Impact of Rhizosphere Microbes of Three Early Colonizing Annual Plants on Improving Soil Fertility During Vegetation Establishment Under Different Fallow Periods Following Shifting Cultivation

Abstract

We assessed the rhizosphere effect of early colonizing annual plants (Ageratum conyzoides, Crassocephalum crepidioides and Bidens pilosa) on microbial biomass C (MBC) and N (MBN), acid phosphatase (APA) and dehydrogenase (DHA) activity as well as bacterial and fungal populations under fallow lands with duration of 1, 5 and 10 years under shifting cultivation in Mizoram. Ageratum conyzoides and B. pilosa were dominant species with IVI (97 in 1-year and 63 in 10-year fallow), whereas these had an equitable dominance in 5 years (IVI, 59–61). In 10 years, the amount of MBC (423 µg g−1) and MBN (39.7 µg g−1) was highest in B. pilosa rhizosphere soil, while it was lowest in 1 year. Similarly, the amount of DHA (16.05 µg TPF g−1 soil h−1) and APA (57 µg PNP g−1 soil h−1) was also highest. Fungal (CFU 103 g−1 soil) and bacterial (CFU 106 g−1 soil) population was highest in B. pilosa rhizosphere soil with 40 and 69, respectively, in 10-year fallow and lowest in C. crepidioides rhizosphere soil of 1-year fallow (20 and 35). Stronger rhizosphere effect (140–150% increase in DHA and APA) was noticed in 1-year fallow compared to 10-year fallow (67–109%). A significant (P ≤ 0.05) increase occurred in soil biochemical and microbial properties in rhizosphere during wet season than dry season. Changes in rhizosphere soil properties in dominant species were greater than codominant species. In conclusion, rhizosphere microbes of early colonizing annual plants accelerate the process of soil fertility improvement in young fallows (1 and 5 years) that potentially boost vegetation succession.