Soil microbial biomass response to application of different organic fertilizers

Abstract

Wastes derived from animal sources have been recognized as alternative sources of plant nutrients and hence have a great potential to be used in sustainable agriculture and circumvent issues posed by the usage of synthetic fertilizers. The aim of the study was to assess the influence of different variations of livestock (pig) waste sources and other amendments on soil microbial biomass. A strictly controlled laboratory experiment was set up with six treatments involving synthetic mineral nitrogen, pig manure, pig manure digestate, pig manure digestate and biochar, pig manure digestate and ash and the unamended. Soil microbial biomass which is used as an early indicator for changes in soil was determined before and after the respective treatments using the fumigation extraction method. The results showed that pig manure digestate amended with ash had the highest percentage increase of 32.16% in soil microbial biomass carbon (SMBC) with control having the least SMBC value of 170.58 μg/g after fertilization. SMBC due to synthetic nitrogen fertilizer application was significantly different (p < 0.05) compared to other treatments. However, pig manure treatment and other co-amendments had significantly higher SMBC after fertilization. Hence, it can be concluded that pig manure digestates could be effectively used, alone or in combination with biochar or ash to increase the soil microbial biomass leading to enhanced nutrient cycling and an overall soil fertility.