Does autumn and winter grazing affect the health of your fields in the spring?
It appears from various studies in the USA that it has a positive effect on crops to let them grow as high as possible (long crop) to enter the winter so that you'll have less weeds in spring.
The results of research from the University of Wisconsin-Madison show that grazing/mowing shorter periods of time will help weed seeds get the light and resources they need for germination and spring.
Agrio-ecology researchers Mark Renz and Marie Schmidt hypothesized that there is less chance of weeds when more residual crops block sunlight from reaching the soil. To test their ideas, they mowed several plots in November to boost grazing at 5 cm, 10 cm, 15 cm and 20 cm.
Because weeds need sunlight to germinate, Renz and Schmidt went back to their test plots in April to measure the amount of weeds present on these plots.
As you can guess; the shorter the crop, the more sunlight falls on the soil. The more weeds germinated.
The study by Renz and Schmidt shows that by leaving a 20cm residue in the winter, the weed pressure is reduced by up to 82%.