Forget compost or plant guilds people, you better get some toads! Some aspects of rituals used in ancient or more recent European agricultural practices:
In the early days of farming, gods didn't give you your crops, they were in them. Like the Corn-Spirit. He would be sitting in the first halms o grain you cut, or hiding in the very last ones. The best thing to do is to choose where you think it sits and bake a bread out of that. Preferably shape this like a little man or woman and parade it around your village. If you eat it, do it solemnly and with a lot of people. In the loaf you are eating is the Corn God. It also helps to have an important person in your neighbourhood to do the distribution of the bread.
Greek and Roman people didn't eat slices of their gods, they would sacrifice some corn to Demeter and Persephone, who were seen as the bringers of food. But you can bury a little doll made of grain and earth and when you dig it up again and it has sprouted, you can use that as a good omen. This sound a bit like using a stick as a weather-forcast; if the stick is wet it is raining.
There were magic rites and ceremonies performed at planting and harvest time to ensure good crops. They ranged from treatments of seed or fields, to elaborate ceremonials lasting several days, like Opensauses. Rain, hail, vermin, disease and pests need repelling or summoning. The simplest remedies seem to involve burying or carrying a toad on a stick or both. You walk around your field several times with the amphibian before you saw your crops, then put the toad in a pot and put it in the ground. This takes care of Sparrows and worms eating the seeds or produce. Please don't forget digging the toad up or the crops will taste bitter.