-80.1 g）, total N （1.31-2.16 g） and proportion of nitrogen derived from the atmosphere （ 0-51%）. A higher nitrogen fixation rate of Robinia trees was associated with higher dry weight. Moreover, the leaves of Robinia proved to adequately represent the nitrogen fixation capacity of entire plants. Our results confirmed that assessment of seed sources is a useful way to improve the nitrogen fixation capacity and therefore the growth rate of Robinia.

Estimating total nitrogen deposition in agroecosystems in northern China during the wheat cropping season

Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.

Nodulation and Fixed Atmospheric Nitrogen of Some Local Lima Bean (<i>Phaseolus lunatus</i>L.) Cultivars Grown in a Coastal Savannah Environment

Legumes, in symbiotic association with Rhizobia, are able to fix atmospheric N. Six local lima bean (Phaseolus lunatus) cultivars were grown under rainfed conditions in a coastal savannah environment. Objectives of the study were to evaluate the nodulation and fixed atmospheric N levels of the six local lima bean cultivars using both the 15N isotope dilution method and N difference method (NDM). The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and NDM, was also assessed. The experiment was arranged in a randomized complete block design (RCBD) in three replicates with seven treatments, comprising six lima bean cultivars (B1, B2, B3, B4, B5 and B6) and the early maturing local maize variety, “Doke”, as the reference crop. Total, effective nodules (EN) and non-effective nodules (NEN) were determined on 42 and 56 days after planting (DAP). The 15N isotopic dilution method and NDM were used to quantify the fixed atmospheric N by the lima bean cultivars on 60 DAP. Effective root nodules per plant (EN) on 56 DAP ranged from 0.71 to 1.22, with the lima bean cultivar B4 having the highest value and cultivars B2 and B5 having the lowest value of EN, respectively. Similarly on 56 DAP, the lima bean cultivar B4 had the highest NEN value while cultivars B1, B2 and B5 had the lowest NEN value of 0.71 per plant. The mean fixed atmospheric N was 8.98 kg&middotha-1, based on the 15N isotope dilution method, which was lower than 10.13 kg&middotha-1 of fixed atmospheric N determined using NDM. The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and that estimated using the NDM, was positive but of average quality as the R2 value was 0.56. Consequently, the linear model obtained from this relationship is moderate as 56% of the data used for the linear regression analysis were accounted for by the linear regression model developed. However, NDM could be used for fast screening to select lima bean cultivars for a more detailed study to identify cultivars with promising fixed atmospheric N capabilities. Generally, results of the study provide opportunities for designing breeding and other agronomic programmes for enhancing the productivity and N-fixing capacity of local lima beans in the coastal savannah environment.

应用^(15)N稀释技术定量华北平原大气氮沉降的输入总量(英文)

本文采用定量氮沉降总量的ITNI(Integrated Total Nitrogen Input)系统,利用^(15)N稀释原理和生物监测技术,定量研究了华北平原大气氮沉降的农田输入总量及其在推荐施肥中的作用。结果表明,以玉米和小麦为指示植物,监测到在玉米-小麦轮作体系中整个华北平原大气氮沉降的输入总量高达80-90 kgN ha^(-1)yr^(-1),对玉米和小麦植物有效性的沉降氮总量约为50 kgN ha^(-1)yr^(-1)。以黑麦草为指示植物,监测到华北平原大气氮沉降的输入总量约为100 kgN ha^(-1)yr^(-1),对其植物有效性的沉降氮约为76 kgN ha^(-1)yr^(-1),占总沉降氮的77%。由于华北平原小麦季扬尘较多,因此干沉降可能是该时期大气氮沉降输入总量的主要贡献。

玉米大豆混作系统氮素转移特性的研究

在不同氮水平土壤上用１５Ｎ同位素稀释法对玉米大豆混作系统氮素转移特性进行了研究。结果表明，低氮和高氮土壤上均发生了固氮产物的转移。低氮土壤混作玉米从大豆固氮产物中获得１４．９４％～２６．９６％的氮，在高氮土壤上仅获得２．５６％～２１．１３％的氮；混作大豆固氮率的提高率，低氮土壤为—１０．３６％～—２１．１４％，高氮土壤为２９．１０％～３２．６９％；混作玉米和混作大豆的植株含氮量，在低氮土壤中均比单作降低，而在高氮土壤上则有不同程度的提高。玉米大豆混作系统在低氮土壤上主要消耗土壤速效氮，在高氮土壤上主要消耗土壤全氮。

土壤硝化和反硝化作用研究方法进展

综述了近年来土壤中硝化、反硝化作用的主要研究方法,如乙炔抑制法1、5N库稀释法、气体分压方法等,并分析了这些方法的优缺点和适用性。

施氏假单胞菌在玉米根际的固氮效率和促生效果研究

非豆科植物根际联合固氮作用广泛存在于水稻、玉米等根际,在农作物节肥增产方面具有巨大的应用潜力。施氏假单胞菌A1501是一株分离自水稻根际的模式联合固氮菌,接种该菌对水稻和玉米均具有良好的促生效果。为了进一步研究根际固氮与促生效果的关系,利用突变型泌铵固氮菌株(1568/pVA3)和转基因氮高效利用玉米品系共同构建高效固氮体系,并在温室条件下进行促生及生物固氮量评价。播种60 d后对玉米生长量和微生物固氮量进行分析,结果表明:固氮施氏假单胞菌接种后氮高效利用和对照玉米品系的地上和地下部生物量都显著高于不接种对照,但是固氮菌接种对氮高效利用玉米和对照玉米的总生物量没有显著影响。氮高效利用玉米接种1568/pVA3菌株后,植株生物量较施肥处理提高25.5%,全氮含量较不接种对照增加39%,15N同位素稀释法测定生物固氮量为0.8 g·株^(-1);接种野生型后植株生物量较施肥处理提高24.8%,生物固氮量为0.64 g·株^(-1)。研究结果表明,通过将固氮菌尤其是泌铵工程菌与氮高效利用玉米建立联合固氮体系可以显著提高根际固氮量和植株生物量,据估算每公顷可节省化肥约23%,而对照体系为7.5%。