Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.9, No.21, 2019 7 Effects of Phosphorus Fertilizer Rates on Soil Properties, Nodulation and Yield of Faba Bean (Vicia faba L.) Varieties in Lemu Bilbilo District of Arsi Zone, South Eastern Ethiopia Gobena Negasa 1* Tolera Abera 2 1.Kulumsa Agricultural Research Center, Ethiopian Institute of Agricultural Research, P. O. Box 489, Kulumsa, Ethiopia 2.Ambo Agricultural Research Center, Ethiopian Institute of Agricultural Research, P. O. Box 37, Ambo, Ethiopia Abstract A field experiment was conducted on farmer’s field during the 2017 main cropping season at Lemu Bilbilo with the objectives to determine the response of faba bean varieties to different rates of phosphorus fertilizer on nodulation and yield components of faba bean and the interaction effect of both phosphorus and faba bean varieties on yield and yield components of faba bean. The treatments include three faba bean varieties (Tumsa, Gebelcho and Dosha) and five phosphorus levels (0, 10, 20, 30 and 40 kg P ha -1 ) from TSP. The experiment was laid out in a randomized complete blocked design with factorial arrangement of 3 x 5 =15 treatment combinations with three replications. Significantly (P< 0.05) higher total number of nodule, effective nodules and non-effective nodules were recorded from Tumsa variety. Number of nodules per plant, and biomass yield were significantly affected by main effect of varieties. Higher total number of nodules per plant (63), number of non-effective nodules per plant (7.82) and nodule volume per plant (1.57 cm 3 ) were obtained from application of 30 kg p ha -1 . Higher biomass yield (14158 kg ha -1 ) and grain yield (6323 kg ha -1 ) were obtained from application of 40 kg P ha -1 . Applications of different rates of P highly significantly (P<0.001) influenced on faba bean agronomic phosphorus use efficiency. Most of the parameters studied were positively correlated to biomass and grain yield of faba bean. Therefore, it can be concluded that application of 30 kg ha -1 of P with faba bean varies was proved to be productive and superior both in grain yield as well as economic advantage and might be recommended for Lemu Bilbilo area. Further study should be repeated both over locations and years in order to give full recommendation for practical application. Keywords: Faba bean, Phosphorus rates, available P, soil pH, basic cations, nodules DOI: 10.7176/JNSR/9-21-02 Publication date: November 30 th 2019 1. INTRODUCTION Faba bean is the most important pulse crop in Ethiopia, occupying about 34% of the total land area under pulses (CSA, 2007). It is one of the major winter sown legume crops grown in the world and has considerable importance as low-cost food rich in proteins and carbohydrates (Sepetoğlu, 2002). It ranked first among cool season food legume based on hectarage, production, and foreign exchange earnings (CSA, 2016). Faba bean has four main functions in agro-ecosystems: providing food and feed that is rich in protein; increasing soil fertility by supplying N to agroeco systems by symbiotic N2 fixation with Rhizobium; diversifying the crop system to reduce constraints on growth and yield by the other crops in the rotation; and reducing fossil energy consumption for crop production (Nikfarjam and Aminpanah, 2015). Faba bean production has been increased in area throughout the different parts of Ethiopia. It is grown from 1300 to 3800 m altitude, but mostly at 2000 to 2500 m (Getachew and Chilot, 2009). However, the average national productivity of faba bean is 2.1 t ha -1 but, is low as compared to the world top producers (CSA, 2017). Several abiotic and biotic factors contributed to this low productivity (Asfaw et al., 1997). (Asfaw et al. 1997) and ICARDA (1989) reported the major ones are poor crop management practices, susceptibility to environmental stresses, pests and diseases, and the inherently low yield potential of the prevalent cultivars due to poor soil fertility, acidity of the soil in high rain fall areas and low existence of effective indigenous rhizobia population are other responsible factors (Carter et al., 1998). However, improved varieties have the capacity to tremendously increase productivity of faba bean, if used along with their optimum recommended inputs and management practices. Of the major cool season grain legumes, faba bean has the highest average reliance on N2 fixation for growth (Adak and Kibritci, 2016). The total amounts of N-fixed by faba bean are between 327-450 kg N ha -1 (Adak and Kibritci, 2016). Savings (up to 100–200 kg N ha -1 ) in the amount of N fertilizer required to maximize the yield of crops grown following faba bean is possible (Jensen et al., 2010). The use of faba bean crop rotation had a significant effect by reducing the amount of chemical nitrogen applied to soil for crop production (Tolera et al., 2015). The straw of faba bean is also used as animal feed and soil fertility restorer (Habtegebriel et al.,