In the BeetClock menu, tap View records. You can view all work ever recorded, or you can view work since a particular date. For example, to view work done since June 1st 2016, tap the Select a New Date button, pick June 01 2016 in the spinners, and tap Select Date.
To view all work done on kale, select Kale in the dropdown menu and tap View Crop Summary. This will list the total labor hours that went into kale since June 1st, and the number of hours that went into each job (note that if two workers weeded kale for three hours each, this is recorded as six hours).
To view all work done on all crops since June 1st (or whatever start date you select under Select a New Date), just tap the View All Records button.