Effects of boron applications on yield and boron conentration of lucerne (Medicago sativaL.) grown on yellow-brown pumice soils

Abstract

Two field trials comparing rates and times of application of borax to lucerne were conducted for 4 years on yellow-brown pumice soils in the Taupo area. Boron deficiency symptoms occurred at one site every year, but only when there was a prolonged dry period. Borax applications prevented boron deficiency symptoms and resulted in dry matter yield increases of 9–43% for individual cuts and an average annual increase of 1530 kg/ha (14%) over the 4 years. No response occurred at the other site where the soil contained a higher level of available boron. Annual rates of application greater than 11.2 kg/ha of borax increased the boron concentration of the lucerne at both sites but did not increase yields. Time of application also had no effect on yield. A single application of 22.4 kg/ha of borax at the start of the trial was as effective throughout the 4 years as repeated annual applications. This rate, applied with the spring topdressing every fourth or fifth year, is recommended to prevent boron deficiency and maintain yields of lucerne hay on the pumice soils in the Taupo area.