Non-symbiotic Nitrogen Fixation Research Articles

Relative rates of denitrification and non-symbiotic nitrogen fixation in the soil-plant system

Potential N 2 fixation was measured in sealed growth chambers by using the C 2H 2 reduction method. Ethylene production was measured over a wide range of soil-plant conditions which were similar to previous denitrification experiments. The rate of N 2 fixation was from 1 to 10 per cent of the rate of denitrification as N 2 evolved over a 40 day period. These variations depended upon the soil type, soil organic matter content and soil water content. Increasing clay, soil organic carbon and water contents favoured N 2 fixation and evolution. In the presence of plants greater amounts of N 2 were evolved but the effect of plant growth on N 2 fixation was inconsistent.

Non-symbiotic nitrogen fixation in the rhizospheres of rice, maize and different tropical grasses

Nitrogenase activity estimated in the rhizospheres of rice, maize and different tropical grasses grown under controlled laboratory conditions was shown to depend upon plant species. High nitrogenase activity (2000–6000 nmoles C 2H 4 h −1 g −1 dry root) occurred in rice rhizosphere, this activity being only 10 times lower than that of symbiotic systems; in the rhizosphere of many other grasses grown in a similar way nitrogenase activity was as low as 10 nmoles C 2H 4 h −1 g −1 dry root. The influence of soil type on nitrogenase activity was impressive; but the exact nature of the factors implicated could not be established. A rather weak flush of nitrogenase activity in the rhizosphere occurred in the early stage of the plant growth; it was probably due to the exudation of compounds from the seed and lasted 2 or 4 days according to the size of the seed. When the plant entered into its intense photosynthetic phase, the nitrogenase activity gradually increased. When the shoots were severed, nitrogenase activity in the rhizosphere ceased. Nitrogenase activity in the rhizosphere responded greatly to light intensity. Extrapolation of these laboratory findings to the field is discussed.

An assessment of non-symbiotic nitrogen fixation in some Nigerian soils by the acetylene reduction technique

Short-term incubation studies of non-symbiotic nitrogen fixation using acetylene as the substrate for nitrogenase were carried out on six soil samples collected from various locations in the Western State of Nigeria, and on one soil sample collected from Wisconsin, U.S.A. Unamended soils reduced a very small amount of acetylene but with added organic materials (5% organic matter, 2% glucose or sucrose) acetylene reduction became substantial and in one case was more than 30,000 times that in the unamended soil. In general, more acetylene was reduced in anaerobic than in aerobic soils. Two of the soils were tested for suppression of acetylene reduction by NH 4 +-N. With the addition of up to 100 ppm nitrogen as (NH 4) 2SO 4 to the soils incubated with sucrose, no depression of acetylene reduction was observed in one soil while it was reduced by about half in the other.

Non-symbiotic nitrogen fixing bacteria in tropical soils

Several aspects of heterotrophic, free-living nitrogen-fixing bacteria specific to tropical environments are presented. WhileAzotobacter chroococcum andA. vinelandii seem to occur throughout the world,A. paspali, Derxia gummosa andBeijerinckia spp. have been found mainly in the tropics. Derxia occurred more frequently than previously supposed and was stimulated by moist soil conditions, particularly after flooding.A. paspali growth in soil even under experimental conditions, was strictly limited to the rhizosphere of a few varieties ofPaspalum notatum and the association took almost a year to become established.

Nitrogen fixation in latosolic soil under grass

Four latosolic soils, varying in total nitrogen content from 0.050 to 0.098 per cent and in organic matter from 0.95 to 1.56 per cent, were collected from the farm of University College, Ibadan, Nigeria. No change in nitrogen content was observed when the soils were kept moist in the greenhouse for four months. Where a legume (Centrosema pubescens) was grown gains of nitrogen in the soil—plant system equivalent to from 100 to 200 pounds nitrogen per acre — 6 inches deep were obtained. Where a grass (Eleusine coracana) was grown gains of nitrogen in the soil—plant system equivalent to from 100 to 130 lb. nitrogen per acre — 6 inches deep occurred in the two soils with low initial nitrogen levels. The possible origin of this nitrogen accretion is discussed. The data support, but do not prove, the hypothesis that it is due to non-symbiotic fixation in the soil. In one of the soils showing a significant nitrogen gain under grass the presence of Azotobacter was not demonstrated and Beijerinckia occurred in only one of 24 samples examined. Thus, if non-symbiotic biological nitrogen fixation did occur, Clostridium and other micro-organisms not belonging to the Azotobacteriaceae must have been the agents of fixation involved. On the other hand, the presence of Azotobacter in the two soils in which no fixation occurred could easily be demonstrated. It is suggested that non-symbiotic nitrogen fixation by soil micro-organisms under grass cover in the humid tropics may be of greater significance than has been believed in the past.

