Above: "Odin and Sleipnir" (1911) by John Bauer.
In 1863, Gunnar Olof Hyltén Cavallius wrote the seminal Wärend och Wirdarne, describing a southern Swedish region believed to preserve ancient Norse traditions in its folklore more strongly than almost anywhere else, continuing to exist side by side with Christianity. One example was an agrarian practice done to promote the fertility of the field for the following year.
Gunnar Olof Hyltén Cavallius expanded further on page 159 of Wärend och Wirdarne:
"Even a few generations ago, the common folk of Wärend used to sacrifice or give to Odin’s horses. This occurred in such a way that during the hay-mowing in the meadow, one either left behind a few green stalks of grass, which were bent down and covered with moss so they would not be touched by the cattle, or else on every bredestad [row of mown hay] left a fresh tuft of hay, protected in the same manner against disturbance. On these occasions, the farmer always expressly announced or commanded that "this Odin shall have for his horses" or "this shall be for Odin’s horses." Should anyone neglect this offering to Odin’s horses, it was believed he would be punished by receiving a poor grass harvest in his meadow the following year."