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1.
Labelled fertilizer N applied to winter wheat as Na15NO3 and (15NH4)2SO4 at a total N dressing of 100kg ha−1 was used in a microplot balance study to investigate the fate of each split fraction at three growth stages: end of tillering,
heading and beginning of flowering.
Results indicated that while the percentage utilization of the applied N by the grain and total crop increased considerably
from the first to the third split application, these values diminished steadily in the straw. Grain recovery values for the
first, second and third split applications were 34.2%, 51.5% and 55.7% for the NO3 and 32.3%, 48.4% and 52.5% for the NH4 carrier, respectively. The corresponding recovery values for the whole plant were 54.6%, 67.8% and 69.9% for the NO3 and 51.7%, 63.5% and 66.1% for the NH4 carrier.
A greater proportion of the fertilizer N applied at the end of tillering stage was found in the vegetative plant components
as compared with the grain. The reverse occurred for the N applied at the heading and at the beginning of the flowering stages.
The residual fertilizer N found in the soil amounted to 18.0%, 10.4% and 11.6% of the applied NO3−N and to 22.5%, 12.7% and 15.2% of the applied NH4−N for the respective split applications.
No differences were found for each split application between the two carriers as far as the unaccounted fertilizer N was concerned.
The losses were 26.6%, 22.3% and 18.6% of the applied N for the three split applications, respectively. The application of
fertilizer N did not lead to any increase in soil N uptake by the crop. 相似文献
2.
In a field experiment performed in microplots, winter wheat was fertilized at two different total N dressings (135 and 180 kg ha–1) split-applied as Na15NO3 in three equal applications at tillering, stem elongation, and flag leaf.No significant differences were found in the percentage recovery values for the entire plant at the three split applications between the two N dressings. The total percentage recovery of fertilizer N by the plant was high and practically equal at both fertilization levels (76.65% and 75.84% for 135 and 180 kg N ha–1, respectively); crop yields were also similar. In contrast, gaseous losses calculated after drawing up the balance sheet were, in absolute values, higher for the tillering and stem elongation split applications when using the 180 kg N ha–1 dressing (7.67 and 4.84 kg N ha–1, respectively) than for the 135 kg N ha–1 dressing (3.45 and 1.26 kg N ha–1, respectively). They were found to be zero at flag leaf at both fertilization levels. The amount of applied fertilizer N did not influence the amount of N taken up from the soil which was about 143 kg ha–1. 相似文献
3.
Effects of Long-Term Fertilization on Leaf Photosynthetic Characteristics and Grain Yield in Winter Wheat 总被引:4,自引:0,他引:4
Based on a 20-year fertilization experiment with wheat-maize double cropping system, the effects of different long-term fertilization treatments on leaf photosynthetic characteristics and grain yield in different winter wheat (Triticum aestivum L.) cultivars were studied in the growing seasons of 2000–2001 and 2001–2002. A total of nine fertilization treatments were implemented, i.e. no fertilizer (CK), N fertilizer (N), N and P fertilizers (NP), N and K fertilizers (NK), N, P, and K fertilizers (NPK), only organic manure (M), organic manure and N fertilizer (MN), organic manure and N and P fertilizers (MNP), and organic manure and N, P, and K fertilizers (MNPK). With the treatments of combined organic manure and inorganic fertilizers (TMI), net photosynthetic rate (P
N), maximal activity of photosystem 2, PS2 (Fv/Fm), and chlorophyll content (SPAD value) of flag leaves and leaf area index (LAI) were much higher at the mid grain filling stage (20 or 23 d post anthesis, DPA), and exhibited slower declines at the late grain filling stage (30 DPA), compared with the treatments of only inorganic fertilizers (TI). The maximal canopy photosynthetic traits expressed as P
N×LAI and SPAD×LAI at the mid grain filling stage were also higher in TMI than those in TI, which resulted in different grain yields in TMI and TI. Among the treatments of TMI or among the treatments of TI, both flag leaf and canopy photosynthetic abilities and yield levels increased with the supplement of inorganic nutrients (N, P, and K fertilizers), except for the treatment of NK. Under NK, soil contents of N and K increased while that of P decreased. Hence the unbalanced nutrients in soil from the improper input of nutrients in NK treatment were probably responsible for the reduced flag leaf and canopy photosynthetic characteristics and LAI, and for the fast declining of flag leaf photosynthetic traits during grain filling, resulting in the reduced yield of NK similar to the level of CK. 相似文献
4.
