scholarly journals Soil organic matter assessments in a long-term cropping system study

2002 ◽  
Vol 33 (13-14) ◽  
pp. 2119-2130 ◽  
Author(s):  
Gary E. Varvel ◽  
Mark A. Liebig ◽  
John W. Doran
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Cropping System ◽  
System Study

scholarly journals Cereal straw management: a trade-off between energy and agronomic fate

2015 ◽  
Vol 10 (2) ◽  
pp. 59 ◽  
Author(s):  
Massimo Monteleone ◽  
Pasquale Garofalo ◽  
Anna Rita Bernadette Cammerino ◽  
Angela Libutti
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Crop Residues ◽  
Ghg Emissions ◽  
Cropping System ◽  
Primary Energy ◽  
Nitrous Oxide Emissions ◽  
Straw Management ◽  
Trade Off

Climate change mitigation is the most important driving force for bioenergy development. Consequently, the environmental design of bioenergy value chains should address the actual savings of both primary energy demand and greenhouse gases (GHG) emissions. According to the EU Renewable Energy Directive (2009/28/EC), no direct impacts and no GHG emissions should be attributed to crop residues (like cereal straws) when they are removed from agricultural land for the purpose of bioenergy utilisation. The <em>carbon</em> <em>neutral</em> assumption applied to crop residues is, however, a rough simplification. Crop residues, indeed, should not be viewed simply as a waste to be disposed, because they play a critical role in sustaining soil organic matter and therefore have an inherent C-capturing value. Moreover, considering straws as an energy feedstock, its status of co-product is clearly recognised and its availability could be obtained according to different cropping systems, corresponding to different primary energy costs and GHG emissions. This paper highlights some <em>hidden</em> features in the assessment of agricultural energy and carbon balance, still very difficult to be detected and accounted for. Although they are frequently disregarded, these features (such as long term dynamic trend of soil organic carbon and annual nitrous oxide emissions from the soil) should be carefully considered in assembling the energy and emission balance. By using a crop simulation model, the long-term soil organic matter and annual N<sub>2</sub>O soil emissions were estimated. Consequently, a comprehensive energy and GHG balance was determined in accordance with the <em>life cycle assessment</em> methodology. Contrasting methods of straw management and wheat cultivation were compared: straw retention <em>vs</em> removal from the soil; conventional <em>vs</em> conservation tillage; wheat cropping system as a single-crop or in rotation. The resulting <em>carbon</em> <em>footprint</em> of straws has different magnitudes with respect to the several experimental conditions. By selecting the best agricultural practices, energy from straw can be optimally coupled with grain productions, without detrimental effects on soil fertility. An improved and specifically tailored cropping system is designed to obtain an optimal trade-off.

Modelling water, nitrogen, and crop yield for a long-term fallow management experiment

1995 ◽  
Vol 35 (7) ◽  
pp. 941 ◽  
Author(s):  
ME Probert ◽  
BA Keating ◽  
JP Thompson ◽  
WJ Parton
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Water ◽  
Cropping System ◽  
Wheat Crop ◽  
Time Step ◽  
Soil System ◽  
N Transformations ◽  
Winter Cereal

Two models that differ markedly in how they represent the crop-soil system have been used to simulate soil processes and crop production in the long-term experiment at Hermitage Research Station, Warwick, Queensland. The experiment was designed to examine the effects of tillage, stubble management, and nitrogen (N) fertiliser on the productivity of a winter cereal-summer fallow cropping system. it commenced in 1968 and the treatments have been maintained until the present. CENTURY operates on a monthly time step, considers all soil N transformations to occur in a single soil layer, and has a very simple crop growth routine that does not deal with crop phenology. APSIM provides a framework whereby a model of a cropping system is configured from component modules, which operate on a daily time step. For simulating the Hermitage experiment, modules to represent the dynamics of soil-water, N, surface residues, and growth of a wheat crop were used. The water and N modules deal with a multi-layered soil, whilst the wheat module develops leaf area, intercepts light, and accumulates and partitions dry matter in response to weather, soil-water, and N. Both models were specified to simulate the whole experimental period (1969-92) as a continuous run. The ability of these models to simulate grain yields, soil-water and drainage, nitrate-N, and soil organic matter were examined. Both models predict, in agreement with the observed data, that for this continuous cereal cropping system there has been a decline in soil organic matter for all the treatments and a reduction through time in the capacity of the soil to mineralise and accumulate nitrate during the fallows. CENTURY performed better than APSIM in predicting the relative yields of the N treatments but was less satisfactory than APSIM for absolute grain yield, soil-water, and drainage. Yield predictions with APSIM were sensitive to carry-over errors in the water balance from one season to the next, so that in some seasons large errors occurred in the predicted relative yields. Both models reproduced the observations well enough to indicate their suitability for providing useful insights into the behaviour of cropping systems where the focus is on depletion of soil fertility.

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