In the first field, there are 13 rows * 4 corn cobs/row = <<13*4=52>>52 corn cobs.
In the second field, there are 16 rows * 4 corn cobs/row = <<16*4=64>>64 corn cobs.
So the farm has grown a total of 52 corn cobs + 64 corn cobs = <<52+64=116>>116 corn cobs.
#### 116