Distribution of carbon and nitrogen in a long-term cropping system and permanent pasture system

1993 ◽  
Vol 44 (6) ◽  
pp. 1323 ◽  
Author(s):  
FA Robertson ◽  
RJK Myers ◽  
PG Saffigna
Keyword(s):  
Microbial Biomass ◽  
Crop Residues ◽  
Perennial Grass ◽  
Cropping System ◽  
N Availability ◽  
Continuous Cropping ◽  
Organic C ◽  
Soil Microbial ◽  
Permanent Pasture ◽  
Standing Dead

Nitrogen (N) limitation to productivity of sown perennial grass pastures on the brigalow lands of S.E. Queensland contrasts with adequate N supply to annual crops grown on the same soil. In order to understand this anomaly, the distribution of N and carbon (C) under permanent green panic pasture and under continuous cropping with grain sorghum was compared in an 18 month field study. Total soil N and organic C (0-10 cm) were, respectively, 0.37 and 3.20% under green panic and 0.23 and 2.31% under sorghum. Soil microbial biomass (0-28 cm) contained 246 kg N and 1490 kg C ha-1 under green panic and 147 kg N and 744 kg C ha-1 under sorghum. Enhanced microbial growth under pasture was attributed to the continuous input of available C from surface litter and roots. The C/N ratio of pasture residues was high (greater than 50) and conducive to immobilization of N. Availability of N under pasture was further reduced by approximately 50% of plant N being immobilized in standing dead tissue. Under sorghum, the microbial biomass was well supplied with N, but was limited by C availability. The soil under sorghum received a single large C input when crop residues were returned after harvest. The differences in N availability, and hence productivity, of these soils under cropping and permanent pasture were due primarily to differences in the timing and quality of C inputs.

Dynamics of carbon and nitrogen in a long-term cropping system and permanent pasture system

1994 ◽  
Vol 45 (1) ◽  
pp. 211 ◽  
Author(s):  
FA Robertson ◽  
RJK Myers ◽  
PG Saffigna
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Cropping System ◽  
Perennial Grasses ◽  
Panicum Maximum ◽  
N Availability ◽  
Continuous Cropping ◽  
Soil Microbial ◽  
Net Mineralization ◽  
C And N

On the brigalow lands of south-east Queensland, productivity of sown perennial grasses is severely limited by N availability, whereas annual crops grown on the same soil are N-sufficient. The dynamics of C and N were compared under in these soils under permanent green panic (Panicum maximum var. trichoglume cv. Petrie ) pasture and continuous cropping with grain sorghum (Sorghum bicolor). Although the sorghum system was more productive, it contained 18% less N and 29% less C. Annual flows of C and N through the soil microbial biomass were, respectively, 4500 and 240 kg ha-1 under sorghum, and 4050 and 60 kg ha-1 under pasture. Over 80% of C and N inputs to the sorghum system occurred after harvest. Under pasture, the continuous supply of residues of high C/N ratio (50-75) enabled the development of a large and active microbial biomass, which competed with the pasture plant for N, resulting in slow net mineralization of N and low levels of inorganic soil N. Under sorghum, the size of the microbial biomass was limited by C availability during the growing season. The sorghum residues had slightly lower C/N ratios (36-46), and their rapid decomposition and net mineralization of N were promoted by the fallow period and soil cultivation. Estimated annual C turnover through the soil microbial biomass was slightly faster under sorghum, and annual N turnover was around seven times faster under sorghum than under green panic. The productivity of these soils under the two management systems was controlled by the amount, quality and timing of organic matter inputs. These in turn controlled the size of the soil microbial biomass and its C and N supply, and hence the balance between immobilization and mineralization of N.

Soil microbial biomass, labile and total carbon levels of grazed sown and native pastures in northern New South Wales

2006 ◽  
Vol 57 (8) ◽  
pp. 837 ◽  
Author(s):  
G. M. Lodge ◽  
K. L. King
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Perennial Grass ◽  
Ground Cover ◽  
Microbial Biomass C ◽  
Organic C ◽  
Soil Microbial ◽  
Labile C ◽  
Microbial Quotient ◽  
Total Organic C

