As 16 year olds you can work without any restrictions in terms of working hours but there are some jobs that are classified as hazardous works that you should not do. However you can work in any farm job at any time.
You should have more chances to apply jobs when you are at least 16 years old or older since many companies set 16 as the minimum age requirement to work in their job advertisement. Therefore you should have a good resume to show that you have the ability and capability to compete with other job applicants. Learn more how to make a good resume as a 16 year old teenager.