What are the big clumps of soil in a ploughed field called?

Clods or clumps are large clumps of soil that remain after a field has been ploughed. 

When the plough breaks up the soil and creates large, compact masses of soil, clods are formed. They can make it difficult to plant crops evenly and can reduce crop yields by limiting water infiltration. 

Clods are typically broken up with a cultivator or harrow, or by walking on the soil to break them down, to prepare the soil for planting. The goal is to make a smooth, well-prepared seedbed that promotes healthy plant growth and development.