scholarly journals ORGANIC C DYNAMICS IN GRASSLAND SOILS. 2. MODEL VALIDATION AND SIMULATION OF THE LONG-TERM EFFECTS OF CULTIVATION AND RAINFALL EROSION

1981 ◽  
Vol 61 (2) ◽  
pp. 211-224 ◽  
Author(s):  
R. P. VORONEY ◽  
J. A. VAN VEEN ◽  
E. A. PAUL
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Management Practices ◽  
State Level ◽  
Microbial Biomass C ◽  
Organic C ◽  
Native Prairie ◽  
Cropping Sequence ◽  
C And N ◽  
Rainfall Erosion

The amounts of organic matter in native prairie and in an adjacent cultivated field were compared with the output from a simulation model describing organic matter dynamics. The effects of past and possible future soil management practices, and the loss of organic C through rainfall erosion were incorporated into the simulation study. Seventy years of cultivation increased the bulk density of the A horizon by an average of 16% along the catena of a Black Chernozemic soil. Organic C had decreased by 36% in the soil profile at the mid-slope position. Losses of organic N were 5–10% less. Depletion of organic C and N from the Ah horizon accounted for > 90% of the total loss from the soil profile. Therefore, extrapolation of data from surface soil, based solely on changes in the concentration of organic C and N, could result in an overestimation of organic matter losses from soils. Microbial biomass in the Ap horizon of the crop-summer-fallow site was 30% less than in the Ah horizon of the native prairie. The model predicted an immediate rise in microbial biomass C upon cultivation of the native prairie due to a large initial input of grassland litter and roots. Subsequently, the microbial biomass C decreased and approached a steady-state level which was 25% less than in the native prairie. The model indicates that large quantities of N released during the initial years of cultivation would not have been totally utilized by the cultivated crops, therefore resulting in major losses to the environment. However, now the organic matter is reaching a steady-state level and only small net release of N can be expected; external N sources are required for optimum crop production. Management practices such as straw removal and cropping sequence have short-term effects on the rate of depletion of soil organic C. Similar equilibrium levels of soil organic matter were predicted after 100 yr of cultivation in simulation studies that did not consider erosion losses. The inclusion of rainfall erosion losses indicated that major organic C and other nutrient losses will occur in management practices that include significant portions of fallow in the cropping sequence.

Effect of crop rotations and cultural practices on soil organic matter, microbial biomass and respiration in a thin Black Chernozem

1991 ◽  
Vol 71 (3) ◽  
pp. 363-376 ◽  
Author(s):  
C. A. Campbell ◽  
V. O. Biederbeck ◽  
R. P. Zentner ◽  
G. P. Lafond
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Cultural Practices ◽  
Respiratory Activity ◽  
Crop Rotations ◽  
Microbial Biomass C ◽  
Soil Organic C ◽  
Organic C ◽  
C And N

The effects of crop rotations and various cultural practices on soil organic matter quantity and quality in a Rego, Black Chernozem with a thin A horizon were determined in a long-term study at Indian Head, Saskatchewan. Variables examined included: fertilization, cropping frequency, green manuring, and inclusion of grass-legume hay crop in predominantly spring wheat (Triticum aestivum L.) production systems. Generally, fertilizer increased soil organic C and microbial biomass in continuous wheat cropping but not in fallow-wheat or fallow-wheat-wheat rotations. Soil organic C, C mineralization (respiration) and microbial biomass C and N increased (especially in the 7.5- to 15-cm depth) with increasing frequency of cropping and with the inclusion of legumes as green manure or hay crop in the rotation. The influence of treatments on soil microbial biomass C (BC) was less pronounced than on microbial biomass N. Carbon mineralization was a good index for delineating treatment effects. Analysis of the microbial biomass C/N ratio indicated that the microbial suite may have been modified by the treatments that increased soil organic matter significantly. The treatments had no effect on specific respiratory activity (CO2-C/BC). However, it appeared that the microbial activity, in terms of respiration, was greater for systems with smaller microbial biomass. Changes in amount and quality of the soil organic matter were associated with estimated amount and C and N content of plant residues returned to the soil. Key words: Specific respiratory activity, crop residues, soil quality, crop rotations

