The field can be fertilized during sowing or before preparing it (even immediately after harvesting). Fertilization provides the same bonus for the first and the same for the second fertilization. Fertilization should be done twice to achieve maximum yield - not in one month but during the entire growth of plants. You can choose from many fertilization options - manure spreaders and natural fertilizers (manure or digestate from a biogas plant), artificial or natural fertilizer like slurry. Fertilization - fertilization is optional, but very profitable.You can read more here - Weeds and weeding. You can use the herbicide preventively and in the second phase of plant growth. The weeder will only work when you use it in the first phase of plant growth (by default after a month).
Weeds should be removed with a weeder or a herbicide. You can reduce the chance of them growing if the field was plowed deep. You can read more here - Sowing and planting. Pay attention to the type of machines - some have cultivators, others fertilizer spreaders. Most plants require seeders/planters from the basic set in the store, excluding potatoes. Sowing and planting - when the field is ready, you can start sowing grains or planting root crops.You can do soil rolling only with special rollers, before or after sowing, but before the growth of plants. It also allows you to level the field after plowing/cultivation - soil rolling ensures a higher yield by 5%. Soil rolling - a simple and fast process of pushing stones into the ground.
Read more about stone picking here: Stone picking. They do not affect the amount of harvest, but the rate of damage to equipment and vehicles working in the field. You can collect them with stone pickers or ignore them.
The stones appear on the field after plowing/cultivation. Even if the field requires periodic lime spreading, you can still sow on it - this is an optional activity. Lime spreading usually requires a newly formed field. You will perform lime spreading with a fertilizer spreader from the store - it will have a lime icon in the list of supported materials. Ignoring it will lead to a decrease in yields by 15%. By default, lime spreading is a periodic activity. If the field requires lime spreading, you will receive information about it on the field map or by personally checking the field.