A comparison of slow-release and conventional nitrogenous fertilizers for an established pangola grass pasture in a sub-tropical environment

Abstract

Three slow-release nitrogen fertilizers, urea formaldehyde, nitrogen-enriched coal (NEC) and corea (a coal-urea formulation) were compared with conventional nitrogenous fertilizers (urea, ammonium nitrate and ammonium sulphate) in a small-plot cutting experiment. The slow-release fertilizers were applied in one 672 kg N ha-1 dressing to an established Digitaria decumbens (pangola grass) pasture on wallum heath in south-east Queensland. Conventional fertilizers were applied in one, two or four applications in one, two or three years respectively, all treatments receiving a total of 672 kg N ha-1. Dry matter production, nitrogen yield and nitrogen recovery were compared over four summer periods. Over four years, pangola grass produced highest dry matter yields when fertilized with urea formaldehyde, the residual effect disappearing in the fourth summer. Annual yield distribution was equivalent to that from regular applications of conventional fertilizers. NEC released little nitrogen for grass growth in four years while corea had little effect on yield after the first summer. Nitrogen recovery from urea formaldehyde was equivalent to that from ammonium nitrate and urea (applied in four dressings of 168 kg N ha-1). Where 672 kg ha-1 of nitrogen was applied in one dressing, nitrogen recovery was in the order urea formaldehyde >> ammonium nitrate > urea >> ammonium sulphate.