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EFFECT OF PREVIOUS CROP ON IRRIGATED WHEAT YIELD

J.A. Thompson, H.G. Beecher, B.W. Dunn, and D.P. Heenan

NSW Agriculture, Agricultural Research and Advisory Station, Deniliquin, NSW 2710
NSW Agriculture, Agricultural Institute, PMB 3, Yanco, NSW 2703
NSW Agriculture, Agricultural Research Institute, PMB, Wagga Wagga, NSW 2650

Break crops, particularly Brassica crops such as canola have been shown to increase wheat yields compared to wheat following wheat (1, 2). This improvement has been attributed to reduced levels of soil borne pathogens, biological fumigation and biological drilling (2).

A rotation experiment with crops grown on permanent raised beds provided two opportunities to assess the yield of wheat following a number of crops including canola.

MATERIALS AND METHODS

The rotation experiment at NSW Agriculture’s Leeton Field Station commenced with wheat in 1984. The soil type was a grey cracking clay (Ug 5.28) which allowed adequate subbing across the beds. Wheat was grown in 1986 following wheat, canola, lupins and fallow. In 1990, wheat followed crops of barley, canola, field peas and faba bean. Agronomy was appropriate for a high fertility site with all crops receiving non„limiting scheduled irrigations. In both 1986 and 1990, sub plots were top dressed with nitrogen in a split application (half at DC15 (3) and half at DC30). All stubbles were burnt. Dry matter production at anthesis and maturity, grain yield and grain protein were measured.

RESULTS AND DISCUSSION

Despite the relatively intensive cropping regime there were no visual symptoms of root disease. In both years wheat yield was not significantly influenced by the previous crop (Table 1). In particular there was no yield advantage from following canola. There was a linear increase in protein content with increasing nitrogen topdressing rate for all rotations, (11.0-4.2% in 1986 and 9.3-11.3% in 1990).

Table 1. Effect of previous crop on grain yield of wheat

Nitrogen

Wheat yield (kg/ha at 12% moisture content)

topdressing

1986

  

1990

rate

____________________________Previous crop_________________________________

(kg.ha)

Wheat

Canola

Lupins

Fallow

  

Barley

Canola

Fieldpea

Faba bean

0

5.3

5.4

5.2

5.3

  

5.9

5.6

6.4

5.9

60

5.8

5.5

4.9

6.2

  

6.1

5.6

6.5

6.3

120

5.5

5.9

4.7

4.7

  

5.8

6.2

6.4

6.7

REFERENCES

1. Angus, J.F., van Herwaarden, A.F. and Howe, G.N. 1991. Aust. J. Exp. Agric. 31, 669-677.

2. Kirkegaard, J.A., Angus, J.F., Gardner, P.A. and Cresswell, H.P. 1993. Proc. 7th Aust. Agronomy Conf., Adelaide, SA. pp. 282-285.

3. Zadoks, J.C., Chang, T.T. and Konzak, C.F. 1974. Weed Res. 14, 415-421.

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