贵州固氮蓝藻室内培养及固氮力研究

为初步筛选出适合贵州气候特点的具有较高生物量和固氮力的蓝藻品系 ,以中国淡水藻种库 (CCCFA)引进的鱼腥藻 112、118、10 17、110 5、10 4 2、HB13和中华植生藻 80 0 ,采用室内继代培养后制成的混合藻种A、B ,经改进后的水生 111无氮培养基 ,通过室内开放式通气培养和静置培养 ,测定不同水深条件下的生长率、固氮力。结果表明 ,固氮蓝藻的生长能改变环境 pH值 ,使之适应藻种的生长 ;水深条件 >10cm有利于提高鲜藻产量 ;固氮蓝藻A组固氮力为 72 15kg·hm- 2 ·a- 1,外泄氮素为 4 72kg·hm- 2 ·a- 1,B组固氮力为 7577kg·hm- 2 ·a- 1,外泄氮素为 4 96kg·hm- 2 ·a- 1。

种植年限对紫花苜蓿人工草地土壤碳、氮含量及根际土壤固氮力的影响

采用田间调查取样和室内分析相结合的方法,以1年生、2年生、3年生、4年生、6年生紫花苜蓿人工草地为研究对象,研究了种植年限对土壤碳、氮含量及根际土壤固氮力的影响。结果表明:随着种植年限的增加紫花苜蓿地土壤有机质、胡敏酸、富里酸、全氮、碱解氮均表现为增加,且种植年限越长增加越明显;根际土壤固氮力以3年生紫花苜蓿地最高(6.79×10-8gg-1(24h)-1),4年生与3年生差异不显著,但二者均与其它年限间根际土壤固氮力差异达到极显著水平。

长白山豆科植物的生态习性、分布、区系分析及其共生固氮能力的调查研究

通过作者的调查研究和总结,基本搞清了长白山豆科植物的种类,并在本文内加以阐述,共计22属48种1变种3变型(不包括栽培的,见表1)。同时本文还阐述了每种植物的生态习性、垂直分布和地理分布情况(表1)并加以比较和讨论。对于区系组成也着重进行了分析,其结果说明,长白山的豆科植物区系,在其区系发生上与日本具有极为密切的关系,与亚寒带的关系也比较密切,在它的系统发生的分布历史上是较为古老和久远的。对于长白山豆科植物的固氮能力,作者在海拔500—2600米的各个垂直分布带内,一共采集测试了14属27种植物,结果表明,每种植物均表现出一定的固氮活性(表2),并可看出种间固氮活性的差异。一个非常有意义的结果是有5个种固氮活性显著较高,它们是:苜蓿、米口袋、东北山黧豆、短萼鸡眼草和草木犀;还有4个种固氮活性也明显高于其余各种,此即是黄耆、大叶野豌豆、广布野豌豆和山黧豆。可以看出,这些植物在其根瘤菌资源的开发利用上是很有前途而值得今后予以充分注意与深入研究的。

Estimation of Biological Nitrogen Fixation Capacity by Sugarcane Using 15N

[ Objective] The study aimed to reveal the biological nitrogen fixation capacity by sugarcane from Brazil under the ecological conditions of Guangxi, and to provide reference for study on the biological nitrogen fixation capacity by sugarcane and related generalization and application. [ Method] The ^15N isotopic fertilizer was solely applied on plants of three sugarcane cultivars planted in greenhouse with no other fertilizer forms applied, meanwhile virus-free stem seedling was regarded as control, to measure their biological nitrogen fixation capacity using ^15N isotope. [ Result ] The nitrogen fixation rate of B8 from Brazil reached 26.91%, while Guitang 11 and RIC16 presented no or poor nitrogen fixation capacity. [ Conclusion] The sugarcane eultivar B8 from Brazil showed some nitrogen fixation capacity under the ecological conditions of Guangxi.

Effects of N,P and K Fertilizers on Growth of Clover Nitrogen-fixing Rhizobia and Soil Fertility after Plantation

In order to develop organic rice and increase paddy soil fertility by cloverorganic rice rotation, the effects of N, P and K fertilizers on growth of clover nitrogen-fixing rhizobia and soil fertility after plantation were investigated, thereby providing certain reference for reasonable cultivation of clover and improvement of soil fertility. A two-year experiment was conducted from 2012 to 2013. The clover was cultivated after rice every year, and different levels of N, P and K fertilizers were applied before winter. In the treatment group, no fertilizer was applied. The effects of different fertilizers and different application amounts on clover yield, nitrogen-fixing rhizobia quantity, nitrogen-fixing rhizobia weight and soil fertility after plantation were analyzed. The results showed that the application of N, P and K fertilizers in the early stage had significantly effect on the growth of clover. When the application amount of N fertilizer was 75 kg/hm^2（N 46%）, the clover yield, nitrogen-fixing rhizobia quantity and nitrogen-fixing rhizobia weight were highest. The soil nitrogen content after plantation increased with the increase of the application amount of N fertilizer, while the P and K content decreased and then increased with the increased application amounts. Soil available P content increased with the increased application amounts of N and P fertilizers, but it did not change significantly with the increased application amount of K fertilizer. Soil available K content increased first and then decreased with the increased application amounts of N and P fertilizers.When the application amounts of N and P fertilizers were 150（N 46%） and 300（P_2O_5 12%） kg/hm^2, soil available K content reached the maximum. Soil organic matter content increased with the increased application amounts of N, P and K fertilizers. Therefore, in the cultivation of clover, appropriate application of N, P and K fertilizers in the early stage can improve clover yield and soil fertility.

