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1.
Cultivating dinitrogen-fixing legume trees with crops in agroforestry is a relatively common N management practice in the
Neotropics. The objective of this study was to assess the N2 fixation potential of three important Neotropical agroforestry tree species, Erythrina poeppigiana, Erythrina fusca, and Inga edulis, under semi-controlled field conditions. The study was conducted in the humid tropical climate of the Caribbean coastal plain
of Costa Rica. In 2002, seedlings of I. edulis and Vochysia guatemalensis were planted in one-meter-deep open-ended plastic cylinders buried in soil within hedgerows of the same species. Overall
tree spacing was 1 × 4 m to simulate a typical alley-cropping design. The 15N was applied as (NH4)2SO4 at 10% 15N atom excess 15 days after planting at the rate of 20 kg [N] ha−1. In 2003, seedlings of E. poeppigiana, E. fusca, and V. guatemalensis were planted in the same field using the existing cylinders. The 15N application was repeated at the rate of 20 kg [N] ha−1 15 days after planting and 10 kg [N] ha−1 was added three months after planting. Trees were harvested 9 months after planting in both years. The 15N content of leaves, branches, stems, and roots was determined by mass spectrometry. The percentage of atmospheric N fixed
out of total N (%Nf) was calculated based on 15N atom excess in leaves or total biomass. The difference between the two calculation methods was insignificant for all species.
Sixty percent of I. edulis trees fixed N2; %Nf was 57% for the N2-fixing trees. Biomass production and N yield were similar in N2-fixing and non-N2-fixing I. edulis. No obvious cause was found for why not all I. edulis trees fixed N2. All E. poeppigiana and E. fusca trees fixed N2; %Nf was ca. 59% and 64%, respectively. These data were extrapolated to typical agroforestry systems using published data on N recycling
by the studied species. Inga edulis may recycle ca. 100 kg ha−1 a−1 of N fixed from atmosphere to soil if only 60% of trees fix N2, E. poeppigiana 60–160 kg ha−1 a−1, and E. fusca
ca. 80 kg ha−1 a−1. 相似文献
2.
Chris van Kessel 《Plant and Soil》1994,164(1):69-76
Although wheat (Triticum aestivum L.) is the dominant crop of the semi-arid plains of Canada and the western United States, lentil (Lens culinaris Medik.) has become an important alternative crop. Sources and seasonal accumulation of N must be understood in order to identify
parameters that can lead to increased N2-fixing activity and yield. Inoculated lentil was grown in a sandy-loam soil at an irrigated site in Saskatchewan, Canada.
Wheat was used as the reference crop to estimate N2 fixation by the A-value approach. Lentil and wheat received 10 and 100 kg N ha−1 of ammonium nitrate, respectively. Crops were harvested six times during the growing season and plant components analyzed.
During the first 71 days after planting the wheat had a higher daily dry matter and N accumulation compared to lentil. However,
during the latter part of the growing season, daily dry matter and N accumulation were greater for lentil. The maximum total
N accumulation for lentil at maturity was 149 kg ha−1. In contrast, wheat had a maximum N accumulation of 98 kg ha−1 in the Feekes 11.1 stage, or 86 days after planting. The maximum daily rates of N accumulation were 3.82 kg N ha−1 day−1 for lentil and 2.21 kg N ha−1 day−1 for wheat. The percentage of N derived from N2 fixation (% Ndfa) ranged from 0 at the first harvest to 92 % at final harvest. Generative plant components had higher values
for % Ndfa than the vegetative components which indicates that N in the reproductive plant parts was derived largely from
current N2 fixation and lentil continued to fix N until the end of the pod fill stage. At final harvest, lentil had derived 129 kg N
ha−1 from N2 fixation with maximum N2-fixing activity (4.4 kg N ha−1 day−1) occurring during the early stages of pod fill. Higher maximum rates of N2-fixing activity than net N accumulation (3.82 kg N ha−1 day−1) may have been caused by N losses like volatilization. In addition, lentil provided a net N contribution to the soil of 59
kg ha−1 following the removal of the grain. 相似文献
3.
