Effect of ammonia treatment conditions of wheat straw on organic matter degradation measured in situ and by the gas test method

Abstract

-Organic matter degradation (OMD) was studied with the techniques of in situ degradation and in vitro gas production (gas test) on 16 straws (TS) treated under different conditions of ammonia concentration (3 and 5%), duration (15, 30, 45 and 75 days) and temperature (15 and 35 o C). Gas production (GP) and OMD were measured at 2, 4, 8, 16, 24 and 48 h. The results showed that after treatment, compared with the untreated straw (US), the OMD at 48 h, GP at 48 h and organic matter theoretical digestibility (OMTD) increased by 31, 25 and 19% (P < 0.01). Among the treatment factors, temperature was mainly involved in the increase in OMD, GP and OMTD. The correlations established between OMD and GP at every kinetic point, and between OMTD and GP at every kinetic point were low. They were high only during the first 24 h of the GP incubation, particularly between OMTD and GP at 8 h. This does not allow the utilisation of the GP method to predict the OMD in situ, but GP at 8 h can be used for a rapid classification of the straws.