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1.
Effects of earthworms on nitrogen mineralization 总被引:13,自引:0,他引:13
The influence of earthworms (Lumbricus terrestris and Aporrectodea tuberculata) on the rate of net N mineralization was studied, both in soil columns with intact soil structure (partly influenced by past earthworm activity) and in columns with sieved soil. Soil columns were collected from a well drained silt loam soil, and before the experiment all earthworms present were removed. Next, either new earthworms (at the rate of five earthworms per 1200 cm3, which was only slightly higher than field numbers and biomass) were added or they were left out. At five points in time, the columns were analyzed for NH
4
+
, NO
3
–
, and microbial biomass in separate samples from the upper and lower layers of the columns. N mineralization was estimated from these measurements. The total C and N content and the microbial biomass in the upper 5 cm of the intact soil columns was higher than in the lower layer. In the homogenized columns, the C and N content and the microbial biomass were equally divided over both layers. In all columns, the concentration of NH
4
+
was small at the start of the experiment and decreased over time. No earthworm effects on extractable NH
4
+
were observed. However, when earthworms were present, the concentration of NO
3
–
increased in both intact and homogenized cores. The microbial biomass content did not change significantly with time in any of the treatments. In both intact and homogenized soil, N mineralization increased when earthworms were present. Without earthworms, both type of cores mineralized comparable amounts of N, which indicates that mainly direct and indirect biological effects are responsible for the increase in mineralization in the presence of earthworms. The results of this study indicate that earthworm activity can result in considerable amounts of N being mineralized, up to 90 kg N ha–1 year–1, at the density used in this experiment. 相似文献
2.
Decomposition of crop residues under laboratory conditions 总被引:1,自引:0,他引:1
Abstract. A laboratory study was designed to provide data on the decomposition of rape, sunflower and soyabean residues put in bags buried in soil. The residue bags were removed at intervals during 1 year, analysed for remaining total mass, organic and water-soluble C, water-soluble sugars, as well as for volatile acids and phenolic compounds. The decomposition dynamics of total mass, total organic and water-soluble organic C, and water-soluble sugars were reproduced satisfactorily by a double-exponential model of the first-order type. Generally, no large differences in the rate and magnitude of decomposition among the residues were observed; the greatest losses of both total mass and chemical components occurred in the first month of the study, during which the volatile acids and phenolic compounds disappeared almost completely. Of the three residues, soyabean showed the lowest loss of organic carbon, losing 66% of the original content over the course of the year compared with 73 and 75% for sunflower and rape, respectively. 相似文献
3.
An understanding of the C and N dynamics of crop residues is important for efficient nutrient management. The present experiment was conducted to determine the rate of mass and N loss from alfalfa, faba bean, barley, and rape crop residues in a subarctic agricultural soil. Mass, C, and N losses were measured from residues contained in mesh bags and placed on the soil surface or buried 15 cm below the surface. The mass loss from October, 1988, to May, 1989, was the same for surface and buried alfalfa, barley, and rape residues, averaging 40, 20, and 61%, respectively, while surface and buried faba bean residue sustained 30 and 40% mass loss, respectively. The mass loss of the buried residues continued over the summer but not of those placed on the soil surface, resulting in an average 23% greater mass loss of the buried materials after 1 year. The N loss from October to May was similar from the surface and from the buried placements for the alfalfa, faba bean, and rape residues, averaging 11.3, 10.3 and 38.4 g N kg-1 residue, respectively, while the surface and buried barley lost 2.9 and 4.2 g N kg-1, respectively. The C:N ratio of all of the residues increased during the winter. These data indicate that the rate of decomposition and N mineralization from crop residues in subarctic environments can equal that measured in temperate climates. Furthermore, the concurrent loss of mass and N combined with an increase in the C:N ratio of the residues suggests that physical rather than biological processes were functioning during the winter. Most of the mass and N loss from these residues occurred during the winter, out of phase with crop demand, thereby creating the potential for N loss from the system and inefficient use of crop residue N. 相似文献
4.
