How to manage and supervise a farm labour gang so work gets done properly?

Managing a gang well is mostly about clear instructions, the right payment basis and fair treatment. Brief the gang leader (maistry/mukadam) clearly on what good work looks like before they start, and let him manage his people rather than you trying to direct each worker. Where you can, use contract or piece rate (per acre, per row, per kg) instead of pure daily wage, because then the gang has a reason to work steadily rather than stretch the day. Check the work at intervals while it is being done, not only at the end, so problems are caught early. Keep them comfortable with water, breaks and a meal or tea, tired workers do poor work. Pay promptly and as agreed. And keep the gangs and leaders who do good work, a known reliable team beats a cheap unknown one every season.