Seasonal variations of the light organic fractions in soils under different agricultural management systems

Conti, M. E.; Palma, R. M.; Arrigo, N. M.; Giardina, Ernesto

doi:10.1080/00103629209368697

Cited by 12 publications

(5 citation statements)

References 5 publications

(4 reference statements)

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“…However, in 1996 only (F)-W was constant with time; both cropped systems increased in late July to early August then decreased again. Our 1996 results therefore support the findings by such workers as Spycher et al (1983) and Conti et al (1992) who observed marked seasonal changes in LF. Our results differed from those of Bremer et al (1994) who found only a minor effect of rotation phase on LF in a long-term crop rotation study in Lethbridge, Alberta.…”

Section: Soil Biochemical Attributessupporting

confidence: 82%

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

Campbell¹,

Biederbeck²,

Geyi³

et al. 1999

Can. J. Soil. Sci.

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. 1999. Seasonal trends in selected soil biochemical attributes: Effect of crop rotations in the semiarid prairie. Can. J. Soil Sci. 79: 73-84. 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 CaCl 2 . 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 (C min ) and N (N min ), 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%, C min and N min 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 N min , 29% for LFC, 52% for C min , 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 Campbell, C. A., Biederbeck, V. O., Wen, G., Zentner, R. P., Schoenau, J. et Hahn, D. 1999. Évolution saisonnière de quelques caractères biochimiques du sol: effets de la rotation des cultures dans la Prairie semi-aride. Can. J. Soil Sci. 79: 73-84. Les mesures des modifications saisonnières affectant les critères biochimiques du sol peuvent nous en app...

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Section: Soil Biochemical Attributessupporting

confidence: 82%

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

Campbell¹,

Biederbeck²,

Geyi³

et al. 1999

Can. J. Soil. Sci.

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“…It is likely that differences in seasonal weather conditions, and their influence on rate of residue decomposition, are major contributors to the conflicting results of LFC responses often reported in the literature. For example, some workers observe significant seasonal variations in LF material (Spycher et al 1983;Conti et al 1992;Campbell et al 1999), whereas others observe only minor differences (Bremer et al 1994). Additional evidence supporting a rapid decomposition of LFC under moister conditions is provided by the lower ratios (0.025 to 0.12) of LFC: OC in 1995 when 335 mm of rain fell during the growing season, compared to ratios of 0.05 to 0.17 in 1996, when only 157 mm of rain was recorded.…”

Section: Soil Biochemical Attributesmentioning

confidence: 90%

Seasonal trends in soil biochemical attributes: Effects of crop management on a Black Chernozem

Campbell¹,

Lafond²,

Biederbeck³

et al. 1999

Can. J. Soil. Sci.

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. 1999. Seasonal trends in soil biochemical attributes: Effects of crop management on a Black Chernozem. Can. J. Soil Sci. 79: 85-97. Knowledge of the response of soil biochemical attributes to crop management and growing season weather is important for assessing soil quality and fertility. Long-term (38-39 yr) crop rotations on a Black Chernozem at Indian Head, Saskatchewan, were sampled (0-to 7.5-cm depth) between early May and mid-October, 11 times in 1995 and 9 times in 1996. We assessed the effect of cropping frequency [fallow-wheat (Triticum aestivum L.) (F-W) vs. F-W-W, vs. Continuous (Cont) W], fertilizers (unfertilized vs. N + P applied), straw harvesting, legume green-manure (GM) in GM-W-W (unfertilized), and legume-grass hay (H) in F-W-W-H-H-H (unfertilized) systems. Changes in organic C and total N (OC, TN), microbial biomass C (MBC), light fraction C and N (LFC and LFN), mineralizable C and N (C min and N min ), and water-soluble organic C (WSOC) were monitored. Organic C and TN were constant and unaffected by rotation phase during the season, but most of the other more labile soil biochemical attributes varied during the season. Much of this temporal variability was associated with changes in soil moisture, temperature and precipitation, and with rhizodeposition in some cases. Whenever conditions favoured rapid decomposition in situ (e.g., high moisture, temperature and/or precipitation) we obtained lower values for the more labile attributes in subsequent laboratory measurements. Seasonal trends in the more labile attriutes were more pronounced in 1995 (a much wetter year) than in 1996, and the proportion of the variability attributable to weather conditions was greater in 1995 than in 1996 (viz., R 2 ranged from 20 to 44% in 1996 and from 37 to 60% in 1995). Seasonal variability was greater in the more fertile treatments [e.g., Cont W (Fert) and F-W-W-H-H-H) than in F-W or Cont W (Unfert). Seasonal variability in LF was unaffected by cropping. Light fraction was lower in 1995 than 1996 because of faster decomposition in 1995 (335 mm of growing season precipitation compared to 157 mm in 1996). Microbial biomass was not influenced by cropping in 1996, but in 1995 it was higher in cropped than in fallow phases of the rotations, suggesting a positive effect of rhizodeposition. Water-soluble organic C was greatest in the more fertile treatments and in cropped than in fallow phases. Mineralizable C and N were greater in cropped than in fallow rotation phases in 1995, but unaffected by cropping in 1996. Further, C min and N min were higher in 1996 than in 1995, likely due to more rapid decomposition in the wetter 1995. Over the last 10 yr of this experiment LFC and C min have increased markedly in the more fertile treatments [e.g., Cont W (Fert), F-W-W-H-H-H], but have hardly changed in the less fertile treatments such as F-W or Cont W (Unfert). In this period the less labile attributes (e.g., OC) have hardly changed in any treatment.Key words: Microbial biomass, carbon, nitrogen, mineralization, water-...

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“…Seasonal variations are less prominent in arable soils (Adams, 1980;Conti et al, 1992), but LF-OM has been found to reflect differences in the cropping and tillage system (Cambardella & Elliott, 1992;Beare et ai., 1994a, b;Biederbeck et al, 1994;Bremer et al, 1994).…”

Section: Light Fraction Organic Matter (Lf-om)mentioning

confidence: 97%

Matching Measurable Soil Organic Matter Fractions with Conceptual Pools in Simulation Models of Carbon Turnover: Revision of Model Structure

Christensen

1996

Evaluation of Soil Organic Matter Models

127

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SummaryA major limitation of current compartment models of soil organic matter (SOM) turnover is that most of the conceptual pools they contain do not correspond to experimentally verifiable fractions. Exceptions are some of the input pools and the microbial biomass. Available information suggests that physical fractionation of soil may delineate SOM fractions that relate more directly to SOM structure and function, and thereby also to biological turnover. Such fractionations may therefore define SOM model pools that are functionally meaningful, leading to a redefinition of the structure of current models and the factors that regulate the material fluxes between compartments. A first approximation to a revised model structure is ventured. It is based on soluble and non-soluble input fractions and separate above-and below-ground input routes. It includes two dynamic pools of particulate organic matter (free and intraaggregate light fraction OM), one pool of inert light fraction OM, and two pools of organomineral associated SOM (siIt-and c1ay-SOM). The need to incorporate soil fauna and soil structural features is stressed.

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Seasonal variations of the light organic fractions in soils under different agricultural management systems

Cited by 12 publications

References 5 publications

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

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

Seasonal trends in soil biochemical attributes: Effects of crop management on a Black Chernozem

Matching Measurable Soil Organic Matter Fractions with Conceptual Pools in Simulation Models of Carbon Turnover: Revision of Model Structure

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