THE EFFECTS OF VOLATILE FATTY ACID EMISSIONS ON CROP ESTABLISHMENT RESULTING FROM SOIL INJECTION OF UNDIGESTED SEWAGE SLUDGE
Report No FR0239
C Atkinson*, M.J. Hann* and J.E. Hall * Silsoe College
To evaluate the potential impact of the injection of undigested sewage sludge on the germination of arable crops.
Crop failures have been attributed to soil injection of sludge prior to sowing.
Volatile fatty acids (VFAs) are produced when sludge decomposes under anaerobic saturated soil conditions which may inhibit germination.
Soil injection should not be carried out in wet soils when crops are to be sown shortly afterwards. Under unfavourable conditions rates of application should be reduced and/or sowing should be delayed for at least ten days.
This report describes laboratory incubations of undigested sludge in sandy loam and clay soils under aerobic and anaerobic conditions. These tests characterised the combination of VFAs produced. Laboratory germination tests using sugarbeet seed were carried out with single VFAs and in the combination indicated by the incubation study. A field trial is described which compared germination following sowing sugar beet at 2, 4, 5, 8 and 10 day intervals after injecting sludge at 0, 80 or 180 m3/ha into a sandy loam soil. There was little evidence of inhibition at 80 m3/ha but comparable levels of germination on the higher rate of application were only apparent if sowing was delayed for 10 days.
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