Apparent recovery of fertilizer n by vegetable crops

Abstract

Apparent recoveries of fertilizer N by crops were studied as their treatment in simulation models is a serious problem. Multi-level N fertilizer experiments in which fertilizer was broadcast and incorporated in soil immediately before drilling were carried out on a range of vegetable crops on adjacent sites of the same field. At final harvest, apparent recovery always declined approximately linearly with the increase in fertilizer N even when less was applied than was needed for maximum uptake; this contrasts with the well-known constancy of apparent recovery of Gramineae (winter wheat and grass) over widely different rates. At the seedling stage (of vegetables), when N-uptakes were very small, N-uptake and invariably dry weight, unexpectedly increased with the increase in fertilizer N until very high levels were reached. A single simulation model, with species differences accounted for by variations in the value of only one coefficient, defined, at least qualitatively, all the various phenomena. It is ar...