The natural abundance of 15N in an irrigated soybean crop and its use for the calculation of nitrogen fixation

1985 ◽  
Vol 36 (3) ◽  
pp. 411 ◽  
Author(s):  
FJ Bergersen ◽  
GL Turner ◽  
RR Gault ◽  
DL Chase ◽  
J Brockwell
Keyword(s):  
Soil Nitrogen ◽  
N2 Fixation ◽  
Plant Size ◽  
Natural Abundance ◽  
Available Nitrogen ◽  
Plant Nitrogen ◽  
Residual Nitrogen ◽  
Stages Of Growth ◽  
Plant Available Nitrogen ◽  
Grain Nitrogen

In a field experiment at Leeton, N.S.W., Chaffey soybeans were grown with irrigation at various plant spacings and with various inoc~ilation treatments and two pre-planting soil treatments. Uninoculated plants were almost completely non-nodulated. Measurements of the natural abundance of 15N (S15N) in the total nitrogen of the plants were made at all stages of growth and in the grain at harvest. The 6lSN in all nodulated treatments declined progressively with time in comparison with un-nodulated plants, due to the incorporation of atmospheric N2 of lower 15N concentration than the soil nitrogen. This enabled calculation of the proportions of plant-nitrogen obtained from the soil and by symbiotic N2-fixation. The main findings were as follows: There was a gradient of S15N in plant-available nitrogen across the experimental area. Therefore, treatments were compared by using the nearest non-nodulated plot for the estimate of S15N in plantavailable soil nitrogen. Despite large differences in plant size due to plant spacing, S15N in mature nonnodulated plants did not differ significantly, indicating that the natural abundance of 15N in plantavailable soil nitrogen was uniform in root zones of different sizes. In well-nodulated plants, the proportion (p) of shoot nitrogen derived from N2-fixation increased with time, reaching approximately 70% and 90% in previously fallowed and previously cropped soil respectively, during a period of rapid growth between 78 and 98 d& after planting. The fixed N, in the best-nodulated treatments at (114 days) was 143 and 244 kg N ha-1 respectively for previously fallowed and previously cropped soil. There were consistent trends for increased N2 fixation with increased inoculation rates. In non-nodulated plants, nitrogen recovered in the grain represented most of that present in the shoots at maturity. In well-nodulated treatments, grain nitrogen, although similar in S15N to that of shoots + fruits, represented only 47 and 59% of the 406 and 348 kg N ha-1 present at maturity in shoots + fruits from previously fallowed and previously cropped soils respectively. After harvesting more than 3 t ha-1 of grain, the nitrogen balance in the previously cropped soil, if all of the residual nitrogen in the soybeans could have been retained in the soil, was positive. In the previously fallowed soil there could have been a net depletion of soil nitrogen.

Effects of available soil N and rates of inoculation on nitrogen fixation by irrigated soybeans and evaluation of δ15N methods for measurement

1989 ◽  
Vol 40 (4) ◽  
pp. 763 ◽  
Author(s):  
FJ Bergersen ◽  
J Brockwell ◽  
RR Gault ◽  
L Morthorpe ◽  
MB Peoples ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Soil Nitrogen ◽  
N2 Fixation ◽  
Xylem Sap ◽  
Available Nitrogen ◽  
Soil C ◽  
Plant Nitrogen ◽  
Winter Cereals ◽  
Wide Range ◽  
High Yields

Nitrogen fixation by irrigated soybeans (Glycine max (L.) Merr. cv. Forrest) was studied in a field experiment on a grey clay soil at Trangie, N.S.W. during the summer of 1985-86. Cropping with oats during the previous winter diminished the concentration of plant-available nitrogen in the soil from 37.6 to 18.5 mg N kg-1 and induced differences in the natural abundance of 15N (S15N) in this nitrogen. Four rates of liquid inoculation with Bradyrhizobium japonicum strain CB 1809, interacted with soil nitrogen to produce a wide range of nodulation of the soybeans. The following main effects on growth and N2 fixation resulted: (a) Initially, growth and accumulation of plant nitrogen was lower in pre-cropped than in prefallowed soil but N2 fixation was higher. (b) Nitrogen fixation during seed development was high in pre-cropped soil and greatest at the highest rate of inoculation. It resulted in high yields of seed (3.5 t ha-1 with 100 times the normal inoculation) with significantly higher concentration of seed nitrogen than from plants grown in prefallowed soil. (c) With increasing rates of inoculation on the pre-fallowed soil, more uniform nodulation was associated with smaller variances in most of the parameters studied. Other findings included further validation of the S15N method of calculating the proportion (p) of plant nitrogen derived from N2 fixation, with good agreement between treatment effects based on such estimates and those based on the relative concentrations of ureides in vacuum-extracted xylem sap. The values of p from S15N measurements on shoot nitrogen were affected little by inclusion of root nitrogen, and similar values were obtained when uninoculated, unnodulated Forrest soybeans, a nonnodulating genotype (non-nod Clark 63) or extractable mineral nitrogen of soil were used to estimate the S15N of plant N assimilated from soil. More dry matter (flowers, young pods and older leaves) containing more nitrogen (23-26 kg N ha-1) fell from the canopy of plants during seed maturation on pre-fallowed soil (high nitrogen) than on pre-cropped soil (13-15 kg N ha-1). Several correlations between the various quantities measured were noted and are discussed. It is concluded that growing winter cereals on land newly broken from pasture, coupled with high rates of inoculation of the following soybeans, may be a profitable way of diminishing plant-available soil nitrogen, thus maximizing the contribution of nitrogen from N2 fixation with benefits in seed yield and protein content.

