Effects of boron and lime on boron concentration and growth of forage legumes under greenhouse conditions 1

Abstract

Maximum yields of red clover, alfalfa, and birdsfoot trefoil were obtained when 0.25 to 1.0 ppm B was added to the soil. An application of lime to raise the soil pH to 5.8–6.3 improved yields, while at pH 6.8 a decline in yield in the first and second cuts of birdsfoot trefoil was noted. There was a marked B x lime interaction on the yield of all cuts of birdsfoot trefoil and first cut of red clover, with much higher yields with high rates of lime at high rates of added B. Levels of 4 to 9 ppm B in the leaf tissue of the three crops were in the deficiency range. Boron concentrations of 21 to 45, 39 to 52, and 30 to 45 ppm in the first cuts of red clover, alfalfa, and birdsfoot trefoil were indicative of sufficiency and were associated with maximum yields, while levels of >59, >99, and >68 ppm, respectively, in the three crops were in the toxicity range. Sufficiency levels of soil B for legumes appeared to be related to pH since B deficiency was more severe at higher pH than at lower pH. Liming of soil from pH 5.3 to 6.8 resulted in decreased concentration of B in all the three crops with the smallest decreases in alfalfa. There was a marked B x lime interaction on the B concentrations of the three crops, with much higher B concentrations in high B treatments at low soil pH than at high pH values.