Successfully establishing a CROP of ryegrass is one of the most challenging tasks facing any farmer.
If we think of a crop of wheat we maybe targeting 250 plants alive in the spring, maybe we plant 350 seeds. With ryegrass our target plant population in the spring could be 500 but then how many seeds do we plant? Well most seed suppliers provide 1 acre bags weighing 14 kg. Our seed rate becomes 34kg/ha or 1700 seeds/m2 (1)
Within a rotation that includes Ryegrass the plant can quickly become a weed as illustrated here in a small field of autumn sown winter wheat that did not receive an autumn herbicide.
There are economic thresholds for a large number of commonly found grass and broad leaf weeds. That is the number of plants /m2 that cause a yield loss in a cereal field. There is however little work on “mixed populations.”
In this case I don’t think I need to worry too much about thresholds more about just killing it all stone dead so that the wheat has a chance.
(1) Diploid Ryegrass, Perennial, Italian or Hybrid.