International Institute of Tropical Agriculture, Humid Forest Eco-regional Center, Cameroon
Six years after establishment and after 5 consecutive maize / cassava intercrops, an alley cropping (hedgerow intercropping) experiment on Ultisol in southern Cameroon was converted to a two-year fallow, one-year groundnut/maize/cassava intercropping system. Biomass production and nutrient uptake of all components in planted Senna spectabilis, Dactyladenia barteri and Flemingia macrophylla hedgerow fallow were determined after three two"=year fallow phases and compared to natural fallow.
Total above-ground biomass dry matter production by the end of each of the three fallow phases was significantly higher in the S. spectabilis system than any other system, due to the significantly higher biomass production of the S. spectabilis. Total above ground biomass production in the F. macrophylla and the D. barteri systems was not different from that in natural fallow. The volunteer biomass between hedgerows was only once significantly reduced by S. spectabilis during the first fallow phase. The amount of litter did not differ between fallow systems. The biomass of S. spectabilis, F. macrophylla and D. barteri comprised 96, 95 and 65% wood, respectively. Relative to the total biomass, wood constituted 67% in S. spectabilis and about 20% in F. macrophylla and D. barteri systems.
Except for Mg, the S. spectabilis system accumulated more nutrients in above ground biomass than any other system. The highest nutrient uptake achieved in the S. spectabilis system was 335kg ha-1 N, 331kg ha-1 Ca, 230kg ha-1 K, and 39kg ha-1 P. Relative to the S. spectabilis system, nutrient accumulation, except for Mg, was the lowest in the natural fallow control followed by the F. macrophylla and the D. barteri system. In F. macrophylla and S. spectabilis, 95% and 85% of the nutrients were accumulated in the wood. In D. barteri the nutrient distribution between leaves and wood was approximately equal. Export of the hedgerow wood would remove between 9 and 16% of the nutrients accumulated in the F. macrophylla and D. barteri systems but between 27 and 53% in the S. spectabilis system.
Keywords: Dactyladenia barteri, fallow, Flemingia macrophylla, nutrient accumulation, planted fallow, Senna spectabilis, Ultisol, wood export