Farm Table says:
What is the problem?
While faba bean, lentil, and chickpea, are generally acknowledged as being sensitive to soil acidity, they are successfully grown on slightly acidic soils (pHCa >5.0 – 6.0) in the high and medium rainfall zones of south-eastern Australia, albeit with somewhat inconsistent yields. This paper focuses on the preliminary findings of an NSW Department of Primary Industries project, supported by GRDC, aimed at identifying factors limiting the production and N2 fixation of pulse crops grown on acidic soils in the grain production regions of southeastern Australia with a long-term average annual rainfall > 500 mm.
What did the research involve?
Method In 2015 and 2016, a total of 39 commercial legume crops were monitored in NSW, Victoria, SA, and Tasmania. The 2015 sites were chosen to achieve geographical spread across acid soil regions of the target zones and included 12 paddocks of faba bean, 2 of narrow-leaf lupin and 1 of field pea. Sodosols were the dominant soil type at these sites. In 2016 an additional 5 growers were engaged in order to investigate a broader range of pulses and soil types – sodosols, chromosol, and rudosols (alluvial). Sites monitored in 2016 were sown to faba bean (14), narrow-leaf lupin (2), chickpea (3) and lentil (3). A uniform, one-hectare area of the crop was selected at each site. Soils were sampled at depths of 0-10 cm and 10-20 cm, with pH measured using the calcium chloride method through Nutrient Advantage Laboratories.
What were the key findings?
Faba bean was the most commonly grown pulse species in this study, enabling us to identify common constraints across NSW, SA and VIC environments, which are also likely to be relevant to other acid-sensitive legume species. We found that modulation of faba bean was adversely affected by low soil pH in 2015 and 2016.
Effective nodulation underpins productive and profitable pulse crops. When detailed soil pH data were aligned to root growth and modulation of pulse crops, it was concluded that the presence of previously undetected, but severely acidic layers was likely to be a major factor responsible for inconsistent ‘performance’ of acid-sensitive pulses on slightly (pHCa >5.0) and moderately acidic soils (pHCa 4.6 to 5.0) of the medium and high rainfall zones.