Abstract
Common bean (Phaseolus vulgaris L.) is an important legume in the tropics, with production limited by low availability of soil phosphorus (P). An experiment was conducted in the glasshouse to evaluate P use efficiency of eight dry bean genotypes (G122, Montcalm, Taylor Horticulture, Cardinal, Bukoba, Kijivu, Rojo and CAL 143) of Andean origin. The treatments included: no P (0 kg P ha-1), normal P (50 kg P ha-1), and high P (100 kg P ha-1). There was variation for the measured traits shoot biomass (g), shoot P (mg kg-1), root P (mg kg-1), seed P (mg kg-1) and seed yield (g) among genotypes and P treatments. Biomass and all P concentrations increased with increasing P level and the genotypes Kijivu, Bukoba, Montcalm and Taylor Horticulture had higher P concentrations than Rojo, G122, Cardinal and CAL 143 across treatments. Genotype × treatment interactions were observed for shoot biomass. For the no P treatment, shoot and root biomass were positively correlated with PUE (phosphorus use efficiency). PUE had higher values and varied more among genotypes in the no P treatment compared to the normal P and high P treatments. The results suggest that seed yield in dry bean can be improved by selecting for genotypes with higher PUE under limiting P. The genotypes Bukoba, Kijivu and Montcalm with the highest values for PUE under no P treatment may be exhibiting some level of tolerance to low soil phosphorus. Higher shoot weight may provide simple criteria for selecting genotypes with greater yield and PUE (phosphorus use efficiency) under limiting P conditions. Therefore, a genotype is desired that can efficiently uptake and utilize available P under limited availability of this nutrient.
Highlights
Phosphorus (P) deficiency contributes to reduced yield potential of dry bean (Phaseolus vulgaris L.)
Results show that when no P is added, the genotype Bukoba had the highest P-use efficiency (PUE) while Taylor Horticulture (Thort), G122 and Cardinal had the lowest
Other traits with significant correlations at P ≤ 0.01 include shoot biomass and root biomass, shoot biomass and shoot P, and shoot P to root P concentration, which indicated that shoot and root biomass and internal P concentrations are associated when beans were grown in P deficient soils
Summary
Phosphorus (P) deficiency contributes to reduced yield potential of dry bean (Phaseolus vulgaris L.). Phosphorus deficiency in dry bean decreases shoot to root biomass ratio but has no effect on the rate of photosynthesis per unit leaf area [2]. Often P is limiting in tropical soils due to low pH of the soils and high P fixation capacity. While applying inorganic fertilizers at low rates can be cost-effective, crop response is often hampered by high P fixation in the soil. Applying rates of inorganic P fertilizers below the crop requirement will contribute to the continuous depletion of soil P [3]. Large application of P fertilizer may be used to circumvent soil depletion but is less effective in tropical soils with low pH where it is immobile nor is it affordable for subsistence farmers. Soil P management is important to insure its availability to crop plants without depleting it from the soil [4]
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