The C and N transformations during decomposition over 26 d of root material from two lines of tobacco plants (Nicotiana tabacum L.) were compared in soil with or without earthworms (Lumbricus terrestris L.). The tobacco plants were either unmodified or genetically modified to reduce the activity of caffeic acid O-methyl transferase (COMT), which leads to plants with altered lignin structure and composition. In the absence of earthworms, C mineralization and net N immobilization were greater for the soil amended with reduced COMT roots than with the unmodified roots. In the presence of earthworms, C mineralization was still significantly greater for reduced COMT roots than for unmodified roots, but the difference was smaller, and the net N immobilization did not differ significantly between the two lines of plants. 相似文献
5.
Jun Tao Bryan Griffiths Shujie Zhang Xiaoyun Chen Manqiang Liu Feng Hu Huixin Li 《Applied soil ecology》2009,42(3):221-226
The effect of earthworms on soil hydrolases (protease, urease, invertase, and alkaline phosphatase) and dehydrogenase activities was investigated in maize residue amended rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and an untreated control. The application of maize residues to soil without earthworms significantly enhanced the five soil enzyme activities compared with the control treatment during rice and wheat cultivation. The presence of earthworms further significantly enhanced protease activity in the soils with both incorporated and mulched maize residues during two cultivation seasons, but only significantly increased alkaline phosphatase activity in the soil with incorporated maize residue during the rice cultivation season. Invertase activity was significantly enhanced by the presence of earthworms in the soil with maize residue incorporation during two cultivation seasons. There were no changes in dehydrogenase activity when earthworms were present. Additionally, the five enzyme activities in earthworm casts were significant higher than those in the surrounding soil, especially dehydrogenase and invertase activities. Whatever the treatment, the values obtained for the enzyme activities in both soil and casts, except for dehydrogenase activity in earthworm casts, were significantly higher under wheat than those in rice-cultivated soil. These results indicate that the presence of earthworms strongly affected soil enzyme activities, depending on the method of organic residue application, and the enhanced enzyme activities of earthworm casts probably contributed to the surrounding soil enzyme activities. 相似文献
6.
Effect of rotation, nitrogen fertilization and management of crop residues on some chemical, microbiological and biochemical properties of soil 总被引:4,自引:0,他引:4
P. Perucci U. Bonciarelli R. Santilocchi A. A. Bianchi 《Biology and Fertility of Soils》1997,24(3):311-316
A long-term experiment, which started in 1971 near Perugia, central Italy, was performed to investigate the effect of different
crop residue management practices and rotation systems on some soil properties. Twenty years after the beginning of the experiment,
chemical (organic C, total N, humified organic C, humic and fulvic acids), microbiological and biochemical parameters (microbial
biomass, global hydrolase activity, dehydrogenase and catalase activities) were investigated. Two crop residue management
practices were used in the experiment, i.e. removal (RCR soils) and burial (BCR soils). These treatments were factorially
combined with eight rotation systems, i.e. five maize-wheat rotations of different lengths (M-1W, M-2W, M-3W, M-4W and M-5W)
and three continuous wheat systems with different fertilization inputs, from 150 to 250 kg N ha–1. Soil samples were collected in the spring of 1991 for chemical determinations, and in the spring and autumn of 1992, 1993
and 1994, for microbiological and biochemical determinations. All soil chemical, microbiological and biochemical parameters
investigated showed significant differences depending on the management of the crop residues. The BCR soils showed more favourable
characteristics. In contrast, few significant effects were observed in relation to rotation and N-fertilization treatment.
Significant correlations were found between organic-C content and all microbiological and biochemical parameters, as well
as between the microbiological and biochemical parameters themselves, indicating that organic-C content plays an important
role in determining the level of soil enzyme activity and, consequently, of soil fertility. This experiment showed that burying
crop residues in soil can be considered good agronomic practice, which may help limit the gradual depletion of soil organic
matter and improve the chemical properties of the soil.
Received: 11 January 1996 相似文献
7.
Whereas non-leguminous cover crops such as cereal rye (Secale cereale) or annual ryegrass (Lolium multiflorium) are capable of reducing nitrogen (N) leaching during wet seasons, leguminous cover crops such as hairy vetch (Vicia villosa) improve soil N fertility for succeeding crops. With mixtures of grasses and legumes as cover crop, the goal of reducing
N leaching while increasing soil N availability for crop production could be attainable. This study examined net N mineralization
of soil treated with hairy vetch residues mixed with either cereal rye or annual ryegrass and the effect of these mixtures
on growth and N uptake by cereal rye. Both cereal rye and annual ryegrass contained low total N, but high water-soluble carbon
and carbohydrate, compared with hairy vetch. Decreasing the proportion of hairy vetch in the mixed residues decreased net
N mineralization, rye plant growth and N uptake, but increased the crossover time (the time when the amount of net N mineralized
in the residue-amended soil equalled that of the non-amended control) required for net N mineralization to occur. When the
hairy vetch content was decreased to 40% or lower, net N immobilization in the first week of incubation increased markedly.
