Answer:
D. Leave the entire field fallow for few years so that the soil can replenish itself
Step-by-step explanation:
If the farmer has been using its land extensively for longer period of time, planting both summer and winter crops, the farmer should leave the land fallow for few years. The reason for this is that the minerals in the soil have been depleted, as it has been used throughout the whole year, not having part of the year to replenish the minerals. By leaving the soil to fallow for few years, the soil will have enough time to replenish its minerals, thus return its fertility. The farmer can of course help in this process, leaving lot of biomass to on the soil, plow it to get the biomass deeper into it, and repeat that throughout the few years of fallow before the soil is used again.