Potassium-use efficiency in common bean genotypes

Potassium (K) is one of the most important nutrients limiting yield of comm on bean in South America. Use of K-efficient crop genotypes along with K fe rtilizer may be a viable strategy to improve yield and reduce cost of produ ction. A greenhouse experiment was conducted to evaluate K-use efficiency o f 10 promising genotypes of common bean (Phaseolus vulgaris L.). The genoty pes were grown on an Oxisol at 0 mg K kg(-1) (low K) and 200 mg K kg(-1) (h igh K) of soil. Shoot dry weight, grain yield, number of pods, number of gr ains, 100-grain weight, grain harvest index, and K harvest index were signi ficantly (P < 0.01) affected by level of K as well as genotype, except for the number of pods by genotype. Significant genotypic differences in K-use efficiency were found. On the basis of K-use efficiency (mg grain weight/mg K accumulated in shoot and grain), genotypes were classified as efficient and responsive (ER), efficient and nonresponsive (ENR), nonefficient and re sponsive (NER), and non-efficient and non-responsive (NENR). Only genotype Diamante Negro was only classified as ER, and genotypes Carioca, Perola, Ro sinha G-2, and Xamego were classified as ENR. Genotypes LM93300166 and LM93 300176 were in the group NER, and in the NENR group were genotypes Irai, Ja lo Precoce, and Novo Jalo. From a practical point of view, genotypes which produce high grain yield at a low level of K and respond well to added K ar e the most desirable because they are able to express their high yield pote ntial in a wide range of K availability.