Nitrogen fixation by irrigated lucerne during the first three years after establishment

1995 ◽  
Vol 46 (7) ◽  
pp. 1401 ◽  
Author(s):  
RR Gault ◽  
MB Peoples ◽  
GL Turner ◽  
DM Lilley ◽  
J Brockwell ◽  
...  
Keyword(s):  
Soil Nitrogen ◽  
N2 Fixation ◽  
Dry Matter ◽  
Growing Season ◽  
15N Natural Abundance ◽  
Natural Abundance ◽  
Dry Matter Production ◽  
Available Phosphorus ◽  
The Third ◽  
Matter Production

Nodulation, N2 fixation (estimated by 15N natural abundance methods) and dry matter production were studied in a lucerne (Medicago sativa) crop managed for hay production at Ginninderra Experiment Station, A.C .T. Measurements were taken in the year of establishment and during two subsequent growing seasons. There were three treatments: (1) no inoculation and no annual fertilizer applied, (2) initial inoculation and superphosphate applied annually, (3) no inoculation, superphosphate applied annually and ammonium sulfate periodically. Before planting and after each growth season, soil was analysed for extractable mineral nitrogen, total nitrogen and the 15N natural abundance of this nitrogen, to the depth explored by lucerne roots. Before planting, no appropriate root-nodule bacteria (Rhizobium meliloti) were detected in the soil and initially plants were nodulated only in the inoculated treatment. Thereafter nodulation increased on the other treatments. Eight months after sowing there were no differences between treatments in numbers of R. meliloti g-l soil or in nodulation. In the third growing season, almost 30 kg ha-1 (dry wt) of nodules were recovered to a depth of 25 cm. These nodules were primarily located on fine, ephemeral roots and many appeared to be renewed after cutting of the lucerne. In the year of establishment, dry matter yields (0% moisture) totalled 3 to 4 t ha-1 in three hay cuts. In succeeding years, total yields were in the range 10 to 13 t ha-1 in four or five cuts per season. Nitrogen removed in the harvested lucerne reached 340 to 410 kg N ha-lyr-l in the second and third years and between 65 and 96% of this N arose from N2 fixation, depending on the method of calculation used. Poorer dry matter production and N2 fixation in treatment 1 in the third growing season was attributed to an insufficient supply of available phosphorus. Fixed N removed in Lucerne hay from treatment 2 totalled at least 640 kg N ha-1 in the three years of the experiment. Also, there were substantial increases in soil nitrogen due to lucerne growth. Although soil compaction made the quantification difficult, at the end of the experiment it was estimated that there was at least an extra 800 kg N ha-1 in the total soil nitrogen under lucerne compared to strips of Phalaris aquatica grown between the lucerne plots. It was concluded that lucerne contributed at least the same amount of fixed nitrogen to the soil as was being removed in the harvested hay.

Isotopic Discriminations During the Accumulation of Nitrogen by Soybeans

1988 ◽  
Vol 15 (3) ◽  
pp. 407 ◽  
Author(s):  
FJ Bergersen ◽  
MB Peoples ◽  
GL Turner
Keyword(s):  
N2 Fixation ◽  
Root Nodules ◽  
Xylem Sap ◽  
Vacuum Treatment ◽  
Natural Abundance ◽  
Mineral Nutrient ◽  
Similar Time ◽  
Total N ◽  
Plant Nitrogen ◽  
Nitrate Treatment

