Silage dry matter content and predicted effluent production in England and Wales 1984-1994

The amount of silage and silage effluent produced 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. (C) 1997 Silsoe Research Institute.