Evaluation of allelochemicals under chemically degraded old tea lands
2001 - 2006
After long periods of tea mono cropping, the yields stagnate or decline as the tea bushes do not respond to the recommended agronomic and/or optimum cultural practices. Uprooting and replanting of such irredeemably uneconomical tea fields with improved or better tea plants becomes essential if the productivity has to be maintained. However, replanted tea plants in such fields yield lower compared to the same cultivars planted on former forest lands and the plants cannot withstand adverse weather, e.g. drought. Other staple food crops do not also grow economically on such old tea lands. Before replanting, soil rehabilitation by a green crop for about two years has been found necessary and is therefore a recommended practice in most tea growing countries. The beneficial effect of the green crop has been demonstrated in India although the exact mechanisms responsible for reconditioning soil was not identified. In Kenya teas replanted on former old tea lands that were rehabilitated for two years still yielded lower compared to the same plants planted on former forest areas implying that the problems may not be similar. This proposal aims at creating an understanding of the factors and mechanisms limiting growth of old and replanted tea and other food crops on old tea lands in Kenya and thereby develop plausible soil management options to lower any toxic levels and improve plant growth and nutrient uptake.