Effects of bare fallowing, previous crop and time of ploughing on soil moisture conservation in Botswana
1989
Jones, M.J. | Sinclair, J. (Dryland Farming Research Scheme, Gaborone (Botswana). Agricultural Research Station)
Four 2-year trials were carried out to test the effect of crop sequence and periods of bare fallowing on the conservation of moisture in soil profiles in the semi arid conditions of Botswana. Amounts of moisture remaining after the harvest of the first year crop were tabulated and in the order: bare fallow cowpea sorghum. Subsequent losses over the crop free winter period were generally low, ranging 0.07-0.17mm per day, according to the initial wetness of the profile and to the use or non use of root harvest tillage to control weeds and crop ratooning. Significant effects of the previous crop on the performance of the second year test crop were seen in all four trials. Yields were consistently high after bare fallow and relatively low after sorghum. Although soil moisture content at planting time was a major factor in these differences, other factors could be important depending on the nature of the season. Such a case was noted when residual nitrogen from the preceding cowpea crop was beneficial when the test crop received good rainfall. Double tillage significantly increased ground yields in all trials. Alternation of short cycle and long cycle crops (cowpea/sorghum) with a short bare fallow is highly recommended.
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