Residue N was significantly correlated with rye biomass (r=0.81, P<0.01) and N uptake (r=0.83, P<0.001), although the correlation was much higher between residue N and the potential initial N mineralization rate for rye
biomass (r=0.93, P<0.001) and N uptake (r=0.99, P<0.001). Judging from the effects of the mixed residues on rye N Concentration and N uptake, the proportion of rye or annual
ryegrass when mixed with residues of hairy vetch should not exceed 60% if the residues are to increase N availability. Further
study is needed to examine the influence of various mixtures of hairy vetch and rye or annual ryegrass on N leaching in soil.
Received: 10 March 1997 相似文献
8.
The aim of this study was to measure the pressures exerted by earthworms during burrowing. For this purpose we developed
two methods with which to quantify the axial and radial pressure. The data were recorded with an electronic balance that was
connected to a PC. Artificial earthworm burrows were used to standardize the measurements. Plexiglas tubes with diameters
ranging from 2 to 6.3 mm which corresponded to the diameter of the earthworms were used. A pin was placed inside the tubes,
on which the earthworms exerted a pressure by peristaltic locomotion. Only the maximum values of the pressure measurement
were taken into account for evaluation, and the arithmetic mean was calculated. The measurements were conducted with Aporrectodea longa, Lumbricus terrestris, Aporrectodea caliginosa, Octolasion cyaneum, Allolobophora chlorotica, Aporrectodea rosea, Lumbricus rubellus and Dendrobaena octaedra. The species examined were classified into ecological groups. The mean axial pressures exerted by each group were in the
order: epigeic (14–25 kPa), endogeic (27–39 kPa) and anecic (46–65 kPa). For the mean radial pressure the order was: epigeic
(39–63 kPa), anecic (72–93 kPa) and endogeic (59–195 kPa). It was apparent from the results that radial pressure is the most
important pressure with respect to the burrowing activity of earthworms.
Received: 28 April 1998 相似文献
9.
Mixing of different mineral soil layers by endogeic earthworms affects carbon and nitrogen mineralization 总被引:1,自引:0,他引:1
The effect of the endogeic earthworm species Octolasion tyrtaeum (Savigny) on decomposition of uniformly 14C-labelled lignin (lignocellulose) was studied in microcosms with upper mineral soil (Ah-horizon) from two forests on limestone,
representing different stages of succession, a beech- and an ash-tree-dominated forest. Microcosms with and without lower
mineral soil (Bw-horizon) were set-up; one O. tyrtaeum was added to half of them. It was hypothesised that endogeic earthworms stabilise lignin and the organic matter of the upper
mineral soil by mixing with lower mineral soil of low C content. Cumulative C mineralization was increased by earthworms and
by the addition of lower mineral soil. Effects of the lower mineral soil were more pronounced in the beech than in the ash
forest. Cumulative mineralization of lignin was strongly increased by earthworms, but only in the beech soil (+24.6%). Earthworms
predominantly colonized the upper mineral soil; mixing of the upper and lower mineral soils was low. The presence of lower
mineral soil did not reduce the rates of decomposition of organic matter and lignin; however, the earthworm-mediated increase
in mineralization was less pronounced in treatments with (+8.6%) than in those without (+14.1%) lower mineral soil. These
results indicate that the mixing of organic matter with C-unsaturated lower mineral soil by endogeic earthworms reduced microbial
decomposition of organic matter in earthworm casts. 相似文献
10.
