Research Note

Nitrogen uptake of a perennial ryegrass–white clover pasture following strategic nitrogen fertiliser application during the cool seasons in the Western Cape province, South Africa

  • J Labuschagne Department of Agronomy, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; current address: Institute for Plant Production, Department of Agriculture Western Cape, Private Bag X1, Elsenburg 7607, South Africa
  • MB Hardy Institute for Plant Production, Department of Agriculture Western Cape, Private Bag X1, Elsenburg 7607, South Africa
  • GA Agenbag Department of Agronomy, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa

Abstract

The effect of four fertiliser nitrogen (N) levels (0, 50, 100 or 150 kg N ha–1) applied as a single dressing in either autumn (late April), early winter (early June), late winter (mid July), early spring (late August) or late spring (early October) on fertiliser N recovery by a perennial ryegrass–white clover pasture five weeks after fertiliser N application was investigated. Herbage N yield (kg N ha–1 uptake) was determined for the pasture from herbage N yield of the perennial ryegrass fraction and the clover fraction. Increased fertiliser N rate resulted in increased perennial ryegrass N yields. Perennial ryegrass N yields tend to be lowest during winter (early as well as late winter). Pasture N yield responses were similar to the perennial ryegrass N yields. Except in 2001, higher clover N yields (kg N ha–1) were recorded when no fertiliser N was applied compared to treatments that received fertiliser N. Clover N yields did not differ in the 50–150 kg N ha–1 range and would therefore not influence pasture N yield in that range. Although season of application influenced N yields the response pattern was not consistent among the years covered by the study. Calculating the apparent N recovery rate (difference between N removed in fertilised plots and control plots) can serve as an important tool to evaluate the efficiency achieved with fertiliser N application. More research is needed to develop N removal as a management tool to be used in strategic N fertilisation programmes.

Keywords: herbage nitrogen yields, nitrogen recovery rate

African Journal of Range & Forage Science 2009, 26(1): 37–42
Published
2009-02-13
Section
Articles

Journal Identifiers


eISSN: 1727-9380
print ISSN: 1022-0119