In most regions, the natural cover is insufficient to build up much organic soil content, and on the steeper mountain slopes much of the original earth cover has been washed away. Although roughly half of Iran is made up of the arid Central Plateau, some of the gentler slopes and the Gulf lowlands have relatively good soils but poor drainage. In the southeast, a high wind that blows incessantly from May to September is strong enough to carry sand particles with it. Vegetation can be destroyed, and the lighter soils of the region have been stripped away. In mountain valleys and in areas where rivers descending from the mountains have formed extensive alluvial plains, much of the soil is of medium to heavy texture and is suited to a variety of agricultural uses when brought under irrigation.
Northern soils are the richest and the best watered.
The land reform program of 1962 affected agricultural lands and the production of crops. Implemented in three stages, the program redistributed agricultural lands to the peasantry, thereby lessening the power of the feudal landlords. By the time the program was declared complete in 1971, more than 90 percent of the farmers who held rights to cultivation had become owners of the land they farmed. The new owners, however, became disillusioned with the government and its policies as their real economic situation worsened by the late 1970s. On average, the minimal landholding for subsistence farming in Iran is about seven hectares.