紫花苜蓿高效共生固氮根瘤菌的筛选

通过8株固氮根瘤菌筛选紫花苜蓿（Medicago？sativa）的高效共生固氮根瘤菌.研究结果显示,8株根瘤菌的接种效果存在明显的差异;在接种之后的干草重、根瘤数与对照相比分别各增加3.82%～26.33%、3%～41.33%;筛选出与紫花苜蓿最佳的共生匹配的固氮根瘤菌ACCC05,该固氮根瘤菌菌株能够显著的增强其固氮效果,提高草产量选择该固氮菌具一定生产与应用的价值.

大豆根瘤菌包衣减氮试验

大豆根瘤菌基本情况,同时进行大豆根瘤菌包衣减氮试验,采用大区试验方式,试验设2个处理。处理1:大豆养分专家决策系统推荐用量,不包衣根瘤菌;处理2:根瘤菌包衣减氮。试验调查:根瘤干重调查、考种,测产。小区两侧各去除两个边行后全区收获脱粒称重,不包衣根瘤菌的折亩产199.4 kg,根瘤菌包衣减氮的折亩产248.1 kg,亩增产48.7 kg,增长24.4%。试验阐述了大豆根瘤菌包衣减氮的意义。

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.

Effects of Different Nitrogen Application Rates and Methods on Root Nodule Growth and Yield of Soybean

This study was conducted wiffl a spring soybean variety Jindou 19 to test file effects of rhizobia inoculation or non-inoculation and nitrogen application rates at 0, 27, 54 and 75 kg/hm^2 （N1-4） on root nodule dry weight, root nodule number, yield and yield components of soybean. The results showed that the nitrogen fertilizer significantly affected soybean root noduce and soybean yield, the dry weight and number of root nodules increased gradually with the increase of nitrogen application rate, and the yield of file rhizobia inoculated treatment was significantly higher than that of file rhizobia non-inoculated treatment; and under file condition of file rhizobia inoculation, with nitrogen application amount at 75 kg/hm^2, file Jindou 19 performed a better nitrogen fixing effect in file growing stage, and its plot yield was 4 997.417 kg/hm^2, 4.06% higher than that of file treatment without inoculating rhizobium and 12.50% higher than that of the treatment without applying nitrogen fertilizer.

Formation of Nodular Structures and Nitrogen Fixation by Rhizobia on Oilseed Rape Roots Following Treatment with Pectinolytic Bacteria

Nodular structures were formed by rhizobia on oilseed rape roots following treatment with pectinolytic bacteria. Nodules developed within 50 days.Photomicrograph of nodule cells showed that the capsulated bacteria were intrarellular.Rhizobia reisolated from the root nodules retained not only the ability of nodulation but also the characteristic of resistance to 100 μg neomycin mL-1.A low nitrogenaSe activity of the nodules was determined by the method of acetylene reduction.

Responses of Nitrogen Metabolism to Rhizobium Inoculation in Abrus mollis Hance

In different periods, the contents of nitrogen, ammonia nitrogen and nitrate nitrogen in different parts of Abrus mollis Hance were determined for each period by nesslerization, ninhydrin method and salicylic acid method in pot experiment. By using related data statistical software, the effects of Rhizobium inoculation on nitrogen metabolism, accumulation and distribution in Abrus mollis Hance were analyzed preliminarily.

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.

Reductive dechlorination of polychlorinated biphenyls is coupled to nitrogen fixation by a legume-rhizobium symbiosis

Chlorinated persistent organic pollutants, including polychlorinated biphenyls （PCBs）, represent a particularly serious environmental problem and human health risk worldwide. Leguminous plants and their symbiotic bacteria （rhizobia） are important components of the biogeochemical cycling of nitrogen in both agricultural and natural ecosystems. However, there have been relatively few detailed studies of the remediation of PCB-contaminated soils by legume-rhizobia symbionts. Here we report for the first time evidence of the reductive dechlorination of 2,4,4＇-trichlorobiphenyl （PCB 28） by an alfalfa-rhizobium nitrogen fixing symbiont. Alfalfa （Medicago sativa L.） inoculated with wild-type Sinorhizobiurn meliloti had significantly larger biomass and PCB 28 accumulation than alfalfa inoculated with the nitrogenase negative mutant rhizobium SmY. Dechlorination products of PCB 28, 2,4＇-dichlorobiphenyl （PCB 8）, and the emission of chloride ion （C1-） were also found to decrease significantly in the ineffective nodules infected by the mutant strain SmY. We therefore hypothesize that N2-fixation by the legume-rhizobium symbiont is coupled with the reductive dechlorination of PCBs within the nodules. The combination of these two processes is of great importance to the biogeochemical cycling and bioremediation of organochlorine pollutants in terrestrial ecosystems.