Sengoku Dynasty game water field issue

Hello, I have problem with water fields (or i am doing something wrong). But as you can see on the video workers don't use full aria inside water fields (not every fields even). On the video i am changing from wasabi to lotus seeds and you clear can see not full aria inside water field are using. On other fields you can see rise is growing but almost half of field is not in use. Only one small field is fully used for planting. I have same issue not only with water field but else with land fields as well. Do fields have some limits? Can this limit be showing while i am making field?