Grain yield makes up 30 to 50 per cent of the total weight of all above ground plant matter and this proportion is called the Harvest Index.
"How much stubble ?,"
Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 33
, Article 8.
Available at: http://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol33/iss1/8