共查询到20条相似文献,搜索用时 689 毫秒
1.
Kiril Mishev Petre I. Dobrev Jozef Lacek Roberta Filepov Bistra Yuperlieva-Mateeva Anelia Kostadinova Tsveta Hristeva 《International journal of molecular sciences》2021,22(24)
Belowground interactions of plants with other organisms in the rhizosphere rely on extensive small-molecule communication. Chemical signals released from host plant roots ensure the development of beneficial arbuscular mycorrhizal (AM) fungi which in turn modulate host plant growth and stress tolerance. However, parasitic plants have adopted the capacity to sense the same signaling molecules and to trigger their own seed germination in the immediate vicinity of host roots. The contribution of AM fungi and parasitic plants to the regulation of phytohormone levels in host plant roots and root exudates remains largely obscure. Here, we studied the hormonome in the model system comprising tobacco as a host plant, Phelipanche spp. as a holoparasitic plant, and the AM fungus Rhizophagus irregularis. Co-cultivation of tobacco with broomrape and AM fungi alone or in combination led to characteristic changes in the levels of endogenous and exuded abscisic acid, indole-3-acetic acid, cytokinins, salicylic acid, and orobanchol-type strigolactones. The hormonal content in exudates of broomrape-infested mycorrhizal roots resembled that in exudates of infested non-mycorrhizal roots and differed from that observed in exudates of non-infested mycorrhizal roots. Moreover, we observed a significant reduction in AM colonization of infested tobacco plants, pointing to a dominant role of the holoparasite within the tripartite system. 相似文献
2.
Assessment of carbon stocks in vegetation and soil is a basic step in evaluating the carbon sequestration potential of an
ecosystem. We collected soil (core and composite) samples from 0–10, 10–20, 20–40, and 40–70 cm depths, or down to the bed
rock, in the soil profile of four types of forest (managed dense Shorea (DS), degraded forest (DF), pine mixed (PS), and Schima–Castanopsis (SC) forest) and two types of cultivated land (irrigated low land (Khet) and rain-fed upland (Bari)) in the Pokhare Khola watershed of Nepal. In addition to other essential properties, soil bulk density and carbon concentration
were assessed. Fine roots were also collected from each sampling site. The biomass of standing trees and shrubs was estimated
by using allometric relationships after measuring their diameter and height, while the biomass of grasses was estimated by
a direct measurement of grass from a defined area. The carbon stocks in all forest vegetation (trees, shrubs, and ground grass)
and in the soil profiles under different land uses were estimated. The vegetation carbon pool was largest in DS forest (219 ± 34 Mg ha−1) and least in SC forest (36 ± 5 Mg ha−1), while its order among forest types was DS > DF > PS > SC. The soil organic carbon (SOC) pool was largest in Bari land (15.7 ± 1.5 kg C m−2) and least in PS forest (6.2 ± 0.5 kg C m−2) but the overall order among land uses was Bari > DF > Khet > SC > DS > PS. The total SOC stock in the whole watershed was 59 815 Mg, of which 36, 32, and 32% were in the 0–20, 20–40,
and >40 cm soil depths, respectively. In the surface layer (0–10 cm), SOC stock was highest in Bari (36%) followed by DS (31%), and least was in PS forest (3%). This distribution pattern can primarily be assigned to SOC concentration
and area covered by these land uses. 相似文献
3.
Growth stimulation of ectomycorrhizal fungi by root exudates of Brassicaceae plants: role of degraded compounds of indole glucosinolates 总被引:6,自引:0,他引:6
Brassicaceae plants are nonmycorrhizal. They were found to inhibit VA mycorrhizal infection in their host plants. We tested if they can influence growth of ectomycorrhizal (ECM) fungi. When roots and leaves of Brassicaceae plants and ECM fungi were cultured together in the same petri dishes, the root exudates of turnip (Brassica rapa), swede (B. napobrassica), cabbage (B. oleracea, var. capitata), broccoli (B. oleracea, var. italica Plenck), kohlrobi (B. caulorapa Pasq.), mustard (B. juncea), radish (Raphanus sativus), and choy (B. napus) significantly stimulated hyphal growth of the ectomycorrhizal fungus Paxillus involutus. Root exudates of turnip and cabbage stimulated hyphal growth of Pisolithus tinctorius and two isolates of P. involutus. Colony area of P. involutus was increased by 452 and 414%, respectively, in the presence of turnip and cabbage germinants. Root exudates of turnip increased the biomass of P. involutus and P. tinctorius by 256 and 122% and cabbage by 220 and 82%, respectively. The stimulatory effect was not affected by autoclaving the root exudates. Root exudates had chemical reactions with glutathione and lysine, which resulted in a reduction of the growth stimulation of ECM fungi. Myrosinase enhanced further the stimulatory effects of turnip on the ECM colony diameter growth by 23%. Autoclaved roots and leaves of turnip did not stimulate fungal growth, but mechanically ground roots and leaves of turnip stimulated growth of involutus by 147 and 135%, respectively. After desulfuration with aryl sulphatase, the glucosinolates (GLSs) in turnip roots and leaves were identified by HPLC. The major ones were indole GLSs. Prominent compounds identified were 1-methoxy-3-indolymethyl GLS and 4-methoxy-3-indolymethyl GLS. The finding provides an opportunity to field test the use of Brassicaceae plants in enhancing ectomycorrhizal formation in conifers by interplanting conifers with Brassicaceae plants in forest tree nursery and agroforestry systems. 相似文献
4.
