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Stubble retention and nitrogen supply on dryland wheat yield

K.V.M. Parameswaran

Dookie Agricultural College, Victoria, 3647

The likely significance of stubble retention in cropping systems, particularly dryland wheat production, is currently being explored in southern Australia. The profitability of stubble cropping is influenced by grain yield. However, the extent of this influence has not been fully explored. This system often results in low crop yields compared to those obtained on burnt paddocks (1), an effect which seems to be associated with poor plant establishment, reduced early plant vigour and the incidence of soil borne diseases.

Methods

Experiments were begun in 1980 at Dookie Agricultural College to study the effect of stubble retention and varying supplies of nitrogen fertilizer on wheat yield. The site was on a red-brown earth type with clay topsoil, which was cropped with wheat in the previous year. Wheat (cv. Egret) was sown either conventionally or direct-drilled on stubble burnt or retained. The stubble was cultivated into the soil in the conventional plots. Nitrogen (34 kg ha 1) was applied as ammonium nitrate at seeding (June 19) or at the double ridge stage of development (48 days after sowing).

Results and Discussion

Table 1. Plant establishment (38 days after sowing), ear production and grain yield of wheat.

Compared with stubble burnt, grain yield was reduced significantly (P=0.05) by stubble retention, the reduction being much higher when the crop was direct- drilled (Table 1). While grain yield increases were observed with the application of nitrogen fertilizer on stubble retention treatments, a general reduction of yield was noted under the stubble burnt conditions. However, these differences were not statistically significant. Although plant establishment was reduced on direct-drilled plots compared with conventional treatments under

the stubble retained and stubble burnt conditions, this alone was not adequate to explain the yield variations. The cultural treatments imposed were successful in producing large effects on crop growth.

1. Doyle, A.D. and Forrester, N.W. 1980. Proc. Aust. Conf. Queensland. 212.

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