RESPONSES OF FABA BEAN (Vicia faba L.) TO PHOSPHORUS FERTILIZER RATES AND PLANT POPULATION AT HARAMAYA EASTERN HARARGHE, ETHIOPIA

Abstract

A field experiment was conducted to study the responses of faba bean (Vicia faba L.) to phosphorus fertilizer rates and plant population at Haramaya University, Rare research site during 2019/2020 cropping season. Factorial combinations of four phosphorus (P2O5) levels (0, 23, 46, and 69 kg/ha) and six plant populations (133,333; 166,667; 200,000; 222,222; 250,000 and 300,000 plants ha-1 respectively were tested. The experiment was laid out in a randomized complete block design (RCBD) replicated three times. Improved faba bean variety (Gachena) was used as a test crop. Phenological parameters, growth, yield and yield components were measured and analyzed using ANOVA. Treatment means with significant differences were separated using least significant difference (LSD) test at 5% probability level. There was highly significant (P<0.01) effect of rate of phosphorus on number of days to flowering and maturity, leaf area, leaf area index, effective nodules per plant, plant height, number of primary tillers plant-1, number of seeds pod-1, hundred seed weight, seed moisture content, grain yield, dry biomass yield and harvest index. The shortet period to flowering (54.83 days) after emergence and maximum plant height (189.7 cm), leaf area (58.42 cm2), number of pods per plant (26.34), number of seeds pod-1(3.378), dry biomass yield (15978 kg ha-1), hundred seed weight (74.22 g) and harvest index (20.32%) were obtained from the highest rate of P (69 kg of P2O5 ha-1), but the highest grain yield (2984 kg ha-1) was obtained from 46 kg of P2O5 ha-1. For all plant populations, leaf area index, number of primary tillers, and pods plant-1, number of seeds pod-1 and hundred seed weight increased as the rate of phosphorus increase and the highest leaf area index (3.376), number of primary tillers per plant (3.278) and hundred seed weight (73.88 g) were recorded for the widest spacing (50 x 15 cm) or for a population density of 133,333 plants ha-1 while the highest total number of nodules (155.2) and number of effective nodules (16.67) resulted from 250,000 plants ha-1 (40 x 10 cm). On the other hand, the interaction of plant population and phosphorus significantly influenced number of seeds per pod-1, above ground dry biomass yield, hundred seed weight, grain yield and harvest index. A population density of 300,000 plants ha-1 (30 x 10 cm) gave the highest dry biomass yield (15676 kg ha-1) and grain yield (2893 kg ha-1), whereas the highest harvest index (22.07%) and number of pods plant-1(26.9) were obtained from 133,333 plants ha-1 (50 cm x 15 cm). Partial budget analyse was also used to analyze the economic benefit gained from the treatments. Thus, it can be concluded that application of 46 kg of P2O5 ha-1 at 30 x 10 cm plant spacing proved to be superior with respect to grain yield on fluvisols of Haramaya area. However, further study is required at least for one more cropping season on different soils to reach at a conclusive recommendation.