scholarly journals Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. II. Total organic carbon and its rate of loss from the soil profile

Soil Research ◽  
1986 ◽  
Vol 24 (2) ◽  
pp. 281 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
Activity Ratio ◽  
Clay Content ◽  
Continuous Cultivation ◽  
Stepwise Multiple Regression ◽  
Annual Rainfall ◽  
Aggregation Index ◽  
Organic C ◽  
Long Term Trends ◽  
Kinetics Of

The kinetics of organic C loss were studied in six southern Queensland soils subjected to different periods (0-70 years) of cultivation and cereal cropping. The equation: Ct = Ce + (C0 - Ce)exp(- kt), where C0, Ce and C, are organic C contents initially, at equilibrium and at time k respectively, and k is the rate of loss of organic C from soil, was employed in the study. The parameter k was calculated both for %C (kc) and for weight of organic C/volume of soil (k,), determined by correcting for differences in sampling depth due to changes in bulk density upon cultivation. Mean annual rainfall largely determined both C, and Ce, presumably by influencing the amount of dry matter produced. Values of kc and kw varied greatly among the soils studied. For the 0-0.1 m depth, kw was 0.065, 0.080, 0.180, 0.259, 0.069 and 1.224 year-1 respectively for Waco (black earth - initially grassland), Langland-Logie (grey brown and red clays - brigalow), Cecilvale (grey, brown and red clays - poplar box), Billa Billa (grey, brown and red clays - belah), Thallon (grey, brown and red clays - coolibah) and Riverview (red earths - silver-leaved ironbark). The k values were significantly correlated with organic Chrease activity ratio (r = 0.99***) and reciprocal of clay content (r = 0.97**) of the virgin soils. In stepwise multiple regression analysis, aggregation index (for kc values) or exchangeable sodium percentage (for kw) and organic C/urease activity ratio of soils were significantly associated with the overall rate of loss of organic C. It was inferred, therefore, that the relative inaccessibility and protection of organic matter against microbial and enzymic attack resulted in reduced organic C loss. Losses of organic C from the deeper layers (0-0.2 m, 0-0.3 m) were observed in Waco, Langlands-Logie, Cecilvale and Riverview soils, although generally rate of loss decreased with depth.

Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. IV. Loss of organic carbon from different density functions

Soil Research ◽  
1986 ◽  
Vol 24 (2) ◽  
pp. 301 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
Clay Content ◽  
Continuous Cultivation ◽  
Heavy Fraction ◽  
Light Fraction ◽  
Organic C ◽  
Ethanol Mixture ◽  
Total Soil ◽  
Long Term Trends ◽  
The Difference

Six southern Queensland soils used for cereal cropping for cultivation periods ranging from 20 to 70 years were subjected to density fractionation. The soils were separated into fractions with densities of <2, 2.0-2.2, 2.2-2.4 and >2.4 Mg m-3 using bromoform-ethanol mixture. The < 2 Mg m-3 fraction (light fraction) contained only 1.8-3.2% of the total soil weight, but accounted for 15-32% of total soil organic C. In five clay soils the rate of loss of organic C from the light fraction was 2-11 times greater than that from the heavy fraction (>2 Mg m-3). The higher the clay content the larger was the difference between these two fractions in rate of loss of organic C. It is inferred that the heavy fraction was closely associated with clay in these soils. In a sandy soil, rate of loss of organic C from the heavy fraction was similar to that from the whole soil.

scholarly journals Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland .V. Rate of loss of total nitrogen from the soil profile and changes in carbon : nitrogen ratios

Soil Research ◽  
1986 ◽  
Vol 24 (4) ◽  
pp. 493 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
Root Zone ◽  
Continuous Cultivation ◽  
N Loss ◽  
Total N ◽  
Cultivation Period ◽  
N Removal ◽  
Long Term Trends ◽  
Red Earth ◽  
Kinetics Of