Inherent soil properties have an influence on microbial activity. These effects were measured in a field trial at Weihenstephan with 30 agricultural and 2 vineyard soils from different sites in Bavaria which had been kept under bare fallow for 6 years. The soils represented a wide range of arable soils from a temperate climate. Unaffected by recent differences in climatic conditions or cropping managements, they were used to assess the relationship between microbial biomass C and a broad spectrum of soil physical and chemical properties (clay content 5–63%, pH 4.5–7.5, organic C 0.55–2.93%). Microbial C was measured using the substrate-induced respiration method. In addition, soil catalase activity and the abundance and biomass of earthworms were determined. Among the soil properties, microbial C was most strongly correlated with organic C (r=0.86, n=29). In a comparison of linear regressions between microbial biomass C and organic C for different cropping managements, the slope under bare fallow was lowest, followed by monoculture and crop rotation. The microbial: organic C ratio ranged from 1.1 to 4.3% and was significantly correlated with soil pH (r=0.66). A positive relationship between microbial C and the clay content (r=0.66) was significantly improved when soils with more than 25% clay were excluded (r=0.80). Partial correlation analysis indicated that clay had a direct influence, hardly affected by an intercorrelation with organic C. Catalase activity was highly correlated with microbial C (r=0.95) and, because a rapid and sensitive method of determination is available, was considered suitable for estimating relative amounts of active microbial biomass. A positive relationship between microbial C and the abundance of earthworms indicated interactions between microorganisms and mesofauna. 相似文献
11.
Stefano Manzoni 《Soil biology & biochemistry》2009,41(7):1355-1379
In the last 80 years, a number of mathematical models of different level of complexity have been developed to describe biogeochemical processes in soils, spanning spatial scales from few μm to thousands of km and temporal scales from hours to centuries. Most of these models are based on kinetic and stoichiometric laws that constrain elemental cycling within the soil and the nutrient and carbon exchange with vegetation and the atmosphere. While biogeochemical model performance has been previously assessed in other reviews, less attention has been devoted to the mathematical features of the models, and how these are related to spatial and temporal scales. In this review, we consider ∼250 biogeochemical models, highlighting similarities in their theoretical frameworks and illustrating how their mathematical structure and formulation are related to the spatial and temporal scales of the model applications. Our analysis shows that similar kinetic and stoichiometric laws, formulated to mechanistically represent the complex underlying biochemical constraints, are common to most models, providing a basis for their classification. Moreover, a historic analysis reveals that the complexity and degree and number of nonlinearities generally increased with date, while they decreased with increasing spatial and temporal scale of interest. We also found that mathematical formulations specifically developed for certain scales (e.g., first order decay rates assumed in yearly time scale decomposition models) often tend to be used also at other spatial and temporal scales different from the original ones, possibly resulting in inconsistencies between theoretical formulations and model application. It is thus critical that future modeling efforts carefully account for the scale-dependence of their mathematical formulations, especially when applied to a wide range of scales. 相似文献
12.
Premasis Sukul 《Soil biology & biochemistry》2006,38(2):320-326
A laboratory experiment was conducted to study the impact of metalaxyl application at different concentration levels on microbial biomass and the biochemical activities in soil. A dissipation study of metalaxyl highlighted 52.5-56.8% loss of metalaxyl due to the presence of microbial activity. However, a small but significant decline in microbial biomass was observed on 60 d of incubation period. Metalaxyl showed a highly significant effect in decreasing total N and organic C content in soil from 0 to 30 d of incubation. Dehydrogenase, phosphatase, urease, arylsulphatase and β-glucosidase activities were monitored in metalaxyl treated soils. Except urease, all the enzymatic activities initially increased and then decreased. Urease activity showed a continuous gradual decrease throughout the experimental period. Thus, metalaxyl might influence the growth and development of crop-plants, since it has direct impact on nutrient recycling and energy flow in soil. 相似文献
13.
