Is intercropping vetch in the Mallee a good idea?

Many growers around the world successfully implement temporary intercropping to improve their crop yields, weed competition, harvestability, disease management and nitrogen inputs (Bedoussac et al. 2015). Studies however are often based in organic farming situations, mixed farming systems or areas that receive higher annual rainfall totals than the Victorian Mallee.  BCG is interested to learn whether temporary intercropping will work in our environment and how we can maximise the benefits of legumes’ nitrogen fixing abilities.

The trial, funded by the Hugh DT Williamson foundation, will run over two years and has an aim to examine how different management techniques of the legume component in a temporary intercropping system affects mineral nitrogen, stored soil water and the yield and quality of the non-legume crop it is grown alongside as well as the subsequent cereal crop in the low rainfall zone.

The first timing of vetch termination has occurred in a temporary intercropping trial located at Woomelang.

Research BCG has conducted in the past has highlighted the importance of getting the termination timing for a vetch brown manure crop correct in the Mallee to find the balance between early enough termination for soil water conservation and late enough termination for greatest biomass production which directly influences N fixation (Ferrier, BCG 2013).

Early results from Woomelang show vetch biomass produced at the first vetch termination timing (85 days after sowing) to be low (0.9t/ha in vetch monoculture and 0.2t/ha intercropped), which is no surprise given the late start to the season in the Mallee. Preliminary nodulation assessments carried out on select treatments show poorer nodulation in vetch intercropped with wheat and receiving unlimited nitrogen (image 1).

A second termination timing is planned for the end of flowering/flat pod formation in the vetch. Yield, grain quality and soil N testing will be undertaken at the end of the year and the trial will be sown to barley to be assessed the following season.

Final results will be published in the BCG season research results.

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