Mark 4:20

And those are they that were sown upon the good ground; such as hear the word, and accept it, and bear fruit, thirtyfold, sixtyfold, and a hundredfold.

The good ground ... is not merely ground of sufficient quality and depth to produce a harvest, but it is likewise unencumbered ground. In the fast-moving current era, perhaps the encumbrances are the greatest deterrent to fruit-bearing.

Thirtyfold, sixtyfold, a hundredfold ... Why the various yields from ground uniformly "good"? As in the agricultural world from which the analogies are drawn, the time of planting, the manner of cultivation, and even many intangible factors enter into the amount harvested.