Nitrogen transfer from nodulating soybean to maize or to nonnodulating soybean in intercrops: the 15N dilution method 总被引:10,自引:0,他引:10
In 1985, 1986 and 1988, maize (Zea mays L.) was monocropped or intercropped with nodulating or nonnodulating soybean (Glycine max [L.] Merr.). In addition, nodulating soybean and nonnodulating soybean were each monocropped and grown as a mixture. In 1985 and 1986, treatments were grown at 0 and 60 kg N ha–1 and in 1988, the treatments were grown without N fertilizer, on N-depeted soil and on non-N-depleted soil. 15N enriched N was applied to soil in all the aforementioned treatments to test for N transfer from nodulating soybean to non-N2-fixing crops by the 15N dilution method.The 15N dilution method did not show the occurrence of N transfer in 1985 and 1986, but the N sparing effect was evident from the total N uptake of nonnodulating soybean, dwarf maize and tall maize, in 1986. In 1988, maize and nonnodulating soybean seed yields and seed N yields were higher on non-N-depleted soil than on N-depleted soil. On N-depleted soil, the 15N dilution method indicated N transfer from nodulating soybean to maize and to nonndulating soybean. At a population ratio of 67% nodulating soybean to 33% nonnodulating soybean, N transfer was also seen on non-N-depleted soil in 1988. 相似文献
5.
The fate of15N labeled nitrogen applied to mature citrus trees 总被引:1,自引:0,他引:1
Summary The efficiency and balance of nitrogen from one year's application was studied in a long-term fertigation experiment. Enriched
nitrogen fertilizer, K15NO3, was applied to a 22-year-old Shamouti orange tree with a history of high N applications (N3) and to an N-starved tree (N1). The distribution of N in the different parts of the trees and in the soil was determined after the experimental trees were
excavated.
Similar total recovery of the labeled fertilizer N was found in the trees and soil in both treatments (N1−61.7% N3−56%). However, the distribution between tree and soil was different. The amount of recovered residual fertilizer in the soil
was much larger in the N3 treatment than in N1. The highest percentage of fertilizer N was found in the new organs,i.e. fruits, twigs and leaves. The roots and branches took up only 6–14% from the labeled fertilizer.
Only 20.9% of the leaf N and 23.4% of the fruit N in the N3 tree originated in the labeled fertilizer, indicating translocation of N from older parts of the tree to new growth.
Evidence was found of storage of N in the wooded branches, while the roots contained a surprisingly small part of labeled
fertilizer.
Contribution 1599E. 相似文献
6.
In the recent past considerable attention is paid to minimize dependence on purchased inputs such as inorganic nitrogen fertilizer. Green manure in the form of flood-tolerant, stem-nodulatingSesbania rostrata andAeschynomene afraspera is an alternative N source for rice, which may also increase N use efficiency. Therefore research was conducted to determine the fate of N applied to lowland rice (Oryza sativa L.) in the form ofSesbania rostrata andAeschynomene afraspera green manure and urea in two field experiments using15N labeled materials.15N in the soil and rice plant was determined, and15N balances established. Apparent N recoveries were determined by non-tracer method.
15N recoveries averaged 90 and 65% of N applied for green manure and urea treatments, respectively. High partial pressures of NH3 in the floodwater, and high pH probably resulted from urea application and favoured losses of N from the urea treatment. Results show that green manure N can supply a substantial proportion of the N requirements of lowland rice. Nitrogen released fromSesbania rostrata andAeschynomene afraspera green manure was in synchrony with the demand of the rice plant. The effect of combined application of green manure and urea on N losses from urea fertilizer were also investigated. Green manure reduced the N losses from15N labeled urea possibly due to a reduction in pH of the floodwater. Positive added N interactions (ANIs) were observed. At harvest, an average of 45 and 25% of N applied remained in the soil for green manure and urea, respectively.Contribution from IRRI, Los Baños, Philippines and Justus-Liebig-University, Giessen, GermanyContribution from IRRI, Los Baños, Philippines and Justus-Liebig-University, Giessen, Germany 相似文献
7.