Studies were conducted at 3 pasture sites in northern New South Wales to examine the effects of grazing treatments over 4 years (spring 1997 to spring 2001) on soil microbial biomass carbon (C), labile C, total C, and total nitrogen (N). These data were collected (0–0.05 m soil depth) at 9 sampling times in 2 replicates of 5 (native pastures) or 4 (a sown pasture) grazing treatments and examined for differences over time using cubic spline analyses. For each site, differences among grazing treatments were also examined in spring 2001 for herbage, litter, and root mass (kg DM/ha), ground cover (%), and perennial grass basal cover (%). Indices were also calculated for the C pool index (CPI), lability index (LI), a carbon management index (CMI), and the microbial quotient. Relationships among microbial biomass C, labile C, total organic C, CPI, LI, CMI, microbial quotient, herbage mass, litter mass, and ground cover were examined by linear regression and correlation analyses. For each of the sites, treatment differences in the linear trend over time for soil microbial biomass C, labile C, total organic C, or total N were not significantly different (P > 0.05). In spring 2001, (4 years after treatments commenced) there were also no significant effects of treatments within sites on soil total organic C and none of the indices (lability of C, CPI, LI, CMI, or the microbial quotient) indicated any distinct trends among treatments. However, in spring 2001, there were significant (P < 0.05) treatment effects at both native pasture sites for herbage mass, litter mass, and ground cover. Similarly, in autumn 2001, herbage mass, root mass, and perennial grass basal cover were lowest (P < 0.05) in the continuously grazed high-stocking rate treatment at the sown pasture site. For all data, microbial biomass C was 10.35% of labile C and labile C was 21.60% of total C. From autumn 1998 to spring 2001, labile C was positively correlated (P < 0.05) with total C (r = 0.72) and in spring 2001, these 2 variables were also highly correlated (r = 0.98).

Relationships between C and N availability, substrate age, and natural abundance 13C and 15N signatures of soil microbial biomass in a semiarid climate

2009 ◽  
Vol 41 (8) ◽  
pp. 1605-1611 ◽  
Author(s):  
Jeff S. Coyle ◽  
Paul Dijkstra ◽  
Richard R. Doucett ◽  
Egbert Schwartz ◽  
Stephen C. Hart ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Natural Abundance ◽  
N Availability ◽  
Soil Microbial ◽  
Semiarid Climate ◽  
C And N ◽  
Substrate Age

Liming improves soil microbial growth, but trash blanket placement increases labile carbon and nitrogen availability in a sugarcane soil of subtropical Australia

Soil Research ◽  
2018 ◽  
Vol 56 (3) ◽  
pp. 235 ◽  
Author(s):  
X. Y. Liu ◽  
M. Rezaei Rashti ◽  
M. Esfandbod ◽  
B. Powell ◽  
C. R. Chen
Keyword(s):  
Soil Ph ◽  
Enzyme Activities ◽  
Nitrogen Availability ◽  
Microbial Community Composition ◽  
Cropping System ◽  
Hot Water ◽  
Microbial Biomass C ◽  
N Availability ◽  
Total N ◽  
Soil Microbial

Liming has been widely used to decrease soil acidity, but its effects on soil nitrogen (N) availability and microbial processes in sugarcane fields are largely unknown. Adjacent sugarcane soils at 26 months after liming (26ML), 14 months after liming (14ML) and with no lime amendment (CK) in Bundaberg, Australia, were selected to investigate the effect of liming on soil N bioavailability and microbial activity in a long-term subtropical sugarcane cropping system. Liming in both 14ML and 26ML treatments significantly increased soil pH (by 1.2–1.4 units) and exchangeable Ca2+ (>2-fold) compared with the CK treatment. The lower concentrations of hot water extractable organic carbon (C) and total N and ammonium-N in the 14ML, compared with the CK and 26ML treatments, can be attributed to the absence of trash blanket placement in the former. Enhanced microbial immobilisation due to improved soil pH by liming (14ML and 26ML treatments) led to increased soil microbial biomass C and N, particularly in the presence of a trash blanket (26 ML treatment), but decreased soil respiration and metabolic quotient indicated that acidic stress conditions were alleviated in the liming treatments. Soil pH was the main factor governing soil enzyme activities, with an overall decrease in all enzyme activities in response to liming. Overall, liming and trash blanket practices improved sugarcane soil fertility. Further study is warranted to investigate the shifts in soil microbial community composition and the diversity and abundance of N-associated functional genes in response to liming in sugarcane fields.

