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1.
The application of herbicides has induced symptoms of nutrient deficiencies under some circumstances. This glasshouse study
examined the effect of chlorsulfuron on the uptake and utilization of copper (Cu) in four cultivars of wheat plants (Triticum aestivum L. cvs. Kulin, Cranbrook, Gamenya and Bodallin) on a Cu-responsive soil. Application of chlorsulfuron depressed the concentration
of Cu in wheat plants receiving either inadequate or adequate Cu. In plants with inadequate Cu supply, chlorsulfuron increased
the severity of Cu deficiency. Shoot weight was markedly decreased by chlorsulfuron at all levels of Cu, through decreasing
the number of tillers and the elongation of leaves. This decreased growth of shoots occurred prior to the effect on Cu concentration
in tissues. The retranslocation of Cu in old tissues over time was unaffected by chlorsulfuron. In all wheat cultivars, the
decreased growth of shoots were correlated with the concentration of Cu in the youngest fully emerged leaf blade with critical
levels of 1.6−1.7 at day 25 and 0.9−1.0 μg g−1 d. wt. at day 60. The application of chlorsulfuron tended to increase the critical level at day 25 but not at day 60. In
addition, Kulin seems to be most, and Cranbrook least, sensitive to chlorsulfuron. This sensitivity was associated with the
sensitivity of the cultivars to Cu deficiency. It is suggested that chlorsulfuron application induces Cu deficiency in wheat
plants mainly due to effects on the uptake of Cu.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
The nitrogen mineralization rate of legume residues in soil as influenced by their polyphenol,lignin, and nitrogen contents 总被引:13,自引:1,他引:12
A 12-week greenhouse experiment was conducted to determine the effect of the polyphenol, lignin and N contents of six legumes on their N mineralization rate in soil and to compare estimates of legume-N release by the difference and 15N-recovery methods. Mature tops of alfalfa (Medicago sativa L.), round leaf cassia (Cassia rotundifolia Pers., var. Wynn), leucaena (Leucaena leucocephala Lam., deWit), Fitzroy stylo (Stylosanthes scabra Vog., var Fitzroy), snail medic (Medicago scutellata L.), and vigna (Vigna trilobata L., var verde) were incorporated in soil at the rate of 100 mg legume N kg-1 soil. The medic and vigna were labeled with 15N. Sorghum-sudan hybrid (Sorghum bicolor, L. Moench) was used as the test crop. A non-amended treatment was used as a control. Net N mineralization after 12 weeks ranged from 11% of added N with cassia to 47% of added N for alfalfa. With the two legumes that contained less than 20 g kg-1 of N, stylo and cassia, there was net N immobilization for the first 6 weeks of the experiment. The legume (lignin + polyphenol):N ratio was significantly correlated with N mineralization at all sampling dates at the 0.05 level and at the 0.01 level at 6 weeks (r2=0.866). Legume N, lignin, or polyphenol concentrations or the lignin:N ratio were not significantly correlated with N mineralization at any time. The polyphenol:N ratio was only significantly correlated with N mineralization after 9 weeks (r2=0.692). The (lignin + polyphenol):N ratio appears to be a good predictor of N mineralization rates of incorporated legumes, but the method for analyzing plant polyphenol needs to be standardized. Estimates of legume-N mineralization by the difference and 15N recovery methods were significantly different at all sampling dates for both 15N-labeled legumes. After 12 weeks, estimates of legume-N mineralization averaged 20% more with the difference method than with the 15N recovery method. This finding suggests that estimates of legume N available to subsequent crops should not be based solely on results from 15N recovery experiments. 相似文献
3.