Summary Six pasture grasses,Paspalum notatum cv batatais,P. notatum cv pensacola,Brachiaria radicans, B. ruziziensis, B. decumbens andB. humidicola, were grown in concrete cylinders (60 cm diameter) in the field for 31 months. The soil was amended with either a single addition of15N labelled organic matter or frequent small (2 kg N. ha–1) additions of15N enriched (NH4)2SO4. In the labelled fertilizer treatment soil analysis revealed that there was a very drastic change in15N enrichment in plant-available nitrogen (NO
3
–
+NH
4
+
) with depth. The different grass cultivars recovered different quantities of applied labelled N, and evidence was obtained to suggest that the roots exploited the soil to different depths thus obtaining different15N enrichments in soil derived N. This invalidated the application of the isotope dilution technique to estimate the contribution of nitrogen fixation to the grass cultivars in this treatment. In the labelled organic matter treatment the15N label in the plant-available N declined at a decreasing rate during the experiment until in the last 12 months the decrease was only from 0.274 to 0.222 atom % excess. There was little change in15N enrichment of available N with depth, hence it was concluded that although the grasses recovered different quantities of labelled N, they all obtained virtually the same15N enrichment in soil derived N. Data from the final harvests of this treatment indicated thatB. humidicola andB. decumbens obtained 30 and 40% respectively of their nitrogen from N2 fixation amounting to an input of 30 and 45 kg N.ha–1 year–1 respectively. 相似文献
8.
Summary Small differences in N2 fixation by nodulated soybeans (Glycine max. (L.) Merr.), inoculated with various strains ofRhizobium japonicum, were assessed in field experiments using15N methodology, and compared with yields of plant dry matter and total N. Percentage of plant-N derived from atmospheric N2 and from fertilizer, and values of %15N atom excess had lower coefficients of variation than did total N and dry matter yield. Nevertheless the precision of estimates of kg N/ha fixed were sufficient to differentiate only the extremes of the range of strains tested, and there were discrepancies between ranking of strains based on % N derived from fertilizer and on total N yield. 相似文献
9.
Although a high proportion of fertilizer N may be immobilized in organic forms in the soil, no studies have examined the long-term
availability of residual fertilizer 15N in forestry situations. We investigated this by growing lodgepole pine (Pinus contorta) seedlings in surface (0–10 cm) soil sample eight years after application of 15N-urea, 15NH4NO3 and NH4
15NO3 to lodgepole pine in interior British Columbia. After nine months of growth in the greenhouse, seedlings took up an average
of 8.5% of the 15N and 4.6% of the native N per pot. Most of the mineral N in the pots without seedlings was in the form of nitrate, while
pots with seedlings had very low levels of mineral N. In contrast to the greenhouse study, there was no significantuptake
of 15N by trees in the field study after the first growing season, although half of the soil organic 15N was lost between one and eight years after fertilization. This indicates the need to understand the mechanisms which limit
the uptake of mineral N by trees in the field, and the possible mismatch of tree demand and mineral N availability. 相似文献
10.
15N labelled (NH4)2SO4 was applied to barley at 5 g N m−2 (50 kg N ha−1) in microplots at sowing to study the timing of the N losses and the contribution of soil and fertilizer N to the plant.
Water treatments included rainfed and irrigation at 45–50 mm deficit beginning in the spring.
Recovery of15N in the plant increased to a maximum of about 20% within 91 days after sowing (DAS 91) and then remained constant. Approximately
16% (0.8 g N m−2) of the fertilizer was in the stem and leaves at DAS 91 and this N was subsequently redistributed to the head. At maturity,
approximately 75% of the15N assimilated by the tops was recovered in the grain. Soil N contributed 3.6 g N m−2 to the head; 2.2 g N m−2 was remobilized from the stem and leaves, and the balance, approximately 1.4 g N m−2, was taken up from the soil between DAS 69 to 91. Effects of irrigation treatments on N accumulation were not significant.
