Each cylindrical mesocosm measured 34cm high and 35cm
diameter. The wheat straw was collected from our long-term DBSR
experimental fields. The soil was collected from a rice paddy field
in the Pailou Experimental Station, Nanjing Agricultural University.
The clay soil contained 10.9 g kg−1 organic matter, 0.89 g kg−1 total
nitrogen, 4.3 g kg−1 total phosphorus, 164mg kg−1 available potassium
and had a pHof 7.2. Dry wheat (var. Yangmai 13) straw (357 g,
an amount equivalent to the amount used in the field experiment,
above) was packed in 1mm-mesh bags and buried at a depth of
20cm in the mesocosm. In total, 15 kg of soil were added on top of
the straw bags in each mesocosm.