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

Long-term effects of NPK fertiliser and manure on soil fertility and a sorghum - wheat farming system

2007 ◽  
Vol 47 (6) ◽  
pp. 700 ◽  
Author(s):  
M. C. Manna ◽  
A. Swarup ◽  
R. H. Wanjari ◽  
H. N. Ravankar
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Soil Organic Matter ◽  
Microbial Biomass ◽  
Aggregate Size ◽  
Microbial Biomass C ◽  
Continuous Cropping ◽  
C And N ◽  
Organic Matter Fractions

Yield decline or stagnation under long-term cultivation and its relationship with soil organic matter fractions are rarely considered. To understand this phenomenon, soil organic matter fractions and soil aggregate size distribution were studied in a long-term experiment at Akola, in a Vertisol in a semiarid tropical environment. For 14 years, the following fertiliser treatments were compared with undisturbed fallow plots: unfertilised (control), 100% recommended rates of N, NP, NPK (N : P : K ratios of 100 : 21.8 : 18.2 and 120 : 26.2 : 50 kg/ha for sorghum and wheat, respectively) and 100% NPK plus farmyard manure (FYM) and continuous cropping with a sorghum (Sorghum bicolor L. Moench) and wheat (Triticum aestivum L.) system during 1988–2001. The significant negative yield trend was observed in unbalanced use of inorganic N application for both crops. However, yields were maintained when NPK and NPK + FYM were applied. Results showed that soil organic C and total N in the unfertilised plot decreased by 21.7 and 18.2%, compared to the initial value, at a depth of 0–15 cm. Depletion of large macroaggregates (>2 mm) accounted for 22–81% of the total mass of aggregates in N, NP and unfertilised control plots compared to fallow plots. Irrespective of treatments, small macroaggregates (0.25–2 mm) dominated aggregate size distribution (56–71%), followed by microaggregates (0.053–0.25 mm, 18–37%). Active fractions, such as microbial biomass C, microbial biomass N, hot water soluble C and N, and acid hydrolysable carbohydrates were greater in NPK and NPK + FYM treatments than in the control. Carbon and N mineralisation were greater in small macroaggregates than microaggregates. Particulate organic matter C (POMC) and N (POMN) were significantly correlated (P < 0.01) with water-stable aggregate C and N (0.25–2 mm size classes), respectively. It was further observed that POMC and POMN were significantly greater in NPK and NPK + FYM plots than N and NP treated plots. Microbial biomass C was positively correlated with acid-hydrolysable carbohydrates (r = 0.79, P < 0.05). Continuous cropping and fertiliser use also influenced humic acid C and fulvic acid C fractions of the soil organic matter. Acid-hydrolysable N proportion in humic acid was greater than fulvic acid and it was greatest in NPK + FYM treatments. Continuous application of 100% NPK + FYM could restore soil organic carbon (SOC) to a new equilibrium level much earlier (t = 1/k, 2.4 years) than N (t = 1/k, 25.7 years), NP (t = 1/k, 8.1 years) and NPK (t = 1/k, 5.02 years). In conclusion, integrated use of NPK with FYM would be vital to obtain sustainable yields without deteriorating soil quality.

scholarly journals Interactive effects of management practices on water-stable aggregation and organic matter of a Humic Gleysol

2001 ◽  
Vol 81 (5) ◽  
pp. 545-551 ◽  
Author(s):  
Nicole Bissonnette ◽  
Denis A. Angers ◽  
Régis R. Simard ◽  
Jean Lafond
Keyword(s):  
Alkaline Phosphatase ◽  
Organic Matter ◽  
Microbial Biomass ◽  
Management Practices ◽  
Surface Soil ◽  
Dairy Manure ◽  
Soil Aggregation ◽  
Silty Clay ◽  
C And N