Anna-Kaisa Kähkölä Pekka Nygren Humberto A. Leblanc Taina Pennanen Janna Pietikäinen 《Nutrient Cycling in Agroecosystems》2012,92(1):51-65
Traditionally cacao (Theobroma cacao L.) is cultivated under legume shade trees, which produce N-rich litter that improves soil organic matter content, microbial
activity, and recycles N to the crop. Arbuscular mycorrhiza forming fungi (AMF) are known to play an important role in plant
nutrient uptake, yet their role in plant N uptake from organic residues in tropical agroforestry systems is not clear. We
studied root and leaf litter of the legume shade tree Inga edulis Mart. as a source of N for cacao and the importance of AMF colonisation in the uptake of litter N under controlled conditions.
Leaf and root litter of I. edulis enriched with 15N was added to cacao pots filled with field soil. Half of the cacao saplings were AMF-inoculated and the soil of non-inoculated
saplings was treated with fungicide to suppress AMF. During the 10-week experiment, young cacao leaves were sampled for 15N analyses and at the end of the experiment whole plants were harvested. Microbial populations in the soil were determined
using phospholipid fatty acid (PLFA) analysis, and AMF structures in the roots were quantified. Fungicide treatment decreased
AMF structures in roots and increased bacterial populations, but did not affect the decomposition rate of either litter type.
Inoculated and non-inoculated cacao saplings used 2.6 and 2.1%, respectively, of N added to the pots in leaf litter and 12.1
and 7.1% of N available in root litter indicating that root litter of I. edulis may be a more efficient N source than leaf litter for cacao. Although the fungicide treatment did not completely suppress
AMF in non-inoculated pots, it created sufficient contrast in root AMF colonisation for concluding that AMF significantly
enhanced cacao N use from both litter types. The role of root litter of shade trees as a N source in agroforestry should not
be neglected. 相似文献
5.
Green leaf manuring with prunings of Leucaena leucocephala is regarded as a useful source of N to plants but the actual substitution of N fertilizer, release and recovery of N as well
as effects on soil fertility are not adequately studied. The present studies investigated the effect of sole and combined
use of Leucaena prunings and urea N fertilizer in different proportions on productivity, profitability, N uptake and balance in maize (Zea mays)–wheat (Triticum aestivum) cropping system at New Delhi during 2002–2003 and 2003–2004. Varying quantities of Leucaena green leaf biomass containing 3.83–4.25% N (18.2–20.5 C:N ratio) were applied to provide 0, 25, 50, 75 and 100% of recommended
N (120 kg ha−1) to both maize and wheat before sowing. In general, direct application of urea N increased the productivity of both crops
more than Leucaena green leaf manure, but the reverse was true for the residual effect of these sources. The productivity of maize increased
progressively with increasing proportions of N through urea fertilizer and was 2.41–2.52 t ha−1 with 60 kg N ha−1 each applied through Leucaena and urea, which was at par with that obtained with 120 kg N ha−1 through urea alone (2.56–2.74 t ha−1). Similarly, wheat yield was also near maximum (4.46–5.11 t ha−1) when equal amounts of N were substituted through Leucaena and urea. Residual effects were obtained on the following crops and were significant when greater quantity of N (>50%) was
substituted through Leucaena. Nitrogen uptake and recovery were also maximum with urea N alone, and N recovery was higher in maize (33.4–42.1%) than in
wheat (27.3–29.8%). However, recovery of residual N in the following crop was more from Leucaena N alone (8.5–10.3%) than from urea fertilizer (1.7–3.8%). Residual soil fertility in terms of organic C and KMnO4 oxidizable N showed improvement with addition of Leucaena prunings, which led to a positive N balance at the end of second cropping cycle. Net returns were considerably higher with
wheat than with maize, and were comparatively lower with greater proportion of Leucaena because of its higher cost. Nonetheless, it was beneficial to apply Leucaena and urea on equal N basis for higher productivity and sustainability of this cereal-based cropping system. 相似文献
6.
