Soil Test Based Phosphorous Fertilizer Recommendation for Tef [Eragrostis Tef (Zucc.)Trotter] Production on Nitisols of Central Ethiopian Highlands

Abstract

Tef, Eragrostis tef (Zucc.) Trotter is an important cereal crop in Ethiopia. Obtaining Low yield of this staple crop is usually a major constraint. Tef grain yield  is  often  affected  by  soil  deficient phosphorous  and   its suboptimal  application  by  farmers. Proper and balanced fertilizer recommendations is of paramount importance in order to confirm security and increase crop productivity in sustainable way for farmers and other stakeholders. Soil test based phosphorous calibration study was conducted for tef on Nitosols of farmers’ fields in the West Shewa, central Ethiopian highlands.  The experiment was arranged in a randomized complete block design with six levels of phosphorous fertilizer (0, 10, 20, 30, 40 and 50 kg ha^-1) with three replications.  The result showed that P fertilizer application significantly affected yield and yield components of tef. Phosphorous fertilizer application at different rates increased grain yield of tef by 48to 70% compared to the control. Available soil test P concentrations analyzed three weeks after planting were affected significantly by P fertilizer application rate. Relative yield and Bray-2 soil test phosphorous value correlation indicated that soil test phosphorous values greater than 12.5 mg kg^-1 was found to be sufficient for tef production. The average phosphorous requirement factor (P_f) calculated from soil test phosphorous values of all treatments for study area was 9.5. Most sites tested had Bray 2 P values <10 mg kg⁻¹. In the absence of a soil test, a recommendation of 30 kg P ha^-1, resulting in the best response overall, could be made for the first year of application. We also recommend that to prevent a potential loss of barley yield, a maintenance application of at least 5–10 kg P ha⁻¹ be applied every year, irrespective of the calculated recommended rate, in order to replace P exported from the field in the form of grain and straw yield. Further field trials are required to determine interactions between P response and N fertilizer and other variables of like climate, soil properties, and other management practices.

Keywords: tef, Phosphorous calibration, Nitisols, phosphorous requirement factor, critical concentration.