Effect of pipeline installation on crop yield and some biological properties of boreal soils

2000 ◽  
Vol 80 (3) ◽  
pp. 483-488 ◽  
Author(s):  
Y. K. Soon ◽  
W. A. Rice ◽  
M. A. Arshad ◽  
P. Mills
Keyword(s):  
Microbial Biomass ◽  
Crop Yield ◽  
Crop Production ◽  
Microbial Biomass Carbon ◽  
Biological Properties ◽  
Hordeum Vulgare L ◽  
Microbial Biomass Nitrogen ◽  
Total N ◽  
Pipeline Construction ◽  
Normal Ranges

Pipeline construction on the Grey soils of the Canadian boreal plains, which have a thin Ah horizon, could have considerable impact on their properties and productivity. This study was conducted because the effects of pipeline installation on crop yield and biological properties of these soils have not been well-documented. Soil was sampled from a Grey Luvisol and a Dark Grey Solod prior to pipeline construction in 1991, and in each of the following 3 yr. The right-of-way (RoW) was divided into three zones: a road (or work) area used for vehicular traffic; a trench where the pipeline was buried; and a pile (or spoil) area where soil was stockpiled during construction. The RoW was cropped to barley (Hordeum vulgare L.) in 1992 through 1994. Barley yield was low in 1992 (830–1120 kg ha−1), and near average (2050–3290 kg ha−1) in 1993 and 1994. Except for low shoot P concentration (1.1–1.3 mg g−1) in 1992, macronutrient concentrations (N, P and K) in barley tissues were within normal ranges. Soil organic carbon was reduced by 12–28% in all RoW areas in 1993 and 1994. Soil total N was reduced by 29–49% in all RoWs in 1992 and increased slightly from those levels in 1993 and 1994. Pipeline construction affected soil microbial biomass carbon (MBC) in the three RoW areas differently, and the effect was not consistent from year to year. However, the average level of MBC was not adversely impacted. In 1994, soil phosphatase activity in the RoW zones tended to be lower as compared to pre-pipeline installation, particularly in the pile area of the Dark Grey Solod. It is concluded that although some soil biological properties were degraded by pipeline construction, and barley yield was reduced in 1992, crop production in the following 2 yr was not significantly affected. Key words: Barley, carbon, microbial biomass, nitrogen, phosphatase, pipeline

scholarly journals Microbial and enzymatic activity as influenced by existing cropping pattern in the soils of Ganges floodplain

2019 ◽  
Vol 6 (3) ◽  
pp. 309-314 ◽  
Author(s):  
Mohammad Zaber Hossain ◽  
Md. Rezaul Karim ◽  
Bina Rani Majumder ◽  
Falguni Akter
Keyword(s):  
Microbial Biomass ◽  
Organic Carbon ◽  
Enzymatic Activity ◽  
Respiration Rate ◽  
Microbial Biomass Carbon ◽  
Cropping Systems ◽  
Cropping Pattern ◽  
Microbial Biomass Nitrogen ◽  
Total N ◽  
Floodplain Soil

Effect of multi cropping (Potato-Jute-Sweetgourd-T.Aman, Sweet gourd-Brinjal-Jute, Cauliflower-Radish-Lentil-Basil, Jute-Lentil-Mustard-Wheat and Sweetgourd-Turnip, designated as P-J-S-T, S-B-J, C-R-L-B, J-L-M-W and S-T, respectively) and mono cropping systems (orchard of Lychee, Teak, Turmeric and Banana) on microbial and enzymatic activity of Ganges floodplain soil was investigated. Organic carbon, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil respiration, total nitrogen and urease activity (UA) of the soils were examined. Upon examination it was observed that soils under mono cropping pattern (Lychee, Teak, and Banana) showed significantly (p?0.05) higher MBC, MBN and UA than those under multi cropping pattern. Highest values of MBC and UA found in teak plant were 95.44 milligram/kilogram (mgkg-1) and 6.51µg N released g-1day-1 respectively while for multi cropping pattern the respective values were 37.52 mgkg-1 and 2.23 µg N released g-1day-1 found in S-T and J-L-M-W cropping pattern. The highest MBN (12.70 mgkg-1) was obtained in soil where lychee was practiced. Multi cropping soil showed significantly (p?0.05) higher respiration rate than mono cropping soil and the highest rate was found 508.75 mg CO2 g-1day-1 in J-M-L-W cropping pattern. Turmeric showed the lowest respiration rate (120.75 mg CO2 g-1day-1) among the cropping pattern studied. Both MBC and UA showed positively significant relation with soil organic carbon, and total N at 0.01 % level. High microbial and enzymatic activity of mono cropping soil represent combined effect of vegetation and low tillage practices in soil.