Archna Suman A. K. Shrivastava Asha Gaur Pushpa Singh J. Singh R. L. Yadav 《Plant Growth Regulation》2008,54(1):1-11
The nitrogen fixing bacterial endophytes Gluconacetobacter diazotrophicus and Herbaspirillum spp. have been proposed to benefit sugarcane (Saccaharum spp. hybrids) growth. Variable populations of these endophytes exist depending upon ontogenic and climatic variations as
well. This study investigates the effect of variable chemical nitrogen application in soil on the population of endophytic
diazotrophs, acetylene reduction ability of excised roots, plant N-nutrient use efficiency and probable interactions among
different parameters in eight commercial sugarcane varieties of subtropical India. Recovery efficiency (RE), agronomic efficiency
(AE), partial factor productivity (PFP) and physiologic efficiency (PE) indicators were used for accounting N-nutrient use
efficiency. The population of G. diazotrophicus was more at N75 compared to N0 and N150, whereas Herbaspirillum population increased from N0 to N150. ARA was positively correlated with Gluconacetobacter population in rhizosphere and root, whereas it had poor correlation with Herbaspirillum population. Positive correlation of RE and AE with ARA of roots, Gluconacetobacter and Herbaspirillum populations in roots and stems indicate their positive contribution in total nitrogen uptake by the plant per kg of N applied.
Average PFP was 808.9 at N75 compared to 408.7 at N150 indicating that N was utilized efficiently at low N input status in sugarcane. Strong positive correlations of AE75 (agronomic efficiency from 75 kg N ha−1 to 150 kg N ha−1) with N-uptake (r
2 = 0.615), cane yield (r
2 = 0.758) and PFP (r
2 = 0.758) and other parameters compared to AE (agronomic efficiency from 0 kg N ha−1 to 75 kg N ha−1 or 150 kg N ha−1) correlations with N-uptake (r
2 = 0.111), cane yield (r
2 = 0.368) and PFP (r
2 = 0.190) indicated that the AE of sugarcane was strongly directed towards producing more cane yield per unit of N fertilizer
once the sugarcane plant has established using initial dose of nitrogen and thus AE75 seems to be a more appropriate indicator for accounting N-nutrient use efficiency in sugarcane. 相似文献
4.
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
5.
Evaluation of N2-fixation and nitrogen economy of a maize/cowpea intercrop system using15N dilution methods 总被引:2,自引:0,他引:2
Yields of above ground biomass and total N were determined in summer-grown maize and cowpea as sole crops or intercrops, with
or without supplementary N fertilizer (25 kg N ha−1, urea) at an irrigated site in Waroona, Western Australia over the period 1982–1985. Good agreement was obtained between
estimates of N2 fixation of sole or intercrop cowpea (1984/85 season) based on the15N natural abundance and15N fertilizer dilution techniques, both in the field and in a glasshouse pot study. Field-grown cowpea was estimated to have
received 53–69% of its N supply from N2-fixation, with N2-fixation onlyslightly affected by intercropping or N fertilizer application. Proportional reliance on N2-fixation of cowpea in glasshouse culture was lower (36–66%) than in the field study and more affected by applied N. Budgets
for N were drawn up for the field intercrops, based on above-ground seed yields, return of crop residues, inputs of fixed
N and fertilizer N. No account was taken of possible losses of N through volatilization, denitrification and leaching or gains
of N in the soil from root biomass. N2-fixation was estimated tobe 59 kg N ha−1 in the plots receiving no fertilizer N, and 73 kg N ha−1 in plots receiving 25 kg N ha−1 as urea. Comparable fixation by sole cowpea was higher (87 and 82 kg N ha−1 respectively) but this advantage was outweighed by greater land use efficiency by the intercrop than sole crops. 相似文献
6.
