To meet somewhat adequately the demands of trade and at the same time to take advantage of the unusual opportunities for gain and enrichment, the Polish landowners turned to agriculture in dead earnest. This caused a change in the method of agriculture and created a great demand for more land and for more labor. Intensive agriculture and large scale production of agricultural products became the rule of the day. From the middle of the fifteenth century on through the sixteenth century the demesne estates of the Polish nobles and of the clergy were in process of enlargement by various methods. Waste and fallow lands were brought under cultivation, swamps were drained and made productive, and forests were cleared and the clearings were converted into fertile farms.[375] Expropriation of village mayorships was another method by which the demesne estates were being enlarged. In the thirteenth and fourteenth centuries Polish princes, and following their example, the magnates and the clergy, in order to encourage colonization, offered special inducements to German colonizing entrepreneurs by allowing them for their services a certain amount of land free of charge and of all public burdens, and by granting them special rights and privileges, which placed them practically on an equal footing with the Polish nobility. These mayorships with their rights and privileges were hereditary. By a statute of 1423, however, the Polish landlords were given the right to buy out these village mayorships from their owners.[376] The steps necessary to be taken were to summon such a village mayor before a “judicium terrestre,” and to notify him of the intention of the lord of the manor to expropriate him. To be sure, the statute declared that this procedure was to be applied only against useless or rebellious mayors; but there was nothing easier to prove than the rebelliousness of a village mayor whom the lord of the manor wanted to expropriate. This method of enlarging the demesne estates was profitable to the lords in more ways than one. It transferred to the seigniorial reserve and its lord not only the land of the expropriated village mayor or mayors, but also the labor, the feudal dues, and all the rights and privileges which the village mayor or mayors formerly enjoyed.[377] This practice lasted from the middle of the fifteenth to the middle of the sixteenth century, and was resorted to by the Polish clergy as well as by the Polish nobility.[378]