Improved pasture response to nitrogen applied in winter after application of urea in autumn

Abstract

Nitrogen fertiliser was applied as urea in autumn (2 April 1983) and late winter (14 July 1983) to a predominantly ryegrass-white clover pasture on a Manawatu dairy farm. Responses in terms of herbage production, botanical composition, and certain other sward characteristics were measured on 22 August. Residual responses from the autumn application were small and were not statistically significant. Spring responses were significant for herbage mass, tiller weight, sward leaf area index, herbage phosphorus (% P) and total P yield (kg P/ha), herbage dry matter content (% DM), and apparent stubble yield (kg DM/ha). There was a significant, positive interaction between autumn and late winter applications of urea in that herbage mass response to 30 kg N/ha in winter was 7, 12, and 19 kg DM/kg N for plots receiving 0, 30, and 60 kg N/ha in autumn respectively. Possible reasons for this interaction are briefly discussed.

Keywords:

• nitrogen fertiliser
• urea
• split application
• interaction between applications
• residual effects