A newly planted walnut tree needs to be well maintained with regular fertilization and irrigation. The first crop of walnuts comes in the 6th year and a properly cultivated acre of mature trees produces 1.5 "inshell" tons per year.
Mechanical tree shakers harvest the nuts in the Fall when the nuts' shells are soft and green and easier to shell. And those shakers are cheap to hire. They work for peanuts!! Get it? Nuts:)