Seasonal variations of soil microbial biomass and activity in warm- and cool-season turfgrass systems 总被引:1,自引:0,他引:1
Plant growth can be an important factor regulating seasonal variations of soil microbial biomass and activity. We investigated soil microbial biomass, microbial respiration, net N mineralization, and soil enzyme activity in turfgrass systems of three cool-season species (tall fescue, Festuca arundinacea Schreb., Kentucky bluegrass, Poa pratensis L., and creeping bentgrass, Agrostis palustris L.) and three warm-season species (centipedegrass, Eremochloa ophiuroides (Munro.) Hack, zoysiagrass, Zoysia japonica Steud, and bermudagrass, Cynodon dactylon (L.) Pers.). Microbial biomass and respiration were higher in warm- than the cool-season turfgrass systems, but net N mineralization was generally lower in warm-season turfgrass systems. Soil microbial biomass C and N varied seasonally, being lower in September and higher in May and December, independent of turfgrass physiological types. Seasonal variations in microbial respiration, net N mineralization, and cellulase activity were also similar between warm- and cool-season turfgrass systems. The lower microbial biomass and activity in September were associated with lower soil available N, possibly caused by turfgrass competition for this resource. Microbial biomass and activity (i.e., microbial respiration and net N mineralization determined in a laboratory incubation experiment) increased in soil samples collected during late fall and winter when turfgrasses grew slowly and their competition for soil N was weak. These results suggest that N availability rather than climate is the primary determinant of seasonal dynamics of soil microbial biomass and activity in turfgrass systems, located in the humid and warm region. 相似文献
14.
Summary The influence of leaf litter from three Salix spp. on fungal growth and microbial decomposition was studied using 1-mm-mesh litter-bags, and the effect on additional soil macrofaunal activity was studied by measuring litter disappearance from 4-mm-mesh bags and under 4-mm-mesh nets. Mineral macro-elements, water-and ethanol-extractable substances, lignin, and protein-precipitating substances (astringency) in the litter were determined, taking contaminating of the litter with soil particles into account. As expected, the litter disappeared more quickly from the large-mesh bags than from the small-mesh bags, which was attributed to earthworm activity. During the 1st year, the rate of leaf disappearance from both types of bags and under the nets was much higher for S. daphnoides than for S. viminalis and S. fragilis. The lower initial astringency, related to the tannin content, of the S. daphnoides litter might account for this difference. Tannin metabolites probably hampered both microbial decomposition and earthworm acceptability for some time also after the astringency was lost. Neither the content of macronutrients nor that of the other organic fractions studied can be assumed to have had any effect on weight losses due to microbial decomposition. Although, the S. daphnoides leaves initially contained the least amount of fungal mycelium (m g-1 dry weight), the increase after contact with soil was most pronounced in this litter. The species composition of Fungi Imperfecti in the leaves of S. viminalis and S. daphnoides differed only for fresh litter, whereas the number of isolates was somewhat higher for S. daphnoides throughout the study. Similar seasonal variations in fungal composition occurred in both the S. viminalis and the S. daphnoides litter. 相似文献
15.
Newton Z. Lupwayi Stewart A. Brandt John T. O’Donovan T. Kelly Turkington 《Soil biology & biochemistry》2010,42(11):1997-2004
The combination of high input costs and low commodity prices is forcing some farmers to consider reducing crop inputs like seed, fertilizer and herbicides. In a field trial in which different canola (Brassica napus L.) and barley (Hordeum vulgare L.) inputs were subtracted from a full package, or added to an empty package, we studied the effects of full or reduced fertilizer and herbicide inputs on soil microbiological characteristics at two sites from 2005 to 2008. The full package consisted of a high-yielding crop variety seeded at an optimum rate, with fertilizers and herbicides applied at recommended rates. The empty package consisted of a less expensive, low-yielding crop variety seeded at a low rate, with no fertilizer or herbicide applied. Between these two extremes were treatments in which fertilizers or herbicides were applied at 50% of recommended rates or not at all. Each treatment was repeated year after year in the same plot, i.e., treatment effects were cumulative. Fertilizer effects on soil microbial biomass C (MBC), β-glucosidase enzyme activity and bacterial functional diversity (based on community-level physiological profiles) were usually positive. Reduced fertilizer application rates reduced the beneficial fertilizer effects. Significant herbicide effects on soil microbiological properties occurred less often, were smaller in magnitude than fertilizer effects, and were mostly negative. Reduced herbicide rates reduced the deleterious herbicide effects. These significant fertilizer and herbicide effects were observed in canola more than barley, and mostly in the final year of the study, indicating the cumulative nature of treatment effects over time. Therefore, repeated applications of agricultural inputs like fertilizers and herbicides can have more significant effects on soil biology and biological processes than single applications indicate. 相似文献
16.