Summary Seed inoculation with Rhizobium and soil inoculation withGlomus fasciculatum increased nodulation, nitrogen and phosphorus concentration in plants and yield of chickpea (Cicer arietinum) var. BG 212 in pots containing unsterilized soil especially with 50kgP2O5 ha−1 in the form of superphosphate.
Inoculation with Rhizobium orG. fasciculatum separately or in combination significantly increased the N2 fixed in straw and grain than uninoculated controls as determined by15N atom percent excess of plants grown in soil amended with labelled ammonium sulphate (15NH4)2SO4) at the rate of 20kg N ha−1. These increases were most pronounced when P was applied at 50kgP2O5 ha−1. 相似文献
7.
The effects on growth, quality and N uptake by turfgrass (Cynodon dactylon L.) during sod production of four fertiliser types applied at three application rates (100, 200 or 300 kg N ha−1 per ‘crop’) under two irrigation treatments (70% and 140% daily replacement of pan evaporation) were investigated. The fertiliser
types were: water-soluble (predominately NH4NO3), control-release, pelletised poultry manure, and pelletised biosolids; and the experiment was conducted on a sandy soil
in a Mediterranean-type climate. Plots were established from rhizomes, with the turfgrass harvested as sod every 16–28 weeks
depending upon the time of the year. Four crops were produced during the study. Applying water-soluble and control-release
fertilisers doubled shoot growth and improved turfgrass greenness by up to 10% in comparison with plots receiving pelletised
poultry manure and pelletised biosolids. Nitrogen uptake into the shoots after four crops (averaged across irrigation treatments
and N rates) was 497 kg N ha−1 for the water-soluble fertiliser, 402 kg N ha−1 for the control-release, 188 kg N ha−1 for the pelletised poultry manure and 237 kg N ha−1 for the pelletised biosolids. Consequently, the agronomic nitrogen-use efficiency (NAE, kg DM kg−1 N applied) of the inorganic fertilisers was approximately twice that of the organic fertilisers. Increasing irrigation from
70% to 140% replacement of pan evaporation was detrimental to turfgrass growth and N uptake for the first crop when supplied
with the water-soluble fertiliser. Under the low irrigation treatment, inorganic N fertilisers applied at 200–300 kg N ha−1 were adequate for production of turfgrass sod.
Section Editor: P. J. Randall 相似文献
8.
Summary The influence of seasonal variation on nitrogenase (N2-ase) activity of undisturbed soil-plant cores ofPanicum maximum var.trichoglume was measured using the C2H2 reduction assay.
The largest N2-ase activity in the field, 14.7 g N ha−1 day−1, occurred in spring when soil moisture was high, soil temperature was low and nitrogenous fertiliser influence was at a minimum.
The potential N2-ase activity of the cores, measured under controlled conditions, reached a maximum of 27.2 g N ha−1 day−1 and averaged 26.3 g N ha−1 day−1 over the 14 month sampling period.
N2-ase activity was positively correlated (P=0.05) with field soil moisture and negatively correlated with field soil temperature (r=0.59 and −0.78 respectively). Multiple
regression showed that 69% of the variation of N2-ase activity in the field was associated with the combined effects of soil moisture and soil temperature.
Nitrogen fixing bacteria were isolated from the roots ofP. maximum and based upon morphology, biochemical tests and fluorescent antibody reaction, were found to be closely related toAzospirillum lipoferum. 相似文献
9.
