Rain received in late August in the northern grains region will help winter crops finish in NSW, but more is needed in September to make a great finish. Growers who have already top dressed should be happy, however the window is closing fast for growers to boost yield with extra nitrogen. Queenslanders have been disappointed in the rain so far, fingers crossed for next week.
Where it falls, the rain will mean increased biomass, and improved yield potential for the 580,000 ha of chickpeas planted in the northern region this year. This should correspond to more nodulation and nitrogen fixation to factor into N budgets as the season progresses. Agronomy trials are showing better nodulation and nitrogen fixation from chickpeas space in rows <50cm apart. Chickpeas following double cropped sorghum will still be short of moisture.
Chickpeas only provide an increase in nitrate-N in the root zone for the following crop when grown in low nitrate soils, where they can add substantially to the soil’s nitrogen balance. In medium or high Nitrate soils legumes recycle soil N. With good soil-stubble contact, legume residues release N faster than Soil Organic Matter (SOM) N.
Chickpeas – yield and Nitrate-N benefit for the following crop in low nitrate soils.
Source: NSW DPI Primefact 1163 Nitrogen benefits of chickpea and faba bean.
Faba bean is a stronger fixer of nitrogen than chickpea in low and especially moderate nitrate soils. However, with their earlier finish, Queensland faba beans will see less difference in N fixation from the August rainfall. In broader terms, increased faba bean biomass generally increases nitrogen fixation, similar to chickpeas.
In NSW, summer crop paddocks still need more rain before planting to look promising, unless on long fallow paddocks with stored soil moisture. Rainfall now will promote further mineralisation of N in fallow paddocks, potentially reducing starter N requirements. Not much double cropping is likely to go ahead in 2015 in NSW at this stage.
NSW DPI: Nitrogen benefits of chickpea and faba bean, 2015 NSW DPI factsheet.
Graeme Schwenke, NSW DPI, Bill Manning, NSW LLS, David Herridge, University of New England, Kaara Klepper, QDAF, Gordon Cumming, Pulse Australia.