Farm product diversification, shade provision and low access to fertilizers often result in the purposeful integration of
upper canopy trees in cocoa (Theobroma cacao) plantations. Subsequent modification to light and soil conditions presumably affects nutrient availability and cocoa tree
nutrition. However, the level of complementarity between species requires investigation to minimize interspecific competition
and improve resource availability. We hypothesized beneficial effects of upper canopy trees on cocoa biomass, light regulation,
soil fertility and nutrient uptake. We measured cocoa standing biomass and soil nutrient stocks under no shade (monoculture)
and under three structurally and functionally distinct shade trees: Albizia zygia (D.C.) Macbr, a nitrogen fixer; Milicia excelsa (Welw.), a native timber species; and Newbouldia laevis (Seem.), a native small stature species. Vector analysis was employed to diagnosis tree nutrition. Cocoa biomass was higher
under shade (22.8 for sole cocoa versus 41.1 Mg ha−1 for cocoa under Milicia), and declined along a spatial gradient from the shade tree (P < 0.05). Percent canopy openness differed between the three shade species (P = 0.0136), although light infiltration was within the optimal range for cocoa production under all three species. Soil exchangeable
K was increased under Newbouldia, while available P decreased and total N status was unaffected under all shade treatments. Nutrient uptake by cocoa increased
under shade (43–80% and 22–45% for N and P, respectively), with K (96–140%) as the most responsive nutrient in these multistrata
systems. Addition of low-density shade trees positively affected cocoa biomass close to the shade tree, however proper management
of upper stratum trees is required for optimum cocoa productivity and sustainability. 相似文献
7.
Masahiro Inagaki Koichi Kamo Jupiri Titin Lenim Jamalung Jaffirin Lapongan Satoru Miura 《Nutrient Cycling in Agroecosystems》2010,88(3):381-395
To investigate soil amelioration effects by older tropical fast-wood plantations, we examined the fine litterfall and accompanying
nutrient flux of a 20-year-old Acacia mangium site over 3 years under a wet tropical climate in Sabah, Malaysia. The litterfall of a Swietenia macrophylla site and an Araucaria cunninghamii site was also examined for comparison. Annual nitrogen (N) flux through litterfall (kg N ha−1) was larger in A. mangium (207–223) than in S. macrophylla (126–153) or A. cunninghamii (72–94), whereas annual phosphorus (P) flux through litterfall (kg P ha−1) was considerably smaller in A. mangium (2.7–3.4) than in S. macrophylla (7.5–15.6) or A. cunninghamii (7.8–9.2). N flux through litterfall, forest floor N, and N concentration in topsoil (0–5 cm) were in the order of A. mangium > S. macrophylla > A. cunninghamii, but other element fluxes were not related to concentrations in soils. Our findings suggest that topsoil N increased because
of a large N flux from litterfall. We conclude that these plantation trees, including A. mangium have the potential to produce a N flux in litterfall for the rapid return of organic N to soils larger than or equivalent
to that in adjacent primary forests. However, the litterfall of a single species may lead to deficits of a particular element
and cause nutrient imbalances. Using a mixture of fertilizer tree species or applying mixed litter might be a better solution. 相似文献
8.
Large amounts of nitrogen (N) fertiliser (150–200 kg N/ha) are currently being applied to perennial ryegrass (Lolium perenneL.) seed crops in New Zealand. Due to increasing requirements for efficient use of N fertilisers and minimising nitrate contamination of the environment, a field experiment was established using 15N-labelled fertiliser to follow the fate of applied N. Urea-15N was applied to a perennial ryegrass seed crop in April (30 kg N/ha), August (30 kg N/ha), September (60 kg N/ha) and October (60 kg N/ha). The urea-15N was applied in solution and watered in to minimise volatilisation loss. At the time of harvest (December), 9% of the applied 15N was in the seed, 29% in the straw, 19% in the roots and 39% in the soil organic matter. Losses of 15N were minimal as the N was applied in several applications, each one at a relatively low rate, and at times when leaching was unlikely to occur. Ryegrass plants used a greater proportion of the N applied in September and October (61–65%) compared with that applied in April (44%). Consequently more N was recovered from the soil in the autumn application (57%) than from the September and October applications (28–44%). The availability of the residual fertiliser N to a subsequent wheat (Triticum aestivum L.) crop was studied in a glasshouse experiment. The residual fertiliser N was present in the soil and ryegrass roots and stubble. The wheat plants only recovered 7–9% of this residual N. Most of the N taken up by the wheat came from the soil organic N pool. Overall, applying a total of 180 kg N/ha to the ryegrass appeared to have minimal direct impact on the environment. In the short term N not used by the ryegrass plants contributed to the soil organic N pool. 相似文献
9.
