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1.
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
2.
Simulating the effects of N availability, straw particle size and location in soil on C and N mineralization 总被引:2,自引:0,他引:2
Predicting the C and N mineralization of straw added to soil is important for forecasting subsequent soil N availability during
and between crop growth cycles. The decomposition module of the STICS model, parameterized under optimal conditions, was used
to predict straw decomposition in sub-optimal conditions, i.e. when contact between soil and residue was poor (due to large
size residues or surface placement) or when mineral N availability was restricted. The data used in the simulations were obtained
from published studies of effects of residue size, location and N availability on C and N mineralization from straw under
controlled laboratory conditions. We selected studies in which the dynamics of C and N mineralization were measured simultaneously.
The dynamics of straw mineralization could be well predicted by the model under optimal conditions with standard parameter
values as derived from measured C/N ratios of the residues, but not under sub-optimal conditions which required a new parameterization. A good fit could be obtained
on these treatments by a marked reduction in the rate constants of residue and microbial biomass decomposition and a marked
increase in the microbial biomass C/N ratio. Our results show the need to include in decomposition models routines for simulating effects of spatial heterogeneity
of residue distribution, different particle sizes and limiting N availability. 相似文献
3.
大气CO2浓度升高对稻季土壤中麦秸降解及氮素分趋的影响 总被引:1,自引:0,他引:1
利用中国唯一的稻麦轮作FACE(free-air carbon dioxide enrichment,开放式空气CO2浓度增高)试验平台,研究大气CO2浓度升高对稻季土壤中小麦秸秆降解速率及其氮素分趋的影响.试验设置Ambient(目前空气对照)和FACE(Ambient+200 μmol·mol-1)两个CO2浓度以及低氮处理(LN,150 kg·hm-2)和高氮处理(HN,250 kg·hm-2)两个氮肥水平,在稻季之初按标记麦秸/土壤重量比0.3%添加15N标记小麦秸秆,根据水稻生长时期依次采样测定秸秆降解速率,并通过分析土壤全氮、植株全氮及其15N丰度来观察已降解秸秆的氮素分趋情况.结果发现,大气CO2浓度升高对高氮处理土壤中小麦秸秆降解速率没有显著影响,但显著促进了低氮处理土壤中小麦秸秆的降解(p < 0.05),使其提高到与高氮处理土壤相当水平;大气CO2浓度升高显著增加了已降解秸秆中氮素的流失,在高氮处理土壤中尤为严重,而对植物吸收已降解秸秆中的氮素没有显著影响.结果表明,大气CO2浓度升高在土壤氮素相对不足时会加速土壤中小麦秸秆的降解,而在土壤氮素相对充足时又会加大降解秸秆中氮素的流失. 相似文献
4.
Measured and predicted mineralization of clover green manure at low temperatures at different depths in two soils 总被引:3,自引:0,他引:3
Tor Arvid Breland 《Plant and Soil》1994,166(1):13-20
Predictive models of the temporal mineralization pattern of organic residues may help in development of strategies to synchronize N mineralization with the crop demand and minimize off-season losses. In the present investigation, two double first-order models with temperature as a driving variable were tested against data on decomposition and N mineralization, respectively, in two field experiments with green manure. On 15 November 1984, mesh bags with red clover (Trifolium pratense L.) shoot material were placed at five depths (0–30 cm) on a sandy-loam and a loam site in south-eastern Norway. 167 days after burial, 73% of the initial clover nitrogen remained on the surface, 62% at 5-cm depth, and 56% at 30-cm depth. The differences among buried samples largely persisted throughout the experimental period (1.5 years). The decomposition rate slowed down appreciably after day 270, when the amount of N in buried bags averaged 33% of the initial N. The effect of site was small and varied during the experiment. The decay model, which was derived from laboratory incubations, predicted the initial observations of remaining clover material fairly well. Later, predicted and measured values diverged because recalcitrant residues decomposed more extensively in the field than in the laboratory. The N mineralization model was tested against net N mineralization from white-clover (T. repens L.) green manure ploughed down in late October. The course of the net N mineralization was well described when disregarding an over-prediction (6–12% of applied clover N), which may be due to N losses not accounted for in the model. The predictions were sensitive to the kind of function applied for correction of decay rates at temperatures below 0° C. The results showed that decomposition of clover green manure is rapid, even at temperatures below 5° C. N-rich plant material, therefore, should be worked into the soil as late as possible in the autumn or, preferably, remain on the soil surface until spring in order to reduce the probability of N losses. 相似文献
5.
