The second cultural revolution occurred around the 1700 and the 1900. During the Second revolution, people started using machinery to farm.
Farming equipment was never used before this period of time.
The third agricultural revolution occurred in the 1970's to the 1980's. During this time, the use of motorized vehicles trickled down to agriculture. Enormous tractors, along with fertilizer was used to maximize production.
Devices like these were way more efficient than the tools they used before.
Genetically modified organisms is the result of a laboratory process where where genes from the DNA of one species are extracted and artificially forced into the genes of an unrelated plant or animal. You can modify plants in basically any way to benefit your farm and maximize efficiency. They aren't always the best for you. However, GMO's are usually always efficient and they last longer on the food shelves.
Agricultural Revolution Video