Residual15N fertilizer in the soil decreased with time from sowing, and at maturity 40% of the applied N was recovered in the surface
0.15 m.15N movement to depth was limited and less than 5% of the fertilizer was recovered below 0.15 m. Irrigation had no effect on
the15N recovery at depth.
Total recovery of the15N varied between 60 and 67% and implies that 33–40% was lost from the soil-plant system. The total recovery in the soil and
plant was not affected by time or irrigation in the interval DAS 39 to 134. Losses occurred before DAS 39 when crop uptake
of N was small and soil mineral N content was high. There was an apparent loss of 1.9 g fertilizer N m−2 (i.e. 38% of that applied) between DAS 1 and 15. This loss occurred before crop emergence when rainfall provided conditions suitable
for denitrification. 相似文献
11.
E. Wada R. Imaizumi Y. Kabaya T. Yasuda T. Kanamori G. Saito A. Nishimune 《Plant and Soil》1986,93(2):269-286
Summary Plants from agricultural and natural upland ecosystem were investigated for15N content to evaluate the role of symbiotic N2-fixation in the nitrogen nutrition of soybean. Increased yields and lower δ15N values of nodulating soybeansvs, non-nodulating isolines gave semi-quantitative estimates of N2 fixation. A fairly large discrepancy was found between estimations by δ15N and by N yield at 0 kg N/ha of fertilizer. More precise estimates were made by following changes in plant δ15N when fertilizer δ15N was varied near15N natural abundance level. Clearcut linear relationships between δ15N values of whole plants and of fertilizer were obtained at 30 kg N/ha of fertilizer for three kinds of soils. In experimental
field plots, nodulating soybeans obtained 13±1% of their nitrogen from fertilizer, 66±8% from N2 fixation and 21±10% from soil nitrogen in Andosol brown soil; 30%, 16% and 54% in Andosol black soil; 7%, 77% and 16% in
Alluvial soil, respectively. These values for N2 fixation coincided with each corresponding estimation by N yield method.
Other results include: 1)15N content in upland soils and plants was variable, and may reflect differences in the mode of mineralization of soil organics,
and 2) nitrogen isotopic discrimination during fertilizer uptake (δ15N of plant minus fertilizer) ranged from −2.2 to +4.9‰ at 0–30 kg N/ha of fertilizer, depending on soil type and plant species.
The proposed method can accurately and relatively simply establish the importance of symbiotic nitrogen fixation for soybeans
growing in agricultural settings. 相似文献
12.
Throughfall nitrogen of a 15-year-old Picea abies (L.) Karst. (Norway spruce) stand in the Fichtelgebirge, Germany, was labeled with either 15N-ammonium or 15N-nitrate and uptake of these two tracers was followed during two successive growing seasons (1991 and 1992). 15N-labeling (62 mg 15N m-2 under conditions of 1.5 g N m-2 atmospheric nitrogen deposition) did not increase N concentrations in plant tissues. The 15N recovery within the entire stand (including soils) was 94%±6% of the applied 15N-ammonium tracer and 100%±6% of the applied 15N-nitrate tracer during the 1st year of investigation. This decreased to 80%±24% and 83%±20%, respectively, during the 2nd year. After 11 days, the 15N tracer was detectable in 1-year-old spruce needles and leaves of understory species. After 1 month, tracer was detectable in needle litter fall. At the end of the first growing season, more than 50% of the 15N taken up by spruce was assimilated in needles, and more than 20% in twigs. The relative distribution of recovered tracer of both 15N-ammonium and 15N-nitrate was similar within the different foliage age classes (recent to 11-year-old) and other compartments of the trees. 15N enrichment generally decreased with increasing tissue age. Roots accounted for up to 20% of the recovered 15N in spruce; no enrichment could be detected in stem wood. Although 15N-ammonium and 15N-nitrate were applied in the same molar quantities (15NH
4
+
: 15NO
3
-
=1:1), the tracers were diluted differently in the inorganic soil N pools (15NH
4
+
/NH
4
+
: 15NO
3
-
/NO
3
-
=1:9). Therefore the measured 15N amounts retained by the vegetation do not represent the actual fluxes of ammonium and nitrate in the soil solution. Use of the molar ammonium-to-nitrate ratio of 9:1 in the soil water extract to estimate 15N uptake from inorganic N pools resulted in a 2–4 times higher ammonium than nitrate uptake by P. abies. 相似文献
13.