The kinetics of total N loss from the top (0-0.1 m) and the subsoil (up to 1.2 m depth) of six southern Queensland soils after different periods (0-70 years) of cultivation and cereal cropping, were studied. The equation: Nt = Ne + (No - N,)exp(- kt), where No, Ne and N, are total N concentrations initially, at equilibrium and at time t, respectively, and k is the rate of loss of total N from soil, described total N loss from only three soils. For the 0-0.1 m depth, the kw values (based on weight of total Nholume of soil) were 0.061, 0.115 and 0.275 year-1, respectively for Waco (black earth; initially grassland), Langlands-Logie (grey, brown and red clays; brigalow) and Cecilvale soil (grey, brown and red clays; poplar box). The kw values decreased to less than half at 0-0.6 m depths of those at 0-0.1 m depth. In the other three soils, Billa Billa (grey, brown and red clays; belah), Thallon (grey, brown and red clays; coolibah) and Riverview (red earth; silver-leaved ironbark), total N declined linearly over the 20-25 years of cultivation period studied. Average annual rates of N loss from the profiles of the six soils, respectively, were 31.3, 67.1, 34.5, 50.8, 35.8 and 32.0 kg N ha-1 year-1 , from Waco, Langlands-Logie, Cecilvale, Billa Billa, Thallon and Riverview soils. Except for Langlands-Logie, these losses could be accounted for by crop N removal. In the Langlands-Logie soil, besides N removal by crop (51 kg N ha-1 year-1, 1982-1984 period), leaching of N below the root-zone appeared to be the likely factor for N loss. C:N ratios generally increased with depth in the five clay soils but decreased with depth in the red earth (Riverview). Cultivation had no significant effect on the C:N ratios of Cecilvale, Thallon and Riverview soils, but it caused a decrease in Langlands-Logie soil (up to 0.6 m depth) and an increase in Waco soil (up to 1.2 m depth). It was inferred, therefore, that in the latter, remaining soil N was likely to mineralise more slowly with increasing period of cultivation, resulting in a fertility loss which may be greater than that shown by the decrease in total N.

Soil organic matter in rainfed cropping systems of the Australian cereal belt

Soil Research ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 435 ◽  
Author(s):  
R. C. Dalal ◽  
K. Y. Chan
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Management Practices ◽  
Performance Indicator ◽  
Annual Rainfall ◽  
Soil Productivity ◽  
Organic C ◽  
Soil C ◽  
Eastern Australia

The Australian cereal belt stretches as an arc from north-eastern Australia to south-western Australia (24˚S–40˚S and 125˚E–147˚E), with mean annual temperatures from 14˚C (temperate) to 26˚C (subtropical), and with annual rainfall ranging from 250 mm to 1500 mm. The predominant soil types of the cereal belt include Chromosols, Kandosols, Sodosols, and Vertosols, with significant areas of Ferrosols, Kurosols, Podosols, and Dermosols, covering approximately 20 Mha of arable cropping and 21 Mha of ley pastures. Cultivation and cropping has led to a substantial loss of soil organic matter (SOM) from the Australian cereal belt; the long-term SOM loss often exceeds 60% from the top 0–0.1 m depth after 50 years of cereal cropping. Loss of labile components of SOM such as sand-size or particulate SOM, microbial biomass, and mineralisable nitrogen has been even higher, thus resulting in greater loss in soil productivity than that assessed from the loss of total SOM alone. Since SOM is heterogeneous in nature, the significance and functions of its various components are ambiguous. It is essential that the relationship between levels of total SOM or its identif iable components and the most affected soil properties be established and then quantif ied before the concentrations or amounts of SOM and/or its components can be used as a performance indicator. There is also a need for experimentally verifiable soil organic C pools in modelling the dynamics and management of SOM. Furthermore, the interaction of environmental pollutants added to soil, soil microbial biodiversity, and SOM is poorly understood and therefore requires further study. Biophysically appropriate and cost-effective management practices for cereal cropping lands are required for restoring and maintaining organic matter for sustainable agriculture and restoration of degraded lands. The additional benefit of SOM restoration will be an increase in the long-term greenhouse C sink, which has the potentialto reduce greenhouse emissions by about 50 Mt CO2 equivalents/year over a 20-year period, although current improved agricultural practices can only sequester an estimated 23% of the potential soil C sink.

