Optimizing non-flooded landscape units to support maize production in the Zambezi Region, Namibia

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Globally, floodplains have experienced floods of different magnitudes at different times. As such the inundations of floodplains affect agricultural activities and such impact is evident. In Namibia, the Zambezi Region has experienced high variability in rainfall patterns, extreme rainfall and flood in space (spatial) and time (temporal) more than any other region as a result of climate variability. The non-flooded landscape units consequently become the only available option for crop farming activities during flooded years. The agronomic productivity status of these non-flooded landscape units in terms of soil and climatic factors as well as their land suitability for maize production in space and time given the prevailing climatic conditions has not been investigated. At the same time our understanding of how small-scale farmers in the region incorporate soil and climate factors into their crop production decisions is limited and affects the provision of extension advice. Yet soil and climatic factors clearly influence land use activities, including rain-fed maize production. The overall objective using maize as a case study crop was to assess possible ways that might optimize the non-flooded landscape units to support arable production in the Zambezi Region. The study was undertaken at both local and regional level using the Kwalala non-flooded landscape unit in the Kabbe North Constituency. Thus, the soil moisture and temperature were measured at various soil depths (20, 40 and 60 cm) between October 2012 and October 2015 using the Decagon data collection system (data loggers and sensors). In addition, secondary climatic and soil data were collected. Hence, Multiple Regression Analysis (model) and the CropWat model (K4 research model) as quantitative methods were used for data analysis. Findings in this study suggests that the observed soil moisture content varied from 9.7 to 33 VWC % loamy sand soils; 7.9 to 26.1 VWC % sandy loamy soils; and 4.9 to 22.9 VWC % sandy soils during the growing period between October and April. At the same time the maize crop water requirements (CWR) and maize water use (ETo) observed for the area ranged from 1.25 to 5.79 mm/day (CWR) and 4.01 to 4.44 mm/day (ETo). Therefore water content sufficiency was significantly (p< 0.05) available to sustain the agronomic crops during the growing period between October and April. Thus these findings implies that the non-flooded landscape units are suitable for rainfed maize production in the context of rainfall, soil type, soil depth, soil temperature, and soil water content sufficiency as well as maize CWR and ETo as long as November is the planting date or 130 days growing period. The incorporation of these findings may mitigate the effects of land conversion by guiding such transformation in an ecologically appropriate direction to ensure sustainable agronomic production, for example, if such non-flooded landscape units are aimed to be used for maize production purposes. It is therefore recommended that further studies on soil moisture induced by the flood be carried out to provide an insight on the soil moisture content driven to top soil surface by flood, since during the period of this study extreme flood did not take place and led to question one of this study not been answered.

University of Namibia
PhD Thesis
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