Effect of Phosphorus fertilizer on grain yield and yield components of field pea (Pisum sativum L.) cultivars.

Field experiments were conducted at Holetta (1996 to 1999) and at Bekoji (1996 to 1998) with the major objective of quantifying the response of Ethiopian field pea cultivars to phosphorus fertilizer on Nitisols. The experimental treatments at both locations consisted of a factorial combination of five phosphorus rates (0, 10, 20, 40 and 60 kg P ha-1) and three-field pea cultivars laid out in a randomized complete block design in four replications, Based on the significance of the F test (either P0.01 or P0.05) outputs for grain yield, pods per plant and above-ground biomass mean data were fitted to A Mitscherlich equation. At Holett the effect of year and phosphorus application rates on grain yield, plant height, above-ground biomass and pods per plant were significant with very few interactions. Differences between cultivars in plant height and aboveground biomass showed no consistency. The average yield of the cultivars, however, increased from less than 1 ton ha-1 with no fertilization to more than 1.2 ton ha-1 with 60 kg P ha-1 application. The low marginal rates of return indicated that indicated that phosphorus fertilization is not economically viable at Holetta location. At Bekoji, on the other hand, significant effects of year, phosphorus application rate and cultivar on grain yield, plant height and pods per plant were found with some interactions between these factors. The interaction between phosphorus application rate and cultivar was significant with regard to grain yield, indicating that the cultivars are not in the same recommendation domain, as the response of cv. Cheffa local to phosphorus application was relatively poor compared to those of cv. Tegegnech high and cv. G22763-2C intermediate. An MRR above 100% was obtained with an application of 20 kg P ha-1 for cv. Tegegnech, 10 kg P ha-1 for cv. G22763-2C and 5 kg P ha-1 for cv. Cheffa local. The improved cultivars' response was economically more viable than t he local cultivar for P fertilization under the scenarios of produce and input price increases. The overall result indicates that field pea cultivars grown on Nitisols at Bekoji require different rates of P fertilizers while minimal p uptake compensation rates are needed for field pea cultivars grown on Holetta Nitisols.