Erik Steen Jensen 《Plant and Soil》1996,182(1):13-23
Field experiments were carried out on a temperate soil to determine the decline rate, the stabilization in soil organic matter and the plant uptake of N from 15N-labelled crop residues. The fate of N from field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) residues was followed in unplanted and planted plots and related to their chemical composition. In the top 10 cm of unplanted plots, inorganic N was immobilized after barley residue incorporation, whereas the inorganic N pool was increased during the initial 30 days after incorporation (DAI) of pea residues. Initial net mineralization of N was highly correlated to the concentrations of soluble C and N and the lignin: N ratio of residues. The contribution of residue-derived N to the inorganic N pool was at its maximum 30 DAI (10–55%) and declined to on average 5% after 3 years of decomposition.Residual organic labelled N in the top 10 cm soil declined rapidly during the initial 86 DAI for all residue types. Leaching of soluble organic materials may have contributed to this decline. At 216 DAI 72, 59 and 45% of the barley, mature pea and green pea residue N, respectively, were present in organic N-forms in the topsoil. During the 1–3 year period, residual organic labelled N from different residues declined at similar rates, mean decay constant: 0.18 yr-1. After 3 years, 45% of the barley and on average 32% of the pea residue N were present as soil organic N. The proportion of residue N remaining in the soil after 3 years of decomposition was most strongly correlated with the total and soluble N concentrations in the residue. The ratio (% inorganic N derived from residues): (% organic N derived from residues) was used as a measure of the rate residue N stabilization. From initial values of 3–7 the ratios declined to on average 1.9 and 1.6 after 2 and 3 yrs, respectively, indicating that a major part of the residue N was stabilized after 2 years of decomposition. Even though the largest proportion of residue N stabilized after 3 years was found for barley, the largest amount of residue N stabilized was found with incorporation of pea residues, since much more N was incorporated with these residues.In planted plots and after one year of decomposition, 7% of the pea and 5% of the barley residue N were recovered in perennial ryegrass (Lolium perenne L.) shoots. After 2 years the cumulative recovery of residue N in ryegrass shoots and roots was 14% for pea and 15% for barley residue N. The total uptake of non-labelled soil N after 2 years of growth was similar in the two residue treatments, but the amount of soil N taken up in each growth period varied between the treatments, apparently because the soil N immobilized during initial decomposition of residues was remineralized later in the barley than in the pea residue treatment. Balances were established for the amounts of barley and mature pea residue N remaining in the 0–10 cm soil layer and taken up in ryegrass after 2 years of decomposition. About 24% of the barley and 35% of the pea residue N were unaccounted for. Since these apparent losses are comparable to almost twice the amounts of pea and barley residue N taken up by the perennial ryegrass crop, there seems to be a potential for improved crop residue management in order to conserve nutrients in the soil-plant system. 相似文献
4.
Manipulation of quality and mineralization of tropical legume tree prunings by varying nitrogen supply 总被引:5,自引:1,他引:4
The effect of N supply on the quality of Calliandra calothyrsus and Gliricidia sepium prunings was studied in a glasshouse over a 7-month growing period. Increasing the concentration of N supplied from 0.625 to 10.0 mM NO3-N resulted in increased N concentration but decreased polyphenol concentration, protein-binding capacity and C:N ratio of prunings from both species. Lignin concentration was not consistently altered by the N treatment. Mineralization of N from the prunings was measured over a 14-week period under controlled leaching and non-leaching conditions. The results indicated a strong interaction between legume species and concentration of N supply in their influence on N mineralization of the prunings applied to the soil. Differences in the %N mineralized were dictated by the quality of the prunings. The (lignin + polyphenol):N ratio was the pruning quality factor which could be used most consistently and accurately to predict N mineralization of the legume prunings incubated under leaching conditions, and the relationship was best described by a linear regression. Under non-leaching conditions, however, the protein-binding capacity appeared to be the most important parameter in determining the patterns of N release from the prunings studied. The relationship between the N mineralization rate constant and the protein-binding capacity was best described by a negative exponential function, y=0.078 exp(–0.0083x). The present study also indicated that the release of N from legume prunings containing a relatively high amount of polyphenol could be enhanced by governing the N availability conditions under which the plant is grown, for example whether or not it is actively fixing nitrogen. Estimates of pruning N mineralization after 14 weeks with the difference method averaged 6% (leaching conditions) and 22% (nonleaching conditions) more than with the 15N method for all legume prunings studied. The recovery of pruning by maize (4–38%) was well correlated with the % pruning N mineralized suggesting that incubation data closely reflect the pruning N value for a given catch crop under non-leaching conditions. 相似文献
5.
