Depends on what kind of fields you're putting them in. Grazing fields don't require farm machinery running through them, and the solar panels allow places for sheep and cattle to rest in the shade. This makes a huge difference to the comfort of the animals here in Australia; there are farms that have already incorporated solar panels for that reason.
The linked article in the earlier reblog is talking about crops like zucchini and eggplant, which afaik are generally harvested by hand. I don't know if such crops are usually planted by machine the way that wheat is, but considering there's an apparent increase in yield while also reducing the water use, the inconvenience would likely be worth it for at least some farms even if it changes the sowing technique. (Or alternately, you only cover part of the field, allowing for space between the rows of panels for machinery to be driven. Now that some tractors can be driven by GPS with minimal control by the farmer, that also reduces the chance of collisions and damage to the panels.)
Additionally, if there was wide uptake, I would expect that solar panels could be placed on higher supports, reducing the amount of stooping required. That's a potentially solvable problem. And with some parts of the world – including Australia – becoming drier as the climate changes, the fact that crops can be grown under solar panels with less water is no small matter. It could mean that more of the dwindling supply of irrigation water could be saved for crops like wheat, which are currently impractical to grow under solar panels.
But even if it isn't practicable for large-scale farming operations to put solar panels over crops, there's still millions of hectares of grazing land that could have solar panels put over it perfectly happily. We don't have to limit ourselves to car parks and canals.