Intercropping cotton (Gossypium hirsutum L.) and cowpea (Vigna unguiculata (L.) Walp) is one of the ways to improve food security and soil fertility whilst generating cash income of the rural poor. A study was carried out to find out the effect of cotton–cowpea intercropping on cowpea N2-fixation capacity, nitrogen balance and yield of a subsequent maize crop. Results showed that cowpea suppressed cotton yields but the reduction in yield was compensated for by cowpea grain yield. Cowpea grain yield was significantly different across treatments and the yields were as follows: sole cowpea (1.6 Mg ha−1), 1:1 intercrop (1.1 Mg ha−1), and 2:1 intercrop (0.7 Mg ha−1). Cotton lint yield was also significantly different across treatments and was sole cotton (2.5 Mg ha−1), 1:1 intercrop (0.9 Mg ha−1) and 2:1 intercrop (1.5 Mg ha−1). Intercropping cotton and cowpea increased the productivity with land equivalence ratios (LER) of 1.4 and 1.3 for 1:1 and 2:1 intercrop treatments, respectively. There was an increase in percentage of N fixation (%Ndfa) by cowpea in intercrops as compared to sole crops though the absolute amount fixed (Ndfa) was lower due to reduced plant population. Sole cowpea had %Ndfa of 73%, 1:1 intercrop had 85% and 2:1 intercrop had 77% while Ndfa was 138 kg ha−1 for sole cowpea, 128 kg ha−1 for 1:1 intercrop and 68 kg ha−1 for 2:1 intercrop and these were significantly different. Sole cowpea and the intercrops all showed positive N balances of 92 kg ha−1 for sole cowpea and 1:1 intercrop, and 48 kg ha−1 for 2:1 intercrop. Cowpea fixed N transferred to the companion cotton crop was very low with 1:1 intercrop recording 3.5 kg N ha−1 and 2:1 intercrop recording 0.5 kg N ha−1. Crop residues from intercrops and sole cowpea increased maize yields more than residues from sole cotton. Maize grain yield was, after sole cotton (1.4 Mg ha−1), sole cowpea (4.6 Mg ha−1), 1:1 intercrops (4.4 Mg ha−1) and 2:1 intercrops (3.9 Mg ha−1) and these were significantly different from each other. The LER, crop yields, %N fixation and, N balance and residual fertility showed that cotton–cowpea intercropping could be a potentially productive system that can easily fit into the current smallholder farming systems under rain-fed conditions. The fertilizer equivalency values show that substantial benefits do accrue and effort should be directed at maximizing the dry matter yield of the legume in the intercrop system while maintaining or improving the economic yield of the companion cash crop. 相似文献
10.
Tree species and wood ash application in plantations of short-rotation woody crops (SRWC) may have important effects on the
soil productive capacity through their influence on soil organic matter (SOM) and exchangeable cations. An experiment was
conducted to assess changes in soil C and N contents and pH within the 0–50 cm depth, and exchangeable cation (Ca2+, Mg2+, K+, and Na+) and extractable acidity concentrations within the 0–10 cm depth. The effects of different species (European larch [Larix decidua P. Mill.], aspen [Populus tremula L. × Populus tremuloides Michx.], and four poplar [Populus spp.] clones) and wood ash applications (0, 9, and 18 Mg ha−1) on soil properties were evaluated, using a common garden experiment (N = 70 stands) over 7 years of management in Michigan’s Upper Peninsula. Soils were of the Onaway series (fine-loamy, mixed,
active, frigid Inceptic Hapludalfs). The NM-6 poplar clone had the greatest soil C and N contents in almost all ash treatment
levels. Soil C contents were 7.5, 19.4, and 10.7 Mg C ha−1 greater under the NM-6 poplar than under larch in the ash-free, medium-, and high-level plots, respectively. Within the surface
layer, ash application increased soil C and N contents (P < 0.05) through the addition of about 0.7 Mg C ha−1 and 3 kg N ha−1 with the 9 Mg ha−1 ash application (twofold greater C and N amounts were added with the 18 Mg ha−1 application). During a decadal time scale, tree species had no effects—except for K+—on the concentrations of the exchangeable cations, pH, and extractable acidity. In contrast, ash application increased soil
pH and the concentration of Ca2+ (P < 0.05), from 5.2 ± 0.4 cmolc kg−1 (ash-free plots) to 8.6 ± 0.4 cmolc kg−1 (high-level ash plots), and tended to increase the concentration of Mg2+ (P < 0.1), while extractable acidity was reduced (P < 0.05) from 5.6 ± 0.2 cmolc kg−1 (ash-free plots) to 3.7 ± 0.2 cmolc kg−1 (high-level plots). Wood ash application, within certain limits, not only had a beneficial effect on soil properties important
to the long-term productivity of fast-growing plantations but also enhanced long-term soil C sequestration. 相似文献
11.
Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N) requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (Nc) dilution curve based on stem dry matter (SDM) and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L.) in east China. Three field experiments with varied N rates (0–360 kg N ha−1) using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. SDM and stem N concentration (SNC) were determined during vegetative stage for growth analysis. A Nc dilution curve based on SDM was described by the equation (Nc = 2.17W−0.27with W being SDM in t ha−1), when SDM ranged from 0.88 to 7.94 t ha−1. However, for SDM < 0.88 t ha−1, the constant critical value Nc = 1.76% SDM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI) and accumulated N deficit (Nand) of stem ranged from 0.57 to 1.06 and 51.1 to −7.07 kg N ha−1, respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or Nand could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The SDM based Nc dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China. 相似文献
12.
Kristell Hergoualc’h Ute Skiba Jean-Michel Harmand Catherine Hénault 《Biogeochemistry》2008,89(3):329-345
The objective of this study was to evaluate the effect of N fertilization and the presence of N2 fixing leguminous trees on soil fluxes of greenhouse gases. For a one year period, we measured soil fluxes of nitrous oxide
(N2O), carbon dioxide (CO2) and methane (CH4), related soil parameters (temperature, water-filled pore space, mineral nitrogen content, N mineralization potential) and
litterfall in two highly fertilized (250 kg N ha−1 year−1) coffee cultivation: a monoculture (CM) and a culture shaded by the N2 fixing legume species Inga densiflora (CIn). Nitrogen fertilizer addition significantly influenced N2O emissions with 84% of the annual N2O emitted during the post fertilization periods, and temporarily increased soil respiration and decreased CH4 uptakes. The higher annual N2O emissions from the shaded plantation (5.8 ± 0.3 kg N ha−1 year−1) when compared to that from the monoculture (4.3 ± 0.1 kg N ha−1 year−1) was related to the higher N input through litterfall (246 ± 16 kg N ha−1 year−1) and higher potential soil N mineralization rate (3.7 ± 0.2 mg N kg−1 d.w. d−1) in the shaded cultivation when compared to the monoculture (153 ± 6.8 kg N ha−1 year−1 and 2.2 ± 0.2 mg N kg−1 d.w. d−1). This confirms that the presence of N2 fixing shade trees can increase N2O emissions. Annual CO2 and CH4 fluxes of both systems were similar (8.4 ± 2.6 and 7.5 ± 2.3 t C-CO2 ha−1 year−1, −1.1 ± 1.5 and 3.3 ± 1.1 kg C-CH4 ha−1 year−1, respectively in the CIn and CM plantations) but, unexpectedly increased during the dry season. 相似文献
13.
In 1981 a two-year field plot experiment was established to assess the effects of quantities (0, 7.5, 15, 30, 60 and 120 t
ha−1) of fresh kelp (Macrocystis integrifolia) on crop growth and nutritional response and chemical properties of a fine-textured soil. Soil was analyzed for NO3−N, NH4−N, electrical conductivity, pH, Cl and exchangeable cations (K, Mg, Ca, Mn and Na). The plots were planted to beans (Phaseolus vulgaris) in the first year and peas (Pisum sativum) in the second year. Marketable bean yields increased in the first year with kelp applications up to 60 t ha−1, with yields, emergence and flowering being reduced by the 120 t ha−1 application. Soluble salts (EC) and Cl concentrations in the soil eight days after application increased linearly and sharply
with increasing quantities of kelp. Increased K concentration and moisture content, characteristics of plants growing in a
salt-stressed soil environment, were measured. A subsequent companion greenhouse experiment confirmed that the reduced bean
emergence and growth with 120 t ha−1 applications of kelp were primarily due to soluble salts. The only growth effects upon peas in the second year was a slight
reduction in leaf plus stem yields with increasing applications of kelp. 相似文献
14.