Soil nitrogen heterogeneity in a Dehesa ecosystem 总被引:1,自引:0,他引:1
The C mineralization and N transformations during the decomposition of sunflower stalks (Helianthus annuus L.) and wheat straw (Triticum aestivum L.) with and without addition of (NH4)2SO4 (27.53 atom% 15N) were studied in a Vertisol. Soil samples were incubated under aerobic conditions for 224 days at 22 °C. The plant residues
were added at a rate of 5.2 g kg-1 soil. Nitrogen was applied at a rate of 50.7 mg N kg-1 soil. Carbon dioxide emission and inorganic N content in soil were periodically determined. Gross N immobilization and remineralization
were calculated on the basis of the isotopic dilution technique. At the end of the incubation period a 15N balance was established. Respectively, 68 and 45% of the applied residue-C mineralized from the sunflower stalks and wheat
straw after 224 days. Both crop residues caused losses of up to 25% of added 15N after 224 days of incubation. These 15N losses were about three times larger than in the control soil, and were probably due to denitrification. The net immobilization
of soil derived N following residue incorporation was largest in the case of wheat straw, depleting all soil inorganic N.
In the wheat straw treatment with added (NH4)2SO4 soil inorganic N remained available, resulting in an enhanced initial C mineralization and N immobilization compared to the
treatment without added N. In the case of the sunflower stalks, the high inorganic N content of the stalks suppressed the
effects of N addition on C mineralization and N immobilization/mineralization. Gross N immobilization amounted to 31.9 and
28.2 mg N g-1 added C after 14 days for wheat straw and sunflower stalks, respectively. At the end of the incubation, about 35% of the
newly immobilized N was remineralized in both plant residue treatments. Gross N immobilization plotted against decomposed
C suggests that fairly uniform C-N relationships exist during the decomposition of divers C substrates. The results demonstrate
that low fertilizer N use efficiencies may be expected in a wheat-sunflower cropping system with incorporation of crop residues,
as the fertilizer N applied becomes largely immobilized in the soil organic fraction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Erick Zagal 《Plant and Soil》1994,160(1):21-31
A pot experiment was conducted in a 14C-labelled atmosphere to study the influence of living plants on organic-N mineralization. The soil organic matter had been labelled, by means of a 200-days incubation, with 15N. The influence of the carbon input from the roots on the formation of microbial biomass was evaluated by using two different light intensities (I). Mineralization of 15N-labelled soil N was examined by following its fate in both the soil biomass and the plants. Less dry matter accumulated in shoots and roots at the lower light intensity. Furthermore, in all the plant-soil compartments examined, with the exception of rhizosphere respiration, the proportion of net assimilated 14C was lower in the low-I treatment than in the high-I treatment. The lower rates of 14C and 15N incorporation into the soil biomass were associated with less root-derived 14C. During the chamber period (14CO2-atmosphere), mineralized amounts of 15N (measured as plant uptake of 15N) were small and represented about 6.8 to 7.8% of the initial amount of organic 15N in the soil. Amounts of unlabelled N found in the plants, as a percentage of total soil N, were 2.5 to 3.3%. The low availability of labelled N to microorganisms was the result of its stabilization during the 210 days of soil incubation. Differences in carbon supply resulted in different rates of N mineralization which is consistent with the hypothesis that roots induce N mineralization. N mineralization was higher in the high-I treatment. On the other hand, the rate of mineralization of unlabelled stable soil N was lower than labelled soil 15N which was stabilized. The amounts of 15N mineralized in planted soil during the chamber period (43 days) which were comparable with those mineralized in unplanted soil incubated for 210 days, also suggested that living plants increased the turnover rate of soil organic matter. 相似文献
7.
Summary A laboratory incubation experiment followed by a greenhouse experiment was made in a silty clay loam at Pantnagar, India, to recycle plant utilizable N from crop residues such as maize stubble, soybean hay andmoong straw. The beneficial effect of recycled N was tested by a wheat crop. Soybean hay yielded the most NO3–N upon mineralization and also gave the highest wheat grain yield. Maize stubble mineralized the least NO3–N and gave the lowest grain yield.Moong straw occupied an intermediate position. An intervening period of 30–45 days would be required for the residues in question to release plant utilizable NO3–N in sufficient quantities. From a practical view point, soybean hay appears to be an ideal choice of a residue capable of providing sufficient supplemental N for a succeding wheat crop and can be easily fitted into the prevalent cropping sequence. 相似文献
8.