The turnover of N derived from rhizodeposition of faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) and the effects of the rhizodeposition on the subsequent C and N turnover of its crop residues were investigated in an incubation experiment (168 days, 15 °C). A sandy loam soil for the experiment was either stored at 6 °C or planted with the respective grain legume in pots. Legumes were in situ 15N stem labelled during growth and visible roots were removed at maturity. The remaining plant-derived N in soil was defined as N rhizodeposition. In the experiment the turnover of C and N was compared in soils with and without previous growth of three legumes and with and without incorporation of crop residues. After 168 days, 21% (lupin), 26% (faba bean) and 27% (pea) of rhizodeposition N was mineralised in the treatments without crop residues. A smaller amount of 15–17% was present as microbial biomass and between 30 and 55% of mineralised rhizodeposition N was present as microbial residue pool, which consists of microbial exoenzymes, mucous substances and dead microbial biomass. The effect of rhizodeposition on the C and N turnover of crop residues was inconsistent. Rhizodeposition increased the crop residue C mineralisation only in the lupin treatment; a similar pattern was found for microbial C, whereas the microbial N was increased by rhizodeposition in all treatments. The recovery of residual 15N in the microbial and mineral N pool was similar between the treatments containing only labelled crop residues and labelled crop residues + labelled rhizodeposits. This indicates a similar decomposability of both rhizodeposition N and crop residue N and may be attributable to an immobilisation of both N sources (rhizodeposits and crop residues) as microbial residues and a subsequent remineralisation mainly from this pool.Abbreviations C or Ndec
C or N decomposed from residues
- C or Nmic
microbial C or N
- C or Nmicres
microbial residue C or N
- C or Nmin
mineralised C or N
- C or Ninput
added C or N as crop residues and/or rhizodeposits
- dfr
derived from residues
- dfR
derived from rhizodeposition
- Ndfr
N derived from residues
- NdfR
N derived from rhizodeposition
- Nloss
losses of N derived from residues
- SOM
soil organic matter
- WHC
water holding capacity 相似文献
17.
Kannan Iyyemperumal 《Soil biology & biochemistry》2007,39(1):149-157
Grazing animals recycle a large fraction of ingested C and N within a pasture ecosystem, but the redistribution of C and N via animal excreta is often heterogeneous, being highest in stock camping areas, i.e., near shade and watering sources. This non-uniform distribution of animal excreta may modify soil physical and chemical attributes, and likely affect microbial community eco-physiology and soil N cycling. We determined microbial population size, activity, N mineralization, and nitrification in areas of a pasture with different intensity of animal excretal deposits (i.e., stock camping, open grazing and non-grazing areas). The pasture was cropped with coastal bermudagrass (Cynodon dactylon L.) and subjected to grazing by cattle for 4 y. Soil microbial biomass, activity and N transformations were significantly higher at 0-5 cm than at 5-15 cm soil depth, and the impacts of heterogeneous distribution of animal excreta were more pronounced in the uppermost soil layer. Microbial biomass, activity and potential net N mineralization were greater in stock camping areas and were significantly correlated (r2≈0.50, P<0.05) with the associated changes in total soil C and N. However, gross N mineralization and nitrification potential tended to be lower in stock camping areas than in the open grazing areas. The lower gross N mineralization, combined with greater net N mineralization in stock camping areas, implied that microbial N immobilization was lower in those areas than in the other areas. This negative association between microbial N immobilization and soil C is inconsistent with a bulk of publications showing that microbial N immobilization was positively related to the amount of soil C. We hypothesized that the negative correlation was due to microbial direct utilization of soluble organic N and/or changes in microbial community composition towards active fungi dominance in stock camping areas. 相似文献
18.
