Silage Dry Matter Content and Predicted Effluent Production in England and Wales 1984–1994

Abstract

The amount of silage and silage effluent pro- duced from grass, maize and arable crops made in England and Wales from 1984-1994 is quantified, both on a basis of MAFF Region and end use of the silage. The total amount of silage made has increased by 148% from 25·30 Mt in 1984 to 37·55 Mt in 1994. In 1984 the proportions made were 97·5% grass, 2·5% maize and nil from arable crops (whole crop cereals). By 1994, the proportions were 90·9% grass, 7·8% maize and 1·3% arable crops. In 1984, grass silage comprised 60·4% first cut, 27·9% second cut and 4·7% third cut bunker-made silage with 7·0% made in bales. By 1994 the relative proportions were 53·3, 24·5, 4·1 and 18·1 % respectively. The average dry matter (DM) content of bunker made grass silage was first cut 241 g/kg, second cut 260 g/kg, third cut 243 g/kg and big bales 345 g/kg. For dairy cow silages it was first cut 233, second cut 268 and big bales 324 g/kg. The corresponding values for beef and sheep were 263, 299 and 385 g/kg. The average DM content of maize silage was 307 and arable 458 g/kg. However, except for arable silage, there were large between-year variations in DM content. The amount of effluent produced each year, calculated from the equation of Bastiman using the proportion of effluent produced at various ranges of DM i.e. <151, 150-170 to >290 g/kg was highly variable. In 1989, when a severe drought occurred, the 33·37 Mt of silage made produced only an estimated 497 Ml of effluent; whilst in 1993, when the silage making season was extremely wet, 37·93 Mt silage produced 1463 Ml of effluent. Overall, silages treated with acid additives constituted 15·9% of grass bunker made silage, but were responsible for 23·7 % of the effluent produced. From 1984-1994 the proportion of silage made as grass, maize and arable was 95·8, 3·7 and 0·5% and the estimated proportion of effluent produced was 97·2, 2·8 and <0·1% respectively. Similarly the proportions of grass silage made as first cut, second cut, third cut and big bales were 55·8, 25·7, 4·3 and 14·2% and the effluent produced 65·8, 23·6, 4·4 and 6·2% respectively. From 1992-1994 the proportion of first cut, second cut, third cut and big bale grass silage made for dairy cows was 27·0, 13·5, 4·5 and 3·6% and that for beef and sheep 27·8, 9·2, nil and 14·4% respectively. The corresponding estimated amounts of effluent were from dairy cow silages 44·2, 12·0, 6·8 and 3·2% and from beef and sheep 22·7, 7·7, nil and 3·4%. Effluent was mainly produced in the west i.e. Midland and West, South West and Wales, which were responsible for 65·4% of the grass silage made and 72·9% of the effluent produced, whilst the East and South East were responsible for 14·8% of the silage made, but only 11·6% of the effluent.