Impacts of different treatment methods for cattle manure on the spread of faecal indicator organisms from soil to lettuce in Nigeria

AIM - This study investigated impacts of different organic waste treatment methods on reduction and spread of faecal indicator organisms to food crops in a developing country.
METHODS AND RESULTS - Fresh cattle manure was subjected to three different treatments; anaerobic digestion, burning and composting. E. coli, coliforms and nitrogen content of cattle manure were measured before and after treatment in the amended soil and harvested lettuce. All treatments significantly reduced E. coli and coliform counts but differed in the ratio of E. coli or coliforms to nitrogen. Application of the recommended nitrogen dose of 120
kg ha-1 21 as bioslurry resulted in significantly lower E. coli and coliform contamination of soil than the same nitrogen rate applied as compost or ash. The E. coli content of lettuces grown on soil amended with treated wastes at recommended rates did not differ between treatments but was significantly lower than in lettuces grown on soil amended with untreated manure.
CONCLUSIONS - Treatment of manure before use as an organic fertiliser significantly reduces potential contamination of both soil and food crops with E.coli and coliforms. To best reduce the spread of E. coli from organic fertilizers, manures should be treated by anaerobic digestion.