Residual nitrogen contribution from grain legumes to succeeding wheat and rape and related microbial process 总被引:10,自引:2,他引:8
Jochen Mayer Franz Buegger Erik Steen Jensen Michael Schloter Jürgen Heß 《Plant and Soil》2003,255(2):541-554
The residual N contribution from faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) to microbial biomass and subsequent wheat (Triticum aestivum L.) and oilseed rape (Brassica napus L.) was studied in a greenhouse experiment. The grain legumes were 15N labelled in situ with a stem feeding method before incorporated into the soil, which enables the determination of N rhizodeposition. Wheat and rape were subsequently grown on the soil containing the grain legume residues (incl. 15N-labelled rhizodeposits) and were harvested either twice at flowering and at maturity or once at maturity, respectively. The average total N uptake of the subsequent crops was influenced by the legume used as precrop and was determined by the residue N input and the N2-fixation capacity of the legume species. The succeeding crops recovered 8.6–12.1% of the residue N at maturity. Similar patterns were found for the microbial biomass, which recovered 8.2–10.6% of the residue N. Wheat and rape recovered about the same amount of residue N. The absolute contribution of soil derived N to the subsequent crops was similar in all treatments and averaged 149 mg N pot–1 at maturity. At flowering 17–23% of the residue derived N was recovered in the subsequent wheat and in the microbial biomass; 70% of the residue N was recovered in the microbial biomass in the flowering stage and decreased to about 50% at maturity. In contrast, the recovery in wheat and rape constituted only 30% at flowering and increased to 50% at maturity in all treatments, indicating that the residual N uptake by the subsequent wheat was apparently supplied by mobilisation of residue N temporarily immobilised in the microbial biomass. 相似文献
9.
Decomposition and Mineralization of Organic Residues Predicted Using Near Infrared Spectroscopy 总被引:1,自引:0,他引:1
Characterization of decomposition characteristics is important for sound management of organic residues for both soils and
livestock, but routine residue quality analysis is hindered by slow and costly laboratory methods. This study tested the accuracy
and repeatability of near-infrared spectroscopy (NIR) for direct prediction of in vitro dry matter digestibility (IVDMD) and C and N mineralization for a diverse range of organic materials (mostly crop and tree
residues) of varying quality (n = 32). The residue samples were aerobically incubated in a sandy soil and amounts of C and N mineralized determined after
28 days. IVDMD and quality attributes were determined using wet chemistry methods. Repeatability was higher with NIR than
the original wet chemistry methods: on average NIR halved the measurement standard deviation. NIR predicted IVDMD and C and
N mineralization more accurately than models based on wet chemical analysis of residue quality attributes: reduction in root
mean square error of prediction with NIR, compared with using quality attributes, was IVDMD, 6%; C mineralization after 28 days,
8%; and N mineralization after 28 days, 8%. Cross-validated r
2 values for measured wet chemistry vs. NIR-predicted values were: IVDMD, 0.88; C mineralization, 0.82; and N mineralization,
0.87. Direct prediction of decomposition and mineralization from NIR is faster, more accurate and more repeatable than prediction
from residue quality attributes determined using wet chemistry. Further research should be directed towards establishment
of diverse NIR calibration libraries under controlled conditions and direct calibration of soil quality, crop and livestock
responses in the field to NIR characteristics of residues. 相似文献
10.
