Full context:   Seeking better financial returns, landowners looked for more efficient farming techniques. They saw enclosure as a way to improve efficiency,[l] however it was not simply the fencing of existing holdings; there was also a fundamental change in agricultural practice. One of the most important innovations was the development of the Norfolk four-course system, which greatly increased crop and livestock yields by improving soil fertility and reducing fallow periods. Wheat was grown in the first year, turnips in the second, followed by barley, with clover and ryegrass in the third. The clover and ryegrass were grazed or cut for feed in the fourth year. The turnips were used for feeding cattle and sheep in the winter. The practice of growing a series of dissimilar types of crops in the same area in sequential seasons helped to restore plant nutrients and reduce the build-up of pathogens and pests. The system also improves soil structure and fertility by alternating deep-rooted and shallow-rooted plants. For example, turnips can recover nutrients from deep under the soil. Planting crops such as turnips and clover was not realistic under the open field system[m] because the unrestricted access to the field meant that other villagers' livestock would graze on the turnips. Another important feature of the Norfolk system was that it used labour at times when demand was not at peak levels.