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The paper presents the influence of bacterial inoculation of perennial legumes (alfalfa, bird's-foot trefoil) in pure culture and cultivated in association with perennial gramineae on fodder yield, fodder quality, and atmospheric nitrogen-fixing ability. Results point out an increase of 10-12% of the yield of dry matter in the variants inoculated. Bacterial inoculation with specific bacterial stems (Sinorhizobium meliloti and Mezorhizobium loti) has a positive influence on fodder quality too, materialised in the raw protein content and the amount of nitrogen fixed biologically. [ABSTRACT FROM AUTHOR]

The present agricultural crop structure is dominated by grains (48%) and by technical plants (21%), detrimental to legumes that share only 11% of the cultivated arable area on Earth. If the area cultivated with legumes doubled, the necessary nitrogen fertilisers would reduce with 50% and production costs would reduce with 30%. The increase of areas cultivated with legumes would also balance the protein balance due to a larger amount of vegetal protein. The present paper points out the impact of nitrogen fertilisation on the nodulation capacity and on atmospheric nitrogen fixation in fodder peas (Pisum arvense L.). Research in the field of nitrogen fixation has pointed out the complexity of the impact of environmental nitrogen taken over by the plants on atmospheric nitrogen fixation. Legumes use nitrogen under nitric form (NO3-), as a result of the oxidation of ammonium nitrogen (NH4+) from the mineral fertilisers of from organic nitrogen. These two sources of nitrogen used by the plants (NO3- and fixed N2) are strongly dependent on the plant species, on the bacterial pool and on the environmental factors. Literature presents a consolidated scientific opinion concerning the impact of mineral nitrogen on biological nitrogen fixation: an increase of the concentration of nitrate or ammonium correlates with a decrease of the legume nodulation activity (DAVIDSON and ROBSON, 1986; EAGLESHAM, 1989). Following this work resulted in the following conclusions:Research in the field of nitrogen fixation points out the complexity of the impact of the nitrogen taken over by the plants from the environment on atmospheric nitrogen fixation. Legumes use nitrogen under nitric form (NO3-) as a result of the oxidation of ammonium nitrogen (NH4+) from mineral fertilisers or from organic nitrogen. Nitrogen fertilisation also impact TN and RP plant content. Daily nitrogen fixation decreases from 0.60 mg/plant/day in the control variant to 0.05 mg/plant/day in the variant treated with N100, while the nitrogen fixation rate in relation to dry matter varies between 14.57 mg/g DM and 1.79 mg/g DM in the variant fertilised with N100. [ABSTRACT FROM AUTHOR]

In any agricultural system based on legumes, nitrogen balance should take into account the flow of N2 by legume species. In this flow, the amount of N2 fixed by legumes is considered a reserve amount of nitrogen which, through harvesting, is removed from the nitrogen balance. The aim of the present paper is to assess the amount of nitrogen fixed biologically (NFB) in some legume species sowed in association and of the share of this amount of NFB of the total amount of nitrogen from the productions obtained. Thus, in the fodder system made up of Italian ryegrass + red clover cultivated for two years, the amount of NFB in the first year was 60 kg/ha. If we relate the amount of NFB to the amount of nitrogen exported through the fodder biomass, we see that the share of NFB varies between 22 and 42%. [ABSTRACT FROM AUTHOR]

The determination of the colonization capacity with permanent nitrogen fixating bacteria has been achieved indirectly through the method of using soil extracts, taken from the rhizosphere of leguminous species existing in the 4 types of permanent grasslands, located on different altitudinal levels (90m, 330m, 900m, 1800m). Treatments with soil extracts taken have been made at three species of legumes (Lotus corniculatus, Trifolium repens, Trifolium pratense), seeded on a sown perlite layer and grown in the growth chamber. Between the total amount of nodosities formed and the altitude of grasslands there is a negative correlation. At treatments with extracts taken from grasslands situated between 90-330m, there has been observed the highest number of nodosities formed on roots of tested leguminous species. [ABSTRACT FROM AUTHOR]

Applying nitrogen fertilisers in legume species has been subjected to scientific research due to the efficacy of these fertilisers on yield (symbiotic atmospheric nitrogen fixation). In general, applying high rates of nitrogen fertilisers on legume species does not correlate directly with green matter production because these species take the necessary nitrogen from the atmosphere. This feature is specific also to bird's-foot-trefoil, which fixes important amounts of atmospheric nitrogen during vegetation. This paper presents the impact of the interaction between organic and mineral fertilisers on bird's-foot-trefoil within a bifactorial experiment. Differences in yield at both unilateral effect of the factors and at that of the interaction of the factors are statistically ensured. [ABSTRACT FROM AUTHOR]

Researches in the field of nitrogen fixation have pointed out the complexity of the impact the nitrogen taken over by the plants from the environment has on the activity of atmospheric nitrogen fixation. Literature considers that an increase of the concentration of nitrate (NO3-) or ammonia (NH4+) in the soil results in a dramatic decrease of the nodosity-formation activity in legume species The paper presents the effect of nitrogen rate application in alfalfa on nodosity-formation capacity, such as pointed out through such features of nodosities as number, weight, and nodular index. [ABSTRACT FROM AUTHOR]

Symbiosis relationships among legumes and nitrogen fixing bacteria play a crucial role in agriculture since they provide the opportunity of converting atmospheric molecular nitrogen into an ammonia form of nitrogen that the plants can use in protein formation. To enhance this process we have selected nitrogen fixing bacterial strains commercialised under different forms depending on the cultivation technologies in legume species. In our research, we have pointed out the efficacy of in situ isolated nitrogen fixing bacteria in alfalfa in two ways: rhizobia taken directly from the nodosities on the alfalfa roots and rhizobia taken from the alfalfa root system. [ABSTRACT FROM AUTHOR]