Farmer and roboticist here.

There is a lot of discussion in a lot of threads about the design of the robot to water "from the top" by spraying the leaves instead of watering directly on the roots, and whether that's a good or bad thing, and whether the designers of the robot thought about it.

Here's the problem with watering the leaves: yes, plants ultimately get their water from rain. But under normal conditions, the rain comes in sporadically in large quantities -- not every day -- and soaks into the soil, which is where the plants actually pick it up. Flood irrigation does largely the same thing. Spray irrigation doesn't attempt to water the soil that deeply, it tends to give the plants just what they need for the next 24-48 hours, and that encourages wilt and fungal infections.

Also, domesticated vegetable crops are far more susceptible to wilt and fungal infections than natives, and than grain crops, which are at the end of the day grasses. So you can in the same garden have perfectly healthy corn but all of your melons and squash have such bad fungal infections that the leaves are literally white. You can criticize the selection of vegetables for yield and not hardiness, but the fact is this is where we are with vegetable crops.

This is an interesting project, but IMHO it isn't practical, and there isn't any way to make it practical. The X-Y gantry design, for gardening, has a number of intractable problems, watering from the top being just one of them. Another is that the design doesn't scale. You can't make this thing handle a 25 by 100 foot grade bed, which is the size you'd need to even start making a serious dent in the nutritional needs of one person. It can't really weed, and there's no way to modify the design to make it weed effectively; you'd have to add degrees of freedom to the gantry so that it could reach down to soil level and grasp roots (or, alternatively, to very selectively apply an herbicide). Garden crops grow to dramatically different heights; micro greens will be a few inches about the soil, zucchini will be three feet high, tomatoes can be 4-5 feet, and corn depending on cultivar can be as much as 9 feet tall.

And finally, watering and weeding, if you know what you're doing are actually the easiest parts of the problem. Preparing the bed so you don't have to weed is a lot more work. To do that, you plant your crops and then apply large amounts of mulch. If you've never prepared beds, shoveled dirty barn straw for mulch or tried to wrangle weed barrier cloth on a hot, humid day, you haven't lived, my friend. That's the physically hard part. THe mentally hard part is diagnosing problems in your crops before they become problems. Noticing that those shiny weird insects flying around are squash vine borer. Looking at the underside of leaves and seeing squash beetle eggs or going around your tomatoes with a blacklight looking for cutworms.

If you want to apply robotics to gardens, you either need a low mobile base, or you need to carefully lay out rows with fixed spacing, and have a high mobile base that can clear the height of the crops, and can take a variety of attachments, e.g. tillers to handle weed control. Which means you need think about monocropping. Which starts to look like the mid 20th century basic garden tractor, the International Harvester Farmall Cub, just with maybe an electric power plant and an autonomy appliqué kit. THis makes sense because the mid 20th century was the last time people in North America practiced gardening as a survival mechanism, and the Farmall Cub was the result of 50 years of practical design by people who knew how to garden when it counted.