The Savanna Concept in Oklahoma

of plantations of red pine, Pinus resinosa Ait., which within 32 years had attained on exposed substrata of coarse glacial outwash an average height of 35 feet and yielded 1,280 cu ft or 17 cords per acre. This performance is fully comparable to that observed in northern Wisconsin on undisturbed, well-drained sandy soils. The rapid growth of trees and the enrichment of the surface layer of scalped soils in nutrients revealed a high capacity of mycotrophic organs of red pine to utilize major (P, K, Ca, Mg) and minor (B, Mn, Zn, Cu, Mo) nutrient elements from unweathered feldspathic and ferromagnesian minerals. These results indicate a need for an increase in strength of extracting solutions used in analyses of soils assigned to reforestation. Enrichment of the soil by about 80 cubic yards of organic matter per acre with subsequent 2 m.e./100 g increase in the exchange capacity of the surface layer is another important soil-ameliorating effect of red pine plantations. Accumulation of total nitrogen in excavated substrata and in the foliage of trees in the absence of legumes suggested non-symbiotic nitrogen fixation. Comparison of the growth of red pine plantations on weed-free scalped lands with growth of neighboring plantations on sod-covered sites indicated a desirability of planting trees in broad furrows at a close spacing. REFERENCES

Non-Symbiotic Nitrogen Fixation in a Soil of the Nigerian Rain-Forest Zone

COMPARATIVELY little is known of the contribution of non-symbiotic nitrogen fixation to the nitrogen economy of tropical soils. In the tropical rain-forest areas it is generally considered that the soil nitrogen supply, depleted by arable cropping, is built up again during the period of ‘bush fallow’, presumably by indigenous legumes (and perhaps certain non-legumes) present in the regrowth. That appreciable non-symbiotic nitrogen fixation may occur in the soils of this area was shown in the experiment described here.

The Influence of Fertilizers and Season on Nonsymbiotic Nitrogen Fixation in Brookston and Bedford Silt Loams1

The Influence of Fertilizers and Season on Nonsymbiotic Nitrogen Fixation in Brookston and Bedford Silt Loams¹

Nonsymbiotic Nitrogen Fixation in Soils of a Semi‐Arid Region of North China1

Agronomy JournalVolume 33, Issue 11 p. 980-992 Article Nonsymbiotic Nitrogen Fixation in Soils of a Semi-Arid Region of North China1 Raymond T. Moyer, Raymond T. Moyer Acknowledgernent is made of assistance given by Dr. J. A. Bizzell, at whose suggestion and under whose direction this work was undertaken; and by Dr. J. K. Wilson, who helped in planning the laboratory experiments reported. Indebtedness is likewise expressed to the National Agricultural Research Bureau, Chungking, China, for permission to quote the results of seven of the fertilizer experiments shown in Table 1 which were carried out under a cooperative arrangement with that body.Search for more papers by this author Raymond T. Moyer, Raymond T. Moyer Acknowledgernent is made of assistance given by Dr. J. A. Bizzell, at whose suggestion and under whose direction this work was undertaken; and by Dr. J. K. Wilson, who helped in planning the laboratory experiments reported. Indebtedness is likewise expressed to the National Agricultural Research Bureau, Chungking, China, for permission to quote the results of seven of the fertilizer experiments shown in Table 1 which were carried out under a cooperative arrangement with that body.Search for more papers by this author First published: 01 November 1941 https://doi.org/10.2134/agronj1941.00021962003300110003xCitations: 1 1 From a thesis submitted to the Faculty of the Graduate School of Cornell University for the degree of doctor of philosophy. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume33, Issue11November 1941Pages 980-992 RelatedInformation