Eight Tonne Wheat Club rule challenge

The Eight Tonne Club was started in 2002 and a feature about management factors has since been published in Primefact 197 (2006, Lacy and Giblin ) of the New South Wales Department of Primary Industries . Many of the factors for achieving eight tones per hectare were obtained from Maarten Stapper’s SIRAGCROP studies of the eighties and his recent ‘High-yielding irrigated wheat crop management’. (read more . . )

The nitrogen management rules, however, have not been confirmed by outcomes in the field. The rule of the last topdressing for yield at flowering was questioned as being too late for yield by Maarten Stapper at the Club’s launch in Finley N.S.W. in 2002.

In irrigated nitrogen-topdressing experiments Tony Fischer had shown yield responses with 8 t/ha yields for topdressing until Z32 (2nd node) with lower responses thereafter (Field Crops Research, 33:37-56). This was confirmed in the current studies with substantial yield loss when delaying topdressing even from Z32 to Z46 (late boot) as shown for example in the Figure below.


Yield response of first topdressing 60 kg N/ha at second-node (Z32, N0N) or late boot (Z46, 0NN) stage followed by second topdressing of 40 kg N/ha at early flowering, Z63, for Arrivato sown on 20 May 2004 at Griffith NSW. Yield l.s.d. is 0.6 t/ha.

Since the launch in 2002 this Club rule has been revised to “between head emergence (Z50) and flowering”. However, it is still only based on evidence of yield responses to late applied nitrogen in mainly lower yielding dryland trials by John Angus and John Lacy (Farming Ahead, no.129, September 2002).

In their studies the only irrigated crop yielded the highest at 8.2 t/ha with topdressing at tillering. Their three dryland crops topdressed at flowering yielded about 7 t/ha and were only significantly different from applied nitrogen at sowing.

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