In general, on the basis of the results obtained, there is no need of applying any type of fertilizer for teff production at Awassa. Value cost ratio continuously decreased with increasing levels of P up to 30 kg/ha resulting in positive economic return, where further increase of P level led to negative return. Highest VCR of 10.83 was obtained with the application of the first 10 kg/ha P. Phosphorus application showed strong positive correlation with soil P, grain yield and straw yield of teff at Hossana. Both N and P, when applied separately, also significantly increased straw yield, but their interaction did not. Application of P up to 30 kg/ha highly significantly increased teff grain yield at Hossana. Highest value cost ratio (VCR) of 10.43 was obtained with application of 10 kg/ha P followed by 3.54 with 20 kg/ha P, after which the economic return declined sharply. Additional grain yield of 394 kg/ha was obtained from application of the first 10 kg/ha P over the check. At Areka, highly significant grain yield difference (up to 20 kg/ha) was obtained for P application, but there was no response to either N alone or its interaction with P. There was no response to any type of fertilizer irrespective of varietals variations for tef production at Awassa. Teff varieties DZ- 01- 354, DZ-01-196 and Dhabi, which are late, medium and early maturity groups, respectively, were used at Areka and Awassa whereas another medium maturity group variety Ajora-1 was planted at Hossana. Factorial randomized complete block design (RCBD) was used in three replications in all cases. Nitrogen was applied at rates of 0, 23, 46 and 69 kg/ha whereas P was applied at 0, 10, 20, 30 and 40 kg/ha. Urea and triple super phosphate (TSP) were used as sources of N and P, respectively, at Hossana whereas urea and diammonium phosphate (DAP) were used at Awassa and Areka as sources of N and P, respectively. Experiments were conducted at Bobicho research site (Hossana), Areka and Awassa on Profondic Luvisols, Haplic Alisols, and Vitric Andosols, respectively, to determine NP fertilizers requirement for tef production. Teff is one of the important crops grown in the southern region.
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