Abstract
Determination of biologically active components of the soil organic matter, such as soil microbial biomass carbon (C) and nitrogen (N) can be used as indicators for variations in soil productivity due to changes in soil management. Soil agronomic management practices bring about changes in the physical and chemical properties of the soil, resulting in variations in soil microbial biomass and microbial diversity. The effects of tillage, mulch and inorganic fertilizers on soil microbial biomass C and N, microbial populations and bacterial diversity were determined from the treatment combinations which had been applied for 5 years in Central Kenyan Highlands. The test crop used was maize (Zea mays L.). The study involved conventional and minimum tillage systems, mulching and inorganic fertilizers (120 kg N/ha). Tillage (P < 0.001), mulch (P < 0.001), and fertilizer (P = 0.009) significantly affected soil microbial biomass C and N whereby minimum tillage and mulch increased soil microbial biomass C and N. Interestingly, minimum tillage and mulch recorded the highest bacteria and fungi CFUs compared to conventional tillage and inorganic fertilizers. Only fertilizer and mulch (P < 0.001) had significant effect on actinobacteria CFUs. Amplified ribosomal DNA analysis (ARDRA) showed that the highest genetic distance of 0.611 was recorded between treatments conventional tillage + no mulch + no NPK fertilizer and conventional tillage + no mulch + NPK fertilizer. The results demonstrate that minimum tillage and mulching are attractive soil agronomic management practices since they increase soil microbial biomass and bacterial diversity in agricultural soils.
Highlights
Soil agronomic management practices, particulary those which improve soil fertility are widely used by farmers to increase crop production in their farms (Balota et al, 2003; Kara and Bolat, 2008)
Soil Management Practices of the living component of the soil organic matter, measurement of soil microbial biomass is vital in decomposition of organic materials in the soil and can be used as an early indicator of the variations in soil physical, chemical and biological properties (Baaru et al, 2007)
The number of bacteria was significantly affected by tillage (P = 0.009), mulch (P = 0.001) and fertilizer (P = 0.001) at vegetative 4 (V4), vegetative 6 (V6) and maize harvest stages
Summary
Particulary those which improve soil fertility are widely used by farmers to increase crop production in their farms (Balota et al, 2003; Kara and Bolat, 2008). Soil Management Practices of the living component of the soil organic matter, measurement of soil microbial biomass is vital in decomposition of organic materials in the soil and can be used as an early indicator of the variations in soil physical, chemical and biological properties (Baaru et al, 2007). These variations in soil properties may be due to use of soil management practices such as organic and inorganic inputs (Nakhro and Dkhar, 2010). Any soil management- induced change at juvenile stage will determine the growth and survival of the plant (Cavaglieri et al, 2009)
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