An evaluation of laboratory ensiling techniques

Silages made from 18 grasses and 8 legumes in test‐tube silos holding 100 g of fresh herbage were compared with those from the same crops ensiled in PVC bags holding 1 tonne of fresh material. For 8 herbages, polythene bags holding 6 kg of fresh material were also employed. Measurement of pH, ammonia‐N, lactic acid and volatile acids was made at the end of the storage period (64–155 days). Measurements made on silages from the test‐tube silos were closely correlated with those from the PVC bags. The correlation coefficients for ammonia‐N (r = +0.978), acetic acid (r = +0.871), propionic acid (r = +0.850) and lactic acid (r = +0.639) were all significant at P < 0.001 and for butyric acid (r = +0.482) at P <0.05. Fermentations which occurred in polythene bags agreed closely with those in both the smaller test‐tube silos and the larger PVC silos. There was good replication of silages from test tubes and polythene bags, the standard deviation for pH for the 26 silages made in test tubes was 0.144 with a coefficient of variation of 3.13%. The results indicate that laboratory silos have considerable potential in research, allowing a wider variety of crops and treatments to be studied than would have been possible on a larger scale.