A field study was conducted on a clay soil (Andaqueptic Haplaquoll) in the Philippines to directly measure the evolution of
(N2+N2O)−15N from 98 atom %15N-labeled urea broadcast at 29 kg N ha−1 into 0.05-m-deep floodwater at 15 days after transplanting (DT) rice. The flux of (N2+N2O)−15N during the 19 days following urea application never exceeded 28 g N ha−1 day−1. The total recovery of (N2+N2O)−15N evolved from the field was only 0.51% of the applied N, whereas total gaseous15N loss estimated from unrecovered15N in the15N balance was 41% of the applied N. Floodwater (nitrate+nitrite)−N in the 5 days following urea application never exceeded
0.14 g N m−3 or 0.3% of the applied N. Prior cropping of cowpea [Vigna unguiculata (L.) Walp.] to flowering with subsequent incorporation of the green manure (dry matter=2.5 Mg ha−1, C/N=15) at 15 days before rice transplanting had no effect on fate of urea applied to rice at 15 DT. The recovery of (N2+N2O)−15N and total15N loss during the 19 days following urea application were 0.46 and 40%, respectively. Direct recovery of evolved (N2+N2O)−15N and total15N loss from 27 kg applied nitrate-N ha−1 were 20% and 53% during the same 19-day period. The failure of directly-recovered (N2+N2O)−15N to match total15N loss from added nitrate-15N might be due to entrapment of denitrification end products in soil or transport of gaseous end products to the atmosphere
through rice plants. The rapid conversion of added nitrate-N to (N2+N2O)−N, the apparently sufficient water soluble soil organic C for denitrification (101 μg C g−1 in the top 0.15-m soil layer), and the low floodwater nitrate following urea application suggested that denitrification loss
from urea was controlled by supply of nitrate rather than by availability of organic C. 相似文献
14.
Spring wheat (Triticum aestivum L. cv. Tonic) was grown for 16 days in a sandy loam soil which was contaminated with 137Cs. The soil was fertilised with K at three rates (0,1 and 2 mmol K per 950 g dry soil) and with NO3
--N at two rates (0 and 2 mmol per 950 g dry soil) in a factorial design. The 137Cs Activity Concentration (AC) in the shoot tissue significantly reduced 8.2-fold (nil N treatment, p<0.001) and 9.3-fold (highest N dose, p<0.001) with increasing K supply. In contrast, the K application increased the 137Cs AC in soil solution 1.7 fold (nil N treatment) or had no significant effect (highest N dose). At similar K application, the application of N increased the 137Cs AC in the shoot compared to the control. This effect is most probably due to the increased NH4
+ concentration in soil solution which increased the 137Cs AC in soil solution. The soil solution composition (137Cs and K concentration) in the rhizosphere was estimated from the average soil solution composition at day 16 and solute transport calculations. The 137Cs AC in the shoot tissue was predicted from the estimated soil solution composition in the rhizosphere and the relationship between K concentration and 137Cs uptake derived from a nutrient solution experiment. The predictions of 137Cs AC's in the shoot are qualitatively correct for the fertiliser effects but underestimate the observations between 1.4 and 9.9 fold. 相似文献
15.
A field study was carried out near Zürich (Switzerland) to determine the yield of symbiotically fixed nitrogen (15N dilution) from white clover (Trifolium repens L.) grown with perennial ryegrass (Lolium perenne L) and from red clover (Trifolium pratense L.) grown with Italian ryegrass (Lolium multiflorum Lam.). A zero N fertilizer treatment was compared to a 30 kg N/ha per cut regime (90 to 150 kg ha−1 annually).
