Abundance and diversity of earthworms following six years of tillage,
fertilizer and weeding regimes in a maize field in northern Zimbabwe
Abstract
Earthworms are a major component of soil fauna communities with positive
effects on soil chemical, biological and physical processes. A study was
carried out at Chinhoyi University of Technology experimental farm,
Zimbabwe, to investigate the medium-term effects of cultural practices
on earthworm communities in a maize-based cropping system. Data were
collected in the 2018/2019 cropping season from a six-year old
experiment with tillage system (conventional, rip line seeding and basin
planting), fertiliser application rate (zero, low: 35.2 kg ha−1 N + 12.2
kg ha−1 P2O5 + 6.6 kg ha−1K2O, medium: 41.5 kg ha−1 N + 14 kg ha−1 P2O5
+ 7 kg ha−1 K2O, and high: 83 kg ha−1 N + 28 kg ha−1 P2O5: 14 kg ha−1
K2O.) and weeding intensity (twice, four times and clean weeding) as the
main, sub- and sub-subplots, respectively. Lumbricus (34.4%) and
Diplocardia (38.3%) were the dominant genera while endogeic earthworms
(48.4%) dominated the community structure among other earthworm
functional groups. Lumbricus abundance, total earthworm abundance, genus
richness and Shannon diversity index were higher in clean weeded plots
under the basin planting system relative to other treatments. Inorganic
fertiliser application in the conventional tillage (CT) system reduced
Eisenia abundance and genus richness. There was a positive correlation
between total earthworm abundance (r = 0.34, P < 0.001) and
negative correlation of Diplocardia abundance (r = -21, P <
0.05) with maize grain yield. These results suggest that in minimum
tillage systems clean weeding has positive effects on earthworms while
in CT, application of high doses of inorganic fertiliser is detrimental
to earthworm communities.