Farmers should be allowed to grow crops on those lands, which is now used for clean power.
You may debate whether it is a good idea to use the land for solar farm or growing crops, but you are wrong to say "somebody should be allowed to do something there".
The land does NOT belong to anybody, neither the farmer, nor the energy company. It is state property, the farmer as well as the energy company are merely tenet of the state. If the state decides to use the land for different purpose, it can do so with non-negotiable amount of compensation.
The bottom line you must be aware is, land in China is NOT private property. Farming land is like factory, farmers are like workers in the factory, factory owner can fire the workers at any time, the compensation is set by the contract and law, in the case of land, by the state.
That bottom line makes China a Socialist State that the state owns very piece of land. Even if the factory built on it belongs to the capitalist, the capitalist is in no position to wrestle with the state. This also defeats the notion of "China is capitalist in essence".