CORRELATIONS BETWEEN HOT CALCIUM CHLORIDE-EXTRACTED BORON AND CHEMICAL AND PHYSICAL ATTRIBUTES OF SOME BRAZILIAN SOILS CORRELAÇÕES ENTRE BORO SOLÚVEL EM CLORETO DE CÁLCIO 0,01 mol L-1 A QUENTE E ATRIBUTOS QUÍMICOS E FÍSICOS DE ALGUNS SOLOS BRASILEIROS

Relationship between soluble boron extracted with a hot CaCl2 0.01 mol L-1 solution and pH; organic carbon; exchangeable cations; cation exchange capacity (CEC); base saturation; total, free and amorphous iron and aluminum oxide contents; clay content; and specific surface area were performed for surface and subsurface samples of five soils. The soils were a Rhodic Hapludox, an Arenic Paleudalf and three Typic Hapludox, all representative soils of the State of São Paulo, Brazil. To quantify the relations between soluble boron and the different soil characteristics, simple linear correlations and multiple regressions, using a stepwise regression program, were performed. Hot-CaCl2 extractable boron (HCB) was significantly correlated with clay content (r = 0.69*), specific surface area (r = 0.68*), CEC (r = 0.63*) and total aluminum oxides (r = 0.70*) in all five soils. In addition, there was a correlation between HCB and organic carbon (r = 0.75*) in the four Oxisols. The correlation coefficient between the product (carbon x clay) and soluble boron contents was also highly significant (r = 0.78**). Multiple regression analysis showed that total aluminum oxide, as well as exchangeable calcium and aluminum, were correlated with HCB, explaining 85% of the variation. The product (carbon x clay) took into account the effect of textural gradient and showed high positive correlation with hot-CaCl2 0.01 mol L-1extractable boron.<br>Teores de boro solúveis em CaCl2 0,01 mol L-1 a quente, de amostras superficiais e subsuperficiais de dois Latossolos argilosos, dois Latossolos de textura média e um Podzólico Vermelho-Amarelo do Estado de São Paulo, Brasil, foram correlacionados com alguns de seus atributos químicos e físicos. As correlações entre boro solúvel e superfície específica (r = 0,68*), argila (r = 0,69*), CTC (r = 0,63*) e alumínio total (r = 0,70*) dos cinco solos e com o teor de carbono orgânico dos quatro Latossolos (r = 0,75*) foram estatisticamente significativas. O coeficiente de correlação entre o produto (carbono x argila) e os teores de boro solúvel também foi altamente significativo (r = 0,78**). Na análise conjunta, alumínio total, cálcio trocável e alumínio trocável foram as variáveis que se correlacionaram significativamente com boro solúvel, explicando 85% da variação. O produto (carbono x argila) levou em conta o efeito do gradiente textural dos solos e apresentou alta correlação positiva com os teores de boro solúvel em CaCl2 (0,01mol L-1) a quente.