Person: Tanner, D.G.
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Tanner
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D.G.
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Tanner, D.G.
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- Agro-ecological decision support systems for wheat improvement in Ethiopia: Climatic characterisation and clustering of wheat growing regions(African Crop Science Society, 1999) Belay Simane; Tanner, D.G.; Tarekegne, A.T.; Asefa TaaWheat production environments in Ethiopia are highly heterogeneous with respect to natural resource characteristics, cropping systems, biotic and abiotic constraints. This paper analyses the agro-climatic resources of 20 representative wheat growing sites in the country and groups them by cluster analysis to develop homogeneous environmental groupings for wheat improvement research. The wheat growing sites are defined and clustered based on precipitation, temperature, altitude, longitude, and length of growing season. Annual precipitation decreases along a west-east axis, ranging from 1784 to 585 mm. The major feature of the precipitation pattern is its seasonality with distinct dry and rainy seasons. Generally, rainy season duration extends from 2.5 to 6.5 months. In the western, central and northern parts of the country, rainfall distribution is generally monomodal. In the eastern part of the country (i.e., 39.4 to 42.5° E) the distribution is bimodal, resulting in two cropping seasons, viz. "belg" (short) and "meher" (main). Of the parameters studied, annual and main season precipitation, and length and end of growing period were negatively correlated with longitude (r = -0.73**, -0.82**, -0.64** and -0.43*). Altitude was negatively correlated only with maximum and minimum temperatures (r = -0.64** and -0.86**). Three main environmental groups (C1, Western; C2, High Altitude; C3, Eastern) and six subgroups (C1-1, C1-2, C2, C3-1, C3-2, C3-3) were identified in the cluster analysis. Such clustering into homogeneous environmental groups should assist the national wheat improvement programme in making decisions about test site selection and proper targeting of released varieties.
Publication - On-farm evaluation of an animal-drawn implement developed in Ethiopia for row placement of wheat seed and basal fertilizer(African Crop Science Society, 1997) Asefa Taa; Tanner, D.G.; Melesse Temesgen; Kefyalew GirmaGrass weeds are difficult to control by hand weeding in a broadcast wheat crop because several species are not easily distinguished from the crop at an early stage. Chemical weed control, on the other hand, can be highly effective, but is limited in Ethiopia by the unavailability and high cost of herbicides. Further, dependence on high efficacy herbicides to control grass weeds can result in weed species shifts and/or the development of resistant weed biotypes. Row sowing of wheat can facilitate hand and/or mechanical weeding by enabling farmers to identify grass weeds in the inter-row spaces. However, manual row seeding is extremely labour intensive and unacceptable to peasant farmers in Ethiopia. Row seeders developed elsewhere have not been accepted in Ethiopia because they were either too labour inefficient or ineffective in cloddy and rough fields. Therefore, a four-row seeder has been developed in Ethiopia with a new type of seed metering mechanism
Publication - Grain yield of wheat as affected by cropping sequence and fertilizer application in Southeastern Ethiopia(African Crop Science Society, 1997) Asefa Taa; Tanner, D.G.; Kefyalew Girma; Amanuel GorfuCropping systems in the Ethiopian highlands consist primarily of cereals in rotation with grain legume and oilseed crops; the proportional allocation among crop species varies with altitude, rainfall, and soil type. Barley (Hordeum vulgare L.) tends to dominate in the highest altitudinal zones, while bread wheat (Triticum aestivum L.) is more common at medium altitudes on well-drained soils. A trial was established in 1992 at the Kulumsa and Asasa research sites in southeastern Ethiopia to evaluate interactions among wheat-based cropping sequences and annual applications of inorganic nitrogen (N) and phosphorus (P) fertiliser. Rotational crops included Ethiopian rapeseed (Brassica carinata L.), faba bean (Vicia faba L.), and barley. The results indicated significant rotational effects on wheat grain yield (GY), including enhanced GY in dicot vs. cereal rotations, in two year vs. three year rotations, in first year wheat after any break crop, and in rotation with faba bean vs. rapeseed. Interactions among cropping sequences and N and P fertiliser were also significant. Response to N was markedly reduced in two year rotations with any break crop, in first year wheat after any break crop, and after faba bean, in particular; this reflected higher soil N status in these cropping sequences. Conversely, P response was significantly enhanced in two year rotations and in the first wheat crop after any break crop, and in dicot-based rotations, particularly with faba bean. Presumably, this enhancement was the result of simultaneous improvement in soil N status and a reduction in wheat root pathogen and grass weed populations in these cropping sequences.
Publication - Grain yield of barley as affected by cropping sequence and fertilizer application in Southeastern Ethiopia(African Crop Science Society, 1997) Asefa Taa; Tanner, D.G.; Kefyalew Girma; Amanuel GorfuCropping systems in the Ethiopian highlands involve rotations of cereals with grain legume and oilseed crops; the proportional allocation among crop species varies with altitude, rainfall, and soil type. Barley (Hordeum vulgare) tends to dominate in the highest altitudinal zones, while bread wheat (Triticum aestivum) is more common at medium altitudes. A trial was established in 1992 at the Bekoji research site in southeastern Ethiopia to evaluate interactions among barley-based cropping sequences and annual applications of inorganic nitrogen (N) and Phosphorus (P) fertiliser. Rotational crops included Ethiopian rapeseed (Brassica carinata), faba bean (Vicia faba), and bread wheat
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