scholarly journals Examination the effects of different herbicides on the soil microorganisms of a calcareous chernozem

2010 ◽  
pp. 121-126
Author(s):  
Zsolt Sándor
Keyword(s):  
Microbial Biomass ◽  
Agricultural Production ◽  
Crop Production ◽  
Soil Microorganisms ◽  
Plant Biomass ◽  
Microbial Biomass Carbon ◽  
The Other ◽  
Co2 Production ◽  
Test Plant ◽  
Microbial Biomass Nitrogen

Pesticides play a key role in fighting weeds, pests and parasitic fungi. According to surveys, pests reduce the yield of agricultural crops by 35% worldwide. Pests, fungi and weeds account for 14%, 12% and 9% yield loss, respectively (Gáborjányi et al., 1995). Chemicals have contributed to increasing and maintaining the yields of crop production for decades. Today, agricultural production (in spite of many efforts) is unthinkable without the use of pesticides (herbicides, insecticides and fungicides). On the other hand, these chemicals contribute to the pollution of the atmosphere, surface and underground waters, and agricultural soils, especially if they are applied improperly.The sustainable agricultural production pays attention to environment-friendly cultivation-technologies; but at the same time it makes an effort to produce good quality and economical products. The examination of the herbicides’ secondary effects, fits into this chain of idas namely, how the herbicides affect – stimulating or inhibiting – the soil microbiological processes, prevention of soil fertility.In the course of the experimental work the effect of herbicides on soil biological properties were examined in different maize (Zea mays) cultures. We wanted wished to know that how the herbicides affect the quantity change of soil microorganisms, the life of different physiological groups of bacteria and the activity of microorganisms. A small pot experiment was set up in 2008 with the application of two herbicides - Acenit A 880 EC and Merlin 480 SC – in the breeding house of the Department. The moisture content and nutrient supply were at optimal level in the experiment.On the basis of results the following can be stated: 1. It can be stated that the two herbicides and all their doses affected negatively the number of total soil bacteria, theinhibiting effects were significant. The quantity of microscopical fungi increased by the effect of Merlin 480 SC and decreased in the treatments of Acenit A 880 EC.2. The Acenit A 880 EC had stimulating effect on the nitrate mobilization. The CO2-production was stimulated by the basic doses of herbicides; the other treatments did not influence the CO2-production significantly.3. The quantity of microbial biomass-carbon –except for only one treatment- decreased significantly by the effect of herbicides. Besides it, the quantity of microbial biomass-nitrogen increased significantly in the treatments of Acenit A 880 EC.4. The biomass of test plant decreased in the treatments of herbicides, their quantities were smaller than in the control. In the pots treated by Merlin 480 SC, parallel with the increase of doses decreased the quantity of plant-biomass.

scholarly journals Changes in soil quality due to converting <i>Pinus</i> to <i>Eucalyptus</i> plantations and subsequent successive <i>Eucalyptus</i> planting in southern China

2014 ◽  
Vol 6 (2) ◽  
pp. 2779-2802
Author(s):  
K. Zhang ◽  
H. Zheng ◽  
F. L. Chen ◽  
Z. Y. Ouyang ◽  
Y. Wang ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Quality ◽  
Microbial Biomass Carbon ◽  
Southern China ◽  
Soil Disturbance ◽  
Biological Properties ◽  
Soil Quality Index ◽  
Microbial Biomass Nitrogen ◽  
Eucalyptus Plantations ◽  
Time Substitution

