Treatments
Treatments consisted of leaf litter from commonly found trees both native and introduced in the Northeast farming system as well as rice straw and Sesbania rostrata Table 2. Straw is available after the rice harvest and S. rostrata is a widely-promoted green manure crop for rice. The organic materials were cut to approximately 1 1 cm size. The application rate was equivalent to 10 t ha–1 DW.
For the submerged experiment, 1 kg of soil uniformly mixed with organic residues was put into a pot of 13.5 cm in diameter and 14 cm in height. Distilled water was added to a depth of approximately 2 cm above the soil surface. This depth was maintained throughout the experiment.
For the aerobic experiment, 100 grams of soil was mixed uniformly with the organic residues and placed in a plastic pot of 6 cm in diameter and 4 cm in height. The soil moisture content was adjusted to field capacity 13% soil dry weight and maintained throughout the experiment.
The experiments were arranged in completely randomized design CRD with 5 replications. They were kept in laboratory conditions with an average ambient temperature of 28 °C.