Effect of nitrogen on microstructure and mechanical properties of Cr Mn Fe VTi6 high entropy alloy

In order to evaluate interstitial strengthening effect on the properties of high entropy alloy(HEA),a nitrogen-doped Cr Mn Fe VTi6 HEA was fabricated by mechanical alloying(MA)and spark plasma sintering(SPS).XRD,SEM,TEM and FIB were used to characterize the phase composition and microstructure of this material.The sintered bulk HEA exhibits a microstructure comprising TiNx,BCC,Laves and B2 phases.The HEA exhibits high yield strength(>2729 MPa)and hardness in lower temperature range of<380℃.Quantitative calculations of the contributions from each strengthening mechanism in the BCC phase indicate that the interstitial strengthening by nitrogen is the dominant mechanism.Nitrogen additions in the BCC phase can produce a yield strength increase of-634 MPa/at.%,which is much higher than the strengthening effects of carbon or boron additions in other alloys.This demonstrates that adding nitrogen is a viable approach for enhancing the strength of HEAs.

Ability of Non Symbiotic Nitrogen-Fixing Bacteria Isolated from Coffee Plant Rhizosphere and Their Effects on Robusta Coffee Seedlings

Nitrogen is one of the most needed elements by coffee plants. Utilization of biological nitrogen fixation by non symbiotic bacteria offers alternative to reduce the N fertilizer usage. This study was focused to obtain aerobic non symbiotic nitrogen-fixing bacteria from coffee rhizosphere. The application of those bacteria was expected to enhance coffee seedling growth. Sixty four aerobic nitrogen-fixing bacterial isolates were isolated from coffee plants rhizosphere from Jember, East Java using several nitrogen free medium, such as Ashby, malate acid, and fahreus agar. The nitrogen fixation ability of the isolates was determined by measuring their ability in pellicle formation on semi solid medium and ammonium excretion on growth medium. Ab Kws.l, Asm E6s.3.a, Asm Bsl.1, and Asm E6s were the isolates which showed the best performance on nitrogen fixation with excreted ammonium concentration ranged from 129.6 up to 239.8 pM/mg dry weight cell. Acetylene reduction assay was used to detect nitrogenase activity. Ab Kws.1 was the isolate which had the highest nitrogenase activity （7.4 mmol N2 fixed/gram dry weight cell/hour）. Inoculation of the four best isolates onto Robusta coffee seedling positively enhanced the seedling growth in this green house experiment. Based on the results of Becton Dickinson＇s （BD） PhoenixTM Automated Microbiology System biochemical tests, Asm Bls.l isolates has similarities with Achromobacter sp., Asm E6s.l and Asm E6s.3.a had similarities with Stenotrophomonas maltophilia, while Ab Kws. 1 had similarities with Leifsonia aquatica.

Efficiency of Biological Nitrogen Fixation of Bradyrhizobium under Different Soil Fertility Levels as Measured by 15N Dilution Analysis

The objective of this study was to determine the efficiency of biological nitrogen fixation （BNF） of local Bradyrhizobium isolates in soil of various fertility levels using 15N dilution technique. Local isolates were obtained from cowpea rhizosphere in fields of different Iraqi provinces. Six isolates were selected in this study, which was conducted as a pot experiment under greenhouse conditions. Effects of the following fertility levels were evaluated： at F1, 0 mg N, P and K was added; at F2, 25 mg N/kg soil, 10 mg P/kg soil and 25 mg K/kg soil were added, respectively; the other two levels were F3 at which 50, 20 and 50 mg/kg soil and at F4 75, 30 and 75 mg/kg soil for N, P and K, respectively, were added. Urea, labeled with 15N 10% access atom （aa）, was used as a source of N. The highest BNF was observed under the lowest fertility level, i.e., F1. BNF across all isolates was markedly decreased with the increase of nutrient application to soil, being totally eliminated at the highest fertility level F4. Numbers of nodules per plant root of all isolates were the least under the zero nutrients application and the highest nodules number were found under the highest levels of N, P and K application. Number of nodules does not necessarily reflect the best BNF efficiency of all isolates. However, fertility levels were of significant effect on average nodule number of all isolates. The lowest plant dry weight was under the first fertility level F1 irrelevant of Rhizobium isolates. In general, the highest plant dry weight was under the second soil fertility level F2.