Anup Das J. M. S. Tomar T. Ramesh G. C. Munda P. K. Ghosh D. P. Patel 《Nutrient Cycling in Agroecosystems》2010,87(1):9-19
The climatic conditions of North East India are favorable for trees to produce biomass in the form of foliage and twigs that
are very rich in essential plant nutrients. Effective recycling of this biomass would help meet the nutritional requirement
of crops. Field experiment was conducted in kharif (June–November) seasons for consecutive 3 years (2003, 2004, and 2005) at a lowland farm, subtropical Meghalaya (950 m asl),
India, to study the effect of incorporating N-fixing tree biomass (leaves and twigs) on productivity and economics of rice
(Oryza sativa L.). Fresh biomass from five tree species including erythrina (Erythrina indica), acacia (Acacia auriculiformis), alder (Alnus nepalensis), tree bean (Parkia
roxburghii), and cassia (Cassia siamea) were applied at a rate of 10 t/ha. A plot with recommended NPK rate (80:60:40 kg/ha) and a control plot were also maintained
for comparison. Among the tree species used, the biomass of E. indica was superior in terms of N (3.2%), P (0.47%), K (1.5%), and organic C (18.8%) contents. In the first and second year, productivity
of rice was high with recommended NPK rate (4.82 t/ha in 2003 and 5.08 t/ha in 2004) followed by rice with incorporation of
E. indica biomass. In the third year of the experiment, effects of tree biomass incorporation on growth, yield and yield attributes
surpassed those of the recommended NPK rate, with the exception of A. nepalensis biomass. In that year, the maximum grain yield was recorded under E. indica treatments, exceeding yields under the recommended NPK rate and control by 10.5 and 69.3%, respectively. Incorporation of
tree biomass significantly improved (14–19% N and 62–83% P over control) the stocks of soil available N and P. Treatment with
A.
auriculiformis and E. indica biomass resulted in significantly higher soil organic C content which exceeded that under the recommended NPK rate by 10.3
and 9.2% and that under the control by 15.2 and 14%, respectively higher by species. The highest net return was recorded with
the recommended NPK rate (381/ha) followed by < i > E. indica < /i > ( 381/ha) followed by E. indica ( 303/ha). Since the local farmers are resource poor and rarely use chemical fertilizers, application of plant biomass,
particularly that of E. indica, to lowland rice is a recommendable option to improve productivity and income, and to sustain soil health. 相似文献
10.
35S-labelled gypsum fertilizer was incorporated under field conditions into pastures which were separated into white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) tops and roots. These were added to four soils from improved and unimproved pastures. The re-utilization of labelled fertilizer sulphur (S) was assessed under growth cabinet conditions (20°C day, 13°C night, daylength 16 h, light intensity 120–170 lx) by growing perennial ryegrass plants for 23 weeks.Mean recoveries of labelled fertilizer S varied from 7 to 20% depending on soil type, form amount and kind of plant residue added. Greater recovery was obtained from clover roots (9.5–16.2%) than grass roots (6.7–12.5%), and from grass tops (13.1–19.7%) than clover tops (9.7–17.9%). These results are related to contents of labelled S, total S, C/N, C/S and N/S ratios in plant residues which also accounted for their relative rates of decomposition. Ground (< 1 mm) and chopped (3 mm) roots increased labelled fertilizer S recovery by about 30% compared with whole roots. Additions of unlabelled fertilizer S influenced the recovery of labelled fertilizer S. This effect depends on the amounts of labelled grass roots and unlabelled fertilizer added.The significance of the findings is discussed with the aid of results from previous field experiments conducted on these soils. 相似文献
11.
