Tillage, Mulching and Nitrogen Fertilization Differentially Affects Soil Microbial Biomass, Microbial Populations and Bacterial Diversity in a Maize Cropping System

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.

Surface runoff and soil erosion from Nitisols and Ferralsols as influenced by different soil organic carbon levels under simulated rainfall conditions

“…This confirmed the positive effect of soil organic matter in reducing runoff through improving soil infiltration and retention capacity [ 87 ]. The observation corroborates findings by Kiboi et al [ 88 ], Bolo et al [ 89 ] and Nyamwange et al [ 90 ] that enhancement of the organic carbon in the soil reduces the exposure of the soil and improves microbial activity which results in improved soil structure. High soil organic carbon levels also appeared to modify the sediment loss at different rainfall intensities.…”

Impact of agroecological practices on farm performance in Botswana

“…This can be explained by farmers' limited knowledge of how to incorporate agroecological practices in their farming operations. Many studies (Lei et al, 2021; Musurmanov, 2021; Nyamwange, Njeru, and Mucheru-Muna, 2021) have shown that minimum tillage and mulching would achieve better effectiveness when they complement each other.…”

Synergistic effect of straw-mulch and mycorrhiza-biofertilizer in increasing yield of black rice intercropped with soybean on raised-beds in aerobic irrigation system

“…In our experiences, one of the disadvantages in growing aerobic rice is competition with weeds. Application of straw mulch, in addition to its function to suppress growth of and competition by weeds (Ghosh et al, 2006;Devasinghe et al, 2011;El-Beltagi et al, 2022), also increases soil moisture (Akhtar et al, 2019), soil carbon balance (Dossou-Yovo et al, 2016), soil microbial biomass C and N (Nyamwange et al, 2021) and decreases soil temperature (Akhtar et al, 2019), as well as increases the availability various nutrients in the long-term (Ghosh et al, 2006;Devasinghe et al, 2011;Akhtar et al, 2019). Weed competition could decrease rice yield by 49.88% during dry season in dry direct-seeded rice and by 22.24% during wet season (Devasinghe et al, 2011).…”

“…El-Beltagi et al (2022) also recently reviewed the advantages of mulching such as reduced soil moisture loss, enriched soil fauna, improved soil properties and nutrient availability. In addition, Nyamwange et al (2021) found that mulching of maize growing system significantly increased soil microbial biomass C and N, but it was better under minimum tillage than conventional tillage, while NPK fertilization reduced them. In contrast, increasing N fertilizer dose from the three treatments of 0, 60 and 120 kg/ha N, under zerotillage and application of 3 ton/ha rice straw mulch, was reported to significantly increase carbon balance of upland rice field due to higher potential C inputs from higher above-ground and root biomass of the rice plants, and under the lowest N dose, much soil carbon loss was due to heterotrophic respiration (Dossou-Yovo et al, 2016).…”