Subsistence agriculture is one in which farming areas consume all, or nearly so, of the products locally grown. It can be grouped into two categories – Primitive Subsistence Agriculture and Intensive Subsistence Agriculture. Primitive Subsistence Agriculture or Shifting cultivation is widely practiced by many tribes in tropics, especially in Africa, south and central America and southeast Asia. The vegetation is usually cleared by fire and the ashes add to the fertility of the soil. It is thus, also called Slash and Burn Agriculture. The cultivated patches are very small and cultivation is done with very primitive tools such as sticks and hoes. After the soil loses its fertility, the farmer shifts to another parts and clears other patches of forests for cultivation. One of the major problems of shifting cultivation is that the cycle of Jhum becomes less and less due to loss of fertility in different parcels. Intensive Subsistence agriculture is largely found in densely populated regions of monsoon Asia. There are two types of intensive subsistence agriculture – intensive subsistence agriculture dominated by wet paddy cultivation. Land holdings are very small due to the high density of population. Farmers work with family members leading to intensive use of land. Use of machinery is limited and most work is done manually. Farm yard manure is used. Yield per unit area is high but per labour productivity is low. Intensive subsistence agriculture dominated by crops other than paddy. Due to difference in relief, climate, soil and some other geographical factors, it is not practical to grow paddy in many parts of monsoon Asia. Wheat, Soyabean, barley and sorghum are grown in northern China, Manchuria, North Korea and North Japan. In India, Wheat is grown in western parts of Indo-Gangetic plains and millets are grown in dry parts of western and southern India. Most of the characteristics of this type of agriculture are similar to those dominated by wet paddy except that irrigation is often used.