Crop yield response to water - Cra

Growth and developmentThe common method of sowing tef is hand broadcasting. The tef seeds are extremely small,weighing 250 to 350 mg per 1 000 seeds (NRC, 1996). Hence, special care is necessary to preparea fine and smooth seed bed. This entails ploughing the field between 3 to 6 times (Aune et al.,2001) to pulverize the soil and cover the seeds lightly after sowing. A seeding rate of 25-30 kg/ha is recommended for broadcast sowing (Fufa, et al., 2000 and Seyfu, 1997). Sowing periodin Ethiopia ranges between mid-July to early August, depending on local climate, soil type andlife cycle length of the cultivar, and usually when the soil water is near field capacity.Emergence takes a few days or longer (between four and 11 days), depending on soil moistureand temperature. Soil temperature below 19 °C slows the rate of emergence. Vegetativegrowth and canopy development (Alemtsehay et al., 2011) follows the common pattern forother crops, as does biomass accumulation. Because tef is usually planted at high density (e.g.2 000 plant/m 2 ), full canopy cover (CC x ) is reached early. Final height of the plant ranges from0.6 m to just above 1 m.Tef is self-pollinating, with very small inconspicuous flowers typical of grasses borne on panicles(Figure 1), which can range from loose to compact (Seyfu, 1997). It is photoperiod sensitiveand its time to flowering is accelerated by short days. Under certain conditions, flowering canstart as early as 40 days after sowing or even earlier. Since the stem terminates at the panicle,the earlier the flowering, the fewer the leaves produced on the stem. Time to floweringranges from about 35 to 65 days, as observed in various studies. Canopy senescence startsFigure 1Tef showing panicle type of inflorescence on the left and panicles bearing seeds on the right.tef 239