Hydroponics. Requires some setup but once it’s in place you have plants growing while consuming up to 90% less water than traditional agriculture, and it’s easy to make the whole system totally passive so that the only labor inputs are putting in new plants and harvesting old ones.

It also turns out that some plants really benefit from being grown hydroponically - put them under a grow light and in a greenhouse and you can grow multiple times as much produce on the same parcel of land while consuming less water and fertilizer to do it.

It’s a process that can be scaled up industrially, but because of the high upfront cost it’s fairly rare, the most mature industrial greenhouses are those in The Netherlands. Once a farm has made the transition there are logistical advantages to hydroponics as well - a farm can stagger grow times to have consistent smaller harvests instead of one or two massive harvests, making staffing and income more consistent.

Not every plant can be grown this way, but those that can absolutely should. Especially in places like California where I live, where we have the financial and technological ability to do so and our environment would greatly benefit from reduced water use.