El Amin Yousif Raddad Ahmed Ali Salih Mohamed Ahmed El Fadl Vesa Kaarakka Olavi Luukkanen 《Plant and Soil》2005,275(1-2):261-269
The symbiotic biological N2fixation by Acacia senegal was estimated using the 15N natural abundance (δ
15N) procedure on eight provenances collected from different environments and soil types grown in a clay soil in the Blue Nile
region, Sudan. Balanites aegyptiaca (a non-legume) was used as a non-N2-fixing reference plant to allow 15N-based estimates of the proportion of the Acacia N derived from atmospheric N2 (Ndfa) to be calculated. Results show variation in leaf δ
15N between A. senegal and the reference plant and among years. The relative δ
15N values (‰) were higher in B. aegyptiaca than in the N2-fixing acacia provenances. Provenances originally collected from clay soils fixed little N in the first year, but the amount
fixed increased as the trees aged. All provenances showed a decrease in δ
15N with age. The Ndfa varied between 24% (Mazmoom provenance) and 61% (Rahad provenance) 4 years after planting. There was no significant difference
in δ
15N between provenance groups based on soil type or rainfall at original growing site. The amount of Ndfa increased significantly with age in all provenances. The above-ground contribution of fixed N to foliage growth in a 4-year-old
A. senegal was highest in the Rahad sand–soil provenance (46.7 kg N ha−1) and lowest in the Mazmoom clay-soil provenance (28.7 kg N ha−1). Our study represents the first use of the δ
15N method for estimating the N input by A. senegal to the clay plain soils of the gum belt in the Sudan. 相似文献
15.
A field experiment conducted at Central Rice Research Institute, Cuttack, during three successive seasons showed that with
the 120-day-duration variety Ratna two dual crops ofAzolla pinnata R. Brown (Bangkok isolate) could be achieved 25 and 50 days after transplanting (DAT) by inoculating 2.0 t ha−1 of fresh Azolla 10 and 30 DAT respectively. One basal crop of Azolla could also be grown using the same inoculum 20 days
before transplanting (DBT) in fallow rice fields. The three crops of Azolla grown—once before transplanting and twice after
transplanting—gave an average total biomass of 38–63 and 43–64 t ha−1 fresh Azolla containing 64–90 and 76–94 kg N ha−1 respectively in the square and rectangular spacings. Two crops of Azolla grown only as a dual crop, on the other hand, gave
26–39 and 29–41 t ha−1 fresh Azolla which contained 44–61 and 43–59 kg N ha−1 respectively.
Growth and yield of rice were significantly higher in Azolla basal plus Azolla dual twice incorporated treatments than in
the Azolla dual twice incorporation, Azolla basal plus 30 kg N ha−1 urea and 60 kg N ha−1 urea treatments. Azolla basal plus 30 kg N ha−1 urea and 60 kg N ha−1 urea showed similar yields but Azolla dual twice incorporation was significantly lower than those. The different spacing
with same plant populations did not affect growth and yield significantly, whereas Azolla growth during dual cropping was
8.3 and 64% more in the rectangular spacing than in the square spacing in Azolla basal plus Azolla dual twice incorporation
and Azolla dual twice incorporation treatments. 相似文献
16.
Jacot Katja A. Lüscher Andreas Nösberger Josef Hartwig Ueli A. 《Plant and Soil》2000,225(1-2):201-211
The significance of symbiotic N2 fixation in legumes (Trifolium alpinum L., T. nivale Sieber, T. pratense L., T. badium Schreber, T. thalii Vill., T. repens L., Lotus alpinus [DC.] Schleicher, L. corniculatus L., Vicia sativa L.) and other N sources for the N budget of grassland ecosystems was studied along an altitudinal gradient in the Swiss Alps.
