EVALUATION OF THE AMMONIUM BICARBONATE DTPA SOIL TEST FOR ASSESSING BORON AVAILABILITY TO ALFALFA

The NH//4HCO//3-DTPA (AB-DTPA) soil test of Soltanpour and Schwab was developed to simultaneously extract plant-available P, K, Zn, Fe, Cu, and Mn. The extractant consists of 1. 0M NH//4HCO//3 and 0. 005M DTPA adjusted to pH 7. 6. Although the AB-DTPA soil test was developed primarily to extract the previously mentioned nutrients, its use for determining plant availability of other nutrients may be feasible. The objective of this study was to evaluate the AB-DTPA soil test for determining plant-available B. Saturation and AB-DTPA extractable B levels were nearly identical while the hot water soil test extracted significantly ( alpha equals 0. 05) higher amounts of B. Alfalfa yields were not significantly ( alpha equals 0. 05) affected by increasing B application rates indicating B deficiency and toxicity conditions were not present.