Abstract. Plants play a key role in maintaining soil quality, but long-term changes in soil quality due to plant species change and successive planting are rarely reported. Using the space-for-time substitution method, adjacent plantations of Pinus and 1st, 2nd, 3rd and 4th generations of Eucalyptus in Guangxi, China were used to study changes in soil quality caused by converting Pinus to Eucalyptus and successive Eucalyptus planting. Soil chemical and biological properties were measured and a soil quality index (SQI) was calculated. Soil organic carbon, total nitrogen, alkaline hydrolytic nitrogen, microbial biomass carbon, microbial biomass nitrogen, cellobiosidase, phenol oxidase, peroxidase and acid phosphatase activities significantly decreased in the 1st and 2nd generations of Eucalyptus plantations after conversion from Pinus to Eucalyptus but gradually recovered in the 3rd and 4th generations. Soil total and available potassium were significantly lower, but total phosphorus was significantly higher in Eucalyptus plantations compared to the Pinus plantation. As an integrated indicator, SQI was highest in the Pinus plantation (0.92), but decreased to 0.24 and 0.13 in the 1st and 2nd generations of Eucalyptus plantations, respectively. However, it recovered to 0.36 and 0.38 in the 3rd and 4th generations, respectively. Changing tree species, reclamation and fertilization may have contributed to the "U" shaped change observed in soil quality during conversion of Pinus to Eucalyptus and successive Eucalyptus planting. Litter retention, keeping understory coverage, and reducing soil disturbance during logging and subsequent establishment of the next rotation should be considered to help improving soil quality during plantation management.

scholarly journals The interaction of seasonal rainfall and nitrogen fertiliser rate on soil N2O emission, total N loss and crop yield of dryland sorghum and sunflower grown on sub-tropical Vertosols

Soil Research ◽  
2016 ◽  
Vol 54 (5) ◽  
pp. 604 ◽  
Author(s):  
G. D. Schwenke ◽  
B. M. Haigh
Keyword(s):  
Crop Yield ◽  
Crop Production ◽  
Field Experiments ◽  
N2o Emission ◽  
N2o Emissions ◽  
N Loss ◽  
N Losses ◽  
Total N ◽  
Tropical Regions ◽  
The Impact

Summer crop production on slow-draining Vertosols in a sub-tropical climate has the potential for large emissions of soil nitrous oxide (N2O) from denitrification of applied nitrogen (N) fertiliser. While it is well established that applying N fertiliser will increase N2O emissions above background levels, previous research in temperate climates has shown that increasing N fertiliser rates can increase N2O emissions linearly, exponentially or not at all. Little such data exists for summer cropping in sub-tropical regions. In four field experiments at two locations across two summers, we assessed the impact of increasing N fertiliser rate on both soil N2O emissions and crop yield of grain sorghum (Sorghum bicolor L.) or sunflower (Helianthus annuus L.) in Vertosols of sub-tropical Australia. Rates of N fertiliser, applied as urea at sowing, included a nil application, an optimum N rate and a double-optimum rate. Daily N2O fluxes ranged from –3.8 to 2734g N2O-Nha–1day–1 and cumulative N2O emissions ranged from 96 to 6659g N2O-Nha–1 during crop growth. Emissions of N2O increased with increased N fertiliser rates at all experimental sites, but the rate of N loss was five times greater in wetter-than-average seasons than in drier conditions. For two of the four experiments, periods of intense rainfall resulted in N2O emission factors (EF, percent of applied N emitted) in the range of 1.2–3.2%. In contrast, the EFs for the two drier experiments were 0.41–0.56% with no effect of N fertiliser rate. Additional 15N mini-plots aimed to determine whether N fertiliser rate affected total N lost from the soil–plant system between sowing and harvest. Total 15N unaccounted was in the range of 28–45% of applied N and was presumed to be emitted as N2O+N2. At the drier site, the ratio of N2 (estimated by difference)to N2O (measured) lost was a constant 43%, whereas the ratio declined from 29% to 12% with increased N fertiliser rate for the wetter experiment. Choosing an N fertiliser rate aimed at optimum crop production mitigates potentially high environmental (N2O) and agronomic (N2+N2O) gaseous N losses from over-application, particularly in seasons with high intensity rainfall occurring soon after fertiliser application.

scholarly journals Straw and early nitrogen fertilization affect soil properties and upland rice yield

2016 ◽  
Vol 46 (3) ◽  
pp. 284-291 ◽  
Author(s):  
Adriano Stephan Nascente ◽  
Anna Cristina Lanna
Keyword(s):  
Microbial Biomass ◽  
Nitrate Reductase ◽  
Grain Yield ◽  
Nitrogen Fertilization ◽  
Upland Rice ◽  
Microbial Biomass Carbon ◽  
Biomass Carbon ◽  
Early Application ◽  
Total N ◽  
Rice Plants

