Hello. I'm a physicist working in agriculture, in Portugal (olive oil, malt cereal, legumes).

There are a lot of things to say about this subject, but I'll stick to the two points that were originally raised.

1. Fully automated farms are possible in theory for a small range of applications (like greenhouses). Human supervision and operation is usually necessary, mainly because of the elements and wildlife (e.g. humidity damages machines/sensors, animals chew wires/irrigation tubes, underground rocks are still invisible to surface dwelling tractors), so failure is a constant. GPS guided machines are now being widely used for sowing and pesticide application, with benefits in terms of both cost and time (fuel) reduction.

Automation in irrigation is now everywhere. One can easily find fully-automated center pivot irrigation systems.

Some fields have been adapted to allow for automation, like olive orchards. Olives can now be harvested in a fraction of the time it used to take, with a single machine and operator (a ~30 ha orchard will take 1-2 days with 1 machine and operator vs. 5-7 days for 2 or 3 machines and a team of 10; in the recent past there would be no machines and a team of 20).

There are some clear benefits in using drones that scan crops for detection of spots where irrigation fails or some fungus is starting to spread in advance, and also allow for better sampling for analysis. Besides any farmer can afford a drone nowadays.

Automation is usually expensive (for the first investment at least), and as such only large scale (corporate) farms can afford it. Cooperative family-scale farming can reduce the cost/acre (e.g. time sharing one single harvest machine) but there are pros and cons.

1.2 IoT in agriculture: please don't.

1.3 There are still fewer people in farming. I don't know if automation is the only one to blame, because either way farming is tough. Perhaps the wages may not be the most interesting for some one not already in the business, as well as the overall lifestyle. The lowest wages correspond to jobs being replaced by automation, so those salaries are dropping even more.

2. Crop yield largely depends on soil quality, proper irrigation and seed variety. Seasonal factors also play an important role, such as unpredicted disease surges. Technology already has the means to improve here, and part of what the future will be resumes to the dissemination of these already known practices.

2.1) One cannot avoid mentioning OGM seeds
OGM seeds are not that impressive for me. Predicted yields from OGM seeds are said to be greater that non-OGM seeds, but the difference can be achieved alone with proper agricultural practices and cheaper non-OGM seeds. I have never tried it, but I suspect that OGM seeds yield in those ideal conditions will converge with non-OGM yields because OGM seeds are not the incredible Hulk, and non-OGM cultivars are pretty great as well. Also, pesticide resistance is not a good thing in itself, allowing for wasteful and unhealthy over-the-top usage, for example. There are many gimmicks in this area, and the possibility for patenting is the major responsible (I think).

2.2) Plasma physics
Plasmas have been used to treat seeds before sowing, apparently with some good results. Still in research, I will not say it works or that it is feasible.

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The future of agriculture can take two distinct directions from now on, in my opinion. It either moves towards scaling up the current technology (corporate agriculture is already doing this) or it will start to incorporate some rather new practices that, although not opposed to machine/chemistry based technology, just do not need them as much. The latter works for both small scale and, to some extent, big scale farming.

In the particular case of olive trees, the dynamics of its auxiliary species is well known. Maintaining the top 4 or 5 species in the local ecosystem can reduce the usage of fungicides, insecticides, as well as erosion and soil correction needs. This is not "new age farming" but mainstream hard science that has been coming out of Universities in the field. But plain old Chemistry is still the farmers' closest friend, unfortunately.

Global warming will change (and to some scale already is changing) everything to the worse. Some bad days are coming.