Effect of manure application on soil microbial activity
de Freitas, J.R.
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Soils from field trials treated with hog and cattle manure in spring of 1997 were sampled in the fall after harvest and soil microbial activity assessed. CO2 evolution measurements indicated that 6 months after addition, hog and cattle manure had little influence on measured microbial activity. In contrast, manure additions greatly stimulated soil microbial activity immediately after application when manure was freshly applied to the soils in the laboratory. For example, the highest level of microbial activity was observed at 3 days after treating the soil in the lab with 400 kg N-ha-l of cattle or hog manure. These initial results indicate that time of sampling is critical when assessing the effect of manure on soil microorganisms, with measurements required immediately after application as well as at longer time intervals. The fresh application of manure stimulated microbial activity by lo-fold compared to that measured in samples taken 6 months after application. However, microbial activity decreased with time and amounts of C evolved leveled out at about 20 p.g Cg-l soil after 38 days, similar to activity observed in the samples after 6 months. Preliminary results on the effects of manure application on the incidence of soil entero-pathogens (fecal coliforms) and wheat root rot incidence are discussed.
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