ABSTRACT The presence of cover crop straw and early application of total N at sowing may provide significant changes in the microbial population, reflecting on the N dynamics in the soil and in upland rice plants. This study aimed at determining the effect of the early application of nitrogen doses as mineral N and microbial biomass carbon in the soil, as well as in the activity of nitrate reductase, and grain yield of upland rice plants cultivated under no-tillage system (NTS). A randomized blocks design, in a split-plot scheme, with four replications, was used. The treatments consisted of N doses (0 kg ha-1, 40 kg ha-1, 80 kg ha-1 and 120 kg ha-1) and the presence or absence of U. brizantha cover straw. Maintaining the straw on the soil surface reduces the ammonium levels and increases the microbial biomass carbon content of the soil. The application of increasing doses of N in the soil provides increases in the levels of nitrate and ammonium in the soil up to 28 days after emergence. The activity of the nitrate reductase enzyme in the plants increases and the contents of ammonium and nitrate in the soil decrease with the crop development. The number of panicles and grain yield of upland rice increase with the increase of the nitrogen fertilization, but decrease in the presence of U. brizantha straw. Thus, it is recommend the use of early N fertilization in upland rice crop.

Soil chemical and biological properties affected by 21-year application of composted manure with chemical fertilizers in a Chinese Mollisol

2012 ◽  
Vol 92 (3) ◽  
pp. 419-428 ◽  
Author(s):  
X. H. Li ◽  
X. Z. Han ◽  
H. B. Li ◽  
C. Song ◽  
J. Yan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Ph ◽  
Enzyme Activities ◽  
Microbial Biomass Carbon ◽  
Biological Properties ◽  
Pig Manure ◽  
Chemical Fertilizers ◽  
Total N ◽  
Available N

Li, X. H., Han, X. Z., Li, H. B., Song, C., Yan, J. and Liang, Y. 2012. Soil chemical and biological properties affected by 21-year application of composted manure with chemical fertilizers in a Chinese Mollisol. Can. J. Soil Sci. 92: 419–428. The effects of 21-yr of application of chemical fertilizers, composted pig manure (CPM) alone, and chemical fertilizers combined with compost on soil chemical and biological properties were investigated. Soil samples (0–20cm) were collected from a long-term fertilization experiment under corn (Zea mays L.) production in 2006, prior to seeding, at the corn tasseling stage and following harvest. Fertilizer treatments were: no fertilizer (CK), nitrogen fertilizer alone (N), N + phosphorus (NP), N + P + potassium (NPK), CPM, N + CPM, N + P + CPM (NP + CPM), and N + P + K + CPM (NPK + CPM). Long-term application of N alone resulted in a reduction of soil pH by 0.38 units and reduced the available P concentration compared with CK. An increase in soil pH was seen with CPM alone and NPK + CPM. Both fertilizers sources, singly and combined, increased the total N and available N concentrations. Total P and total K concentrations were greatest with the NPK + CPM treatment. All fertilizer treatments increased the soil organic carbon (SOC), light fraction organic carbon (LFOC) and microbial biomass carbon (MBC) concentrations significantly (P < 0.05) at the tasseling stage. The NPK + CPM treatment showed the greatest increase in SOC (12%), LFOC (78%) and MBC (44%) concentrations, compared with CK. Soil enzyme activities (invertase, urease, acid and alkaline phosphatases) tended to be greater at tasseling than other sampling dates, with highest enzyme activities in the NPK + CPM treatments. These findings suggest that a long-term application of CPM combined with NPK is an efficient strategy to maintain or increase soil quality in Mollisols for sustainable agriculture.

Seasonal trends in selected soil biochemical attributes: Effects of crop rotation in the semiarid prairie

1999 ◽  
Vol 79 (1) ◽  
pp. 73-84 ◽  
Author(s):  
C. A. Campbell ◽  
V. O. Biederbeck ◽  
G. Wen ◽  
R. P. Zentner ◽  
J. Schoenau ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Microbial Biomass ◽  
Microbial Biomass Carbon ◽  
Light Fraction ◽  
Water Soluble ◽  
Microbial Biomass C ◽  
Weather Variables ◽  
Total N ◽  
Organic C ◽  
C And N

