Graingrowers planning to establish a lucerne pasture in 2004 following one more cereal this season might consider combining the two now, to smooth the sometimes costly transition.

WA growers are Australia’s most intense continuous cereal croppers, reflecting a reluctance to rotate to lower income pulses and pastures, despite their proven farming system benefits.

Among pastures, lucerne has become increasingly popular for its ability to dry the soil profile and diminish recharge to the watertable, while its vigorous roots also aerate the soil and ease the path of subsequent cereal roots.

But despite a 30-fold explosion in the area sown to lucerne since the mid 1990s, many growers prefer not to forgo valuable cereal production while grappling with the upfront establishment cost and risk of failure associated with it.

However, research supported by growers and the Federal Government through the Grains Research & Development Corporation (GRDC) at the Centre for Legumes in Mediterranean Agriculture (CLIMA) recently road tested the ‘cover-cropping’ technique, which had been touted as an economically attractive establishment alternative.

Cover-cropping involves planting lucerne with an annual crop, such as barley, at the end of the cereal phase. The cover-crop is harvested at season’s end to provide income during lucerne establishment.

Previous GRDC supported research on a south coast farm showed that a three year lucerne phase in a six year lucerne/crop rotation could provide a $30 per hectare benefit to growing systems through increased cereal yields and quality. Profitable management of the rotation to lucerne would make this more positive.

CLIMA’s Sharon Dawson and Tom Bailey compared the traditional establishment of lucerne as a monoculture against cover-cropping, with different row configurations and seeding rates at Meckering and Pingrup. Lucerne row spacing was 20 cm, 40 cm and 80 cm with a barley cover-crop seeded at 40 kg/ha and 80 kg/ha.

At harvest (November 2002) the lucerne monoculture at each site had the highest plant density and produced the most feed. Satisfactory plant densities (20 – 30 plants per m²) were achieved in most cover-cropping treatments, except where lucerne was sown at 80cm with 80 kg/ha barley.

Barley cover-crop yields of 0.6 t/ha at Pingrup and 1.2 – 2.1 t/ha at Meckering helped cut the lucerne establishment cost, however lucerne biomass production was lower in these treatments. Since harvest, Meckering had received no rainfall. Under these conditions, monoculture density dropped to 11 plants/m², while cover-cropped densities plunged to 2-5 plants/m², which is insufficient for maximum productivity, water-use or nitrogen fixation. Treatments at Pingrup maintained a density of 30 plants/m² in the monoculture and 15-18 plants/m² with a cover-crop.