<P> From 100 BC to 1600 AD, world population continued to grow along with land use, as evidenced by the rapid increase in methane emissions from cattle and the cultivation of rice . </P> <P> From the 8th century, the medieval Islamic world underwent a transformation in agricultural practice, described by the historian Andrew Watson as the Arab agricultural revolution . This transformation was driven by a number of factors including the diffusion of many crops and plants along Muslim trade routes, the spread of more advanced farming techniques, and an agricultural - economic system which promoted increased yields and efficiency . The shift in agricultural practice changed the economy, population distribution, vegetation cover, agricultural production, population levels, urban growth, the distribution of the labour force, cooking, diet, and clothing across the Islamic world . Muslim traders covered much of the Old World, and trade enabled the diffusion of many crops, plants and farming techniques across the region, as well as the adaptation of crops, plants and techniques from beyond the Islamic world . This diffusion introduced major crops to Europe by way of Al - Andalus, along with the techniques for their cultivation and cuisine . Sugar cane, rice, and cotton were among the major crops transferred, along with citrus and other fruit trees, nut trees, vegetables such as aubergine, spinach and chard, and the use of spices such as cumin, coriander, nutmeg and cinnamon . Intensive irrigation, crop rotation, and agricultural manuals were widely adopted . Irrigation, partly based on Roman technology, made use of noria water wheels, water mills, dams and reservoirs . </P> <P> The Middle Ages saw further improvements in agriculture . Monasteries spread throughout Europe and became important centers for the collection of knowledge related to agriculture and forestry . The manorial system allowed large landowners to control their land and its laborers, in the form of peasants or serfs . During the medieval period, the Arab world was critical in the exchange of crops and technology between the European, Asia and African continents . Besides transporting numerous crops, they introduced the concept of summer irrigation to Europe and developed the beginnings of the plantation system of sugarcane growing through the use of slaves for intensive cultivation . </P> <P> By AD 900, developments in iron smelting allowed for increased production in Europe, leading to developments in the production of agricultural implements such as ploughs, hand tools and horse shoes . The carruca heavy plough improved on the earlier scratch plough, with the adoption of the Chinese mouldboard plough to turn over the heavy, wet soils of northern Europe . This led to the clearing of northern European forests and an increase in agricultural production, which in turn led to an increase in population . At the same time, some farmers in Europe moved from a two field crop rotation to a three field crop rotation in which one field of three was left fallow every year . This resulted in increased productivity and nutrition, as the change in rotations permitted nitrogen - fixing legumes such as peas, lentils and beans . Improved horse harnesses and the whippletree further improved cultivation . </P>

The beginnings of farming took place about how many years ago