Hillside Ditches Performance In Controlling Soil Erosion In Banana-Maize Farming System In Kiroka Village, Morogogo, Tanzania

BSTRACT

Soil erosion by water is a growing problem in Tanzania particularly in mountainous areas. The control of soil erosion is one of the most significant issues, which results in improving crop production as well as smallholders income. A study was carried out to assess hillside ditches performance in controlling soil erosion in a banana-maize farming system in Kiroka Village, Morogoro, Tanzania. The study intended to characterize the soils, determine soil loss and assess the social economic benefits of the hillside ditches. The methods used were reconnaissance survey, dug of soil profile pit, runoff plots of 12m x 3m with gerlach trough and base line survey using a questionnaire. A checklist and key informants interview were performed respectively.

The data were analysed by using Microsoft Excel computer program and Statistical Package for Social Science (SPSS). Two soil profile pits were characterized at slopes of 26% (named MAH-P1) and 55% (named MAH-P2) at Mahembe hamlet. Both soil profile pits were described during the end of rainy season in July 2015 under the following diagnostics soil properties ustic moisture and iso-hyperthermic temperature regimes. Eleven soil samples from different horizons within the same profile pit were analyzed for physico-chemical properties. Both profiles had dark reddish brown sandy clay loam and sandy clay top soils overlying dominantly clayey subsoils. Both profiles indicated clay eluviations-illuviation as dominant pedogenic process with slightly acidic soil conditions.

Available phosphorus in MAH-P1 was low to medium ranges from 0.91 g/kg to 9.24 g/kg while in MAH-P2 varied from medium to high ranges from 7.8 g/kg to 118.04 g/kg. Organic carbon (OC) in MAH-P1 ranged from 0.12% to 1.70% that is very low to medium and in MAH-P2 ranged from 0.26% to 1.54% also is very low to medium. The

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nitrogen in MAH-P1 ranged from 0.06% to 0.27% that is very low to medium and in MAH-P2 ranged from 0.06% to 0.11% that is very low to low. C/N ratio for both profiles ranged from 2 to 14. Both profiles had low to very low exchangeable bases except Ca that varied from 17.35 to 2.71 cmol+/kg and CEC in both profiles were high to very high. CEC clay values in both profiles were less than 24 cmol (+)/kg. In the USDA Soil Taxonomy, both profiles were classified as Alfisols that correspond to Luvisols in World Reference Base (WRB).

The results on soil loss showed that the mean seasonal soil loss was 0.067 t/ha with hillside ditches and 0.17 t/ha without hillside ditches. Runoff was 467.5 mm with hillside ditches and 1237.25 mm without hillside ditches. Maize yields were 5911.10 kg/ha with hillside ditches and 2808.611 kg/ha without hillside ditches. The socio-economic study, results showed that, majority of the respondents (76.3%) were aware on soil erosion and Soil and Water Conservation (SWC) techniques. The major constraint facing farmers during crop production was shortage of rainfall.

The Gross Margin Analysis (GMA) for maize under conserved fields was 64.6%, while that under non-conserved fields was 57.2%. The GMA for banana was 48% under conserved fields, while that under non-conserved fields was 43%. According to this study hill side ditches are good in controlling soil erosion, improving crop yields and retention of soil moisture. The study recommends the following farmers should use manure, compost and plants residue to increase soil fertility and construct as much as they can the hillside ditches or using any other soil conservation techniques to reduce soil erosion.