Effects of fertilisers on the contents of copper and molybdenum in herbage cut for conservation

Abstract

AbstractThe effects of the application of fertilisers, especially N, and trace elements on the contents of Cu and Mo in mixed grassland herbage and its main constituent species, have been studied. Results have been obtained from field experiments on three mineral soils and on a deep acid peat, the herbage having been cut at stages of growth considered suitable for conservation as silage three or four times per year for at least three successive years.Applying N without Cu reduced the Cu content in herbage in three experiments. At these three sites, applied Cu produced slightly higher yields and a small increase in the Cu content in herbage, which was greater with than without applied N. In the fourth experiment, on a soil containing adequate Cu, applying N increased the Cu content in mixed herbage, ryegrass and cocksfoot, except with 56 kg ha−‐1 per cut, where the content in mixed herbage was reduced slightly by the elimination of clover. Where the soil was adequately supplied with Cu, either naturally or from additions of this element, clovers contained more Cu than grasses. The Cu content was higher in herbage from the October than the June cuts, the mid‐summer cuts having intermediate contents. Cu extracted by 0.05M EDTA from the soils agreed with the effects on herbage contents, but a higher level of extractable Cu may be required for intensive grass than for optimum cereal production.Applying Mo had no effect on yield, but produced a large increase in the Mo content in herbage on a mineral soil; the increase was greater in clover than in ryegrass. On peat, applied Mo had much smaller effects on herbage contents, giving similar increases in both clover and ryegrass. Applying N reduced the Mo content in herbage, both in the absence and presence of added Mo. The effects of the latter decreased gradually in successive years. Applying P, especially at high rates, resulted in slightly lower Cu and Mo contents in herbage.