Boron Fertilization of Alfalfa and Other Legumes in Oregon 1

I a previous report, Powers (9)3 discussed the historical development of the use of boron. In the Oregon studies, application of a solution containing ~ p.p.m, of boric acid corrected yellowing of alfalfa which occurred with four out of five soils included in a green~ house trial in ~936. Field applications where similar yellowing occurred in the spring of ~937 resulted in striking improvement in growth and yields and established the economic value of boron for alfalfa and some other crops, particularly on the leached soils of northwestern Oregon. Yellow-top of alfalfa has been found on leached soils in a dozen or more states and the trouble has been corrected by boron applications. Since the concentration range of boron between the minute amount necessary and that toxic is small, attention has been given recently to analytical determination of the amounts in available form in Oregon soils and the normal and critical concentrations in plants showing response. While several legumes have shown response to boron, only the alfalfa data will be summarized herein. If carefully observed, the appearance of alfalfa yellow-top in dry weather may help to reveal the extent of boron-deficient areas. Alfalfa, when in need of boron, makes a staggy growth, the upper leaves turn reddish or bronze and then yellowish and shatter readily. The terminal bud becomes blighted and blooming and branching are restricted. Old stands of alfalfa may be most affected. Application of an aqueous olution of i/~ p.p.m, of boric acid as a spray on young sprouts of alfalfa may result in improvement in color and growth within a week. Branching, blooming, and seed formation may be aided later (Figs. 2 and 3)Analysis of Oregon soil types by the method of Berger and Truog (I) is helping to locate boron-deficient areas, while analysis of alfalfa tissue is making possible the formulation of standards of critical and optimum boron levels with which new determinations can be compared.