Comparison of three carbon determination methods on naturally occurring substrates and the implication for the quantification of 'soil carbon'

Soil Research ◽  
2011 ◽  
Vol 49 (1) ◽  
pp. 27 ◽  
Author(s):  
M. K. Conyers ◽  
G. J. Poile ◽  
A. A. Oates ◽  
D. Waters ◽  
K. Y. Chan
Keyword(s):  
Soil Carbon ◽  
Annual Variation ◽  
Organic Substrates ◽  
Test Procedures ◽  
Organic C ◽  
Soil C ◽  
Long Term Trends ◽  
Carbon Determination ◽  
Almost All

Accounting for carbon (C) in soil will require a degree of precision sufficient to permit an assessment of any trend through time. Soil can contain many chemically and physically diverse forms of organic and inorganic carbon, some of which might not meet certain definitions of ‘soil carbon’. In an attempt to assess how measurements of these diverse forms of C might vary with analytical method, we measured the C concentration of 26 substrates by three methods commonly used for soil C (Walkley–Black, Heanes, and Leco). The Heanes and Leco methods were essentially equivalent in their capture of organic C, but the Leco method captured almost all of the inorganic C (carbonates, graphite). The Heanes and Walkley–Black methods did not measure carbonates but did measure 92% and 9%, respectively, of the C in graphite. All three of the common soil test procedures measured some proportion of the charcoal and of the other burnt materials. The proportion of common organic substrates (not the carbonates, graphite, or soil) that was C by weight ranged from ~10% to 90% based on the Heanes and Leco data. The proportion of the organic fraction of those same substrates, as measured by loss-on-ignition, that was C by weight ranged from 42% to 100%. The relationship between Walkley–Black C and total C (by Heanes and Leco) showed that Walkley–Black C was a variable proportion of total C for the 26 substrates. Finally, the well-known, apparent artefact in the Cr-acid methods was investigated: dichromate digestion should contain at least 7–10 mg C in the sample or over-recovery of C might be reported. Our observation that common soil C procedures readily measure C in plant roots and shoots, and in burnt stubble, means that there will likely be intra-annual variation in soil C, because avoidance of these fresh residues is difficult. Such apparent intra-annual variation in soil C will make the detection of long-term trends problematic.

scholarly journals Long-term trends of climate change and its impact on crop growing season on Montreal Island

2016 ◽  
Vol 8 (1) ◽  
pp. 78-88
Author(s):  
Erika Bouchard ◽  
Zhiming Qi
Keyword(s):  
Climate Change ◽  
Daily Rainfall ◽  
Growing Season ◽  
Annual Rainfall ◽  
Climate Trends ◽  
Growing Season Length ◽  
Mk Test ◽  
Long Term Trends ◽  
Increasing Trends

Long-term trends in air temperature and precipitation under climate change were analyzed for two meteorological stations on the Island of Montreal: McGill (1872–1986) and Pierre-Elliott-Trudeau (P-E-T, formerly Dorval) Airport (1942–2014). A linear trendline analysis, the Mann–Kendall (MK) test and the two-sample Kolmogorov–Smirnov (KS) test were conducted to assess specific climate trends. On a 100-year basis, temperature increased 1.88°C (34%) and 1.18°C (19%) at the McGill and P-E-T Airport sites, respectively, while annual rainfall increased 23.9 mm y−1 (2.3%) and 138.8 mm y−1 (15%) over the same period. The frequency of 50% (every other year) and 95% (every year) annual maximum daily rainfall events showed decreasing trends for the McGill station, but increasing trends for the P-E-T Airport station. Growing degree-days and growing season length are prone to being influenced by climate change and are critical to managing agricultural activities in the Montreal region; both showed increasing trends. At the same time, the onset of the growing season occurred earlier as time progressed.

scholarly journals LE PRÉLÈVEMENT DU K PAR LA LUZERNE (Medicago sativa L.) ET SA DYNAMIQUE DANS 30 SOLS DU QUÉBEC

1990 ◽  
Vol 70 (3) ◽  
pp. 379-393 ◽  
Author(s):  
R. R. SIMARD ◽  
J. ZIZKA ◽  
C. R. DE KIMPE
Keyword(s):  
Crop Yields ◽  
Clay Content ◽  
State Level ◽  
Mineralogical Composition ◽  
Monovalent Cation ◽  
K Uptake ◽  
Exchangeable K ◽  
Medicago Sativa L ◽  
Kinetics Of

