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On 18 farmer-managed fields in the Forest-Savannah Transitional zone of Ghana, the response of unfertilized maize was investigated as influenced by either a previous short season natural fallow or Mucuna pruriens (L.) DC var. utilis (Wright) Burck. Comparative vector diagnosis of three weeks old seedlings revealed that N was limiting maize growth. The previous Mucuna fallow was at least partly able to compensate N while there was a dilution of all the other macronutrients due to an increased uptake in the Mucuna system. Maize yields were on average 51% higher after Mucuna fallow with 2850 kg ha-1 compared with 1880 kg ha-1 after natural fallow, but the variability between farmers' fields was high. Adaptability analysis revealed that the slash-andmulch leguminous fallow system was most effective at locations of high productivity while the yield difference to the slash-and-burn natural fallow system was small in farming environments with low productivity. It was concluded that M. pruriens var. utilis fallow is not a suitable technology to reclaim degraded land or to restore soil fertility if growth-limiting factors are not eliminated. Low available P levels and later maize planting significantly reduced the yield difference and hence the risk for M. pruriens to be outperformed by the natural fallow system increased up to 41% with lower values of plant available P and later maize planting. Besides individual yield components such as cob number and cob seed weight, plant population at final harvest accounted for 58% of the variation in yield. Nutrient use efficiency improved significantly for all macronutrients except P but the harvest index was significantly lower at 0.40 after Mucuna fallow compared with 0.43 after natural fallow. N supplied by the Mucuna fallow supported a better growth of the succeeding maize crop but only in the beginning of the cropping season. When the yield level a farmer usually experiences with his common practice on a specific field was applied to the regression models of the adaptability analysis it was possible to make sitespecific yield predictions for the M. pruriens system. It was concluded that the application of the adaptability analysis and individual risk assessments might serve as valuable tools to give more site-specific recommendations to farmers instead of blanket messages for entire regions. [ABSTRACT FROM AUTHOR]

Weeding requires a major proportion of labour in farming of smallholders in Africa. Any technology that can effectively reduce the weeding requirement increases the productivity of the household. Studies were conducted on farmers' fields in the Sunyani District (2°8' to 2°31' W latitude, 7°7' to 7°36' N longitude), located in the Forest-Savannah Transitional Zone of Ghana in 1999 and 2000 to assess the impact of two different slash-and-mulch Mucuna fallow systems on weed dry matter (DM), weed density and frequency in succeeding maize compared with the prevailing slash-and-burn natural fallow system. Late maturing Mucuna pruriens (L.) DC var. utilis (Wright) Burck reduced weed DM by 58% in 1999 and 68% in 2000. The system with the local early maturing Mucuna variety did not reduce weed DM significantly. On the whole, 58 weed species from 27 families were identified. The most dominant species were Chromolaena odorata (L.) R.M. King & Robinson, Centrosema pubescens Benth., Euphorbia heterophylla Linn. and Mucuna spp. volunteer seedlings. The M. pruriens system reduced eight persistent weeds (frequency of occurrence > 20%) both in frequency and average density compared with the short season natural fallow treatment. In contrast, only two persistent weed species were affected in the same way by the system with the local Mucuna variety, while six persistent weeds increased in frequency of occurrence and seedling density. Poaceae species were negatively affected by the Mucuna systems. While in the natural fallow treatment Poaceae comprised 27.8% of all species identified, their proportions were reduced to 23.1% and 21.7% after fallow with the local Mucuna variety and M. pruriens, respectively. The greater weed suppressing effect of M. pruriens is considered to be a result of its longer life span than the early maturing local variety. [ABSTRACT FROM AUTHOR]

Examines the use of Orobanche aegyptiaca fungi as biological agents for weeds in Nepal. Cultivation of the specie; Determination of fungi associated with the specie; Identification of strains with mycoherbicidal potential.