A Presentation made by the Ugandan team During the Closing Conference of the Conservation and Sustainable management of the Below Ground Biodiversity Project

1. Effect of earthworm inoculation and application of organic residues on water- stable aggregates,
soil moisture and maize yields in Uganda
C. Nkwiine1 *, M. C. Rwakaikara- Silver1, M. Isabirye2, B. Isabirye3 and P. Ssenyonga3
1Soil Science Department, Makerere University, 2 National Agricultural Research Organisation (NARO) Kawanda, 3 Below Ground Biodiversity Project, Makerere University * Principal author; Address:
Department of Soil Science, Makerere University, P.O. Box 7062 Kampala, Uganda. Email; cnkwiine@agric.mak.ug.ac
Introduction
Soil
S il aggregation i an i
i is important characteristic of soil structure that stabilizes the soil surface, allowing water to i fil
h i i f il h bili h il f ll i infiltrate and sustain soil productivity. P bl
d i il d i i Problem of soil structure d
f il deterioration and
i i d
negative impact on yield is rampant in Uganda. The effect of earthworm inoculation and application of organic residues( maize stover or mucuna biomass) on soil aggregate distribution(%) and
stability, level of aggregation, soil moisture and maize ((Zea mays) yields was investigated on fields formerly abandoned due to poor soil structure.
Materials and methods
Researcher-farmer managed experiment was carried out at Bulyantente,
Mukono district, Uganda on abandoned the field. Treatments were: surface
, g
mulch of chopped maize stover (MS) and mucuna biomass (MC) at 5 ton ha-1,
earthworm inoculation (EI ) at 250 worms/plot (4x3m) , combinations of EI+MC
& EI +MS, and the control with 3 replicates. Allolobophora rosea species (Plate
1 ) was used and maize variety Longe 5 (Plate 2) was grown as a test crop.
Soil sample collection, preparation, determination water stable aggregate
(WSA)-size distribution and mean weight diameter (MWD) determination was
according to standard wet sieve technique (Plate 3 ). Two seasons yields of a
g q ( ) y
maize test crop were assessed. All data were subjected to ANOVA and LSD
test for treatment significant differences. Plate 3: Wet sieve technique Plate1: Allolobophora rosea Plate 2: Maize (Zea mays)
Results
Earthworm Inoculation and application of organic residues increased proportion of large macro-aggregates, degree of soil aggregation (MWD), soil moisture (Table 1) and maize yield : 700 to 1100 kg ha-1
increase( Figure 1 ).However, variations among treatments were not significant. Lack of significant differences among the treatments was attributed to the short duration of experiment. A long term experiment
was recommended.
3000
Table 1 Large macro-aggregates ,MWD, soil moisture earthworm density
1. macro aggregates MWD moisture,
and biomass
ae r ni d / )
2500
Mz g i y l ( g a
a e kh
Mean weight
Large macro- diameter Soil Earthworm Earthworm 2000
aggregates (MWD) moisture density biomass
1500
( %) gg-1 (%) ( Inds./m-2) ( g m-2) 1000
i
R2 0.34 0.34 0.34 0.28 0.61
500
EI + MS 35 0.79 18 149 6.9
EI + MC 35 0.75 18 64 1.1 0
EI+MS EI+MC MS MC EI Control
MS 16 0.48 16 64 2.3
Treatments ( 1st season p =0.128; 2nd season p= 0.022)
MC 22 0.58 16 43 1.4 1st season Maize grain yield Kg/ha 2nd season Maize grain yield Kg/ha
EI 19 0.5 14 32 0.8
CONTROL 18 0.53 15 59 1.5
Figure 1:Two seasons maize yields ( EI= earthworm inoculation, MS= maize stover, Mc= mucuna biomass)
Conclusion
C l i
Earthworm inoculation together with application of organic matter have potential to progressively improve soil structure and increase crop yields .