The understanding of the kinetics of K uptake by plants is necessary for the development of predictive models aimed at optimum fertilizer use and crop yields. The objective of this work was to study the kinetics of K uptake by alfalfa, in a long-term growth chamber experiment (366 d), on 30 soils from Quebec. The soils varied in mineralogical composition and by the amounts of available K in soluble, rapidly and slowly exchangeable forms. In 28 of the 30 soils, a minimal, steady-state level of NH4OAc-K was reached after 208 d and six cuts of alfalfa. This minimal level and the K uptakes were qualitatively related to soil texture. Only soils with clay content greater than 35% were still able to supply enough K to maintain alfalfa yields. The kinetics of K uptake was described by two parabolic diffusion equations. In the first 208 d, the rate and amounts of K uptake were better predicted by extracting procedures using a monovalent cation for the exchange. The amount of HNO3-K in the soils was very significantly related to the rate (r = 0.90**) and amount of slowly exchangeable K uptake (r = 0.89**) in the last 158 d of growth. The availability of K was greater in soils rich in feldspar and vermiculite than in soils where illite is a major component. The results of this study indicate that the amounts of HNO3-K and/or the clay content should be integrated into alfalfa fertilizer requirement tables along with amounts of K in soluble and rapidly exchangeable forms for maintenance of alfalfa fields. Key words: Slowly exchangeable K, alfalfa, uptake kinetics, HNO3-K, diffusion, K uptake

scholarly journals Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland .VIII. Available nitrogen indexes and their relationships to crop yield and N uptake

Soil Research ◽  
1990 ◽  
Vol 28 (4) ◽  
pp. 563 ◽  
Author(s):  
RC Dalal ◽  
RJ Mayer
Keyword(s):  
N Uptake ◽  
Continuous Cultivation ◽  
Annual Rainfall ◽  
Soil Series ◽  
Total N ◽  
Available N ◽  
Organic C ◽  
Winter Cereals ◽  
Nitrate N ◽  
Mineralizable N

Six major soil series of southern Queensland were studied for the changes in the levels of available N indices (determined by both biological and chemical methods) and nitrate-N, with continuous cultivation and cereal cropping for up to 70 years. The biological N indices, measured in soil collected at planting of winter cereals, were anaerobic mineralizable N, aerobic mineralizable N and nitrate-N down to 1.2 m depth. The chemical indices were autoclave N and oven N. The predictive capabilities of various available N indices, and total N and organic C, were assessed from dry matter and N uptake of winter cereals in the field in 1983 as well as in the glasshouse. Anaerobic mineralizable N levels increased with mean annual rainfall but decreased with mean annual temperatures of the sampling sites of the six soil series. Therefore, it was possible to predict closely anaerobic mineralizable N from soil total N, and mean annual rainfall and temperature. Autoclave N showed no such trends. Anaerobic mineralizable N declined with period of cultivation, exponentially in Waco, Langlands-Logie and Cecilvale soils (0.112, 0.111 and 0.247 year-1, respectively) and linearly in the other three soil series. No consistent trends were discerned in autoclave N and oven N in four of the soil series with period of cultivation. Generally, nitrate-N (measured at planting) declined with period of cultivation. However, in Billa Billa soil, it increased in the soil profile (0-1.2 m) during the initial 7 years of cultivation and declined rapidly after 12 years. Although a number of available N indices, including total N and organic C, were significantly correlated with crop dry matter yield and N uptake, the best prediction of crop performance was provided by a combination of anaerobic mineralizable N (0-0.3 m) and nitrate-N (0-0 6 m) in the six soil series.

The potential effects of anthropogenic climate change on evaporation from water storage reservoirs within the Lockyer Catchment, south-east Queensland, Australia

2016 ◽  
Vol 67 (10) ◽  
pp. 1512 ◽  
Author(s):  
Ryan McGloin ◽  
Hamish McGowan ◽  
David McJannet
Keyword(s):  
Climate Change ◽  
Water Storage ◽  
Annual Runoff ◽  
Anthropogenic Climate Change ◽  
Annual Rainfall ◽  
Air Temperatures ◽  
Storage Reservoirs ◽  
The Future ◽  
Long Term Trends

