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Effects of water stress on yield and the components of yield in canola and Indian mustard

P.R. Wright, J.M. Morgan', R.S. Jessop and A. Cass

Department of Agronomy and Soil Science, University of New England Armidale NSW 2351
NSW Agriculture, Agricultural Research Centre, Tamworth NSW 2340

Canola, Brassica napus, has achieved a reputation for high yields under water limiting conditions when compared with Indian Mustard, B. juncea. This reputation is based on the relative field performance of these crops in both India and Canada. However, published data to substantiate this are virtually non-existent and comparative work in Australia has been very limited. This paper describes preliminary findings from a field and raincover trial.

Methods

A field trial with three cultivars of each species was sown at Tamworth (8 June 1990) in 1.5 x 15 m plots with two watering regimes and three replicates. The watering regimes were rainfed only and irrigation during pod-filling (a total of 196 mm applied in six approximately equal applications). A rain exclusion trial with the same cultivars as used in the field trial and the addition of one further cultivar per species was sown under a raincover at Tamworth (4 September 1990) in 1 x 2 m plots with four replicates. This crop was grown on water stored in the profile prior to sowing.

Results and discussion

Under well watered conditions (irrigated and rainfed) Mustard yields were similar to those of Canola (Table 1). This came about because greater dry matter production tended to compensate for the inferior harvest index of Mustard. Under extreme stress (rain exclusion) the mean grain yield of three Mustard cultivars (0.4 t/ha) was approximately four times greater than for three Canola cultivars (0.1 t/ha). Greater total dry matter production (2.3 compared to 1.8 t/ha) and higher harvest index (15 to 4%) appear to be the chief factors in this yield advantage. A higher number of pods/m2 (1478 to 265) was also an important factor as was the greater number of seeds per pod (10.1 to 6.0).

Table 1. Effect of water regime on grain yield (t/ha), total dry matter production (t/ha) and harvest index (%) of Canola and Indian Mustard cultivars

These results suggest that the role of Mustard in Australian agriculture may not be confined to water limiting environments. Further work is required to understand the mechanisms underlying the performance of Mustard under drought.

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