Anneli Partala Timo Mela Martti Esala Elise Ketoja 《Nutrient Cycling in Agroecosystems》2001,61(3):273-281
Reed canary grass (Phalaris arundinacea L.) is apotential crop for production of bioenergy and biomass in northern Europe. In this study labelled 15N was used to follow the fate of applied N in roots and shoots of reed canary grass during a year. Two rates of15N fertiliser were applied in spring 1995 and 1996 to a clay (50 kg ha−1 and 100 kg ha−1) and an organic soil (30 kg ha−1 and 60 kg ha−1). The data did not indicate significant differences between recoveries of nitrogen following application of fertiliser at
recommended and half of the recommended rates. The recovery of added N in shoots was highest at midsummer. The median values
were 68% and 58% inorganic soil and 42% and 65% in clay soil, in 1995 and 1996respectively. Some of the N utilised by shoots
was remobilised to the roots during autumn. The highest median recovery of applied N in roots was 19%in clay soil in October
1996, corresponding to a 13 percentage unit increase in recovery during autumn. In contrast, the lowest remobilisation was
recorded after a rainy spring in clay soil, being only 3 percentage units. During winter the loss of N and fertiliser N from
the shoots continued, and consequently the total N content in shoots was about half of that for autumn. In spring, one year
after N application, the shoots contained 9–20% of applied N. The data suggest both intensive uptake and remobilisation of
fertiliser N during over a year, following delayed harvest, and indicate the importance of the rhizome system in N turnover.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
Rudrappa T Bonsall J Gallagher JL Seliskar DM Bais HP 《Journal of chemical ecology》2007,33(10):1898-1918
Phragmites australis is considered the most invasive plant in marsh and wetland communities in the eastern United States. Although allelopathy
has been considered as a possible displacing mechanism in P. australis, there has been minimal success in characterizing the responsible allelochemical. We tested the occurrence of root-derived
allelopathy in the invasiveness of P. australis. To this end, root exudates of two P. australis genotypes, BB (native) and P38 (an exotic) were tested for phytotoxicity on different plant species. The treatment of the
susceptible plants with P. australis root exudates resulted in acute rhizotoxicity. It is interesting to note that the root exudates of P38 were more effective
in causing root death in susceptible plants compared to the native BB exudates. The active ingredient in the P. australis exudates was identified as 3,4,5-trihydroxybenzoic acid (gallic acid). We tested the phytotoxic efficacy of gallic acid on
various plant systems, including the model plant Arabidopsis thaliana. Most tested plants succumbed to the gallic acid treatment with the exception of P. australis itself. Mechanistically, gallic acid treatment generated elevated levels of reactive oxygen species (ROS) in the treated
plant roots. Furthermore, the triggered ROS mediated the disruption of the root architecture of the susceptible plants by
damaging the microtubule assembly. The study also highlights the persistence of the exuded gallic acid in P. australis’s rhizosphere and its inhibitory effects against A. thaliana in the soil. In addition, gallic acid demonstrated an inhibitory effect on Spartina alterniflora, one of the salt marsh species it successfully invades.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
A. R. Sharma Ratan Singh S. K. Dhyani R. K. Dube 《Nutrient Cycling in Agroecosystems》2010,87(2):187-197
Mulching with vegetative materials is a highly beneficial and widely-investigated agro-technique in rainfed areas but the
adoption of this practice has been constrained due to non-availability of mulch biomass locally. Live mulching with fast-growing
annual green manure legumes like sunnhemp (Crotalaria juncea) or prunings of Leucaena leucocephala grown as hedge rows can be done for moisture conservation as well as nutrient cycling in the maize–wheat cropping system,
which is predominantly followed in the high rainfall sub-mountainous region of north-western India. A field experiment was
conducted at Selakui, Dehradun during 2000–2004 to study the effect of legume mulching, viz. in situ grown sunnhemp and Leucaena prunings, along with varying N levels, viz. 0, 30, 60 and 90 kg N ha−1 (to maize), and 0, 40 and 80 kg N ha−1 (to wheat) on productivity, soil moisture conservation and soil physico-chemical properties. Intercropped sunnhemp added
0.75–1.45 t dry matter and 21.6–41.3 kg N ha−1 at 30–35 days, while Leucaena twigs added 1.89–4.15 t dry matter and 75.2–161.3 kg N ha−1 at 60–65 days of maize growth. Live mulching with sunnhemp or Leucaena biomass improved soil moisture content at maize harvest (+1.15–1.57%) and crop productivity by 6.8–8.8% over no mulching.
