Decomposition of black oat straw and pig slurry in a soil under no-tillage

The use of pig slurry in no-tillage systems is relatively recent in South Brazil, so it is important to evaluate the decomposition of pig slurry as well as its effects on the cover crop residue decomposition in this system. The objective of this study was to evaluate the pig slurry decomposition and its influence on the decomposition rate of black oat straw in a soil under no-tillage. Two experiments were carried out under field conditions in an experimental area of the Federal University of Santa Maria (UFSM), on a Hapludalf. The CO2-C emission was measured right after the application of 0 and 40 m(3) ha(-1) of pig slurry in static chambers, in the absence or in the presence of oat straw on the soil surface. The CO2-C emission was monitored for 62 days in experiment 1 and for 97 days in experiment 2. Pig slurry and oat straw showed a different decomposition pattern. While the pig slurry had an initial phase of fast CO2-C mineralization followed by a slower phase, CO2-C-liberation by oat straw was more constant. About one third of C added through pig slurry and oat straw was emitted to the atmosphere in the form of CO2-C. Results of this study showed that the decomposition rate of black oat straw was not influenced by pig slurry application in soil under no-tillage system.