Measurements of seasonal changes in soil biochemical attributes can provide valuable information on how crop management and weather variables influence soil quality. We sampled soil from the 0- to 7.5-cm depth of two long-term crop rotations [continuous wheat (Cont W) and both phases of fallow-wheat (F–W)] at Swift Current, Saskatchewan, from early May to mid-October, 11 times in 1995 and 9 times in 1996. The soil is a silt loam, Orthic Brown Chernozem with pH 6.0, in dilute CaCl2. We monitored changes in organic C (OC) and total N (TN), microbial biomass C (MBC), light fraction C and N (LFC and LFN), mineralizable C (Cmin) and N (Nmin), and water-soluble organic C (WSOC). All biochemical attributes, except MBC, showed higher values for Cont W than for F–W, reflecting the historically higher crop residue inputs, less frequent tillage, and drier conditions of Cont W. Based on the seasonal mean values for 1996, we concluded that, after 29 yr, F–W has degraded soil organic C and total N by about 15% compared to Cont W. In the same period it has degraded the labile attributes, except MBC, much more. For example, WSOC is degraded by 22%, Cmin and Nmin by 45% and LFC and LFN by 60–75%. Organic C and TN were constant during the season because one year's C and N inputs are small compared to the total soil C or N. All the labile attributes varied markedly throughout the seasons. We explained most of the seasonal variability in soil biochemical attributes in terms of C and N inputs from crop residues and rhizodeposition, and the influences of soil moisture, precipitation and temperature. Using multiple regression, we related the biochemical attributes to soil moisture and the weather variables, accounting for 20% of the variability in MBC, 27% of that of Nmin, 29% for LFC, 52% for Cmin, and 66% for WSOC. In all cases the biochemical attributes were negatively related to precipitation, soil moisture, temperature and their interactions. We interpreted this to mean that conditions favouring decomposition of organic matter in situ result in decreases in these attributes when they are measured subsequently under laboratory conditions. We concluded that when assessing changes in OC or TN over years, measurements can be made at any time during a year. However, if assessing changes in the labile soil attributes, several measurements should be made during a season or, measurements be made near the same time each year. Key words: Microbial biomass, carbon, nitrogen, mineralization, water-soluble-C, light fraction, weather variables

REDUCTION OF SECONDARY TILLAGE IN MOULDBOARD-PLOUGHED SYSTEMS FOR SILAGE CORN AND SPRING CEREALS IN MEDIUM-TEXTURED SOILS

1990 ◽  
Vol 70 (1) ◽  
pp. 1-9 ◽  
Author(s):  
M. R. CARTER ◽  
R. P. WHITE ◽  
R. G. ANDREW
Keyword(s):  
Soil Properties ◽  
Crop Yield ◽  
Prince Edward Island ◽  
Crop Production ◽  
Sandy Loam ◽  
Soil Depth ◽  
Nutrient Content ◽  
Slight Reduction ◽  
Hordeum Vulgare L ◽  
Spring Cereals

Minimum tillage for soils that require regular cultivation consists of reducing the degree of secondary tillage and number of passes over the field. This study was conducted to determine whether one-pass mouldboard-ploughed systems were suitable for production of silage corn (Zea mays L.) and spring cereals (Hordeum vulgare L., Triticum aestivum L.) on loam to sandy loam soils (Humo-Ferric Podzol and Gray Luvisol) in the perhumid soil climate of Prince Edward Island. The effects of reduction in secondary tillage were gauged by characterizing crop yield and nutrient content, soil properties and structure, and relative economics. Plant growth, crop yield, and nutrient content were similar in all the mouldboard-ploughed systems. Soil chemical properties were not affected by reduction in secondary tillage, but the one-pass plough system did result in a macro-aggregate distribution with a greater proportion of large soil aggregates (9.5–16 mm) and a slight reduction in soil strength over the 10- to 25-cm soil depth. Macroporosity and soil density in the top 8 cm of soil were similar between tillage systems. Reducing both the degree of secondary tillage and number of tillage operations decreased both estimated cultivation costs and time of tillage per hectare by 26 and 39%, respectively. One-pass mouldboard-ploughed systems appear suitable for annual crop production on medium-textured soils under the soil environment of Prince Edward Island. Key words: One-pass tillage, soil properties, crop growth