Combined use of both the mulching materials was more effective in improving the soil moisture content (+2.08–2.29%) and grain
yield (15.1%) over their single application. Response of maize to N fertilizer application was significant up to 90 kg N ha−1, and it was relatively more pronounced under the mulching treatments. Residual effect of mulching on wheat showed an increase
in yield of 10.2% with sunnhemp or Leucaena, and 27.9% with sunnhemp + Leucaena. There was an improvement in organic C and total N status of soil, and a decrease in bulk density associated with an increase
in infiltration rate due to mulching at the end of 4 cropping cycles. It was concluded that legume mulching is a highly beneficial
practice for enhanced moisture and nutrient conservation, leading to increased productivity and soil health of maize–wheat
cropping system under Doon valley conditions of north-western India. 相似文献
14.
Pekka Nygren María P. Fernández Jean-Michel Harmand Humberto A. Leblanc 《Nutrient Cycling in Agroecosystems》2012,94(2-3):123-160
We compiled quantitative estimates on symbiotic N2 fixation by trees in agroforestry systems (AFS) in order to evaluate the critical environmental and management factors that affect the benefit from N2 fixation to system N economy. The so-called ??N2-fixing tree?? is a tripartite symbiotic system composed of the plant, N2-fixing bacteria, and mycorrhizae-forming fungi. Almost 100 recognised rhizobial species associated with legumes do not form an evolutionary homologous clade and are functionally diverse. The global bacterial diversity is still unknown. Actinorrhizal symbioses in AFS remain almost unstudied. Dinitrogen fixation in AFS should be quantified using N isotopic methods or long-term system N balances. The general average?±?standard deviation of tree dependency on N2 fixation (%Ndfa) in 38 cases using N isotopic analyses was 59?±?16.6?%. Under humid and sub-humid conditions, the percentage was higher in young (69?±?10.7?%) and periodically pruned trees (63?±?11.8?%) than in free-growing trees (54?±?11.7?%). High variability was observed in drylands (range 10?C84?%) indicating need for careful species and provenance selection in these areas. Annual N2 fixation was the highest in improved fallow and protein bank systems, 300?C650?kg?[N]?ha?1. General average for 16 very variable AFS was 246?kg?[N]?ha?1, which is enough for fulfilling crop N needs for sustained or increasing yield in low-input agriculture and reducing N-fertiliser use in large-scale agribusiness. Leaf litter and green mulch applications release N slowly to the soil and mostly benefit the crop through long-term soil improvement. Root and nodule turnover and N rhizodeposition from N2-fixing trees are sources of easily available N for the crop yet they have been largely ignored in agroforestry research. There is also increasing evidence on direct N transfer from N2-fixing trees to crops, e.g. via common mycelial networks of mycorrhizal fungi or absorption of tree root exudates by the crop. Research on the below-ground tree-crop-microbia interactions is needed for fully understanding and managing N2 fixation in AFS. 相似文献
15.
J. Bayala J. Balesdent C. Marol F. Zapata Z. Teklehaimanot S. J. Ouedraogo 《Nutrient Cycling in Agroecosystems》2006,76(2-3):193-201
The origin of organic matter was studied in the soils of a parkland of karité (Vitallaria paradoxa C.F. Gaertn) and néré (Parkia biglobosa (Jacq.) Benth.), which is extensively cultivated without the use of fertilisers. In such systems, fertility (physical, chemical
and biological) gradients around trees have been attributed by some authors to a priori differences in fertility, allowing
for better tree establishment on richer sites. In reverse, other workers believed that these gradients are due to the contribution
of trees to the formation of soil organic matter through litter and decay of roots. Measurements of the variations in the
13C isotopic composition allowed for a distinction between tree (C3) derived C and crop and grass (C4) derived C in the total soil organic C content. The organic carbon contents of the soils were recorded under the two species
at two soil depths and at five distances going from tree trunk to the open area and their C isotopic signatures were analysed.
The results showed that soil carbon contents under karité (6.43 ± 0.45 g kg−1) and néré (5.65 ± 0.27 g kg−1) were significantly higher (p<0.01) than in the open area (4.09 ± 0.26 g kg−1). The δ13C of soil C was significantly higher (p<0.001) in the open area (−17.5 ± 0.3‰) compared with the values obtained on average with depth and distance from tree under
karité (−20.2 ± 0.4‰) and néré (−20.1 ± 0.4‰). The C4-derived soil C was approximately constant, and the differences in total soil C were fully explained by the C3 (tree) contributions to soil carbon of 4.01 ± 0.71, 3.02 ± 0.53, 1.53 ± 0.10 g kg−1, respectively under karité, néré and in the open area. These results show that trees in parklands have a directly positive
contribution to soil carbon content, justifying the need to encourage the maintenance of trees in these systems in semi-arid
environments where the carbon content of soil appears to be the first limiting factor for crop growth. 相似文献
16.
