Alternativas al método de extracción Mehlich-I para estimar la necesidad de P en suelos guatemaltecos

lack of accessibility and cost of soil analysis in both developed and developing countries reduce the effectiveness of fertilizers, and insufficient funds promote the use of soil analysis procedures with minimal validation. of the many potential methods for p extraction and analysis, five of them are promising, but is needed further research to improve validation. a survey study was done at 26 farmer-field locations (multiple sites study) and three controlled studies were performed with identical fertilizer treatments (soil incubation, greenhouse, and field). in the multiple sites study, phw (pressurized hot water) and olsen extractable p positively related to maize yield (r=0.60 and 0.75, respectively), but relationships of mehlich-i and bray-i extractable p to yield were negative (r=-0.83 and -0.74, respectively). in the greenhouse study, yield, vegetative p concentration and the total p absorption were effectively predicted by all five methods. in the controlled field experiment, grain yield did not improve with p application, but leaf p content related to extractable p for all but the mehlich i extraction method (r2 from 0.57 to 0.70). extractable p was least related to p application rate with mehlich i (r2 of 0.51 compared to 0.96 to 0.99 with other extraction methods). overall the studies, the phw and olsen methods were similar and most effective, the bray-1 and mehlich-iii methods were less consistent, and the mehlich-i method was the least consistent of the five extraction methods tested