Effect of Faba Bean (Vicia faba L.) Genotypes, Plant Densities and Phosphorus on Productivity, Nutrients uptake, Soil Fertility Changes and Economics in Central Highlands of Ethiopia

Abstract

A field experiment was conducted at Ambo University research farm with the objective to determine the optimum P rate and population densities in faba bean (Vicia faba L.) genotypes grown on vertisols. The treatments comprised three genotypes (Hachalu, Walki and Local), three spacings ( 30 cm x 7.5 cm, 40 cm x 5.0 cm and 60 cm x 5.0 cm) and two Phosphorus levels (0 kg P205/ha and 46 kg P205/ha,) which were laid out in a split- split plot design with three replications. The results showed that the improved genotype, Walki (3,407 kg/ha) was comparable with Hachalu (3,037 kg/ha) and gave substantially greater seed yield than the local cultivar (2,833 kg/ha). Seeding at 44 plants/m2 resulted in substantially higher seed and biological yields (3,815 kg/ha and 7,894 kg/ha) than 50 plants/m2 (3,074 kg/ha and 6,570 kg/ha) and 33 plants/m2 (2,388 kg/ha and 4,696 kg/ha); although the harvest index was unaltered. Fertilization of faba bean with 46 kg P205/ha resulted in substantial increase in seed (3,531 kg/ha) and biological yields (7,172 kg/ha) over no fertilizer check (2,654 kg/ha seed and 5,602 kg/ha haulm yield). The harvest index tended to improve with P nutrition (49.7) over no phosphorus (47.4). Correlations between yield and growth and yield components showed a significant positive corelation between seed yield and plant height at different stages, leaf area/plant, leaf area index, biological yield and seed yield/plant. Biomass yield is correlated with leaf area/plant, leaf area index, and plant height. Nutrient (NP) removal of genotypes both in seed and haulm was greater in Walki and Hachalu than in the local cultivar. The N removal in seed and haulm of Walki was 107 kg/ha and 58 kg/ha; and the corresponding removal of Hachalu was 95 kg/ha and 52 kg/ha; while that of the local cultivar was 89 kg/ha and 48 kg/ha. The N uptake in seed and haulm has been greater with 44 plants/m2 (120 kg/ha and 66 kg/ha) in comparison with 50 plants/m2 (97 kg/ha and 54 kg/ha) and 33 plants/m2 (75 kg/ha and 37 kg/ha). The uptake of p in seed and haulm increased with p application (11.3 kg/ha and 3.6 kg/ha) over no p-application (8.5 kg/ha and 2.7 kg/ha). In protein yield, Walki and Hachalu were better than the local variety. Maintaining 44 plants/m2 performed better than 50 and 33plants/m2. Application of 46 kgP2O5/ha out yielded no P check. Nutrient dynamics of soil after harvest of crop showed that there was an increase in soil N status ranging from 0.00 to 0.05 percent but a sharp decline in soil P and K contents after the crop harvest due to greater removal by the crop, which ranged from 4.03 to 4.27 ppm of P and 0.15 to 0.01 meq/100g of K. Economic analysis of the genotypes showed that Walki gave the highest net returns (ETB 29,642/ha) followed by Hachalu (ETB 24,827/ha) and the local cultivar (ETB 22,178/ha). Maintaining 44 plants/m2 gave higher net return (ETB 34,938/ha) than 50 plants/m2 (ETB 25,309/ha) and 33 plants/m2 (ETB 16,401/ha). Phosphorus fertilization resulted in a net return of ETB 31,247/ha compared with ETB 21,233/ha obtained with no phosphorus.