Biological and chemical properties of arable soils affected by long-term organic and inorganic fertilizer applications 总被引:17,自引:0,他引:17
M. Šimek D. W. Hopkins J. Kalčík T. Picek H. Šantrůčková J. Staňa K. Trávník 《Biology and Fertility of Soils》1999,29(3):300-308
Using soils from field plots in four different arable crop experiments that have received combinations of manure, lime and
inorganic N, P and K for up to 20 years, the effects of these fertilizers on soil chemical properties and estimates of soil
microbial community size and activity were studied. The soil pH was increased or unaffected by the addition of organic manure
plus inorganic fertilizers applied in conjunction with lime, but decreased in the absence of liming. The soil C and N contents
were greater for all fertilized treatments compared to the control, yet in all cases the soil samples from fertilized plots
had smaller C:N ratios than soil from the unfertilized plots. The soil concentrations of all the other inorganic nutrients
measured were greater following fertilizer applications compared with the unfertilized plots, and this effect was most marked
for P and K in soils from plots that had received the largest amounts of these nutrients as fertilizers. Both biomass C determined
by chloroform fumigation and glucose-induced respiration tended to increase as a result of manure and inorganic fertilizer
applications, although soils which received the largest additions of inorganic fertilizers in the absence of lime contained
less biomass C than those to which lime had been added. Dehydrogenase activity was lower in soils that had received the largest
amounts of fertilizers, and was further decreased in the absence of lime. This suggests that dehydrogenase activity was highly
sensitive to the inhibitory effects associated with large fertilizer additions. Potential denitrification and anaerobic respiration
determined in one soil were increased by fertilizer application but, as with both the microbial biomass and dehydrogenase
activity, there were significant reductions in both N2O and CO2 production in soils which received the largest additions of inorganic fertilizers in the absence of lime. In contrast, the
size of the denitrifying component of the soil microbial community, as indicated by denitrifying enzyme activity, was unaffected
by the absence of lime at the largest rate of inorganic fertilizer applications. The results indicated differences in the
composition or function of microbial communities in the soils in response to long-term organic and inorganic fertilization,
especially when the soils were not limited.
Received: 10 March 1998 相似文献
19.
No information is available on the role of particle size of canola (Brassica napus) residue in altering C mineralization and nutrient (N, S) cycling in soil. We studied decomposition of canola residue (at 20±1 °C temperature and 10% moisture (w/w) for 6 months to elucidate the effect of its particle size (<1, 5-7, and 20-25 mm) on dynamics of C, N and S turnover following incorporation into a nutrient-poor sandy soil.Averaged over time, particle size of canola residue did not significantly affect C mineralization rate, the size of microbial-C and microbial-N pools, or the extent of CaCl2-extractable S immobilization, but altered the extent of mineral-N immobilization and water-soluble organic C (W-SOC) depletion. A rapid decrease in C mineralization rate in the first week matched the rapid depletion of W-SOC, especially for the <1 mm residue treatment. Over 6 months, mineral-N in the amended soils rarely increased beyond the starting level (0.8-1 mg kg−1 soil for all the treatments), whereas nitrate-N increased 19-fold in the non-amended soil. This suggests an occurrence of strong N immobilization in the amended soils; such immobilization was high for the <1 mm residue treatment. On a cumulative basis, 33-35% of C added in canola residues to the soil was respired in 6 months. The microbial-C and microbial-N pools peaked by day 4 for all the residue treatments (compared to time zero, 58-122% increase for microbial-C and 36-57% for microbial-N). Averaged over time, amended soils contained approx. 40% more microbial-C and microbial-N than the non-amended soil. An addition of canola residue (regardless of the size) to soil increased the extractable S significantly (3.4-fold) on day 0; this initially increased S level decreased by one-third over 6 months. In conclusion, particle size of canola residue did not affect temporal pattern of C and S mineralization in a nutrient-poor sandy soil, but altered N cycling. 相似文献
20.
Yanfei Liang Mengling Nong Hui Luo Jianhua Zhang 《Communications in Soil Science and Plant Analysis》2016,47(1):19-31
The thin-shallow-wet-dry irrigation (TIR) method is one of water-saving irrigation methods of rice cultivation. The effects of TIR method on water-use efficiency (WUE) of rice and soil microbial activities were investigated under three rates of nitrogen (N) compared to conventional flood irrigation. The TIR method decreased total water consumption (21.7–23.5%) and increased rice WUE (17.8–27.2%). At high N level, the TIR method significantly increased the number of nitrifying bacteria; the activities of catalase, invertase, and urease in soil at the jointing, booting, and milky stages; and the number of denitrifying bacteria at the milky stage. Increased N rate increased grain yield and water consumption simultaneously, and middle N level increased microbial biomass carbon (MBC) and N, the number of nitrifying and denitrifying bacteria, and the activities of catalase, urease, and invertase. Thus the TIR method at the middle N level can effectively improve rice WUE and soil MBC and enzyme activity. 相似文献