Key points are not available for this paper at this time.
University of California 1 The senior author is indebted to R. H. Allee, Director of the International Institute of Agricultural Sciences at Turrialba, Costa Rica, for arranging the author's sojourn at the Institute, and to N. C. Ives and S. Bonilla for assistance in collecting soil samples and conducting experiments.
Jenny et al. (Thu,) studied this question.