I am modeling the C inputs to several replicated cropping systems and
comparing this model with C retained in the respective soil systems as
different C fractions. The soils in the more complex systems appear to be
accumulating more C in the top 7.5 cm...
In contrast, the total C inputs to the soil of these more complex systems
appears to less than that of some of less complex systems such as
continuous corn systems... the more complex systems include some chisel
tillage while the continuous corn systems with and without a rye cover
crop are no-till..
The more complex systems are the only ones containing wheat in the
rotation. I think this inclusion of wheat may have a role in the greater
C accumulation in the 0-7.5 cm layer...
I am wondering if anyone can refer me to literature describing
any of the following:
Root:shoot ratios for cover crops (specifically cereal rye and hairy
vetch)
Lignin content of crop roots (Corn, wheat, soybeans... )
Differences in root:shoot ratios for the same crop under different
management systems
Amount of litter (o horizon) dry matter that can accumulate in a no-till
corn system
*****************************************************
Food for thought
Lignin contained in the above ground
biomass of corn, soybeans and wheat
from
Principles and Applications of Soil Microbiology by Sylvia et
al., 1998
corn = 5.6% lignin, soybean = 11.9 % lignin and wheat = 14.1 % lignin
At the agronomy meetings this fall, I heard someone suggest (I think it
was Dr. E. Paul) that the simplest way to increase SOM levels would be to
breed grain corn varieties with a greater lignin content in their stover
*****************************************************
Joel Gruver
Soil Quality Research
U of MD
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