In order to effectively manage water storage reservoirs, it is essential to be able to anticipate how components of the water balance will react to predicted long-term trends in climate. This study examines the potential impacts of anthropogenic climate change on evaporation from small reservoirs in the Lockyer catchment, a productive agricultural region in south-east Queensland, Australia. Future projections of evaporation, made using the most likely future emissions scenario, suggested that evaporation is expected to increase by ~6% by the year 2050. In addition, rainfall is expected to decrease by ~8%. These projected increases in evaporation and reductions in rainfall, combined with the knowledge that changes in annual rainfall are known to be amplified in annual runoff, mean that the availability of water resources in the Lockyer catchment region may be greatly diminished in the future. In addition, increases in water scarcity, combined with higher future air temperatures and population growth, are likely to result in a greater demand for irrigation in the future.

scholarly journals Secular Variation in Rainfall Intensity and Temperature in Eastern Australia

2013 ◽  
Vol 14 (4) ◽  
pp. 1356-1363 ◽  
Author(s):  
Yi-Ru Chen ◽  
Bofu Yu ◽  
Graham Jenkins
Keyword(s):  
Minimum Temperature ◽  
Rainfall Intensity ◽  
Annual Rainfall ◽  
Maximum Temperature ◽  
Trend Test ◽  
Long Duration ◽  
Eastern Australia ◽  
Long Term Trends ◽  
The Mean

Abstract It is generally assumed that rainfall intensity will increase with temperature increase, irrespective of the underlying changes to the average rainfall. This study documents and investigates long-term trends in rainfall intensities, annual rainfall, and mean maximum and minimum temperatures using the Mann–Kendall trend test for nine sites in eastern Australia. Relationships between rainfall intensities at various durations and 1) annual rainfall and 2) the mean maximum and minimum temperatures were investigated. The results showed that the mean minimum temperature has increased significantly at eight out of the nine sites in eastern Australia. Changes in annual rainfall are likely to be associated with changes in rainfall intensity at the long duration of 48 h. Overall, changes in rainfall intensity at short durations (&lt;1 h) positively correlate with changes in the mean maximum temperature, but there is no significant correlation with the mean minimum temperature and annual rainfall. Additionally, changes in rainfall intensity at longer durations (≥1 h) positively correlate with changes in the mean annual rainfall, but not with either mean maximum or minimum temperatures for the nine sites investigated.

scholarly journals Changes in the Intensity and Variability of Precipitation in the Central Region of Argentina between 1960 and 2012

Climate ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 66 ◽  
Author(s):  
Antonio de la Casa ◽  
Gustavo Ovando ◽  
Olga Nasello
Keyword(s):  
Central Region ◽  
Rainfall Intensity ◽  
Temporal Trends ◽  
Annual Rainfall ◽  
Rainfall Time Series ◽  
Total Annual Rainfall ◽  
Annual Frequency ◽  
Long Term Trends ◽  
Long Term Trend

This study analyzes the temporal variation of different rainfall features in the central region of Argentina between 1960 and 2012, and evaluates the dynamics of temporal trends by using the Mann–Kendall–Sneyers (MKS) and Tomé–Miranda (TM) procedures. Under different criteria and levels of significance, rainfall time series show homogeneous behavior in more than 80% of cases. Only 18 of the 42 annual cases analyzed reached a significant long-term trend (p < 0.10). Total annual rainfall (AR) showed a significant increase only in Laboulaye Aero (LB) and Villa Dolores Aero (VD), but this does not currently persist. A decrease in the annual frequency of rainy days (DPF) is more widespread in the region. Thus, the increase in mean annual rainfall intensity (INT) seems to be particularly associated with the decrease in annual frequency of events (DPF) in the central region of Argentina. However, the increase in INT currently persists only at the Córdoba Observatorio (BO), as INT stopped growing for LB, Río Cuarto Aero (RC), and VD in the mid-1990s. The variation coefficients of total annual rainfall (ARCV) and DPF (DPFCV) have increased in the region, but with the former restricted locally to the Pilar Observatorio (PI), RC, and VM, and the latter to BO and RC. Long-term changes of the pluvial regime in the central region of Argentina appear to be not only local and restricted to some properties of rainfall during the period, but also reveal a particular dynamic where the long-term trends of the evaluated properties have now changed sign or maintain a certain constancy at present.

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