The effects of tungstate and nitrogen source on the dry weight and nitrogen yields,and molybdenum and tungsten content,of white clover (Trifolium repens)

Summary The effect of tungstate on the growth of white clover was investigated in sand cultures in a glasshouse, using three different nitrogen sources; symbiotic nitrogen fixation, nitrate, and ammonium. Each nitrogen treatment solution was subdivided into three groups containing 0, 5 and 50 ppm tungsten as tungstate and the effect on dry weight and nitrogen yields, and molybdenum and tungsten content, was determined for each treatment.Where atmospheric fixation was the only source of nitrogen the addition of tungstate had a slight negative effect on the dry weight and nitrogen yields. With combined nitrogen however, the presence of tungstate resulted in significant increases in yields. Ammonium-fed plants had far lower molybdenum contents although in all nitrogen treatments, the addition of tungstate resulted in an increased uptake of molybdenum. Unlike molybdenum, which was concentrated in the shoots on a mass basis, tungsten was concentrated in the roots in all cases. Reasons for these findings are discussed. re]19750303