6.
Quantification of canola root morphological traits under heat and drought stresses with electrical measurements 总被引:1,自引:0,他引:1
Background and aims
Crop residues and soil types play an important role in soil C and N storage. The objectives of this study were to quantify the effects of crop residue quality and interactions with soil type on soil C and N, in the short- and medium-term, and to determine the responses related to the priming effect (PE).Methods
Residues of vetch (Vicia sativa L.), pea (Pisum sativum L.) and wheat (Triticum aestivum L.) crops with different chemical compositions and labelled with 13C and 15N were left to decompose on the surface of either a sandy-loam soil or a clay soil incubated under laboratory conditions at 25 °C for 360 days. We measured the total CO2-C and CO2-13C emitted during decomposition, the soil mineral N content and the amounts of 13C and 15N remaining in both the surface residue particles and the bulk soil.Results
Over the short-term, the vetch residues decomposed faster than those of wheat and pea on the soil surface due to their more favourable chemical composition for biodegradation; after one year, however, this difference disappeared. We observed extra soil C mineralization in all cases, i.e., the PE was positive for all treatments and was directly related to the water-soluble (vetch > pea > wheat) and soil C contents (clay soil > sandy-loam soil). Conversely, the fate of the added 15N and net N mineralization differed considerably between the three residues and was strongly related to the initial N content of the residue.Conclusions
Crop residue quality and soil type affected the soil PE and soil C balance but not the fate of crop residue-C after one year. Net soil N mineralization was observed in all crop residues, with large early differences (vetch > pea > wheat), which were maintained on a medium-term basis. Our results emphasize the need to jointly consider C and N dynamics as well as short- and medium-term effects to manage agricultural and environmental services provided by the recycling of crop residues to agricultural soils.7.
秸秆全量还田对稻田土壤溶解有机碳含量和水稻产量的影响 总被引:2,自引:2,他引:0
以南粳44为供试材料,在粘土和砂土土壤中,设置麦秸秆不还田和全量还田(6000 kg·hm-2)及3种施氮量(0、225、300 kg·hm-2)试验,研究了麦秸秆全量还田的腐解率和有机碳释放量动态变化,及其对稻田0~45 cm土壤溶解有机碳(DOC)含量和水稻产量的影响.结果表明: 麦秸秆还田的前期(0~30 d)其腐解率和有机碳释放量最高,腐解率为35.0%(粘土)和31.7%(砂土),有机碳释放率为34.1%(粘土)和33.1%(砂土);30 d后两者均减小.施用氮肥可显著促进秸秆腐解和有机碳释放量,粘土中麦秸秆腐解率和有机碳释放量明显大于砂土.麦秸秆还田后土壤DOC含量逐渐增加,至25 d达最大值,粘土和砂土分别为60.18和56.62 mg·L-1,此后逐渐减小并趋于稳定.麦秸秆还田处理15 cm处土壤DOC含量显著高于未还田处理,但两者在30和45 cm处土壤DOC含量差异不显著,说明秸秆还田主要增加了稻田0~15 cm土层DOC含量.与不施氮处理相比,施氮处理土壤DOC含量降低,2种施氮处理间差异不显著.秸秆还田减少了水稻前期分蘖发生量,显著降低了有效穗数,增加了穗粒数、结实率和千粒重,显著提高了水稻产量. 相似文献
8.
