Prevention of damage to grass swards from applications of silage effluent by neutralization or dilution of effluent acids

Estimates of the total acidity of silage effluent from a range of first-cut silages varied from 1025 to 21,125 mg Ca CO₃ per l with a weighted mean of 8817 mg l^-1. Quick-lime (CaO), hydrated lime [Ca(OH)₂] or caustic soda (NaOH) were found to be effective neutralizing agents when thoroughly mixed with the effluent. Results from seven field-plot experiments carried out between 1973 and 1977 involving application of silage effluent to grass swards are reported. Leaf scorch occurred when silage effluent with a total acidity equivalent to more than 6000 mg CaCO₃ per l was applied at rates exceeding 50 m³ ha^-1 to swards with several weeks regrowth. Scorch was most severe when applications were made during periods of dry sunny weather and to mechanically damaged swards. In these conditions reducing the total acidity to below 2000 mg CaCO₃ per l by neutralization or dilution allowed rates of over 100 m³ ha^-1 to be applied without harmful effects.
Acid neutralization was found to be unnecessary when silage effluent was applied to recently cut swards. Here rates of up to 150 m³ ha^-1 were applied without adverse effects and generally resulted in increased grass growth.