Precursor crop and vertisols type influences on teff (Eragrostis tef) response to fertilizer rates in the central highlands of Ethiopia.

Optimization of fertilizer-N and -P is important to highland production of teff () on Vertisols of central Ethiopia but may be affected by precursor crop and Vertisols type. On-farm experiments were conducted in three major teff growing districts of North Shewa (Moretina jiru, Ensaro, and Merhabete) in 2019 and 2020 with the main objectives was to determine the effect of precursor crops and Vertisols type on teff response to N and P rates. The N x P factorial combinations include 0, 60, 120, 180, and 240 kg N ha and 0, 30, 60, and 90 kg P ha applied each to light and heavy Vertisols with either cereal or pulse precursor crops in each district. In Merhabete, grain yield was significantly influenced by x Vt x N and x Vt x P but always with the lowest and highest grain yield with 0 and 240 kg N ha, respectively. Yield was 394 % more with 240 kg N ha compared with no N and P applied. The Vt x  × N interaction affected teff yield in Moretina Jiru as application of 240 kg N ha increased teff yield by 440 %, 30 %, 23 %, and 7 % on light Vertisols compared with 200 %, 16 %, 13 %, and 2 % on heavy Vertisols. The 4-way interaction of Vt x x N x P affected grain yield in Ensaro due to the low N and P status of the soil coupled with the distinct Vertisols type in the district. In all districts, yield response to N was greater with pulse compared with cereal precursor crops and with a greater response for heavy compared with light Vertisols in Moretina Jiru and Ensaro. In Moretina Jiru, application of 170 kgN and soil maintenance level of 30 kg of P ha are recommended as an economic optimum rate (EOR). In Ensaro, the EOR for teff following cereal on light Vertisols are 166 kg N ha and 65 kg P ha. At Ensaro, needed rates for teff following pulse on light Vertisols are 198 N ha and 48 kg P ha. At Ensaro, needed rates for teff following cereal on heavy Vertisols are 240 N ha and 90 kg P ha. At Ensaro, needed rates for teff following pulse on heavy Vertisols are 240 N ha and 80 kg P ha. In Merhabete, the EOR for teff following cereal on light Vertisols are 182 kg N ha and 60 kg P ha. In Merhabete, needed rates for teff following pulse on light Vertisols are 206 N ha and 64 kg P ha. In Merhabete, needed rates for teff following cereal on heavy Vertisols are 240 N ha and 90 kg P ha. In Merhabete, needed rates for teff following pulse on heavy Vertisols are 218 N ha and 58 kg P ha. Therefore, those N and P rate are recommended for the study area, soil type and precursor crops.