Nitrogen fixation

About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.

Effects of Temperature, Nitrogen Fertilization, and Plant Age on Nitrogen Fixation by Setaria italica Inoculated with Azospirillum brasilense (strain cd)

Abstract: The association between the nitrogen-fixing bacterium Azospirillum brasilense (strain cd) and the grass Setaria italica was studied under different environmental and soil conditions. Highest acetylene reduction rates in intact plants were observed at the booting stage of Setaria (2350 nmol ethylene produced hour−1 plant−1) at 27 C. Higher temperatures, up to 32 C, enhanced ethylene reduction. Significant increases in shoot dry weight, panicle weight, and length were obtained in inoculated plants fertilized with suboptimal NH4NO3 levels. The increase in nitrogen content of plants inoculated with A. brasilense was shown to be due to N2 fixation. This was demonstrated by growing plants in washed quartz sand with no combined nitrogen. The bacteria also increased branching and development of roots. It was concluded that inoculation of Setaria with A. brasilense may lead both to increases in plant yield and saving of nitrogen fertilizer.

Nitrogen metabolism in lakes i. measurement of nitrogen fixation with n151

Abstract: A method for measuring the rates of nitrogen fixation in samples of lake water using N15 as a tracer is described, and a detailed description of glassware required is provided. The nitrogen present in the water is removed by flushing with Hc-O mixture and then replaced by the labeled nitrogen. After incubation and treatment, the isotope ratio in the organic material is determined on a mass spectrometer. Analyses of lake water and (NH4) SO4 as isotope ratio blanks are described and a resume of statistical data from these analyses is presented.

Biomass increase and associative nitrogen fixation of mycorrhizal Pinus contorta seedlings inoculated with a plant growth promoting Bacillus strain.

Abstract: One-month-old Pinus contorta Dougl. seedlings were inoculated with mycorrhizal fungi (Wilcoxina mikolae isolate R947), plant growth promoting bacteria capable of fixing nitrogen (Bacillus strain L6...

Improving nitrogen-fixing systems and integrating them into sustainable rice farming

Abstract: This paper summarizes recent achievements in exploiting new biological nitrogen fixation (BNF) systems in rice fields, improving their management, and integrating them into rice farming systems. The inoculation of cyanobacteria has been long recommended, but its effect is erratic and unpredictable. Azolla has a long history of use as a green manure, but a number of biological constraints limited its use in tropical Asia. To overcome these constraints, the Azolla-Anabaena system as well as the growing methods were improved. Hybrids between A. microphylla and A. filiculoides (male) produced higher annual biomass than either parent. When Anabaena from high temperature-tolerant A. microphylla was transferred to Anabaena-free A. filiculoides, A. filiculoides became tolerant of high temperature. Azolla can have multiple purposes in addition to being a N source. An integrated Azolla-fish-rice system developed in Fujian, China, could increase farmers' income, reduce expenses, and increase ecological stability. A study using Azolla labeled with 15N showed the reduction of N losses by fish uptake of N. The Azolla mat could also reduce losses of urea N by lowering floodwater-pH and storing a part of applied N in Azolla. Agronomically useful aquatic legumes have been explored within Sesbania and Aeschynomene. S. rostrata can accumulate more than 100kg N ha-1 in 45 d. Its N2 fixation by stem nodules is more tolerant of mineral N than that by root nodules, but the flowering of S. rostrata is sensitive to photoperiod. Aquatic legumes can be used in rainfed rice fields as N scavengers and N2 fixers. The general principle of integrated uses of BNF in rice-farming systems is shown.

Nitrogen Fixation by Native Australian Legumes

Abstract: Nitrogen fixation was studied by the acetylene-reduction technique in root nodules of 10 native Australian legumes in three habitats in Victoria: low open-forest. sandy heathland and coastal sand dunes. Nodular activity reached a maximum in spring (and in autumn in sand-dune species), declined to a minimum in late summer and continued at a low level throughout winter. Mean nitrogenase activity was 1.73 μmol C2H2 reduced g-1 fresh wt nodules h-1, with spring maxima 8-250 times summer minima. It is suggested that variations in rainfall and temperature were the major factors influencing seasonal variations in nodular activity. Estiniates of minimum acetylene reduction per hectare per year were derived from measurements of seasonal and diurnal variations in acetylene reduction and abundance of nodules per hectare, and were used to derive approximate minimum values for nitrogen fixation of 0.004-0.746 kg ha-1 yr-1. The quantities of nitrogen fixed are compared with other reports and the significance of nitrogen fixation by these native legumes is discussed.