Selective weedicide in india - for lawn maintenance

Hello guys

does any of you know about weedicides that are being used to maintain lawn turfs and gardens ?
i have an acre of lawn in my farmhouse and its really troublesome to appoint labour and get the weeds plugged out every 15 days, since its a totally open area emergence of weeds is quite fast and in huge quantity.

how do you suggest should i maintain my lawn, what measures and weedicides should i use ?