The effect of fertiliser N rates on growth of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown at high soil water levels under controlled conditions

Labuschagne J. ; Agenbag G.A. (2006)

Article

The response of perennial ryegrass and white clover to fertiliser N rates of 0, 30, 60, 120 and 180 kg N ha-1 when grown at soil water potentials of -10, -20, -25 and -35 kPa were investigated. Increasing fertiliser N levels from 0 to 120 kg N ha-1 resulted in increased (P=0.05) perennial ryegrass primary dry matter production (PDM) at the end of the first regrowth cycle (31 days). Ryegrass PDM yield was influenced (P=0.05) by soil water potential, with higher yields recorded at the -10 and -20 kPa treatments compared to the -25 and -35 kPa treatments. White clover PDM production was not influenced by N rate or soil water potential. Carry-over fertiliser N caused increased (P=0.05) ryegrass residual dry matter (RDM) yields as fertiliser N rate was increased from 0, 30, or 60 kg N ha-1 to 120 and 180 kg N ha-1, while clover RDM production increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher (-10 and -20 kPa) soil water levels caused increased ryegrass RDM production, a response not observed in clover. Total dry matter (TDM) production (the accumulative dry matter production during a 60 day period following fertiliser N application) of ryegrass was significantly increased as fertiliser N rate was increased from 0 to 180 kg N ha-1. Higher ryegrass TDM yields at-10 kPa and -20 kPa were recorded at the higher (120 and 180 kg N ha-1) N application rates, but water content did not influence TDM production at the lower (0, 30 and 60 kg N ha-1) fertiliser N application rates. Clover TDM production was not influenced by the treatments applied.

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