Within agriculture, convertible husbandry, also known as alternate husbandry, ley husbandry or up-and-down husbandry, was a process used during the 16th century through the 19th century by "which a higher proportion of land was used to support increasing numbers of livestock in many parts of England." In the words of historian Eric Kerridge, convertible husbandry consisted of "the floating of water-meadows, the substitution of up-and-down husbandry for permanent tillage and permanent grass or for shifting cultivation, the introduction of new fallow crops and selected grasses, marsh drainage, manuring, and stock breeding." Convertible husbandry is considered one of the most important changes of the agricultural revolution.
Convertible husbandry was a process that consisted of "alternating arable and pasture on a given piece of land…[by doing so]… farmers almost eliminated the need for fallows between their grain crops and were able to control the quality of their pasture by sowing grass seeds." Alternate husbandry has also been praised as the "best way to keep high fertility on both arable and pasture and to retain excellent soil texture and composition." This system utilized fertilizer in the form of animal manure. Fertilizer was used in greater quantities due to the increase in animal husbandry and resulted in benefiting crop yields when it was time for tillage. Convertible husbandry also came with the added benefit of allowing variations in the types of soils and the extent of leys used in rotation because it was a system in which multiple variables could be modified to suit the needs of the location/type of land/type of soil.
Before the 16th and 17th centuries, farmlands had mostly been founded on the idea of simple alternations of tilling and fallowing during different seasons over several years. However, as livestock became an increasing staple in the lives of farmers and society alike in the midlands, the "rising population…density of settlements, lack of wastelands into which cultivation could expand…and 15th century enclosures for sheep" all led to a need for an improved system of agriculture that allowed for increasing numbers of livestock and a greater increase in crop output compared to input. "The introduction of up-and-down husbandry…helped solve the problems of the midland by providing a measured pasture and arable rotation which not only produced the same amount of grain on a much reduced area, but broke the agrarian cycle of diminished returns by allowing more sheep and cattle to be kept, animals whose dung maintained the fertility of the arable." Another factor that increased the popularity of convertible husbandry had to do with the fact that skill levels of workers were changing and the skills needed to manage a permanent grassland system were acquired too slowly to respond adequately to the growing demand of the population at the time.