Soybeans were grown in a glasshouse in sand-vermiculite medium supplied daily with a mineral nutrient solution essentially free of combined N or containing 5 mM nitrate of known 15N abundance. The natural abundance of 15N in parts of plants and in nitrogen remaining in the medium was determined from 15 days after planting until fruiting. In nodulated plants completely dependent on N2 fixation for growth, the δ15N of plant nitrogen was uniformly negative at 56 days (overall mean: -0.90� 0.17) after adjustment for the effect of seed nitrogen. The δ15N of root nodules increased with time (max. 9.6‰), as that of shoots declined (min. - 1.3 ‰). The δ15N of every mainstem trifoliolate leaf and of the first (unifoliolate) leaf declined from initially positive values (0.5 to 2 ‰) to about - 2‰ with similar time courses, irrespective of the time of initiation. There were no significant losses of N from the plants during growth. There were differences between the δ15N of the total N of root-bleeding xylem sap and of sap extracted by vacuum treatment of stems. These were due to differences between the proportions of ureide-N and amino-N and between the δ15N values of these components. When nodulated plants were supplied daily with 5 mM nitrate (δ15N = 7.68‰) between 21 and 35 days, N2 fixation was reduced to 63% of N assimilated but growth and accumulation of nitrogen were affected little. Following removal of nitrate, there were changes in growth which led to enhanced nodulation and N2 fixation. The δ15N of the total N of trifoliolate leaves which were initiated or expanded before or during the period of nitrate treatment remained positive; those expanded or initiated after the treatment became negative in δ15N, as in the corresponding leaves of untreated nodulated plants. The δ15N of nodules was unaffected by the nitrate treatment. In plants (non-nod. Clark '63) supplied continuously with nitrate, the δ15N of the total N of entire plants rose quickly from values for seeds, but to values significantly higher than in the nitrate. These results are discussed in relation to the effects on the use of 15N natural abundance data for estimating utilisation of atmospheric N2 by nodulated plants.

Differences in natural abundance of 15N in the extractable mineral nitrogen of cropped and fallowed surface soils

1987 ◽  
Vol 38 (1) ◽  
pp. 15 ◽  
Author(s):  
GL Turner ◽  
RR Gault ◽  
L Morthorpe ◽  
DL Chase ◽  
FJ Bergersen
Keyword(s):  
Total Nitrogen ◽  
Soil Nitrogen ◽  
Mineral Nitrogen ◽  
Natural Abundance ◽  
Mineral N ◽  
Plant Nitrogen ◽  
Red Earth ◽  
Time Courses ◽  
Soil Nitrogen Cycle ◽  
Made In

The natural abundances (S15N with reference to atmospheric N2) of the stable isotope of nitrogen (15N) in the total nitrogen and in KCl-extractable mineral nitrogen (typically 96% NO-3-N and 4% NH+4-N) were measured in the surface 10 cm of a transitional red earth at Yanco, N.S.W., and of a grey soil of heavy texture at Trangie, N.S.W. Measurements were made in Autumn (May), prior to planting crops of winter oats, at the time of harvest (October) and in December, using both cropped and continuously fallowed soils. At Trangie, additional measurements were made in September, near the beginning of rapid growth in spring. Despite differences in soil type, pH .and location, both sites showed: (i) S15N in extractable mineral nitrogen varied with time (decreasing from 18.7 to 6.0% in fallowed soil at Yanco, and increasing from 5.8 to 12.0%~ under oats at Trangie), and in cropped versus fallowed treatments (12.0 and 5.3% respectively in December at Trangie), and values were different from those of the total soil nitrogen, in which S15N remained virtually unchanged (over all times and sites, S15N = 8.2 � 0.2 at Trangie); (ii) after removal of the crop, S15N in increments of extractable mineral nitrogen were higher than in the total nitrogen of previously cropped soils, whilst in the continuously fallowed soils, S15N of extractable mineral nitrogen was lower than in the total nitrogen. In addition, at Trangie, S15N in the extractable mineral nitrogen was highest late in growth of the oat crop, and this was reflected in the values for S15N of nitrogen assimilated in the crop. Values of the S15N of plant nitrogen agreed well with the S15N of extractable mineral N when the former were determined in increments of plant N during fixed periods of growth and plotted appropriately (the mid-point between sampling times) in relation to the time courses of changes in the mineral N. These results are discussed in relation to the use of 15N natural abundance techniques for estimating nitrogen fixation by nodulated legumes and in the study of other aspects of soil nitrogen cycle processes.

EFFECT OF VARIOUS PERIODS OF SEED-DOWN TO ALFALFA AND BROMEGRASS ON SOIL NITROGEN

1971 ◽  
Vol 51 (1) ◽  
pp. 65-73 ◽  
Author(s):  
W. S. FERGUSON ◽  
B. J. GORBY
Keyword(s):  
Total Nitrogen ◽  
Soil Nitrogen ◽  
Nitrogen Loss ◽  
Nitrogen Absorption ◽  
Aerobic Incubation ◽  
Available Nitrogen ◽  
Plant Nitrogen ◽  
Acid Hydrolysate ◽  
Total Soil ◽  
Total Soil Nitrogen

