The modern food production systems which developed over the course of the twentieth century are only part of the story of agricultural development that has taken place over millennia, as man has learnt how to make land, crops and animals more and more productive. However, what took place from the around the Second World War onward was a remarkable leap forward, as science was rigorously applied to the task of raising food production after the shortages of the war years. Improved varieties of crops and superior strains of animals together with new agricultural techniques increased crop yields and productivity substantially, and enabled swelling populations to be fed. The impact of these changes was felt first in developed countries, but in later decades the uptake of these new technologies, particularly irrigation, in parts of the developing world led to the so-called ‘green revolution’ where food production was also raised substantially.
Though much of this development can be put down to improved plant and animal breeding and improvements in farming skills and practice, there is a significant underpinning provided by sources of energy. To understand this, we need to look back at the significance of soil fertility to food production. The earliest farmers would simply move on when their soil became unproductive – leaving the land fallow for several years would allow its fertility to slowly re-build. As populations grew, there was less room to leave land fallow, and other methods came into use: In the not-too distant past, the only way to improve soil fertility was by using the wastes from animals in the form of manure, in some parts of the world human excreta was (and still is) used for this purpose. Farmers also made use of leguminous crops which fix nitrogen from the air through symbiotic relationships with bacteria attached to their roots. A productive system could be maintained by rotating nitrogen fixing and nitrogen-using crops, and incorporating animals into the system as well. This all changed with the introduction of fertilizer in the 19th century. Initially this came from natural sources such as guano (vast deposits of seabird and other animal droppings) which were mined, transported and spread on the land. The mineral content of these fertilizers was high, particularly in nitrogen, potash and phosphates, the three key minerals needed for plant growth, and the effects could be clearly seen in improved crop growth and increased yields. But as the guano began to be used up, farmers had to look elsewhere for sources of fertility.
Chapter 6. “No oil in the lamp”