Farm Table says:
What is the problem?
This paper reports several approaches that were applied to crop and soil data collected from an on-farm field experiment to determine the apparent net mineralisation rate of N from either lupin stubble remaining after grain harvest, or a brown manured (BM) lupin killed with herbicide prior to grain filling (a strategy deployed by some local farmers to control herbicide resistant weeds), and the apparent recovery of the lupin N by a following crop of wheat
What did the research involve?
The experiment was located at an on-farm field site located near Junee, NSW, Australia
Each plot consisted of six crop rows 305 mm apart with measurements restricted to the four middle rows of
At the end of April 2012, plots were sampled to 1.6 m for soil N analysis, and all treatments were sown to
wheat (cv Spitfire) in mid-May
What were the key findings?
Of the three different measures of apparent mineralisation of legume N examined here, perhaps the estimate
of around 7 kg additional soil mineral N/ha per tonne legume stubble DM might be the simplest ‘rules-of-thumb’
for farmers and their advisors to apply.
More experimental data for different legume species and diverse environments and soil types are currently being
collated to ascertain how robust the various determinations of mineralisation and crop recovery of legume and
fertiliser N may be for other dryland grain production systems of south-eastern Australia.
Results from the experimentation indicated that concentrations of soil mineral (inorganic) nitrogen (N) measured just prior to sowing wheat in 2012 (0-1.6m) were 42 or 92 kg N/ha greater following lupin grown for either grain or brown manure (BM) than where the preceding crop in 2011 had been wheat or canola