Nitrogen cycling and management decision making in Central Queensland farming systems – N availability and recovery across the farming system – N impacts on productivity – implications for management in CQ

Abstract

Take home messages
The nitrogen (N) fertiliser demand for cereal cropping systems can increase due to two factors:
1. A reduction in the amount of soil organic N mineralised due to the continued decline of natural capital (soil organic carbon and total nitrogen) that occurs under cropping; and
2. An increased crop N demand due to higher yield potentials resulting from optimising other components of the cropping system.

The amount of biological N fixation by pulse crops (chickpea/mungbean) is related to the crop yield and biomass and the availability of soil mineral N from mineralisation or carry-over of residual fertiliser. Where deep phosphorus (P) and potassium (K) application increases chickpea biomass (and grain yield), there is generally more N fixed. While some of this is re-exported in grain, the greater residue return means more N is carried forward to the next crop.

Growers have a selection of fertiliser N management practices that have differing strengths and weaknesses – it is not a one-size-fits-all model for CQ (or northern region) farming systems. The 4R framework allows choice of rate, source, time and place for any nutrient applied to be implemented suiting each growers’ preferences, with on-going research addressing several themes in regional Qld.