EVALUATION OF DIFFERENT AVAILABLE BORON EXTRACTION METHODS AND THEIR EVALUATION WITH THE B ABSORBED BY THE COWPEA (VIGNA UNGUICULATA) CROP IN THREE SOILS OF CÓRDOBA.

Abstract

In order to evaluate six methods of extraction of available boron and its correlation with the B absorbed by the bean crop, three representative soils of acid, neutral and alkaline pH of the department of Cordoba were used for physico-chemical characterization. A block design with a 6x3 factorial arrangement was used. Six doses of B were applied to each soil from a concentrated boric acid solution (0.0, 0.25, 0.6, 1.3, 2.0, 3.0 mg kg-1), with three replicates per treatment for a total of 54 experimental units. In addition to boron application, each EU was fertilized with macro and micronutrients so that the result was not altered by nutritional deficiencies. After a soil incubation with the B doses, 8 seeds per EU of bean variety L-0.42 were established, with thinning 15 days after germination, leaving only 3 plants per EU. The accumulated B content in all leaf tissue was determined 35 days after sowing, while the soils were determined for available B content with the six extractive methodologies (hot microwave water, calcium chloride 0.05 mol L-1, hydrochloric acid 0.05 mol L-1, monobasic phosphate 0.008 mol L-1, Melich-1 and hydrochloric acid 0.05 mol L-1 + barium chloride 0.075 mol L-1). The statistical analysis of the results showed that the method with the highest extraction of available B was Mehlich-1 in the three soils; while in the acid and alkaline soils the method with the lowest extraction was CaCl2 0.05 mol L-1 and in the neutral soil it was HCl 0.05 mol L-1. Likewise, the contents of B absorbed by the crop were proportional to the applied dose of this nutrient. The methods that best correlated between the B absorbed by the bean were: hot water with r > 0.92 in the acid soil, Ca(H2PO4)2 H2O r = 0.99 in the neutral soil and CaCl2, hot water, Mehlich-1 and HCl with r > 0.93 for the alkaline soil.