Cover crop roots and shoots release carbon (C) and nitrogen (N) compounds in situ during their decomposition. Depending upon the season, these C and N compounds may be sequestered, the C may be respired or the N may be leached below the root zone. A field study was established to identify the contributions of cover crop root and shoot N to different regions within aggregates in the Ap horizon of a Kalamazoo loam soil. Fall-planted rye plants (Secale cerealeL.) were labeled the next May with foliar applications of solutions containing 99% atom (15NH4)2SO4. Isotopic enrichment of soil aggregates ranging from 2.0 to 4.0, 4.0–6.3 and 6.3–9.5 mm across was determined following plant residue applications. Concentric layers of aggregates were removed from each aggregate by newly designed meso soil aggregate erosion (SAE) chambers. Non-uniform distributions of total N and recently derived rye N in soil macroaggregates, across time, suggested that the formations and functions of macroaggregates are very dynamics processes and soil aggregates influence where N is deposited. Early in the season, more 15N migrated to the interior regions of the smallest aggregates, 2–4 mm across, but it was limited to only surfaces and transitional regions of the larger aggregates, 6.3–9.3 mm across. Exterior layers of aggregates between 6.0 and 9.5 mm retained 1.6% of the Nderived from roots in July 1999, which was three times more than their interior regions. This was slightly greater than the % Nderived from shoot. One month later, as the maize root absorption of N increased rapidly, % Nderived from roots and % Nderived from shoot were nearly equal in exterior layers and interior regions of soil aggregates. This equilibrium distribution may have been from either greater diffusion of N within the aggregates and/or maize root removal form aggregate exteriors. Results supported that most of roots grew preferentially around surfaces of soil aggregates rather than through aggregates. Cover crop roots contributed as much N as cover crop shoots to the total soil N pool. Subsequent crops use N from the most easily accessible zones of soil structure, which are surfaces of larger soil aggregates. Therefore maintaining active plant roots and aggregated soil structure in the soil enhances N sequestration and maximize soil N availability. These studies suggest that the rapid and perhaps bulk flow of soil N solutions may bypass many of the central regions of soil aggregates, resulting in greater leaching losses. 相似文献
11.
Thomas Larsen Antonie Gorissen Paul Henning Krogh Marc Ventura Jakob Magid 《Plant and Soil》2007,295(1-2):253-264
It has been demonstrated that plant roots can take up small amounts of low-molecular weight (LMW) compounds from the surrounding
soil. Root uptake of LMW compounds have been investigated by applying isotopically labelled sugars or amino acids but not
labelled organic matter. We tested whether wheat roots took up LMW compounds released from dual-labelled (13C and 15N) green manure by analysing for excess 13C in roots. To estimate the fraction of green manure C that potentially was available for root uptake, excess 13C and 15N in the primary decomposers was estimated by analysing soil dwelling Collembola that primarily feed on fungi or microfauna.
The experimental setup consisted of soil microcosm with wheat and dual-labelled green manure additions. Plant growth, plant
N and recoveries of 13C and 15N in soil, roots, shoots and Collembola were measured at 27, 56 and 84 days. We found a small (<1%) but significant uptake
of green manure derived 13C in roots at the first but not the two last samplings. About 50% of green manure C was not recovered from the soil-plant
system at 27 days and additional 8% was not recovered at 84 days. Up to 23% of C in collembolans derived from the green manure
at 56 days (the 27 days sampling was lost). Using a linear mixing model we estimated that roots or root effluxes provided
the main C source for collembolans (54−79%). We conclude that there is no solid support for claiming that roots assimilated
green manure derived C due to very small or no recoveries of excess 13C in wheat roots. During the incubation the pool of green manure derived C available for root uptake decreased due to decomposition.
However, the isotopic composition in Collembola indicated that there was a considerable fraction of green manure derived C
in the decomposer system at 56 days thus supporting the premise that LMW compounds containing C from the green manure was
released throughout the incubation.
Responsible Editor: A. C. Borstlap. 相似文献
12.
C and N mineralization kinetics of 25 catch crop (CC) residues, whose organic C:N ratio varied from 9.5 to 34.0, were studied during soil incubations under controlled conditions. Decomposition rates were rather similar for the different CC residues, 59% to 68% residue-C being mineralized after 168 days incubation. C mineralized during the first weeks was mainly correlated to the soluble C content of the residue. N mineralized from CC residues was much more variable (?4.9 to +38.0 mg N g?1 added C at day 168), and was mainly related to the organic N content in residues. C and N mineralization kinetics were simulated with STICS residue decomposition model, using the previous parameterization mostly based on mature crop residues (Nicolardot et al. Plant Soil 228:83–103, 2001). A reasonable agreement was found between measured and simulated C kinetics but N mineralization was underestimated by the model. A new parameterization was carried out to improve N predictions. The fitting procedure was first applied independently to each CC residue in order to optimise the five parameters of the model. The relationships found between each optimised parameter and the C:N ratio of CC residues were similar to those obtained previously, indicating that the same model was applicable to all residues. The parameters of these relationships were fitted on a combined dataset including CC and mature residues. The new parameterisation lead to better simulations for CC residues, the errors of prediction (RMSE) for C and N mineralization being 32 and 1.8 mg g?1 added C, respectively. For the whole dataset (68 residues), the RMSE were 50 and 3.3 mg g?1 added C. The prediction quality is satisfactory with respect to the model simplicity and the single criterion of residue quality (C:N ratio). 相似文献
13.