Enhanced nitrogen mineralization in mowed or glyphosate treated cover crops compared to direct incorporation 总被引:1,自引:0,他引:1
Information on how management by mowing and herbicide alter residue quality and nitrogen (N) inputs would be valuable to improve prediction of N availability. Mowing and glyphosate application are widely used by growers to limit cover crop growth and facilitate incorporation. A mixture of cover crops, hairy vetch (Vicia villosa L.), oriental mustard (Brassica junceaL.) and cereal rye (Secale cerealeL.), was investigated as a means to improve soil quality and optimize N availability. There is limited information on how mowing or glyphosate application influence cover crop decomposition and N mineralization from these heterogeneous residues. A rye cover crop was grown in the field over the winter and transferred to containers as an intact soil profile to conduct a greenhouse study. Management treatments (mowing and glyphosate) were imposed eight days before incorporation. Plant and soil N dynamics were monitored. The experiment was repeated with the addition of a tri-mixture cover crop. Inorganic NO3– in bare soil ranged from 6 to 10 g N g soil–1 over 39 days. Similar or lower levels of soil NO3– were observed after rye residue incorporation, from 2 to 6 g N g–1; consistent with N-immobilization. Application of untreated, mixed cover crop residues generally was associated with higher levels of soil inorganic NO3–, from 3 to 11 g N g–1. For both rye and mixed residues, management by mowing or glyphosate enhanced N mineralization by 10 to 100%, compared to untreated residues. At the same time, application of mowing or glyphosate 8 days before cover crop incorporation seemed to reduce the amount of residues by about half compared to untreated controls. Belowground biomass was reduced more than aboveground, although recovery of senescent roots may have been incomplete. Management by glyphosate or mowing enhanced soil inorganic N availability in the short-term while simultaneously reducing carbon and N inputs. 相似文献
9.
Denaturing gradient gel electrophoresis (DGGE) of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of crop residues in agricultural soils. Ten strains were tested, and eight of these strains produced a single band. Furthermore, a mixture of strains yielded distinguishable bands. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. A field experiment performed with litter in nylon bags was used to evaluate the bacterial diversity during the decomposition of readily degradable rye and more refractory wheat material in comparable luvisols and cambisols in northern, central, and southern Germany. The amount of bacterial DNA in the fresh litter was small. The DNA content increased rapidly after the litter was added to the soil, particularly in the rapidly decomposing rye material. Concurrently, diversity indices, such as the Shannon-Weaver index, evenness, and equitability, which were calculated from the number and relative abundance (intensity) of the bacterial DNA bands amplified from genes coding for 16S rRNA, increased during the course of decomposition. This general trend was not significant for evenness and equitability at any time. The indices were higher for the more degradation-resistant wheat straw than for the more easily decomposed rye grass. Thus, the DNA band patterns indicated that there was increasing bacterial diversity as decomposition proceeded and substrate quality decreased. The bacterial diversity differed for the sites in northern, central, and southern Germany, where the same litter material was buried in the soil. This shows that in addition to litter type climate, vegetation, and indigenous microbes in the surrounding soil affected the development of the bacterial communities in the litter. 相似文献
10.
Denaturing gradient gel electrophoresis (DGGE) of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of crop residues in agricultural soils. Ten strains were tested, and eight of these strains produced a single band. Furthermore, a mixture of strains yielded distinguishable bands. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. A field experiment performed with litter in nylon bags was used to evaluate the bacterial diversity during the decomposition of readily degradable rye and more refractory wheat material in comparable luvisols and cambisols in northern, central, and southern Germany. The amount of bacterial DNA in the fresh litter was small. The DNA content increased rapidly after the litter was added to the soil, particularly in the rapidly decomposing rye material. Concurrently, diversity indices, such as the Shannon-Weaver index, evenness, and equitability, which were calculated from the number and relative abundance (intensity) of the bacterial DNA bands amplified from genes coding for 16S rRNA, increased during the course of decomposition. This general trend was not significant for evenness and equitability at any time. The indices were higher for the more degradation-resistant wheat straw than for the more easily decomposed rye grass. Thus, the DNA band patterns indicated that there was increasing bacterial diversity as decomposition proceeded and substrate quality decreased. The bacterial diversity differed for the sites in northern, central, and southern Germany, where the same litter material was buried in the soil. This shows that in addition to litter type climate, vegetation, and indigenous microbes in the surrounding soil affected the development of the bacterial communities in the litter. 相似文献
11.
秸秆在土壤内分解初期氮素矿化与固持的模拟测定 总被引:9,自引:2,他引:7
利用模拟软件Modelmaker对3种作物秸秆在土壤内分解初期氮素循环转化过程进行了模拟,取得了土壤铵态氮、硝态氮、微生物氮及其15N丰度等个变量模拟值和测定值的良好一致性.模型模拟对氮转化速率测定的结果表明,土壤微生物主要固持铵态氮,对硝态氮固持非常微弱.氮矿化主要发生于作物秸秆,腐殖质氮的矿化极其微弱.一级动力学方程对秸秆氮素矿化过程的描述优于零级动力学方程.微生物固持氮的再矿化过程落后于氮固持过程,假定再矿化不发生或认为再矿化与固持化同时进行可导致氮矿化与固持速率测定的严重误差.忽略氮硝化过程和挥发损失将导致氮矿化和固持速率的测定值偏低.净固持或净矿化的产生不仅与秸秆碳氮比有关,而且与秸秆在土壤内分解时间有关. 相似文献
12.
