Establishing inoculant chickpea rhizobia in soils with background populations - a case of wishful thinking?

In 2012, chickpea ('Cicer arietinum' L.) was sown across 560,000 ha in Australia, with close to 80% of this area in northern NSW and southern Queensland (ABARES 2014). Chickpea is popular with northern grain growers - it is adapted to the neutral-alkaline clay soils typical of the region, it produces a high-value grain and is an effective rotation crop for the region's cereal production systems (e.g. Felton et al. 1998). The foliar disease aschochyta blight, caused by the fungus 'Phoma rabiei', decimated Australian chickpea crops during the period 2000-05. Measures to manage the disease included the use of fungicides, development of resistant/tolerant varieties and crop hygiene. For the latter, the general recommendation was that chickpea should not be planted in the same field more than once every 3-4 years (Pande et al. 2005). The measures were largely successful because the national area sown to chickpea increased from a low of 113,000 ha in 2004 to 650,000 in 2010. In northern NSW and southern Queensland, estimated chickpea areas were 350,000-550,000 ha during the past 5 seasons (ABARES 2014). Assuming that the region's farmers followed the recommendations about crop hygiene and rotations, it is possible that 1.0-1.5 Mha of cropping land in northern NSW and southern Queensland has now been sown to chickpea and that the commercial chickpea inoculant strain CC1192 has been introduced into these soils.