D. Djumaeva J. P. A. Lamers C. Martius A. Khamzina N. Ibragimov P. L. G. Vlek 《Nutrient Cycling in Agroecosystems》2010,88(3):329-339
Afforestation with fast growing N-fixing trees is an option for ecological restoration of highly-salinized irrigated croplands,
but information about the N-fixing capability of trees on saline soils is sparse. The 15N-enrichment technique (15NET) and the A value (AV) method were used to quantify in lysimeters the proportion of atmospheric N2 (%Ndfa) fixed by Elaeagnus angustifolia L., with a reference to non-N-fixing Gleditsia triacanthos L. and Ulmus pumila L. Twenty kg N ha−1 of 5 atom %15N excess ammonium nitrate (35% N) was applied to 1-year-old trees in 2007 and 2-year-olds in 2008. Since this rate was insufficient
for the older reference trees, 60 kg N ha−1 was applied in 2008. With 15NET, the %Ndfa of E. angustifolia in 2007 was 79% when referenced against U. pumila and 68% against G. triacanthos. With the AV method, the %Ndfa of 2-year-old E. angustifolia was 80 and 68% when referenced against U. pumila and G. triacanthos, respectively. Over 2 years, E. angustifolia fixed 17 kg N ha−1 when related to U. pumila and 14 kg N ha−1 with G. triacanthos (assumed density: 5,000 trees ha−1). N-fixing E. angustifolia has the potential to be self-sufficient in N when planted in the strongly saline soils. 相似文献
17.
Rebbie Harawa Johannes Lehmann Festus Akinnifesi Erick Fernandes George Kanyama-Phiri 《Nutrient Cycling in Agroecosystems》2006,75(1-3):271-284
In Malawi, agroforestry is very promising for N replenishment; however, there are still large variations in the performance of these agroforestry technologies on farmers’ fields. A study was conducted on-farm to determine the influence of three landscape positions on N dynamics in maize (Zea mays L.)-based agroforestry systems. The agroforestry systems were relay fallow using Sesbania sesban (L.) Merr or Tephrosia vogelii (Hook F.), simultaneous fallow using Gliricidia sepium(Jacq.) Walp., and maize without trees as a control. Sesbania was superior to other systems in the bottom slope, producing the highest tree biomass (1,861 kg ha−1), whereas, gliricidia gave the highest tree biomass production in the mid-slope (2,147 kg ha−1) and upper slope (1,690 kg ha−1). Preseason inorganic N, maize flag leaf N concentration, maize total N uptake and maize yields followed a similar trend to tree biomass production with tree-based cropping systems exhibiting higher productivity (P < 0.05) than the cropping systems without trees. Nitrogen leaching from gliricidia agroforestry systems was lower than in the other agroforestry systems across all landscape positions as evidenced by 17% lower amounts (P < 0.05) of inorganic N adsorbed to ionic exchange resin membranes at 60 cm soil depth most likely due to the permanent root system of gliricidia. The difference between δ15N values of the trees and the soil did not change between landscape positions suggesting that if the leguminous trees fixed atmospheric N2, the proportion of total N uptake was identical at all locations. We concluded that landscape positions have a significant effect on tree performance with sesbania remarkably adapted to the bottom slope, gliricidia to the mid-slopes and tephrosia fairing similar in both the bottom slope and mid-slopes. 相似文献
18.
Tonny P. Tauro Hatirarami Nezomba Florence Mtambanengwe Paul Mapfumo 《Nutrient Cycling in Agroecosystems》2010,88(1):91-101
Developing soil fertility management options for increasing productivity of staple food crops is a challenge in most parts
of Sub-Saharan Africa, where soils are constrained by nitrogen (N) and phosphorus (P) deficiencies. A study was conducted
to evaluate the response of indigenous legume populations to mineral P application, and subsequently their benefits to maize
yield. Mineral P was applied at 26 kg P ha−1 before legume species were sown in mixtures at 120 seeds m−2 species−1 and left to grow over two rainy seasons (2 years). Application of P increased overall biomass productivity by 20–60% within
6 months, significantly influencing the composition of non-leguminous species. Dinitrogen fixation, as determined by the
N-difference method, was increased by 43–140% although legume biomass productivity was apparently limited by nutrients other
than P and N. Crotalaria pallida and C. ochroleuca accounted for most of the fixed N. Improved N supply increases the abundance of non-leguminous species, particularly Conyza sumatrensis and Ageratum conyzoides. However, abundance of common weed species, Commelina benghalensis, Richardia scabra and Solanum aculeastrum, declined by up to18%. Application of P did not significantly influence productivity of those legume species that reached
maturity within 3 months. There was increased N2-fixation and biomass productivity of indifallows as influenced by specific legume species responding to P application. Compared
with natural (grass) fallows, indigenous legume fallows (indifallows) increased subsequent maize grain yields by ~40%. Overall,
1- and 2-year indifallows gave maize grain yields of >2 and 3 t ha−1, respectively, against <1 t ha−1 under corresponding natural fallows. Two-year indifallows with P notably increased maize yields, but the second year gave
low yields regardless of P treatment. Because of their low P requirement, indigenous legume fallows have potential to stimulate
maize productivity under some of the most nutrient depleted soils. 相似文献
19.