The total annual symbiotic N2 fixation was compared with other sources of N for plant growth of the total plant community (mineralisation and wet deposition).
The contribution of symbiotically fixed N to total above-ground N yield of the swards decreased from at least 16% to 9% with
increasing altitude where legumes were present. This decrease was due to a decrease in the yield proportion of legumes from
15% at 900 and 1380 m a.s.l. to 5% at 2100 and 2300 m a.s.l. (no legumes were found above 2750 m a.s.l.) and not to a decline
in the activity of symbiotic N2 fixation. With increasing altitude legumes are more patchily distributed. The high symbiotic N2 fixation of individual plants up to their altitudinal limit is not primarily the result of low mineral N availability since
an addition of NH4
+ or NO3
− fertiliser at 2300 m a.s.l. led either to no decrease or only to a minor decrease in symbiotic N2 fixation. At 1380 m a.s.l., N mineralisation (13.45 g N m−2 yr−1) appeared to be the main source of N for growth of the sward; N from symbiosis (at least 1.0 g to 2.6 g N m−2 yr−1) and wet deposition (0.4 g to 0.6 g m−2 yr−1) was not a significant N source for plant growth at this altitude. At 2100 m a.s.l., the combined amounts of N from symbiotic
N2 fixation (at least 0.1 g N m−2 yr−1) and wet deposition (0.3 g N m−2 yr−1) appeared to be similarly important for plant growth as soil N mineralisation (0.47 g N m−2 yr−1). At high altitudes, wet N deposition and symbiotic N2 fixation together represent a significant source of N for the grassland ecosystem while at low altitudes these N inputs appear
to be much less important.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
Nitrogen fixation was measured in monocropped sweet-blue lupin (Lupinus angustifolius), lupin intercropped with two ryegrass (Lolium multiflorum) cultivars or with oats (Avena sativa) on an Andosol soil, using the 15N isotope dilution method. At 117 days after planting and at a mean temperature below 10°C, monocropped lupin derived an average
of 92% or 195 kg N ha−1 of its N from N2 fixation. Intercropping lupin with cereals increased (p<0.05) the percentage of N derived from atmospheric N2 (% Ndfa) to a mean of 96%. Compared to the monocropped, total N fixed per hectare in intercropped lupin declined approximately
50%, in line with the decrease in seeding rate and dry matter yield. With these high values of N2 fixation, selection of the reference crop was not a problem; all the cereals, intercropped or grown singly produced similar
estimates of N2 fixed in lupin. It was deduced from the 15N data that significant N transfer occurred from lupin to intercropped Italian ryegrass but not to intercropped Westerwoldian
ryegrass or to oats. Doubling the 15N fertilizer rate from 30 to 60 kg N ha−1 decreased % Ndfa to 86% (p<0.05), but total N fixed was unaltered. These results indicate that lupin has a high potential for N2 fixation at low temperatures, and can maintain higher rates of N2 fixation in soils of high N than many other forage and pasture legumes. 相似文献
18.