The annual yield of clover N derived from symbiosis averaged 131 kg ha−1 (49 to 227 kg) without N fertilization and 83 kg ha−1 (21 to 173 kg) with 30 kg of fertilizer N ha−1 per cut in the seeding year. Values for the first production year were 308 kg ha−1 (268 to 373 kg) without N fertilization and 232 kg ha−1 (165 to 305 kg) with 30 kg fertilizer N ha−1 per cut. The variation between years was associated mainly with the proportion of clover in the mixtures. Apparent clover-to-grass
transfer of fixed N contributed up to 52 kg N ha−1 per year (17 kg N ha−1 on average) to the N yield of the mixtures.
Percentage N derived from symbiosis averaged 75% for white and 86% for red clover. These percentages were affected only slightly
by supplemental nitrogen, but declined markedly during late summer for white clover. It is concluded that the annual yield
of symbiotically fixed N from clover/grass mixtures can be very high, provided that the proportion of clover in the mixtures
exceeds 50% of total dry mass yield. 相似文献
16.
J. V. D. K. Kumar Rao J. A. Thompson P. V. S. S. Sastry K. E. Giller J. M. Day 《Plant and Soil》1987,101(1):107-113
Two experiments were carried out from 1981 to 1983 in Vertisol field at ICRISAT Center, Patancheru, India to measure N2-fixation of pigeonpea [Cajanus cajan (L.) Millsp.] using the15N isotope dilution technique. One experiment examined the effect of control of a nodule-eating insect on fixation while another
in vestigated the effect of intercroping with cereals on fixation and the residual effect of pigeonpea on a succeeding cereal
crop. Although both experiments indicated that at least 88% of the N in pigeonpea was fixed from the atmosphere, one result
is considered fortuitous in view of the differential rates of growth of the legume and the control, sorghum [Sorghum bicolor (L.) Moench]. The difference method of calculation in dieated negative fixation and the results emphasized the problem of
finding a suitable nonfixing control. In a second experiment, when all plants were confined to a known volume of soil to which15N fertilizer was added in the field, these problems were overcome, and isotope dilution and difference methods gave similar
results of N2-fixation of about 90%. In intercropped pigeonpea 96% of the total N was derived from the atmosphere. This estimate might
be an artifact. There was no evidence of benefit from N fixed by pigeonpea to intercropped sorghum plants. Plant tissue15N enrichments of cereal crops grown after pigeonpea indicated that the cereal derived some N fixed by the previous pigeonpea.
Thus residual benefits to cereals are not only an effect of ‘sparing’ of soil N. 相似文献
17.
The temporal N-uptake patterns of white clover (Trifolium repens L.) mixed with perennial ryegrass (Lolium perenne L.) and of red clover (Trifolium pratense L.) mixed with Italian ryegrass (Lolium multiflorum Lam.) were determined in successive harvests of herbage within the growth cycles of a ley established near Zürich (Switzerland). Rooting patterns were examined by injecting15N-fertilizer at soil depths ranging from 10 to 40 cm. The results were analyzed to determine the effect of variations in time and depth of N-uptake on the15N-based measurement of N from symbiosis (Nsym) and N from transfer (Ntrans).Grasses in mixture appeared to have deeper rooting systems than grass monocultures, which led to an overestimation of N transfer from white clover to perennial ryegrass if15N was spread on the soil surface.White clover generally lagged behind grass in soil N- uptake. Soil N-uptake of red clover slowed down before that of the grass because % Nsym almost reached 100% during the second half of each growth cycle. However, the effect of these dissimilarities on the seasonal average of %Nsym did not exceed 2%.It is concluded that at the observed high levels of N2 fixation, failure to account for the N-uptake patterns of the test and reference crops only slightly affected the estimates of % Nsym and % Ntrans, and did not invalidate the observed differences between species. 相似文献
18.