Dynamics of soil microbial biomass C, soluble organic C and CO2 evolution after three years of manure application

1998 ◽  
Vol 78 (2) ◽  
pp. 283-290 ◽  
Author(s):  
P. Rochette ◽  
E. G. Gregorich
Keyword(s):  
Microbial Biomass ◽  
Soil Respiration ◽  
Soil Temperature ◽  
Soil Microbial Biomass ◽  
N Fertilizer ◽  
Microbial Biomass C ◽  
Organic C ◽  
Soil Microbial ◽  
Manure Amendments ◽  
Soluble C

Application of manure and fertilizer affects the rate and extent of mineralization and sequestration of C in soil. The objective of this study was to determine the effects of 3 yr of application of N fertilizer and different manure amendments on CO2 evolution and the dynamics of soil microbial biomass and soluble C in the field. Soil respiration, soluble organic C and microbial biomass C were measured at intervals over the growing season in maize soils amended with stockpiled or rotted manure, N fertilizer (200 kg N ha−1) and with no amendments (control). Manure amendments increased soil respiration and levels of soluble organic C and microbial biomass C by a factor of 2 to 3 compared with the control, whereas the N fertilizer had little effect on any parameter. Soil temperature explained most of the variations in CO2 flux (78 to 95%) in each treatment, but data from all treatments could not be fitted to a unique relationship. Increases in CO2 emission and soluble C resulting from manure amendments were strongly correlated (r2 = 0.75) with soil temperature. This observation confirms that soluble C is an active C pool affected by biological activity. The positive correlation between soluble organic C and soil temperature also suggests that production of soluble C increases more than mineralization of soluble C as temperature increases. The total manure-derived CO2-C was equivalent to 52% of the applied stockpiled-manure C and 67% of the applied rotted-manure C. Estimates of average turnover rates of microbial biomass ranged between 0.72 and 1.22 yr−1 and were lowest in manured soils. Manured soils also had large quantities of soluble C with a slower turnover rate than that in either fertilized or unamended soils. Key words: Soil respiration, greenhouse gas, soil carbon

C and N availability affects the 15 N natural abundance of the soil microbial biomass across a cattle manure gradient

2006 ◽  
Vol 57 (4) ◽  
pp. 468-475 ◽  
Author(s):  
P. Dijkstra ◽  
O. V. Menyailo ◽  
R. R. Doucett ◽  
S. C. Hart ◽  
E. Schwartz ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Soil Microbial Biomass ◽  
Natural Abundance ◽  
Cattle Manure ◽  
N Availability ◽  
Soil Microbial ◽  
C And N ◽  
N Natural Abundance

Management of sugarcane harvest residues: consequences for soil carbon and nitrogen

Soil Research ◽  
2007 ◽  
Vol 45 (1) ◽  
pp. 13 ◽  
Author(s):  
Fiona A. Robertson ◽  
Peter J. Thorburn
Keyword(s):  
Microbial Biomass ◽  
Soil Fertility ◽  
Microbial Activity ◽  
Soil N ◽  
Soil Organic C ◽  
Total N ◽  
Organic C ◽  
Soil Microbial ◽  
C And N

The Australian sugar industry is moving away from the practice of burning the crop before harvest to a system of green cane trash blanketing (GCTB). Since the residues that would have been lost in the fire are returned to the soil, nutrients and organic matter may be accumulating under trash blanketing. There is a need to know if this is the case, to better manage fertiliser inputs and maintain soil fertility. The objective of this work was to determine whether conversion from a burning to a GCTB trash management system is likely to affect soil fertility in terms of C and N. Indicators of short- and long-term soil C and N cycling were measured in 5 field experiments in contrasting climatic conditions. The effects of GCTB varied among experiments. Experiments that had been running for 1–2 years (Harwood) showed no significant trash management effects. In experiments that had been running for 3–6 years (Mackay and Tully), soil organic C and total N were up to 21% greater under trash blanketing than under burning, to 0.10 or 0.25 m depth (most of this effect being in the top 50 mm). Soil microbial activity (CO2 production) and soil microbial biomass also increased under GCTB, presumably as a consequence of the improved C availability. Most of the trash C was respired by the microbial biomass and lost from the system as CO2. The stimulation of microbial activity in these relatively short-term GCTB systems was not accompanied by increased net mineralisation of soil N, probably because of the greatly increased net immobilisation of N. It was calculated that, with standard fertiliser applications, the entire trash blanket could be decomposed without compromising the supply of N to the crop. Calculations of possible long-term effects of converting from a burnt to a GCTB production system suggested that, at the sites studied, soil organic C could increase by 8–15%, total soil N could increase by 9–24%, and inorganic soil N could increase by 37 kg/ha.year, and that it would take 20–30 years for the soils to approach this new equilibrium. The results suggest that fertiliser N application should not be reduced in the first 6 years after adoption of GCTB, but small reductions may be possible in the longer term (>15 years).

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