Total soil nitrogen decreased substantially during the 12-year period (1954 to 1965) in a coarse-textured Chernozemic soil located at Brandon, Manitoba. The amount of nitrogen loss was related to cropping practices. The loss was 24% when the soils were continuously summerfallowed and 16% when the soil was producing alfalfa, during eight of the 12 years. Other perennial crops (bromegrass, and a mixture of bromegrass and alfalfa) had similar effects on total nitrogen to those of alfalfa. The loss of soil nitrogen was inversely proportional to the intensity of cropping during the 12-year period. The availability of soil nitrogen, as assessed for wheat production during the four-year period 1966 to 1969, was directly proportional to the intensity of cropping during 1954 to 1965, and was increased by alfalfa production. The total nitrogen absorbed by three crops of wheat was closely related to the amount of nitrate nitrogen in the soil to a depth of 122 cm at the beginning of the three years of production. It was not related to total soil nitrogen. The protein content of the grain was related to intensity of cropping and alfalfa production. The change in the amount of nitrogen in the amino acid, hexosamine, ammonia, and unidentified fractions of an acid hydrolysate of these soils was proportional to the change in total soil nitrogen. It did not appear to be related to changes in available nitrogen as measured by soil nitrate, plant nitrogen absorption or nitrate released on aerobic incubation.

Soil Nitrogen Movement under Sustainable Vegetable Production Systems

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 494f-495 ◽  
Author(s):  
Amy M. Johnson ◽  
Greg D. Hoyt
Keyword(s):  
Pest Management ◽  
Soil Nitrogen ◽  
Conservation Tillage ◽  
Management Strategies ◽  
Conventional Tillage ◽  
Plant Diseases ◽  
Vegetable Production ◽  
Beneficial Arthropods ◽  
Weed Species ◽  
Available Nitrogen

An experiment was established to determine the effect of different tillage practices, vegetable crop rotations, and pest management strategies on crop yield, plant diseases, pest and beneficial arthropods, weed species changes over time, and soil environmental consequences. This poster describes nitrogen movement from the various treatments over a 3-year rotation. The treatments are: 1) conventional tillage with chemically based IPM; 2) conventional tillage with biologically based IPM; 3) conservation tillage with chemically based IPM; 4) conservation tillage with biologically based IPM; and 5) conventional tillage with no fertilizer or pest management. Mid-season soil analyses with depth showed chemical-fertilized plowed and conservation-tilled treatments with more soil available nitrogen at most depths compared to the biological-based IPM systems (soybean meal was used as a nitrogen source). However, the biological-based systems did supply enough soil nitrogen to produce similar yield results as the chemical-based systems. Less soil nitrate was measured in the 30- to 90-cm depths at harvest from the biological-based systems than chemical-based systems. Conservation-tilled systems had greater nitrate with depth compared to conventional-tilled systems.

Concerning the Heterogeneity of the Natural Abundance of 15N in Soil Nitrogen

1981 ◽  
Vol 45 (2) ◽  
pp. 450-451 ◽  
Author(s):  
Daniel H. Kohl ◽  
Barbara A. Bryan ◽  
Georgia Shearer ◽  
Ross A. Virginia
Keyword(s):  
Soil Nitrogen ◽  
Natural Abundance

Response of winter wheat to prolonged waterlogging under outdoor conditions

1981 ◽  
Vol 97 (3) ◽  
pp. 557-568 ◽  
Author(s):  
R. K. Belford
Keyword(s):  
Winter Wheat ◽  
Water Table ◽  
Stem Elongation ◽  
Soil Surface ◽  
Root Production ◽  
Or Efficiency ◽  
Plant Nitrogen ◽  
Stages Of Growth ◽  
Nodal Root ◽  
Waterlogging Treatment

SUMMARYThe response of winter wheat cv. Maris Huntsman to waterlogging was studied in two experiments in soil columns outdoors. Winter waterlogging treatments increased nodal root production and the proportion of aerenchyma within roots, but caused chlorosis and premature senescence of leaves, and decreased tillering. For all treatments, grain losses were much less than expected from the extent of tiller loss in winter; losses after single waterlogging events ranged from 2% (after 47 days with the water-table at 5 cm) to 16% (after 80 days with the water-table at the soil surface). Yield losses after three waterloggings at the seedling, tillering and stem elongation stages of growth were additive, and totalled 19%. In many treatments, grain loss was associated with lighter individual grain weights, suggesting that the size of the root system or efficiency of water and nutrient uptake by roots at the later stages of growth may have been less after earlier waterlogging. The importance of nitrogen fertilizer in maintaining a satisfactory plant nitrogen status was shown when nitrogen was with held before a 3-week waterlogging treatment during stem elongation; tiller and floret survival was subsequently greatly restricted and grain yields decreased 22% below those of plants waterlogged at the same stage of growth but supplied with nitrogen.

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