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
14.
Fractional changes in phenolic acids composition in root nodules of Arachis hypogaea L. 总被引:1,自引:0,他引:1
Phenolic acids are active antimicrobial compounds and root signaling molecules that play important roles in plant defense
responses. They are generally present in plants as glycosides or esters. A range of soluble and bound phenolic acids were
detected in roots and root nodules of Arachis hypogaea L., among which five were identified by high performance liquid chromatography (HPLC) coupled with UV–Vis diode array detector
(DAD), viz., p-coumaric acid (p-com), p-hydroxybenzaldehyde (HBAld), p-hydroxybenzoic acid (HBA), caffeic acid (CA) and protocatechuic acid (PA). Para-coumaric acid was constitutively present
in all fractions whereas HBA was present in the soluble form only in young nodules. CA and PA were mostly present in the wall
bound fraction. The root nodules contain higher concentration of phenolic acids than non-nodulated roots and presence of peroxidase
and polyphenol oxidase indicate the metabolism of phenolic acids in roots and root nodules. These results indicate that phenolic
acids (p-com and CA) in bound-glycosidic or ester forms were major components in cell wall fortification which provide protection
to the root nodule from pathogen attack. 相似文献
15.
N2O emission from soil following combined application of fertiliser-N and ground weed residues 总被引:1,自引:0,他引:1
Emissions of N2O and CO2 were measured following combined applications of 15N-labelled fertiliser (100 μg N g−1; 10 atom % excess 15N) and organic olive crop weed residues (Avena sativa, Ononis viscosa, Ridolfia segetum and Olea europea; 100 μg N g−1) to a silt loam soil under controlled environment conditions. The objective was to determine the effect of varying combinations
of inorganic fertiliser and plant residues on these emissions and soil mineral N dynamics. Emissions were generally increased
following application of residues alone, with 23 ng N2O–N g−1 soil (2 ng N2O–N g−1 soil mg−1 biomass) and 389 μg CO2–C g−1 soil (39 μg CO2–C g−1 soil mg−1 biomass) emitted over 28 days after addition of the Ridolfia residues in the absence of fertiliser-N. N2O emissions from these residue-only treatments were strongly negatively correlated with residue lignin content (r = −0.91; P < 0.05), total carbon content (r = −0.90; P < 0.05) and (lignin + polyphenol)-to-N ratio (r = −0.70; P < 0.1). However, changes in the net input of these compounds through application of 25:75, 50:50 and 75:25 proportional mixtures
of Avena and Ononis residues had no effect on emissions compared to their single (0:100 or 100:0) applications. Addition of fertiliser-N increased
emissions (by up to 30 ng N2O–N g−1 28 days−1; 123%), particularly from the low residue-N treatments (Avena and Ridolfia) where a greater quantity of biomass was applied, resulting in emissions above that of the sum from the unfertilised residue
and fertilised control treatments. In contrast, fertiliser application had no impact on emissions from the Olea treatment with the highest polyphenol (2%) and lignin (11%) contents due to strong immobilisation of soil N, and the 15N–N2O data indicated that residue quality had no effect on the denitrification of applied fertiliser-N. Such apparent inconsistencies
mean that before the potential for manipulating N input (organic + inorganic) to lower gaseous N losses can be realised, first
the nature and extent of interactions between the different N sources and any interactions with other compounds released from
the residues need to be better understood. 相似文献
16.