R. W. L. Kimber 《Plant and Soil》1973,38(3):543-555
Summary Proximity of new wheat straw residues to sown wheat seed has an effect on germination, plant growth and ultimate yield. Decomposition
of wheat straw may produce toxins or it may cause immobilization of nitrogen in, or applied to the soil.
In pot experiments, it has been shown that germination of wheat was depressed when large amounts of straw were decomposed
on the surface for up to 18 days; after 54 days it had no effect on germination. Immobilization of nitrogen occurred mainly
when the straw was mixed with the soil, or when surface-rotted straw was ploughed into the soil just before seeding. The latter
effect could not be overcome by the addition of mineral nitrogen.
Part II, Plant and Soil 38, 347–361 (1973). 相似文献
13.
Interactions of water,mulch and nitrogen on sorghum in Niger 总被引:17,自引:0,他引:17
We tested the hypothesis that plants only stimulate net mineralization of N when intense competition for N exists between plants and heterotrophs. Nitrogen mineralization in the soil used was insensitive to the range of moisture fluctuations that were inevitable during plant growth. Pots were planted to wheat (Triticum aestivum L.) or left unplanted and received no straw, straw added in one central layer, or straw added uniformly through the whole soil volume. Through the addition of15 N-labelled nitrate, initial soil inorganic N was increased to 17 g g–1 in unplanted treatments and to 17 g g–1 and 72 g g–1 in planted treatments. Straw addition increased microbial immobilization of labelled N (soil inorganic N at planting), but did not reduce net mineralization of unlabelled soil N (soil organic N at planting), indicating that straw decomposers immobilized N early in the growth period. Plant growth did not reduce immobilization of N by straw decomposers. Net mineralization of N was not affected by plant growth at the low rate of N addition, but was reduced at the high rate of N addition. We conclude that the influence of wheat growth on net mineralization of N depends on soil N availability, with reductions in net mineralization at high N levels due to increased immobilization. 相似文献
14.
Nitrogen mineralization and denitrification as influenced by crop residue particle size 总被引:3,自引:1,他引:2
Managing the crop residue particle size has the potential to affect N conservation in agricultural systems. We investigated the influence of barley (Hordeum vulgare) and pea (Pisum sativum) crop residue particle size on N mineralization and denitrification in two laboratory experiments. Experiment 1: 15N-labelled ground (3 mm) and cut (25 mm) barley residue, and microcrystalline cellulose+glucose were mixed into a sandy loam soil with additional inorganic N. Experiment 2: inorganic15 N and C2H2 were added to soils with barley and pea material after 3, 26, and 109 days for measuring gross N mineralization and denitrification.Net N immobilization over 60 days in Experiment 1 cumulated to 63 mg N kg-1 soil (ground barley), 42 (cut barley), and 122 (cellulose+glucose). More N was seemingly net mineralized from ground barley (3.3 mg N kg-1 soil) than from cut barley (2.7 mg N kg-1 soil). Microbial biomass peaked at day 4 with the barley treatments and at day 14 with the cellulose+glucose whereafter the biomass leveled out at values 79 mg C kg-1 (ground), 104 (cut), and 242 (cellulose+glucose) higher than for the control soil. Microbial growth yields were similar for the two barley treatments, ca. 60 mg C g-1 substrate C added, which was lower than the 142 mg C g-1 C added with cellulose+glucose. This suggests that the 75% (w/w) holocelluloses and sugars contained with the barley material remained physically protected despite grinding. In Experiment 2 gross mineralization on day 3 was 4.8 mg N kg-1 d-1 with ground pea, twice as much as for all other treatments. On day 26 the treatment with ground barley had the greatest gross N mineralization. In static cores ground barley denitrified 11-fold more than did cut barley, whereas denitrification was similar for the two pea treatments. In suspensions denitrification was similar for the two treatments both with barley and pea residue.We conclude that the higher microbial activity associated with the initial decomposition of ground plant material is due to a more intimate plant residue-soil contact. On the long term, grinding the plant residues has no significant effect on N dynamics. 相似文献
15.