A field experiment was conducted using15N methodology to study the effect of cultivation of faba bean (Vicia faba L.), pea (Pisum sativum L.) and barley (Hordeum vulgare L.) on the N status of soil and their residual N effect on two succeeding cereals (sorghum (Sorghum vulgare) followed by barley). Faba bean, pea and barley took up 29.6, 34.5 and 53.0 kg N ha–1 from the soil, but returned to soil through roots only 11.3, 10.8 and 5.7 kg N ha–1, respectively. Hence, removal of faba bean, pea and barley straw resulted in a N-balance of about –18, –24, and –47 kg ha–1 respectively. A soil nitrogen conserving effect was observed following the cultivation of faba bean and pea compared to barley which was of the order of 23 and 18 kg N ha–1, respectively. Cultivation of legumes resulted in a significantly higher AN value of the soil compared to barley. However, the AN of the soil following fallow was significantly higher than following legumes, implying that the cultivation of the legumes had depleted the soil less than barley but had not added to the soil N compared to the fallow. The beneficial effect of legume cropping also was reflected in the N yield and dry matter production of the succeeding crops. Cultivation of legumes led to a greater exploitation of soil N by the succeeding crops. Hence, appreciable yield increases observed in the succeeding crops following legumes compared to cereal were due to a N-conserving effect, carry-over of N from the legume residue and to greater uptake of soil N by the succeeding crops when previously cropped to legumes. 相似文献
19.
Effect of plant genotype and nitrogen fertilizer on symbiotic nitrogen fixation by soybean cultivars
Summary Isotopic as well as non-isotopic methods were used to assess symbiotic nitrogen fixation within eight soybean [Glycine max (L.) Merr.] cultivars grown at 20 and 100 kg N/ha levels of nitrogen fertilizer under field conditions.The15N methodology revealed large differences between soybean cultivars in their abilities to support nitrogen fixation. In almost all cases, the application of 100 kg N/ha resulted in lower N2 fixed in soybean than at 20 kg N/ha in the first year of the study. However, N2 fixed in one cultivar, Dunadja, was not significantly affected by the higher rate of N fertilizer application. These results were confirmed by measurements of acetylene reduction activity, nodule dry weight and N2 fixed as measured by the difference method. Further proof of differences in N2 fixed within soybean cultivars and the ability of Dunadja to fix similar amounts of N2 at 20 and 100 kg N/ha was obtained during a second year experiment. Dunadja yield was affected by N fertilizer and produced larger yield at 100 kg N/ha than at 20 kg N/ha. This type of cultivar could be particularly useful in situations where soil N levels are high or where there is need to apply high amounts of N fertilizer.The present study reveals the great variability between legume germplasms in the ability to fix N2 at different inorganic N levels, and also the potential that exists in breeding for nitrogen fixation associative traits. The15N methodology offers a unique tool to evaluate germplasms directly in the field for their N2 fixation abilities at different N fertilizer levels. 相似文献
20.
Three separate experiments were conducted in the nursery using grassland soil as a growing medium. The first experiment was
conducted to assess the nodulation of the two legume trees grown in unamended soil, the second was done to determine the effects
of N-fertilizer application on the interaction of the five Rhizobium isolates withA. falcataria and the third experiment was conducted to determine the effects of liming on theRhizobium × A. mangium interaction.
Three local Rhizobium isolates, A16, A18, and A14 were effective forA. falcataria with A16 as the most promising strain under the conditions described. In general, application of combined nitrogen suppressed nodulation
ofA. falcataria. Nodulation in the absence of combined N exceeded those fertilized with 30 kg N ha−1 by 114.0%, 60 kg N ha−1 by 209.6% and 100 kg N ha−1 by 237.1%.
Two local isolates, Am10 and Am2, and an introduced strain, NA 1533 from Australia were promising forA. mangium. Unlike inA. falcataria, the application of combined nitrogen at the rate of 100 kg N ha−1 did not suppress nodulation inA. mangium. Liming the soil to pH 6.5 regardless of nitrogen fertilizer application improved the performance of the Rhizobium—A. mangium symbiosis. 相似文献