No abstract

-In Ethiopia, food production for a rapidly growing population from a continually shrinking farm size is a prime developmental challenge. Rising input costs, decline in soil quality, and buildup of insect pests, diseases and weeds have threatened the ecological and economic sustainability of crop production. To address those issues, intercropping of cereals with pulse crops could increase total grain production, provide diversity of products, stabilize yield over seasons, reduce economic and environmental risks common in monoculture systems, and thereby enhance sustainability. Here, mixed intercropping of wheat (Triticum aestivum L.) with faba bean (Vicia faba L.) was compared with sole culture of each species in 2002 and 2003 at Holetta Agricultural Research Center, in the central highlands of Ethiopia. The treatments were sole wheat at a seed rate of 175 kg ha −1 , sole faba bean at a seed rate of 200 kg ha −1 , and an additive series of 12.5, 25, 37.5, 50 and 62.5% of the sole faba bean seed rate mixed with the full sole wheat seed rate. Our results showed that mixed intercropping increased the land equivalent ratio by +3% to +22% over sole cropping. Increasing the faba bean seed rate in the mixture from 12.5 to 62.5% reduced wheat grain yield from 3601 kg ha −1 to 3039 kg ha −1 but increased faba bean grain yield from 141 kg ha −1 to 667 kg ha −1 . Sole culture grain yield exceeded mixed culture grain yield by +5 to +25% for wheat and by +172 to +1190% for faba bean. Nonetheless, we obtained the highest total grain yield of 4031 kg ha −1 , gross monetary value of US$ 823, system productivity index of 4629 and crowding coefficient of 4.70 when wheat at its full seed rate was intercropped with faba bean at a rate of 37.5%. On average, weed biomass was reduced from 40.4 g m −2 in sole wheat to 31.1 g m −2 in mixed culture and the chocolate spot disease score was reduced from 5.1 in sole faba bean to 3.4 in mixed culture. In conclusion, intercropping of wheat with faba bean may increase total yield and revenue, reduce weed and disease pressure, increase land-use efficiency, and thereby enhance sustainability of crop production in Ethiopian highlands. aggressivity / crowding coefficient / faba bean / land-use efficiency / intercropping / wheat

Mixed cropping of teff (Eragrostis tef ) with faba bean (Vicia faba) was compared with sole cropping in the 2002 and 2003 growing seasons at Holetta Research Centre, in the central highlands of Ethiopia. The treatments were sole teff (25 kg seed ha −1 ), sole faba bean (200 kg seed ha −1 ) and 12.5, 25, 37.5, 50 and 62.5 % of the sole seed rate of faba bean mixed with a full teff seed rate. A randomized complete block design replicated four times was used. Treatment effects were significant for seed and biomass yields of each crop species. Increasing the seed rate of faba bean in teff/faba bean mixture increased faba bean seed yield but decreased teff grain yield. Nonetheless, mixed cropping of faba bean with teff increased land use efficiency and gave higher total yields compared to growing either species in sole culture. Teff yield equivalent, land equivalent ratios (LERs) and system productivity index (SPI) of the mixtures exceeded those of sole crops especially when the seed rate of faba bean in the mixture was increased to 50 kg ha −1 (25 %) or more. The relatively high crowding coefficient values indicated yield advantages from mixed cropping of the two species. The highest values of teff yield equivalent, LER and SPI were obtained when faba bean was mixed at a rate of 62.5 % with the full seed rate of teff. We suggest that, at the current prices of the respective crops, up to 62.5 % of faba bean can be mixed in normal teff to get better total yield and income than sole culture of either species.

The faba bean is among the major grain legumes cultivated in Ethiopia and is used extensively as a break crop in the highlands. Although a blanket application of DAP (diammonium phosphate) at the rate of 100 kg · ha−1 has been practised in faba bean production in the country, this was not based on research results. In addition, little information is available on the response of the crop to N and P fertilizers under diverse environmental conditions. Hence, field experiments were carried out at three locations in 1991, seven locations during 1992 and 1993 and at one location in both 1993 and 1995 to determine faba bean response to N and P fertilization. Five levels of N (0, 9, 18, 27 and 36 kg N · ha−1 as urea) in factorial combinations with four levels of P (0, 23, 46 and 69 kg P2O5 · ha−1 as TSP [triple super phosphate]) were studied in a randomized complete block design with four replications in the first year. In the remaining years four levels of N (0, 18, 27 and 36 kg N · ha−1 as urea) in factorial combinations with four levels of P (0, 23, 46 and 92 kg P2O5 · ha−1 as TSP) were used in a randomized complete block design with three and four replications at one and seven locations, respectively. Results indicated that a positive linear response of faba bean seed yield was noted at all locations (except Debre Zeit and Burkitu) to P fertilization, while a significant quadratic response was also found at Holetta. In addition, plant height, above ground biomass and number of pods per plant were positively influenced by P application while the effect of N on these was mostly nonsignificant. Faba bean seed yield response to N was noted at only two out of eight locations; in most cases, nonsignificant and inconsistent seed yield responses to N fertilization were obtained. There was nonsignificant N × P rate interaction. In conclusion, we do not recommend supplemental N application to faba bean at six out of eight locations but we recommend the application of P fertilizer to faba bean at almost all locations (with the exception of Debre Zeit) and for other soils deficient in available P. Further work is recommended on the determination of critical levels for soil‐available P, below which P fertilization should be practised for optimum faba bean seed yield.