'Water Used to be Scattered in the Landscape': Local Understandings of Soil Erosion and Land Use Planning in Southern Zimbabwe.

Abstract

This article presents some local understandings of ecological history in a semi-arid area of Zimbabwe as an exploration of how changes in land use that reflect both local initiative and state planning have transformed the hydrology of local catchments of heavy clay 'mopani soils' and greatly accelerated soil erosion. Local explanations provide a wide-ranging and challenging analysis of the dynamics of watersheds situated within a complex social and historical context. In conjunction with the spread of ox-ploughing and population growth and redistribution, a range of ill-conceived and authoritarian 'conservation' and 'development' interventions by the colonial state are argued by local intellectuals to be the major causes of accelerated soil erosion. Particular attention is given to how government imposed the deforestation and intensive use of difficult top land soils, and then transformed that uneven heterogeneous landscape into a smooth bare land connected by contour ridges and paths so that water concentrates, erodes, and then leaves the desiccating land to silt the rivers. The existence of sophisticated 'indigenous knowledge' systems in Africa has now been widely accepted, but this case study suggests that their very depth, variability and complexity means that attempts to harness local ecological knowledge for the understanding of Ð or development action about Ð environmental change may be more problematic than is often assumed. Researchers, government and conservation and development organisations need to do much more than seek to 'tap' such knowledge. Real understandings and 'sustainable development' can only flow from new power relationships with rural people and their knowledge.

Conservation tillage of rainfed maize in semi-arid Zimbabwe: A review

“…Grant et al (1979); Vogel (1993); Munodawafa and Zhou (2008) Clean ripping Clean ripping entails ripping land in between the previous season's crop rows with a rigid ripper tine attached to animal-drawn plough frame; no crop residues are left in the field; planting is done into the rip mark line; ripping depth ranges from 0.15 to 0.25 m and spacing is usually similar to that in conventional tillage. Nyagumbo (1999); Vogel (1993) Elwell (1981); Wilson (1995); Hagmann (1996), Whitlow (1988) Fanya juus (bench terraces)…”

“…Riches et al (1997); Nyamudeza (1999); Munodawafa and Zhou (2008) Holing out Land is cleared of previous season crop residues and weeds; shrubs coppice regrowth is cut; planting holes are dug using a hand hoe (badza); and usually digging is restricted to preparing planting stations without soil disturbance in between the planting holes. Vogel (1993); Wilson (1995) Ridging Ridge/furrow system at 1% slope; spacing ranges from 1.0 to 2.0 m and ridge height ranges from 0.1 to 0.4 m with narrower spaced ridges being shorter; 1.0 m-spaced ridges can be constructed using a high wing ridger or a mouldboard plough but wider-spaced ridges require tractor-drawn ploughs; and planting is done on top of the ridge. Vogel (1993); Nyamudeza (1999); Motsi et al (2004); Munodawafa and Zhou (2008) Tied ridging (furrow diking)…”

“…Soil erosion and land degradation had become severe and the colonial government intervened using the Native Land Husbandry Act of 1951 which enforced compulsory construction of contour ridges (Hagmann and Murwira, 1996;Whitlow, 1988;Wilson, 1995).…”

“…Holing out is a traditional tillage method which was used prior to the advent of the plough in the 1920s (Whitlow, 1988;Wilson, 1995). Land is cleared of previous season crop residues and weeds; usually shrubs coppice regrowth is cut without stumping.…”

“…Conventional tillage has been criticised for its failure to alleviate the destructive effects of long dry spells on rainfed crops and its failure to combat land degradation due to soil erosion (Bultena and Hoiberg, 1983;Whitlow, 1988;Willcocks and Twomlow, 1993;Wilson, 1995). An estimated 50-80 t ha À1 yr À1 of soil is lost annually from crop fields (Munodawafa and Zhou, 2008).…”