In many soils, the content and quality of organic matter (OM) control water-stable aggregation, which in turn preserves soil surface integrity. The effects of management practices on soil OM and aggregation remain to be determined for certain soils and climatic conditions. We assessed the effects of eight management systems involving two crop sequences: [barley ( Hordeum vulgare L.) monoculture (M) and barley in rotation (R) with a forage mix of red clover ( Trifolium pratense L.) and timothy ( Phleum pratense L. ‘Champ’)], two fall tillage [moldboard plowing (MP) and chisel plowing (CP)] and two nutrient sources [liquid dairy manure (LDM) and mineral fertilizers (MIN)] on soil aggregation and OM fractions of a silty clay Humic Gleysol. Soil samples from the 0–7.5 cm layer were taken periodically during 7 yr, and the total C and N, microbial biomass C (MBC) and carbohydrate (AHC) contents, alkaline phosphatase activity (APA), and water-stable aggregation were determined. By the 7th yr, initial total C and N contents of the surface soil had increased by 35 and 45%, respectively, in R-CP-LDM. They were slightly increased in R-CP-MIN an d R-MP-LDM, whereas they decreased by an average of 19% in R-MP-MIN and all monoculture plots. Increases in C contents were attributed to higher annual C inputs from forage residues and LDM, less frequent tillage in the rotation, and shallower tillage with CP. The MBC, APA, AHC and aggregation generally responded faster and to a greater degree to conservation management practices than total C and N. Overall, conservation tillage and manure applications resulted in greater improvement in surface soil conditions when used in a rotation system rather than in a monoculture. The rapid rate of changes in soil properties suggests that the surface quality of this cold silty clay soil can be improved relatively quickly with selected management combinations. Key Words: Cropping systems, total soil C, microbial biomass, carbohydrate, alkaline phosphatase, soil aggregation, liquid dairy manure, reducted tillage, rotations

scholarly journals Changes in Soil Labile Organic Matter as Affected by 50 Years of Fertilization with Increasing Amounts of Nitrogen

Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2026
Author(s):  
Nikola Koković ◽  
Elmira Saljnikov ◽  
Frank Eulenstein ◽  
Dragan Čakmak ◽  
Aneta Buntić ◽  
...  
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Quality Parameters ◽  
Light Fraction ◽  
Microbial Biomass C ◽  
Microbial Biomass N ◽  
Sensitivity Index ◽  
Strong Impact ◽  
Labile Organic Matter ◽  
C And N

Microbially mediated soil organic matter is an extremely sensitive pool that indicates subtle changes in the quality parameters responsible for the soil’s ecological and productive functions. Fifty years of mineral fertilization of a wheat-corn cropping system has a strong impact on soil quality parameters. The goal of the research was to study the dynamics and quality of soil biological parameters affected by increasing amounts of mineral nitrogen. Soil respiration, potentially mineralizable C and N, microbial biomass C and N and light-fraction OM on Cambisol were analyzed in the following treatments: (1) Control (without fertilization); (2) NPK (60/51/67); (3) NPK (90/51/67); (4) NPK (120/51/67); (5) NPK (150/51/67 kg ha−1). The parameters studied were significantly affected by the long-term application of mineral fertilizer compared with both the control and the adjacent native soil. The highest amounts of nitrogen (N150) did not significantly differ from N120 and N90 for most of the parameters studied. Potentially mineralizable C represented the largest labile carbon pool, while microbial biomass N was the largest labile nitrogen pool. The mineralization rates for C and N were oppositely distributed over the seasons. The sensitivity index correlated with the amount of light-fraction OM. The results give a deeper insight into the behavior and distribution of different pools of labile SOM in the agro-landscapes and can serve as a reliable basis for further research focused on zero soil degradation.

scholarly journals Sheep Grazing Enhances Coarse Relative to Microbial Organic Carbon in Dryland Cropping Systems

