Soil productivity potential under indigenous fallow systems (Afub owondo) in the humid forest zone of southern Cameroon.

摘要

This study investigates soil productivity in the indigenous system (afub owondo) in Southern Cameroon in order to identify areas for improving soil and crop productivity, and food production. A challenge in most of Africa, is the continuous use of indigenous systems with slash-and-burn clearing like the afub owondo to meet food demand for the increasing population.; The objectives were to test the hypothesis that soil productivity is higher in long than short fallow fields in the humid forest of Southern Cameroon, to identify factors affecting crop yields at field level, to test crop yield response to chemical fertilizer of soils under fallow, to propose alternative land use options to afub owondo, and to attempt an assessment of indigenous land use types in different fallow fields.; A combination of land evaluation and farming system approaches (LEFSA) were used at three levels of survey: the regional, the village, and the field level. At the regional and village levels, the benchmark sites were defined, research villages selected, and three fallow field types stratified by age of vegetation (short fallow 0-6 years, long fallow 7-15 years and mature forest {dollar}>{dollar}15 years). At the field level, a type II experimental procedure was used to collect soils, topographical position, field location and management data in the three fallow field types. Yield data were collected for maize, groundnut and cassava in short and long fallow fields cultivated to mixed cropping. Fertilizer trials to test the productivity response of soils in fallow fields used maize as a test crop. Data were collected for three seasons.; The hypothesis that soil productivity was higher in long than short fallow fields in Southern Cameroon was not borne out. There were no statistically significant differences in soil chemical and physical properties between the long and short fallow fields. Crop yields in indigenous fallow fields (maize, cassava, and groundnut) were not significantly different between long and short fallow fields. Maize yields in trials that received (60 kg N, 30 kg P and 42 kg K/ha) were 17 times higher than from indigenous maize yields; yields responded significantly to nitrogen but not to phosphorus. The most important factors influencing crop yields on farmers fields were soil acidity, land workability, and crop density. When interviewed, farmers indicated that pests and diseases were the most important factors affecting crop yield, and adapt to declining soil productivity by reducing the number of crops in fields, frequent mounding, and ridging.; The study shows that the present afub owondo system in Southern Cameroon is inadequate for sustained food production without external inputs. To increase food production, the intensification of the system is a necessity, and consideration should be given to the improvement of groundnut (Arachis hypogea) and melon (Cucumeropsis mannii), which have high economic and food value. Any intensification strategy should be incremental. A two-pronged approach for the intensification of afub owondo is proposed. The strategies involve using managed fallows with leguminous and economic plant species, followed by either relay cropping or mixed cropping in which crops are separated by their growing cycles.