Low plant available water and susceptibility to flower loss from chilling appear to contribute to disappointing chickpea yields in south west Queensland and north west New South Wales.

That's what CSIRO/APSRU* joint venture researcher Jeremy Whish and consultant Paul Castor told the recent Focus 2005 - Chickpeas in Farming Systems conference in Goondiwindi.

Goondiwindi consultants Michael Castor and Associates and CSIRO/APSRU have been collaborating for three years on a Grains Research & Development Corporation (GRDC) supported project to identify restraints to chickpea and mungbean yields in the northern grains region.

The aim is to improve grower and adviser confidence in the two crops and potentially lead to a dramatic increase in the area sown to pulses.

Mr Castor told the Focus 2005 - Chickpeas in Farming Systems conference it was common for growers and advisers to report that good looking chickpea crops failed to yield as well as they should, the vegetative growth not being converted to grain yield.

³And the further north and west you go, into more marginal growing environments, the more this is an issue,² he said.

³Last season we monitored fruiting losses - from flower shedding and podding failure, where fruit set and later fail to fill - and found losses can be significant and variable.

³In 2004, fruiting losses averaged 60 per cent and ranged from 40 to 83 per cent. Flower shedding occurs in the lower nodes of the chickpea plant - we think because of sensitivity to chilling - while pollination failure occurs on the upper nodes, probably through moisture stress.²

Mr Castor told the conference that one consideration in managing these issues of disappointing yields would be to delay planting until at least late May, reducing early biomass in a chickpea crop and delaying flowering into warmer temperatures.

The incorporation of chilling tolerance into locally adapted varieties was also likely to give chickpea growers some ability to manage the problem.

Dr Whish stressed the importance of plant available water, telling the conference that, to grow a yield of one tonne to the hectare - considered to be the ³break even² point for a chickpea crop - a grower would need to have 100 mm of available water at planting.

The current project had shown high salt concentrations in the rooting zone could halve the amount of soil water available to chickpeas, with salinity limiting water availability to a higher extent than in wheat, whose extraction capability was about 16% better than chickpea.

Similar evidence was emerging from the GRDC supported Subsoil Constraints project.

At one site with chloride levels of more than 500 parts per million in shallow layers a chickpea crop had died, most probably from chloride toxicity.

Plant available water decreased as chloride concentrations increased and, at 800 to 900 ppm there was no water extraction at all by the chickpeas.

The APSIM decision support model had been successful in modelling crop biomass and yield at most sites, and the research team was more confident that it could be used to decide what starting water was required for profitable yields.

* The Agricultural Production Systems Research Unit (APSRU) is an unincorporated joint venture between the state of Queensland through its Department of Primary Industries and Fisheries and Department of Natural Resources and Mines, CSIRO through its Divisions of Sustainable Ecosystems and Land & Water, and The University of Queensland.