Reduced nodulation of faba bean on acidic soils; the role of topsoil pH stratification

Helen Burns1, Mark Norton1 and Peter Tyndall1

1 NSW Department of Primary Industries, Pine Gully Rd, Wagga Wagga, NSW, 2650,


The performance of most pulse species on the acidic soils of south eastern Australia is spatially and seasonally variable. Our research, aiming to identify reasons for this variability, reports the detrimental effects of acidic soils on nodulation of the sensitive pulse crops, mainly faba bean.   A survey of 39 commercial pulse crops, conducted across this zone in 2015 and 2016 found nodulation to be inhibited at pHCa < 5.2 in the 0-10 cm layer. Follow-up investigations found acidic soil layers below 5 cm negatively impacted nodulation, root growth and vigour of faba bean crops. Moderately (pHCa 4.5-5.0) and severely (pHCa <4.5) acidic layers in the 5-20 cm soil profile were not detected using soil samples collected at sampling depths of 0-10 cm and 10-20 cm. Sampling at 5 cm intervals is recommended to detect pH stratification. The industry practice of spreading lime with no incorporation and sowing with minimum soil disturbance, confines the lime effect to the shallow surface layers (0-5 cm). A rapid solution to intensely stratified pH in the soil surface (0-10 cm) requires an aggressive approach including appropriate lime rates and strategic cultivation to a depth of 10 cm, at least 12 months prior to sowing sensitive species. The pH stratification presented in this paper is more intense and widespread than previously reported. Further investigation is needed to: (i) assess the effectiveness of current approaches to acid soil management, and (ii) quantify the impact of pH stratification on more acid-tolerant species including canola, cereals, lucerne and clovers).


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

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