how is commercial grain farming different from that of intensive farming ?

Commercial grain farming is an extensive and mechanised form of agriculture. This is a development in the continental lands of the mid-latitudes, which were once roamed by nomadic herdsmen.
The continental position, well away from maritime influence, and the low precipitation (between 305 and 660 mm/12 and 26 inches) make crop cultivation a calculated risk. It was the invention of farm machinery which enabled farmers to cultivate grain on a large scale, and there is a marked specialisation in wheat monoculture in many areas. Communication with the outside world is mainly by railways and the bulk of the grain harvest is exported.
Location: The largest one, in Eurasia, stretches from Kiew in southern Russia to Onsk in western Siberia in a width of about 1,000 km from Caucasus to Saratov on the Volga River.
 
In North America, there are several areas of commercial grain farming. The largest area runs from Alberta, through Saskatchewan and Manitoba to Dakotas. Another centre is in Kansas and spills over into neighbouring states. Smaller regions appear in eastern Washington and Oregon, eastern Illinois and northern Iowa.
In South America, Argentina has a large region of commercial grain farming. Australia has two areas, one in the south-west and another in the south-east. In fact, commercial grain farming is a mid-latitude activity and mostly done in between 30° to 55° N and S latitudes.
Characteristics:
(i) Specialisation in single crop:
Commercial grain farming is highly specialised and generally one single crop is grown. In most commercial grain regions that crop is wheat. Both winter wheat and spring wheat is grown in these areas.
(ii) Farms are very large:
The wheat farms in mid-latitudes are very large, ranging from 240 to 16,000 hectares. Though average size of the farm in the USA is about 400 hectares. In these areas land is cheap that makes it possible for a farmer to own very large holdings.
(iii) Highly mechanised:
The commercial grain farming is highly mechanised. Cultivation from ploughing to harvesting is often entirely mechanised. The use of tractors ploughs drills and combines harvests which reap, thresh, winnow and sack the grain all in one operation is common.
(iv) Low yield per acre but high yield per man:
In this farming wheat grown gives comparatively low yields. The average yield is seldom more than 1,700 kg per hectare, whereas under intensive cultivation the yield is more in many countries. But because of mechanisation, less labour force is required; therefore, yield per man is high.
Other features of the commercial grain farming are:
(a) Lack of irrigation
(b) Farm ownership
 (c) Prone to climatic hazards
(d) Dependance on market fluctuations, etc.
Intensive farming or intensive agriculture is a kind of agriculture where a lot of capital and labour are used to increase the yield that can be obtained per area. The use of large amounts of pesticides for crops, and for medication for animal stocks is common. This is a contrast to ŧraditional agriculture, which does not get as much output per area. When agriculture is intensified, this means that the amount of work needed goes up, until the worker is replaced by a machine. At that point, there will only need to be a few workers to operate the machines. Intensive farming has often been done as a response to rising population levels. It is criticised, because the standards of animal welfare are low.^[1] Intensive animal farming leads to increased pollution and to health issues.
Modern day forms of intensive crop based agriculture involve the use of mechanical ploughing, chemical fertilizers, plant growth regulators or pesticides. It is associated with the increasing use of agricultural mechanization, which have enabled a substantial increase in production, yet have also dramatically increased environmental pollution by increasing erosion and poisoning water with agricultural chemicals.