2016 ◽  
Vol 5 (2) ◽  
pp. 1
Author(s):  
Joy L. Barsotti ◽  
Upendra M. Sainju ◽  
Andrew W. Lenssen ◽  
Zach J. Miller ◽  
Patrick G. Hatfield
Keyword(s):  
Organic Matter ◽  
Microbial Biomass ◽  
Spring Wheat ◽  
Crop Residue ◽  
Management Practices ◽  
Cropping Systems ◽  
Ovis Aries ◽  
Sheep Grazing ◽  
Herbicide Application ◽  
Organic C

Sheep (<em>Ovis aries </em>L<em>.</em>) grazing, a cost-effective method of weed control compared with herbicide application and tillage, may influence soil C fractions by consuming crop residue and weeds and returning C through feces and urine to the soil. We examined the effect of three weed management practices (sheep grazing, herbicide application, and tillage) and two cropping sequences (continuous spring wheat [<em>Triticum aestivum </em>L.] [CSW] and spring wheat-pea [<em>Pisum sativum </em>L.]/barley [<em>Hordeum vulgare </em>L.] mixture hay-fallow [W-P/B-F]) on soil microbial biomass C (MBC), potential C mineralization (PCM), and particulate organic C (POC) in relation to soil organic C (SOC) at the 0- to 30-cm depth from 2009 to 2011 in southwestern Montana. The MBC at 0 to 5 cm was greater with tillage on CSW than tillage on W-P/B-F in 2009 and 2011, but was greater with herbicide application on CSW than tillage on CSW in 2010. The POC at 0 to 5 cm and 15 to 30 cm was greater with sheep grazing than herbicide application on CSW and W-P/B-F, but at 5 to 15 cm was greater with grazing on CSW. The MBC, PCM, and POC at all depths decreased from 2009 to 2011. Crop residue incorporation into the soil increased MBC with tillage on CSW. Lower proportions of labile than nonlabile organic matter through feces and urine probably reduced MBC at the soil surface, but increased POC with sheep grazing compared with herbicide application on CSW and W-P/B-F. Sheep grazing may increase coarse soil organic matter compared with microbial biomass in dryland cropping systems.

Decomposition of plant material in Australian soils. III. Residual organic and microbial biomass C and N from isotope-labelled legume material and soil organic matter, decomposing under field conditions

Soil Research ◽  
1985 ◽  
Vol 23 (4) ◽  
pp. 603 ◽  
Author(s):  
JN Ladd ◽  
M Amato ◽  
JM Oades
Keyword(s):  
Microbial Biomass ◽  
South Australia ◽  
Experimental Period ◽  
Decay Rates ◽  
Microbial Biomass C ◽  
Plant Residues ◽  
Total Biomass ◽  
Organic C ◽  
Air Temperatures ◽  
C And N

After eight years decomposition of 14C, 15N-labelled legume (Medicago littoralis) material previously mixed into topsoils (0-10 cm) at four field sites in South Australia, residual organic 14C and 15N to 30 cm depth accounted for respectively 11-13% of input 14C, and 31-38% of input 15N. About 90% of the residual organic 14C and 70-80% of the residual l15N was recovered in topsoils. For sites in similar rainfall areas, soils of heavier texture retained slightly greater amounts of 14C and15N-labelled residues. Throughout the eight-year experimental period, the rates of decline of residual organic 14C and 15N exceeded those of native soil organic C and N. A comparison of the decline of organic 14C in topsoils, averaged for the four South Australian sites, with the average decline reported for 14C-labelled plant residues in soils at English and Nigerian field sites, suggests that net decomposition rates doubled approximately for an 8-9�C rise in mean annual air temperatures. Microbial biomass 14C and 15N of topsoils with time accounted for decreasing proportions of total biomass C and N, and of residual organic I4C and I5N. The relatively greater retention after eight years of biomass 14C and 15N in soils of heavier texture is consistent with the concept that the net decay of C and N in soils is dependent upon the turnover of biomass C and N, and that decay rates are decreased in soils which have the greater capacity to protect decomposer populations.

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