根据下面资料，回答题
My father was a foreman of a sugar-cane plantation in Rio Piedras, Puerto Rico. My first job was to drive the oxen that plowed the cane fields. I would walk behind an ox, guiding him with a broomstick. For $1 a day, I worked eight hours straight, with no food breaks.
It was very tedious work, but it prepared me for life and taught me many lasting lessons. Be-cause the plantation owners were always watching us, I had to be on time every day and work as hard as I could. I' ve never been late for any job since. I also learned about being respectful and loyal to the people you work for. More important, I earned my pay.
I was only six years old, but I was doing a man' s job. Our family needed every dollar we could make because my father never earned more than $18 a week. Our home was a three-room wood shack with dirty floor and no toilet. Nothing made me prouder than bringing home money to help my mother, father, two brothers and three sisters. This gave me self-esteem, one of the most important things a person can have.
When I was seven, I got work at a golf course near our house. My job was to stand down the fairway and spot the balls as they landed so the golfers could find them. Losing a ball meant you were fired, so I never miss one. Some,nights I would lie in bed and dream of making thousands of dollars playing golf and being able to buy a bicycle.
The more I dreamed, the more I-thought. Why not? I made my first golf club out of guava limb and a piece of pipe. Then I hammered an empty tin can into the shape of a ball. And finally I dug two small holes in the ground and hit the ball back and forth. I practiced with the same devo-tion and intensity I learned working in the field--except now I was driving golf balls with club, not oxen with a broomstick.
 What was the writer' s first job?