Can the Biochemical Features and Histology of Wheat Residues Explain their Decomposition in Soil? 总被引:1,自引:0,他引:1
Isabelle Bertrand Brigitte Chabbert Bernard Kurek Sylvie Recous 《Plant and Soil》2006,281(1-2):291-307
The biochemical characteristics or quality of crop residues is an important factor governing soil residue decomposition. To
improve C and N biotransformation models the process underlying this decomposition needs to be better understood and new quality
criteria found to describe it. The aims of this explorative study were to (i) improve our understanding of residue decomposition
from detailed studies of cell wall biochemical compositions and tissue architecture (ii) find new ways of exploring generic
indicators of organic matter quality. To do this, the cell wall composition and tissue architecture of wheat leaves, internodes
and roots, before and after their incorporation into soil were determined. Results showed that leaves which were poorly lignified
decomposed faster in soil than internodes and roots. Cellulose was the most degraded polysaccharide irrespective of wheat
residue. However, cellulose was much more degraded in the case of leaves as compared to internodes and roots. Leaves also
presented a highly condensed lignin structure and the extent to which uncondensed leaf lignin was affected by soil decomposition
suggests that the contribution of leaf lignin to C mineralization during incubation was very low. Roots which contained similar
amounts of lignin than the internodes decomposed more slowly. Roots were enriched in phenolic acids, and more particularly
p-coumaric acid (pCA) and presented a more condensed lignin structure than internodes. Phenolic acids are involved in the formation
of lignin–polysaccharide complexes known to be recalcitrant to enzymatic attack. Microscopic investigations confirmed that
the vessels were the most resistant tissues to decomposition in soil and this could be related either to their lignin content
or to the quality of this lignin (condensed-like type lignin). Therefore, cell wall biochemical analyses have revealed that
phenolic acids, which in their esterified form represent only 0.1–1% of plant dry matter, have cross link functions within
the cell walls that could be of major interest in estimating soil residue degradability. Lignin quality (monomers, level of
condensation) was another crucial criterion that could explain why residues with similar amounts of lignin decomposed at different
rates in soil (roots vs. aerial parts). Visualization of residue cell walls before and after decomposition in soil underlined
the interest of a microscopic approach coupled with image analysis. This study, corroborated by the extensive literature on
forage digestibility, confirmed that the proportions of vascular tissue and sclerenchyma cells in plant material are determinant
factors affecting plant degradability. In the future, classification of plant material based on these criteria could lead
to the definition of new quality parameters for models of C and N biotransformation in soil. 相似文献
17.
A method is evaluated that employs variation in stable C and N isotopes from fractionations in C and N acquisition and growth
to predict root biomasses of three plant species in mixtures. Celtis laevigata Willd. (C3), Prosopis glandulosa Torr. (C3, legume) and Schizachyrium scoparium (Michx.) Nash (C4), or Gossypium hirsutum L. (C3), Glycine max (L.) Merr. (C3 legume), and Sorghum bicolor (L.) Moench (C4) were grown together in separate, three-species combinations. Surface roots (0–10 cm depth) of each species from each of
the two combinations were mixed in various proportions, and the relative abundances of 15N and 14N and 13C and 12C in prepared mixtures, surface roots of single species, and roots extracted from the 80-cm soil profile in which each species
combination was grown were analyzed by mass spectrometry. An algebraic determination which employed the δ 13C, % 15N, and C and N concentrations of root subsamples of individual species accounted for more than 95% of the variance in biomass
of each species in prepared mixtures with G. max, G. hirsutum, and S. bicolor. A similar analysis demonstrated species-specific differences in rooting patterns. Root biomasses of the C4 monocots in each combination, S. scoparium and S. bicolor, were concentrated in the upper 20 cm of soil, while those of G. hirsutum and the woody P. glandulosa were largest in lower soil strata. Analyses of stable C and N isotopes can effectively be used to distinguish roots of species
which differ in ratios of 15N to 14N and 13C to 12C and thus to study belowground competition between or rooting patterns of associated species with different C and N isotope
signatures. The method evaluated can be extended to quantify aboveground and belowground biomasses of component species in
mixtures with isotopes of other elements or element concentrations that differ consistently among plants of interest. 相似文献
18.
Cowpea [Vigna unguiculata (L). Walp.] has great potential as green manure due to its rapid N accumulation and efficient N2 fixation. The objective of this study was to measure the rate of N mineralization from cowpea plant parts harvested at onset
of flowering (5 weeks) and mid pod-fill (7 weeks) under near optimum conditions. Cowpeas were grown in a greenhouse and supplied
with 15NH4
15NO3 to isotopically label tissue. Cowpea leaves, stems, and roots were incorporated into a sandy soil (Psammentic Paleustalf)
and net N mineralized was measured several times during a 10 week incubation. The amount of N accumulated in 7-week old cowpeas
was more than double that in 5-week old cowpeas. The portion of N mineralized after 10 weeks was 24% for 5-week old cowpeas
and 27% for 7-week old cowpeas. The rate of N mineralization from leaves and stems increased with plant age, but decreased
for roots. The amount of N mineralized from 7-week old cowpeas was more than double (235%) that from 5-week old cowpeas due
to greater N accumulation and a more rapid rate of N mineralization of the more mature cowpeas. The greatest amount of N was
released from leaves, which amounted to 74 and 65% of total N mineralization from 5- and 7-week old cowpeas, respectively.