The contribution of biologically fixed dinitrogen (N2) to the nitrous oxide (N2O) production in grasslands is unknown. To assess the contribution of recently fixed N2 as a source of N2O and the transfer of fixed N from clover to companion grass, mixtures of white clover and perennial ryegrass were incubated
for 14 days in a growth cabinet with a 15N2-enriched atmosphere (0.4 atom% excess). Immediately after labelling, half of the grass–clover pots were sampled for N2 fixation determination, whereas the remaining half were examined for emission of 15N labelled N2O for another 8 days using a static chamber method. Biological N2 fixation measured in grass–clover shoots and roots as well as in soil constituted 342, 38 and 67 mg N m−2 d−1 at 16, 26 and 36 weeks after emergence, respectively. The drop in N2 fixation was most likely due to a severe aphid attack on the clover component. Transfer of recently fixed N from clover to
companion grass was detected at 26 and 36 weeks after emergence and amounted to 0.7 ± 0.1 mg N m−2 d−1, which represented 1.7 ± 0.3% of the N accumulated in grass shoots during the labelling period. Total N2O emission was 91, 416 and 259 μg N2O–N m−2 d−1 at 16, 26 and 36 weeks after emergence, respectively. Only 3.2 ± 0.5 ppm of the recently fixed N2 was emitted as N2O on a daily basis, which accounted for 2.1 ± 0.5% of the total N2O–N emission. Thus, recently fixed N released via easily degradable clover residues appears to be a minor source of N2O.
An erratum to this article is available at . 相似文献
20.
Gilbert C. Sigua Robert K. Hubbard Samuel W. Coleman Mimi Williams 《Nutrient Cycling in Agroecosystems》2010,86(2):175-187
Despite substantial measurements using both laboratory and field techniques, little is known about the spatial and temporal
variability of nitrogen (N) dynamics across the landscapes, especially in agricultural landscapes with cow–calf operations.
This study was conducted to assess the comparative levels of total inorganic nitrogen, TIN (NO3–N + NH4–N) among soils, forage, surface water and shallow groundwater (SGW) in bahiagrass (Paspalum notatum, Flueggé) pastures. Soil samples were collected at 0–20, 20–40, 40–60, and 60–100 cm across the pasture’s landscape (top
slope, TS; middle slope, MS; and bottom slope, BS) in the spring and fall of 2004, 2005 and 2006, respectively. Bi-weekly
(2004–2006) groundwater and surface water samples were taken from wells located at TS, MS, and BS and from the run-off/seepage
area (SA). Concentrations of NH4–N, NO3–N, and TIN in SGW did not vary with landscape position (LP). However, concentrations of NH4–N, NO3–N, and TIN in water samples collected from the seep area were significantly (P ≤ 0.05) higher when compared to their average concentrations in water samples collected from the different LP. Average concentrations
of NO3–N (0.4–0.9 mg l−1) among the different LP were well below the maximum, of 10 mg l−1, set for drinking water. The maximum NO3–N concentrations (averaged across LP) in SGW for 2004, 2005 and 2006 were also below the drinking water standards for NO3–N. Concentration of TIN in soils varied significantly (P ≤ 0.05) with LP and soil depth. Top slope and surface soil (0–20 cm) had the greatest concentrations of TIN. The greatest
forage availability of 2,963 ± 798 kg ha−1 and the highest N uptake of 56 ± 12 kg N ha−1 were observed from the TS in 2005. Both forage availability and N uptake of bahiagrass at the BS were consistently the lowest
when averaged across LP and years. These results can be attributed to the grazing activities as animals tend to graze more
at the BS. The average low soil test value of TN (across LP and soil depth) in our soils of 10.9 mg kg−1 (5.5 kg N ha−1) would indicate that current pasture management including cattle rotation in terms of grazing days and current fertilizer
application (inorganic + feces + urine) for bahiagrass pastures may not have negative impact on the environment. 相似文献