The intrinsic energy of soil aggregates affected by soil organic matter
Zhaolong Zhu1, Damien Field2, Budiman Minasny3
1
College of Mechanical and Electronic Engineering, Northwest A&F University, China, [email protected]
2
epartment of Environmental Sciences, Faculty of Agriculture and Environment, The University of Sydney, NSW, 2006,
D
[email protected]
3
epartment of Environmental Sciences, Faculty of Agriculture and Environment, The University of Sydney, NSW, 2006,
D
[email protected]
It is known that that the presence of organic matter can increase the stability of soil aggregates requiring
more energy input for this disruption and dispersion. This study investigates the link between soil aggregates
and energy involving the use of a clay soil collected from the field. Half the air-dried soil sampled was
passed through a 2 mm sieve and stored, while the other half of the soil was then puddled to destroy most
of the inherent soil macro- and microaggregates. The sieved and puddled soil was then incubated in pots
housed in sealed containers for a period of up to 3 months. In addition to the controls three levels (1, 2, &
3% organic matter) of two types of organic matter (alfalfa; C:N 10:1, and ; barley straw C:N 50:1) where
incubated in the soil. The change in soil organic carbon was assessed at days 14 and 28 of each month for the
three months. Two vials of NaOH were placed in each of the sealed containers to capture the CO2 generated
during the incubation which were sampled at 7,14,21 and 28 days of each month that the experiment was
conducted over. Soil was sampled at the end of each of the three months and the change in aggregation was
assessed using a combination of end-over-end shaking and wet sieving for 5 time periods for each sample.
This enabled the dynamics of aggregate breakdown to be assessed by scaling the exponential curves fitted
for each sample. From this samples were selected and the kinetics of breakdown assessed using ultrasonic
agitation so that the energy consumed could be measured. We will show the dynamics of soil aggregate
formation and will able to infer energy of aggregate formation. From the study, we will discuss how this
information can provide strategies that produce more stable aggregates, and more protected soil carbon.