Modeling Biodegradation of Subsurface Oil in Sand Beaches Polluted with Oil

2014 ◽  
Vol 2014 (1) ◽  
pp. 1113-1125
Author(s):  
Xiaolong Geng ◽  
Michel C. Boufadel
Keyword(s):  
Microbial Biomass ◽  
Galvanized Steel ◽  
Sensitivity Analyses ◽  
Parameter Estimates ◽  
Model Parameters ◽  
Zone Model ◽  
Residual Oil ◽  
Monod Kinetics ◽  
Microbial Biomass Nitrogen ◽  
Total N

ABSTRACT In April 2010, the explosion of the Deepwater Horizon (DWH) drilling platform led to the release of nearly 4.9 million barrels of crude oil into the Gulf of Mexico. The oil was brought to the supratidal zone of beaches (landward of the high tide line) by waves during storms, and was buried during subsequent storms. The objective of this paper is to investigate the biodegradation of subsurface oil in a tidally influenced sand beach located at Bon Secour National Wildlife Refuge and polluted by the DWH oil spill. Two transects were installed perpendicular to the shoreline within the supratidal zone of the beach. One transect had four galvanized steel piezometer wells to measure the water level. The other transect had four stainless steel multiport sampling wells that were used to collect pore water samples below the beach surface. The samples were analyzed for dissolved oxygen (DO), nitrogen, and redox conditions. Sediment samples were also collected at different depths to measure residual oil concentrations and microbial biomass. As the biodegradation of hydrocarbons was of interest, a biological model based on Monod kinetics was developed and coupled to the transport model MARUN, which is a two dimensional (vertical slice) finite element model for water flow and solute transport in tidally influenced beaches. The resulting coupled model, BIOMARUN, was used to simulate the biodegradation of total n-alkanes and polycyclic aromatic hydrocarbons (PAHs) trapped as residual oil in the unsaturated zone. Model parameter estimates were constrained by published Monod kinetics parameters. The field measurements, such as the concentrations of the oil, microbial biomass, nitrogen, and DO, were used as inputs for the simulations. The biodegradation of alkanes and PAHs was predicted in the simulation, and sensitivity analyses were conducted to assess the effect of the model parameters on the modeling results. Simulation results indicated that n-alkanes and PAHs would be biodegraded by 80% after 2 ± 0.5 years and 3.5 ± 0.5 years, respectively.

Changes in microbial biomass C, extractable C and available N during the early stages of decomposition of residue mixtures

Soil Research ◽  
2014 ◽  
Vol 52 (4) ◽  
pp. 366 ◽  
Author(s):  
Andong Shi ◽  
Petra Marschner
Keyword(s):  
Microbial Biomass ◽  
Microbial Biomass Carbon ◽  
Expected Value ◽  
Microbial Biomass C ◽  
Decomposition Rates ◽  
Hordeum Vulgare L ◽  
Available Nitrogen ◽  
Available N ◽  
Early Stages ◽  
The Individual

Decomposition of mixed residues is common in many ecosystems, with residues from different species or above- and below-ground residues from the same species. Although decomposition of litter mixtures has been extensively studied, little is known about the changes in microbial biomass carbon (C) and available nitrogen (N) in the early stages of decomposition of mixtures of shoots and roots. An incubation experiment was carried out in a sandy clay loam with shoot and root residues of two grasses, annual barley (Hordeum vulgare L.), and perennial Stipa sp., added separately or as mixtures. Soil respiration was measured continuously, and soil microbial biomass C, extractable C and available N were measured by destructive sampling on days 0, 3, 6, 9, 12 and 18. Cumulative respiration and microbial biomass C concentration were higher with barley shoots alone or in mixtures than with Stipa residues alone. In the mixture of Stipa shoots and roots, which had similar decomposition rates when incubated individually, the measured cumulative respiration was greater than the expected value (average of the cumulative respiration of the individual residues), but this did not result in greater microbial biomass or changes in available N concentration compared with the individual residues. Cumulative respiration of barley shoots alone was higher than of barley root and Stipa shoot incubated individually. In the mixtures of barley shoots with barley roots or Stipa shoots, the measured cumulative respiration was either lower than the expected value or similar. Compared with barley shoots alone, microbial biomass C concentrations in the mixtures were generally lower in the first 3 days. It is concluded that mixing of residues with similar decomposition rates can stimulate microbial activity (respiration) but has little effect on microbial growth or concentrations of available N. Further, our findings provide information about extractable C and N dynamics during the early stages of decomposition of individual residue and residue mixtures.

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