The importance of solid cattle manure application on soil microorganisms in organic and conventional cultivation

Abstract

Microbial communities are integral parts of the soil and their activity is very important to the functioning of the soil but the impact of different factors on soil microbial community composition is not well researched. Many studies have focused only on a few species. The aim of this study was to investigate the impact of treatment and sampling date on soil pH, abundance of total number of bacteria, molds, yeasts, mesophilic spore-forming bacteria, Fusarium spp., actinomycetes, azotobacteria, cellulose decomposers, denitrifying and nitrifying bacteria in organically (ORGGRM – green manure, and ORGFYM – green manure, solid cattle manure) and conventionally (CONFYM – solid cattle manure + mineral fertilizer and pesticides) cultivated soil.

Fertilization with manure had positive direct- and after-effect (p<0.05) on the total number of bacteria, mesophilic spore-forming bacteria, nitrifying bacteria and cellulose decomposers, even in the CONFYM treatment. The abundance of yeasts was higher (p<0.05) in ORGFYM treatment (3.35×10³) and 34–48% lower in CONFYM and ORGGRM treatments.

The abundance of molds, Fusarium spp., and actinomycetes during the study in different treatments was similar but their abundance was significantly higher (p<0.05) when the weather in the sampling time was warm and humid.

The negative impact of pesticides in CONFYM treatment occurred on the total number of bacteria, yeasts, molds, and denitrifying bacteria. The yeasts were most sensitive to pesticides; in study years, when the use of pesticides was very intensive, their abundance in CONFYM treatment decreased 72% compared with the ORGFYM treatment.

The 4-year test results showed that although green manuring is considered an important management practice in organic cultivation, to maintain and increase the abundance of microbes in different microbial communities it is important to use other organic fertilizers such as animal manure in addition to green manure.

Keywords:

• Cattle manure
• green manure
• organic and conventional cultivation
• soil microorganisms (CFU g⁻¹ dry soil)
• soil pH

Acknowledgements

This work was funded by the Estonian Ministry of Agriculture. The authors would like to thank Helgi Laitamm for her great work in the laboratory.