Peng Wang Liesje Mommer Jasper van Ruijven Frank Berendse Trofim C. Maximov Monique M. P. D. Heijmans 《Plant and Soil》2016,406(1-2):55-69
Background &; aims
Elevated atmospheric CO2 (eCO2) can affect soil-plant systems via stimulating plant growth, rhizosphere activity and the decomposition of added (crop residues) or existing (priming) soil organic carbon (C). Increases in C inputs via root exudation, rhizodeposition and root turnover are likely to alter the decomposition of crop residues but will ultimately depend on the N content of the residues and the soil.Methods
Two soil column experiments were conducted under ambient CO2 (aCO2, 390 ppm) and eCO2 (700 ppm) in a glasshouse using dual-labelled (13C/15N) residues of wheat (Triticum aestivum cv. Yitpi) and field pea (Pisum sativum L. cv. PBA Twilight). The effects of eCO2 and soil N status on wheat rhizosphere activity and residue decomposition and also N recovery from crop residues with different N status (C/N ratio 19.4–115.4) by different plant treatments (wheat, wheat + 25 mg N kg?1 and field pea).Results
Total belowground CO2 efflux was enhanced under eCO2 despite no increases in root biomass. Plants decreased residue decomposition, indicating a negative rhizosphere effect. For wheat, eCO2 reduced the negative rhizosphere effect, resulting in greater rates of decomposition and recovery of N from field pea residues, but only when N fertiliser was added. For field pea, eCO2 enhanced the negative rhizosphere effect resulting in lower decomposition rates and N recovery from field pea residue.Conclusions
The effect of eCO2 on N utilisation varied with the type of residue, enhancing N utilisation of wheat but repressing that of field pea residues, which in turn could alter the amount of N supplied to subsequent crops. Furthermore, reduced decomposition of residues under eCO2 may slow the formation of new soil C and have implications for long-term soil fertility.16.
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
17.
18.
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
19.
Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories 总被引:15,自引:0,他引:15
Ruirui Chen Mehmet Senbayram Sergey Blagodatsky Olga Myachina Klaus Dittert Xiangui Lin Evgenia Blagodatskaya Yakov Kuzyakov 《Global Change Biology》2014,20(7):2356-2367
The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding C4‐sucrose or C4‐maize straw to C3‐soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects – microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K‐strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β‐glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r‐strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K‐ and r‐strategists were beneficial for priming effects, with an increasing contribution of K‐selected species under N limitation. Thus, the priming phenomenon described in ‘microbial N mining’ theory can be ascribed to K‐strategists. In contrast, ‘stoichiometric decomposition’ theory, that is, accelerated OM mineralization due to balanced microbial growth, is explained by domination of r‐strategists. 相似文献
20.
Organic waste materials like crop residues, well-decomposed cow dung, composts, and other rural and urban wastes are considered highly useful resources in enhancing soil fertility and also in build-up of soil organic matter. Organic matter decomposition provides plant nutrients in soil, which in turn increases crop productivity. Availability of nutrients and nitrogen (N) and phosphorus from organic waste materials is dependent upon the nature of organic residues, climatic conditions, and soil moisture activity. Keeping these factors in view, the present investigation was undertaken to study the transformation of N from different organic waste materials in two contrasting soils from an eastern India, subtropical region. The results showed that the amounts of ammoniacal-N (NH4-N), nitrate-N (NO3-N), hydrolysable N (HL-N), and nonhydrolysable (NHL-N) were increased for up to 60 days of soil submergence and increased further with the increase (1% by weight of soil) of organic residue application. Considering the effect of various organic waste materials, it was found that the amounts of NH4-N, NO3-N, HL-N, and NHL-N were higher with the application of groundnut hull as compared to wheat straw and potato skin, which may be due to relatively narrow carbon:N ratio of groundnut (22:43) than that of wheat straw (62:84) and potato skin (71:32); however, the results showed that the release of NH4-N, NO3-N, HL-N, and NHL-N was in the order of groundnut hull > wheat straw > potato skin. 相似文献