Jean-Michel Harmand Hector Ávila Etienne Dambrine Ute Skiba Sergio de Miguel Reina Vanessa Renderos Robert Oliver Francisco Jiménez John Beer 《Biogeochemistry》2007,85(2):125-139
Nitrogen fertilization is a key factor for coffee production but creates a risk of water contamination through nitrate (NO3−) leaching in heavily fertilized plantations under high rainfall. The inclusion of fast growing timber trees in these coffee
plantations may increase total biomass and reduce nutrient leaching. Potential controls of N loss were measured in an unshaded
coffee (Coffea arabica L.) plot and in an adjacent coffee plot shaded with the timber species Eucalyptus deglupta Blume (110 trees ha−1), established on an Acrisol that received 180 kg N ha−1 as ammonium-nitrate and 2,700 mm yr−1 rainfall. Results of the one year study showed that these trees had little effect on the N budget although some N fluxes
were modified. Soil N mineralization and nitrification rates in the 0–20 cm soil layer were similar in both systems (≈280 kg N ha−1 yr−1). N export in coffee harvest (2002) was 34 and 25 kg N ha−1 yr−1 in unshaded and shaded coffee, and N accumulation in permanent biomass and litter was 25 and 45 kg N ha−1 yr−1, respectively. The losses in surface runoff (≈0.8 kg mineral N ha−1 yr−1) and N2O emissions (1.9 kg N ha−1 yr−1) were low in both cases. Lysimeters located at 60, 120, and 200 cm depths in shaded coffee, detected average concentrations
of 12.9, 6.1 and 1.2 mg NO3−-N l−1, respectively. Drainage was slightly reduced in the coffee-timber plantation. NO3− leaching at 200 cm depth was about 27 ± 10 and 16 ± 7 kg N ha−1 yr−1 in unshaded and shaded coffee, respectively. In both plots, very low NO3− concentrations in soil solution at 200 cm depth (and in groundwater) were apparently due to NO3− adsorption in the subsoil but the duration of this process is not presently known. In these conventional coffee plantations,
fertilization and agroforestry practices must be refined to match plant needs and limit potential NO3− contamination of subsoil and shallow soil water. 相似文献
19.
Summary Tillage has been shown to affect the uptake of phosphorus (P) and yield of soybeans, [Glycine max (L.) Merr.], but there is little information concerning the effects of P fertilization on nitrogen (N2) fixation in soybeans under no-tillage. Two field experiments were conducted in 1980 and 1981 to determine the effects of
soil P on N2 fixation under no-tillage and to study the interaction of P fertilization and tillage of N2 fixation, nutrient uptake, and yield of soybeans. In Exp. I, P was applied in 1977 at five rates up to 384 kg P ha−1 and the effects of residual soil P were evaluated in 1980 and 1981 under no-tillage management. Nitrogen fixation rates,
as measured by acetylene reduction assay, were significantly affected by soil P in Exp. I, but the assay proved to be a poor
technique for estimating total plant N in these tests. Acetylene reduction rates and plant P increased rapidly as soil P increased
from 2 to 20 mg kg−1, with little additional increase above 20 mg P kg−1.
In Exp. II, rates (0, 32, 64, and 128 kg P ha−1) and time (fall, spring and fall plus spring) of P application were compared under conventional tillage and no tillage. However,
plant P increased with increasing levels of applied P. Applied P had no affect on acetylene reduction rates but rates were
greater for no-tillage than conventional tillage at the V9 and R5 stages of growth in 1981. Plant uptake of P was more efficient
under no-tillage than under conventional tillage in 1980 and 1981. Application of 64 kg P ha−1 under no-tillage resulted in equivalent plant P levels as the 128 kg P ha−1 applied under conventional tillage. 相似文献
20.
Effects of N-fertilizers,straw, and dry fallow on the nitrogen balance of a flooded soil planted with rice 总被引:1,自引:0,他引:1
Teresita Santiago-Ventura Marjorie Bravo C. Daez V. Ventura I. Watanabe A. A. App 《Plant and Soil》1986,93(3):405-411
Summary Nitrogen balance studies were made on rice (Oryza sativa) grown in flooded soil in pots. A low rate of fertilizer (5.64 mg N. kg−1 soil) did not depress the N gain, but a high rate (99.72 mg N. kg−1 soil) elminated the N gain. Soil N loss was negligible since15N applied as ammonium sulfate and thoroughly mixed with the soil was recovered from the soil-plant system after 3 crops. The
observed N gain, therefore, was caused by N2-fixation, not by a reduction of soil N loss.
Straw enhanced N gain at the rate of 2–4 mg per g straw. However, this gain was not observed when soil N availability was
high. Dry fallow between rice crops decreased the N gain. 相似文献