By Damian Jones, ICC
A demonstration was started by ICC in 2013 to measure the N added to the soil by green manuring a crop of faba beans. A crop of barley was sown over the green manured area in 2014.
Faba beans proved fantastic at fixing atmospheric nitrogen and adding N to the system for the next crop via the stubble. The stubble must be broken down (mineralised) before the N fixed by the plant is released.
What was observed on the Trial Block in 2014 was that where the barley crop was sown on faba stubbles, it remained green and healthy compared to the barley sown on cereals during the waterlogged June-July period. This may be due to the N from the fabas being a little deeper in the soil profile, below where the microbes are busy converting nitrate to nitrogen gas. This healthier crop also translated to higher yields, but interestingly enough, not higher protein.
Previous trials comparing crop rotations saw better grain protein in the cereals following fabas despite the same level of N being supplied to the crop. Looking at the results, it appears the barley on cereals ran out of moisture with low retention (45%) and subsequent high protein (12.9%). The barley on fabas had lower protein (9.9%) but higher retention (76%).
The stubble project – maintaining profitable farming systems in Victoria and Tasmania with retained stubble (project number BWD00024) is funded by the GRDC.