As an old legend says, the Inca Village in the location "Otherworldly Fields" is connected to another world, where giants are working on their fields. The Inka's harvest is connected to theirs.
No wonder there isn't any harvest in the human world. A colony of white bats settled nearby and they are eating everything Inka grow.
In order to find something to repel them, Diggy needs to ask the other two giants.
Well, the first one doesn't help much:
Go to the second giant and you will hear about small flowers that repel the bats. Due to the fact that the soil is too dry for them to bloom, please visit a temple in the mountains west from the giant where you can make the river flow again:
There are three stages inside the temple where the stones needed to be placed as follows:
3rd stage where Diggy needs to pull the lever once the gate is open:
Then, please return to the giant and take the blooming flowers to protect the giants' fields from the white bats:
Once you collect all flowers, please return to the first giant and put those flowers on the 6 stones around the field to repel the bats:
Perfect! The smell of flowers will repel those bats and now let's make a fertilizer. Go to the cave near the river and bring the giant 10 piles of guano:
Bring the guano to the giant and he gives you the bag with the fertilizer. Please drag it across the field to make the mushrooms grow:
And finally, the crops are growing aplenty once again!