How much N does a legume crop give a following cereal crop?
A review looked at the $ value of Nitrogen (N) fixed by legume crops (chickpeas or lupins) to a following cereal crop around Australia. This work will be presented at the Agronomy Conference in September 2015 in Hobart.
The value of the fixed N available to the following crop was in the order of $13 per hectare, if N in fertilizer is valued at $1/kg of N. This value would rise with the price of N fertilizer.
Looking at the results only from the point of view of N dynamics it was usually more economical to apply fertilizer N than to grow a legume crop for the resulting fixed N.
Price for the legume crop remains the strong driver for a decision to grow a legume crop, along with a break crop’s role in integrated weed and disease management.
In 2014 $400 per ton for chickpeas was the tipping point, above which a chickpea crop was worthwhile in the northern region regardless of the fertilizer price. If the N fertiliser price increased to $2/kg of N, then a legume crop may be worthwhile at $300 per ton for the crop.
Roger Lawes, CSIRO , Kaara Klepper, QDAFF & Charlie Walker, Incitec Pivot.