Bacteria in manure and on manured and NPK-fertilised silage crops

Abstract

Abstract The numbers of bacteria belonging to Enterobacteriaceae (enterobacteria), lactic acid bacteria, Bacillus‐ and Clostridium spores were enumerated in manure and on manured and NPK‐fertilised silage crops. The enterobacteria were biochemically characterised by means of the Minitek system (BBL). More than 90% of the enterobacteria on crops belonged to the genus Enterobacter. A majority of these (72%) were identified as E agglomerans. Manuring did not increase the number of enterobacteria on silage crops. E coli was the most frequent species in manure but was present at 10−3 times that of the total number of enterobacteria on the crop one week after manuring. The number of Bacillusspores was 20–40 times higher on manured crops and the number did not decline with time, whereas Clostridium spores, coliforms capable of growing at 44°C and E coli were reduced 6, 40 and 20 times respectively between manuring and harvesting (7 weeks). Mechanical harvesting increased the number of Bacillus spores and coliforms capable of growing at 44°C on NPK fertilised crops probably due to soil contamination. Enterobacteria and lactic acid bacteria increased during wilting. The most representative enterobacteria on wilted crops was a specific biovariant, possibly E agglomerans or Rahnella aquatilis.