Phosphorus Critical Level and Optimum Nitrogen Rate Determination on Teff for Sustainable Soil Fertility Management and Economical Teff Production at Lume Area of Oromia Region, Ethiopia

Abstract

Nutrient management is fundamental activity of the grower for crop production and productivity increments on different soil types. Accordingly, soil test based teff  response P fertilizer calibration study  was made from 2010-2012 at Lume district on eutric vertisol,  because soil nutrient calibration study is pertinent to increase the use efficiency of inorganic fertilizer like DAP and Urea. The objective of the experiment was to determine economically optimum N, and to determine Phosphorus critical (Pc) and Phosphorus requirement factor for teff at Lume district. The experiment were contained factorial combination of four  levels of N (0, 46, 92 and 138 Kg ha-1) and P (0, 23, 46 and 92 Kg ha-1) chemical fertilizer laid out in randomized complete block design with two replications that had 40m² plot area for each. After 21 days intensive soil samples were collected from each plot for the determination of available P in ppm.  Plant height, biomass and grain yield data were collected from 9m². The collected data were subjected to two way factorial analysis of variance (ANOVA) using the General Linear Model (GLM) procedures of SAS (SAS, 2001). Comparison of treatment means was performed using Fisher’s Least Significant Difference test at P < 0.05 probability level.  The application of N indicated that significant difference between plant height, biomass and grain yield teff. However the application of P was not significant on plant height, straw yield and grain yield at Lume. The interaction effect of N and P application was not significant to grain yield, plant height and straw yield correlation.  Furthermore, the study was revealed that phosphorus critical (Pc) point for teff was 13, and phosphorus requirement factor was also 3.65. In addition, a partial budget analysis made using the annual average teff grains prices showed 46 kg ha^-1 gave a marginal rate of return of 271.95%, which are above acceptable minimum rate of return.

Keywords: Calibration, P- critical, P- requirement factor, partial budget, Acceptable minimum rate of return