Effects of cultivation frequency on the survival of seeds of six weeds commonly found in Zimbabwe Rhodesia.
The effects of deep cultivation (to 22.5 cm) either monthly, quarterly, annually or not at all on the survival of 6 common Rhodesian weeds was investigated over 10 years. Cultivation reduced reserves of the smaller and shallow-germinating seeds of Nicandra physalodes and Eleusine indica more rapidly than no cultivation. Frequent cultivation exhausted the seed reserves of N. physalodes within 10 years. Relatively few E. indica seeds survived after 10 years regardless of cultivation frequency. Rottboellia exaltata and Acanthospermum hispidum seeds lost their viability after 2 and 8 years, respectively, irrespective of treatment. Seed reserves of Datura stramonium declined rapidly in all the cultivation treatments, while in undisturbed soil seedlings still emerged in the 10th year. Ipomoea plebeia showed long-term viability in all the treatments. In general, the greatest number of seedlings emerged in the first year with a subsequent rapid decline on undisturbed plots and a slower decline on disturbed plots. From summary.