Differential Effects of Phosphorus Fertility on Soybean Varieties

Abstract

Abstract Chief and Lincoln soybeans, previously shown to be tolerant and intolerant, respectively, to very high P levels were grown in the greenhouse in soil admixed with ordinary superphosphate at rates varying from 0 to 4,400 pounds of P per acre. The varieties were similar in P response, dry weight, and mineral composition to around 870 pounds per acre of added P. Higher levels of added P were better tolerated by Chief than by Lincoln. At 2,620 pounds or more P per acre, marginal browning of the leaves, chlorosis, leaf drop, and severe stunting occurred in the Lincoln variety. In the Chief variety, stunting occurred only at much higher levels of P and the other toxicity symptoms never developed. Number of nodules, but neither size nor appearance, was reduced more on the Lincoln variety than on the Chief at intermediate P levels. At highest levels of P, no nodules were found on either variety. In mineral composition, Lincoln increased more than Chief in percent P and K as the P additions increased. Percent P and percent Si showed a reciprocal relationship in both varieties. No striking differences between varieties were observed in the contents of Fe, Mn, Ca, Mg, and B.