Reddish and chlorotic leaf tips and margins are associated with B deficiency and can be confused with potassium deficiency or drought like symptoms. Alfalfa leaves can show up with reddish purple on the underside and yellow on top, sometimes reddish on top of the leaf. The plants will have a yellowish overall look. When growing, the internode length between leaves, will be stunted and then later exhibit the color deficiency From the OSU Soil Fertility Guide for alfalfa, applications are suggested on a trial basis if the soil test value is less than 0.3 ppm. One can use that as a ball park number and starting point as well.
Zinc deficiency can show up with white or striped leaves.
It is usually found on acid, sandy soils, that have been recently limed. Of course pH can affect the availability of these and other nutrients, as well as nodulation. PH's lower than 6.5 can have an effect on the availability of the boron and zinc for alfalfa. Some people can't leave anything alone. But maybe that's not all bad.