The percentage of N mineralized by 10 weeks was linearly related to the tissue N concentration of the plant parts and to their
C/N ratio. These relationships allow a quick estimation of the amount of N that would mineralize from cowpea residues incorporated
into soil based on their N concentration or C/N ratio. 相似文献
19.
Tesfay Teklay 《Plant and Soil》2004,267(1-2):297-307
Foliar inputs from indigenous agroforestry trees and shrubs could provide sufficient nutrients and organic matter to sustain
crop growth. However, concentrations of foliar nutrients and organic constituents show considerable seasonal, inter- and/or
intra-species variations. To determine this variability, green and senesced leaves were sampled during dry and wet seasons
from Cordia africana, Albizia gummifera and Milletia ferruginea trees at Wondo Genet, southern Ethiopia. Cordia is a deciduous, non-leguminous tree, while Albizia and Milletia are semi-deciduous and leguminous trees. Leaves were analyzed for concentrations of ash, N, P, K, cellulose, lignin, soluble
polyphenols, and condensed tannins. Results from statistical analyses showed significant seasonal variations (P < 0.001) in concentrations of all leaf constituents, except for P and cellulose. Foliar concentrations of ash, N, soluble
polyphenols, and condensed tannins were higher during the wet season while those of K and lignin were higher during the dry
season. Green leaves had significantly higher (p < 0.001) N and P concentrations than senesced leaves, while senesced leaves had higher concentrations of K, cellulose, soluble
polyphenols, and condensed tannins. The ‘ Relative Percentage Changes’ in concentration of N and P in senesced leaves, i.e.,
their enrichment or depletion with such nutrients relative to those in green leaves, were significantly higher (P < 0.001) for Cordia than Albizia and Milletia. On the other hand, there was no consistent pattern in the enrichment or depletion of senesced leaves with organic constituents,
but these leaves were in most cases more enriched with organic constituents than green leaves. Over all, the percentage depletion
or enrichment ranged from about 8% to 38% for N; 24% to 63% for P; −141% to 48% for K; −44% to 15% for cellulose; −44% to
51% for lignin; −203% to −61% for soluble polyphenols; and −290% to 11% for condensed tannins. It was concluded that variations
in species and life-form (legume versus non-legume), season, and developmental stage of leaves could affect the quality of
organic material from agroforestry species, which has important implications for management of organic residues in tropical
agricultural systems. 相似文献
20.
Decomposition of roots of black alder and hybrid poplar in short-rotation plantings: Nitrogen and lignin control 总被引:4,自引:0,他引:4
The decomposition of the roots (0–2 mm, 2–5 mm and 5–10 mm) of black alder (Alnus glutinosa (L.) Gaertn.) and hybrid poplar (Populus nigra L. X Populus trichocarpa Torr & Gray) was followed over a 462-day period in pure and mixed plantings in southern Quebec. Small roots of alder had the highest initial concentrations of nitrogen and lignin, and lost 9 and 10% less mass than medium and large roots, respectively. Large roots of poplar had the highest lignin-to-nitrogen ratio and showed the smallest loss of mass over the total incubation period. Slow root decomposition of black alder and hybrid poplar was characterized by a greater proportion of initial root nitrogen immobilized per unit of carbon respired. Lignin concentration in roots of alder and poplar increased rapidly at the beginning of the incubation. Our results suggest that high levels of nitrogen in roots of alder could contribute in slowing the rate of decomposition by allowing the formation of nitrogen-lignin derivatives and low levels of nitrogen in roots of poplar may limit the growth of microorganisms and the rate of root decomposition. A multiple regression was developed using initial nitrogen, lignin concentration and the ratio of lignin to nitrogen to produce an index of the rate of root decomposition. The correlation between the index values and the percentage of residual root mass was significant (r=0.98, p<0.01). 相似文献